Crop-Science-1.ppt

Science of Crop

1. Crop Science
NATURE AND
IMPORTANCE OF
AGRICULTURE

2. INTRODUCTION
The word agriculture is a late
Middle English adaptation of
Latin agricultūra, from ager,
"field", which in its turn
came from Greek αγρός, and
cultūra, "cultivation" or
"growing".

3. INTRODUCTION
Agriculture is an art and science of
raising plants and animals. It is an art
because raising plants and animals
require skills and practice to produce
beauty and pleasant arrangements of
plants and animal combination to
satisfy man’s aspiration for perfection
of his environment.

4. INTRODUCTION
•It is also a science because
knowledge and skills are
learned through systematic
discovery of facts and
principles. It is through the
formulation of hypothesis,

5. INTRODUCTION
•testing of hypothesis, designing of
experiments, gathering of facts, analysis and
interpretation of facts until a general
conclusion and recommendation are arrived
which ultimately become a general practice
and a law.

6. •The first civilization flourished near the
Nile River, Indus and Tigris Euphrates
(Fertile Crescent) as primitive men began
to settle and had division of labor.
INTRODUCTION

7. :
•Evidences of progress and civilization could
be seen by the ‘seven’ wonders of the
worldsuch as the
1. Hanging Garden of Babylon,
2. Pyramid of Egypt,
3. Leaning Tower of Pisa,
4. TajMajalof India,
5. Great Wall of China,
6. Rice Terraces and
7. Underground River in the Philippines.

8. The Development of Agriculture
•Agriculture is the systematic raising
of useful plants and livestocks under
usefulmanagement of man.

9. •Hunting or collectional economy is using randomly
acquired weapons, man lived on the gift of nature,
gathering wild plants for their medicinal, cosmetic,
aphrodisiac properties, as well as for their food value.

10. •Middle Stone Age (from 8,000 B.C.)
•a. use of bow and arrow
•b. catching, drying and storage of fish
•c. stored seeds, nuts and fruits

11. •New Stone Age or Neolithic Age (started between
6,000 to 7,000 B.C.)
•a. discovered the relation of seed plant
•b. domestication of plants and animals

12. •Domesticationwas the intervention that made
possible the development of pastoral and agricultural
economies and therefore, made populous and complex
human societies possible.

13. •It has proven to be the single most important
intervention man has ever made in his environment

14. •Vegeculturerefers to the vegetatively propagated
plants like taro, sweet potato, yam, banana, arrowroot,
etc. while the former includes most of the cereals and
grain legumes whose culture requires the clearing of
vast areas and seeds are sown en masse and harvested
at the same time.

15. •Center of Origin—Asia (eastern half of China)
where its close relative and likely progenitor,
Glycine ussuriensis(wild soybean) is abundant.

16. •Cushites, who not only experimented with plants as
food source, but also attempted their culture; in effect
these people may be regarded as the first
agriculturists.

17. •The Cushites are believed to have been semi-
nomadic, establishing a community on burned land,
planting their gardens with stored seeds, and then
experimenting with domestication of ant suitable local
vegetation.

18. The Origin and domestication of
Soybeans
•The soybean Glycine max is a member of the
Leguminoceae family and subfamilty Papilionoideae.
Beginning its history as a human food, later
developing as a hay and forage crop and finally as a
vegetable oil; protein source, it now occupies a
position of pre-eminence as the world’s largest source
of vegetable oil.

19. •Asia where its close relative and likely progenitor,
Glycine ussuriensis (wild soybean) is abundant.
Hymowitz (1970) suggests that historical and
geographical evidence points to the esteem of soybean
commenced around the 11th century B.C.

20. •Nagata (1960) postulated that cultivated soybean
reached Korea directly from China between 200 B.C.
and 300 AD and from Korea it was introduced to
Japan from where it was widely distributed
throughout Asia.

21. •Europians knew of the crop in the 17th century as an
exotic Oriental crop but have succeeded in
establishing a commercial crop.

22. •According to Morse and Carter (1973), the first
mention of soybeans in the U.S. was in 1804 when a
clipper ship captain carrying soybean from China,
sold the beans in San Francisco

23. •Systematic introduction of soybean germplasm was
continued by the USDA so that by 1923 more than
700 additional lines were introduced from China,
Manchuria, Korea, Japan and India.

24. The Origin and Domestication of
Sorghum
•In order of importance of world cereal grains,
Sorghum vulgare ranks 4th behind wheat, rice and
maize.

25. •Doggett (1970) concluded that the cultivated
sorghums originated from Abyssinia (Northeast
Africa) and were probably first domesticated about 3-
4, 000 BC in Africa around Ethiopia by the Cushites,
who subsequently spread the culture to both West and
East Africa.

26. The Origin and Domestication of
Maize
•While Asia served as a center or origin for soybeans
and Africa for sorgum, maize has the Central and
Southern portion of the Americas (Mexico through
Andean regions of Latin America) as its center of
origin (Purseglove, 1972).

27. The Origin and Domestication of Rice
•The cultivated rice Oryza sativa is a semi-aquatic
annual grass that grows erect. It has been cultivated
for several thousand years as the principal cereal of
Southeast Asia. In terms of hectarage, the major
products are China, India, Indonesia, Bangladesh,
Japan and Thailand.

28. •Oryza sativa is thought to have been domesticated in
India more than 4,000 years ago from the wild species
of O. peennis. The only other cultivated species n the
genus is O. glaberrima, African rice, which probably
originated around the swampy headwaters of Niger
River in West Africa.

29. •Basmati is a variety of long, slender-grained aromatic
rice which is traditionally from the Indian
subcontinent.

30. •Based on the chemical characteristics of the starch
and grain aroma, rice may be classified as either(a)
waxy or glutinous (endosperm contains no amylose,
(b) common type (endosperm contains 14 amylose
and ¾ amylopectin, and (c) aromatic or scented types

31. The Origin and Domestication of Other Crops of
Importance to the Philippines
•OIL CROPS
•1. Peanut –native of South America
•2. Coconut –center of bio-diversity in North-West
South America, but was widely spread and dispersed;
and domesticated in Papua New Guinea.

32. VEGETABLE CROPS
•1. Beans, snap or green and Lima beans –probably
native to tropical America. Phaseolus vulgaris is the
most widely grown of the 4 cultivated species of
Phaseolus. The most important grain legume for
human consumption of the world.

33. •Eggplant–also known as eggfruit, audergine, or
guinea squash is probably native to South and Eastern
Asia, but was also grown in China for many centuries.
It is thought to have been domesticated in India where
wild plants now grow, but it has spread throughout the
warn topics.

34. •Muskmelon(reticulata group)-is believed to have
originated in Asia, particularly in Iran and India.

35. •Okra–also called as gumbo, gombo, gobo or lady’s
finger is either Asia or African in Origin.

36. •Tomatoes–native to tropic Central and South
America where it was cultivated in pre Columbian
times. Its wild progenitor is thought to have been the
cherry tomato which now grows in the wild in Peru-
Ecuador area though tomatoes were probably
domesticated from weedy forms which had spread as
far as Mexico.

37. •Asparagus–thought to be native to Southern
Russia, has been found growing wild in Europe,
England, Poland, and around the Mediterranean Sea.

38. •Onion–an ancient crop thought to have been
domesticated in Central Asia,
•thought its wild ancestor is unknown, nor do onions
occur as wild plants

39. CULTIVATED TROPICAL FRUITS
•Bananas–appear to have originated in Southeast
Asia, spreading to India, Africa and finally to tropical
America

40. •Citrus –original home of the genus Citrus is not
known with certainty, but the history of the cultivated
species suggests that they may have been
domesticated in the dries tropics of South-east Asia.
Though the crop is of tropical origin, it is now
cultivated more extensively in the sub-tropics with
Mediterranean climate.

41. •Mango–originated in the India-Bangladesh-Burma
region, and had spread into cultivation and common
use in the Indian sub-continent by 2,000 BC.

42. •Papaya–probably originated in central America,
perhaps as a natural hybrid between other species.

43. ORIGIN OF SOME CUTFLOWERS
•Chrysanthemums–native to China and was
brought to Europe sometime in 1789 by captain M.
Blanchard of Marseiles.

44. •Carnation–indigenous to the Meditteranean area.
Cultivated by man for over 2,000 years. Man’s
improvement of the native Dianthus (Greek world
which

45. •means Divine Flower) began in the 16th Century. The
perpetual flowering race which gave rise to the
American types was developed in France in 1840.

46. •Rose–native to the northern temperate zone. The
earliest record of a rose is thought to be of a
Damascene rose, a natural hybrid between Rosa
gallica and Rosa phoenicea, found in frescoes at
Knossos, a ruined city on the island of Create and at
one time capital of the Minoan civilization, about
3,000 –1100 BC.

47. •Gladiolus–gladiolus species were recognized over
2,000 years growing in the field of Asia Minor and
were called “corn lilies”. Modern hybrids designated
as G. grandiflorus, are a complex of at least 1 species.

48. •Easter lily –Lilium longiflorum is a ntive of Japan
and its center of origin is apparently Japan’s three
small southernmost islands. The local counterpart of
Easter lily which is endemic to the Philippines is
Lilium philippinense.

49. •Man has domesticated plants and transferred them
from their centers of origin to other continents.
Purseglove (1968) and Jennings and cock (1977) have
shown that the principal production areas for many
major economic crops are distant from the regions in
which they originated.

50. CENTERS of Early Agriculture
•Southwestern Asia –includes most of what is now
called the MIDDLE EAST area where the earliest
agricultural activities were observed, “the cradle of
civilization”

51. •Egypt–basic agricultural ideas spread fro SW Asia
into Egypt before 4,500 BC. Flood from the Nile
River made farming along its banks productive.
Production practices like land preparation, irrigation
and pruning were introduced.

52. •Europe –the basic pattern of plant domestication
which was imported from Asia Minor before 6,000
BC further developed. The Greeks devoted their
genius to Botany and this aided the transition to
scientific agriculture.

53. •The Romans adopted and improved many Greek
agricultural practices such as crop rotation, manure
fertilization, weed control, grafting and budding such
as crop use for greenhouse or Specularia.

54. •The Romans amy be credited for developing the
practice of postharvest storage. It was also during the
Roman times that ornamental horticulture developed
considerably.

55. •Africa–south of the coastal strip of Africa received
the earliest crops by diffusion along the Nile River.

56. •Southern Asia -first crops spread over land from
Iran in SA about 3,000 B.C in southern India and
Ceylon, irrigation reservoirs were constructed as early
as 1,500-1,300 B.C

57. •Central Asia –Wheat and barley farming pattern
was established and spread overland through Iran.
Other crops include grapes, peaches, apricots and
melon.

58. •Eastern Asia –diffusion of SW Asian wheat complex
by mainland diffusion. Root crops like yams and taro,
bananas, bamboo, sorghum, soybeans and rice are
native to the tropical Far East region. Agriculture
flowed from China and Thailand to Malaysia,
Indonesia and Philippines.

59. •Plowingin China probably started before the Han
dynasty (202 B.C to 220 A.D). Horses were used for
plowing around 100 B.C. after the invention of the
horse collar by Chinese.

60. •Japan adapted rice farming from China via Korea but
Northern Japan remained as a hunting and fishing
area. In the 12th century, Tea was introduced to Japan
by Chinese.

61. •Southern Asia –Agriculture consisted of growing
various root crops. Indigenous plant in each area may
have from China, Vietnam, Indonesia, Malaysia,
Ceylon and the Philippines. Many crops may have
been interchange with other crops such as spices and
dye plants.

62. •Oceania–Agriculture in New Guinea and Pacific
Island remained somewhat primitive until modern
times. Crops are taro, yams, coconut, bananas,
sugarcane, mangoes, breadfruit, bottle gourds and
melon.

63. •The Americas –North and South Americas
agriculture stems the domestication of indigenous
American plant.

64. •Southern Mexico –first center of the New World of
Agriculture

65. Southern America –focal area for some major
domestication. The tropical forest lowlands of Southern
America develop agricultural based on root crops like
sweet potato, cassava, peanut also raises gourds,
pineapple, tobacco, dyestuff, beans and cotton.

66. World food situation and centers of
production
•World population is increasing at the rate 2%, and
2.68%over the next 45 years from 6.58today to9.18
in 2050. Much of the increase will be from
developing countries. The population in developing
countries will increase from 5.38to 7.8 Bin 2050.

67. •Great pressure is being placed on
agricultural lands hence, it is
imperative to increase current levels of
food production to provide an adequate
supply of food to increasing population.

68. •This population includes about 5.95 million members
of indigenous cultural communities and 2.55 million
migrant from the lowland groups.

69. •One third of the upland forest inhabitants are
displaced lowland farmers and this group is estimated
to grow at the rate of about 2.27% to 2.92% during
the next 25 years.

70. •Thus by the year 2015 the density will be about 371
persons per square kilometer (U.P. population
institute).

71. Population and Food Supply
•Thomas Malthus, 18th century British Economist,
made a prediction about population growth and
world’s supply (or the world’s population will
increase logarithmetically, while that of food
supply will only increase arithmetically).

72. PHILIPPINE AGRICULTURE
•Pre-colonial period
•Indo-Malayan migrants brought with them wet-rice
agriculture and carabao was also used as source of
animal power for cultivation.

73. •Slash-and-burn kaingin culture or non-plow
farming predominated in other areas.
•This indicated shifting agriculture rather than
sedentary type of rice culture and the tribe were
mainly nomadic.

74. •Main crops consisted of rice, gabi, yams,
bananas, corn millet, coconuts, citrus,
ginger, clove, cinnamon and nutmeg.

75. •Most barangays were self-sufficient. Land was
abundant and population was estimated to be about
500,000 by the mind-16th century. Private land
ownership did not exist.

76. •Spanish Regime
•to recognize all lands in the Philippines as part of
public domain regardless of local customs communal
ownership of land gradually and slowly took the
backseat

77. •encomienda system in the Spanish colonies began as a
result of a Royal Order promulgated in December of
1503
•Hacienda systems, tenants land owners/ tenurial
systems

78. •This period introduced a non-producing class for
which Filipinos produced surpluses, include:
mulberry, cacao, wheat, peas and other vegetables.
•The development of haciendas allowed for the
introduction of technological innovations in
production and processing. e.g. steam or hydraulic-
powered sugar mills.

79. •American Regime
•March 6, 1909-the College of Agriculture founded in
Los Banos as a unit of the University of the
Philippines.
•Intensified Free Trade
•Export Raw Materials

80. •New land policy 3 Ways on how Americans improved
land policy in the Philippines
•1. Friar lands were resold to Filipino farmers

81. 2. Homestead Act in 1924 allowed any Filipino to own
up 24 hectares of public land.
3. All lands had to be registered, and their owners got
Torrens tittles.

82. •Agricultural increase
•After the fought in the revolution, they cooperated
with the Americans revive agriculture.
• Bureau of agriculture (1902) -The first
government agency in the new American colony.

83. •In 1903, the American congress sent a $3 million
emergency fund to import rice and carabaosfrom
other Asian countries. Modern farm tools from the
United States were introduced

84. •Post-War Period
•Introduction of technological improvements:
•50’s-campaign for use of modern farm inputs and
farm mechanization
•60’s-building up of market for tractors and power
tillers

85. •Development Programs
•Import Raw Materials & Processed
Products
•Land Registration Act
Land Reform Act
•Agricultural Land Reform Code
•Establishment of International Rice
Research Institute(IRRI) in 1960

86. Green Revolution
•Introduction of high yielding varieties
•Further development and expansion of international
agricultural trading especially for coconut and its by-
products, tobacco, sugar, pineapple, etc.

87. •Pres. Marcos introduced the
MASAGANA 99 for rice
intensification to yield 99cavans
per hectare, in line with the ultimate
goal of GREEN REVOLUTION to
combat malnutrition and increase rice
yields tremendously.

88. •Rice variety IR-18was developed by scientists in
IRRI which required intensive irrigation, plenty of
fertilizer, and chemical pesticides, to flourish.

89. •Output doubled. Between 1962 to 1964 and 1983 to
1985, with steady increases in between, rice yields
rose from 1.24 to 2.48 metric tons of palay per
hectare.

90. •Along with the GR’s boon, the setbacks account to
costly investment for the package of technologies
(POTs) of high-yielding varieties (HYV’s) due to
massive use of agro-chemicals, resulting to
the loss of traditional varieties.

91. Post Dictatorship Rule (Cory Aquino
Administration)
•This led to the drafting of CARP, which took the
Congress a year to make. On June 10, 1988, Republic
Act No. 6657, also known as the Comprehensive
Agrarian Reform Law (CARL), was passed to
promote social justice and industrialization.

92. •This was due to the fact that Aquino assigned 4
different DAR secretaries.

93. Ramos Administration
•the era of globalization: GATT, Trade Liberalization,
AFMA (RA 8435) with DA Secretary Edgardo
Angara.
•embarked a development plan ‘The Philippines
2000’

94. •Five-Point Program:
•Peace and Stability
•Economic Growth and Sustainable Development
•Energy and Power Generation
•Environmental Protection
•Streamlined Bureaucracy

95. Estrada Administration
•The Estrada administration widened the coverage of
the Comprehensive Agrarian Reform Program
(CARP) to the landless peasants in the country side.

96. •The latter's administration distributed more than
266,000 hectares of land to 175,000 landless farmers
(1.52 hectare each), including land owned by the
traditional rural elite. (Total of 523,000 hectares to
305,000 farmers during his 2nd year as President).

97. •On September 1999, he issued Executive Order (EO)
151, also known as Farmer's Trust Fund, which allows
the voluntary consolidation of small farm operation
into medium and large scale integrated enterprise that
can access long-term capital.

98. •President Estrada launched the Magkabalikat Para sa
Kaunlarang Agraryo or MAGKASAKA

99. •In 1999 a huge fund was allocated to agricultural
programs. One of which is the "Agrikulturang
Maka Masa",

100. GMA Administration
•Secretary Leonardo Q. Montemayor implemented
the AFMA with special emphasis on its social equity
aspect
•He launched the Ginintuang Masaganang Ani
Countrywide Assistance for Rural Employment and
Services (GMA-CARES).

101. •Secretary Luis P. Lorenzo Jr.,took the helm of
the Department in December 2002 and spearheaded
the launching of the Roll-On, Roll-Off or RORO
transport program. The hybridization programs of the
Department were intensified and interventions were
focused on the Mindanao regions.

102. •Secretary Arthur C. Yap, appointed on August
23, 2004, continued to uphold the vision of a
modernized smallholder agriculture and fisheries, a
diversified rural economy that is dynamic,
technologically advance and internationally
competitive.

103. •Under his term, Goal 1 (develope two million
hectares of new lands for agribusiness to contribute
two million to 10 million jobs targeted by 2010)

104. •Goal 2 (make food plentiful while keeping the price
of "wage goods" at low prices) were unveiled

105. •During Panganiban’s 2nd term as Secretary, a total of
203,000 hectares of idle lands and 313,000 jobs were
developed under Goal 1 and ten Huwarang Palengke
(outstanding markets) were identified under Goal 2.

106. •Food lanes were designated for easier, faster and
kotong-free transport of
agricultural products.

107. •When Secretary Yap took the agri seat on October
23, 2006, he has aggressively and consistently
implemented various projects and policies towards the
attainment of food security and self-sufficiency

108. •FIELDS, the government’s centerpiece program on
agriculture, unveiled during the 2008 Food Summit,
Yap has set achievement records for the Philippine
agri and aqua sectors.

109. •Secretary Bernie Fondevilla continued DA’s
mandate of providing sufficient food and sustainable
livelihood for the Filipino people through modernized
technologies and facilities when he took the agri seat
on March 2010

110. NoyNoy Aquino Administration
•On June 30, 2010, President BenignoS. Aquino III
appointed two-term congressman of Quezon and civil
engineer by profession ProcesoJ. Alcalaas
Secretary.

111. Proceso J. Alcala
•One of the principal authors of
Republic Act 10068, or the
Organic Agriculture Act of 2010

112. •He introduced the concept of
AgrikulturangPilipino or Agri-
Pinoyas the Department of
Agriculture's over-all strategic
framework that serves as a guide in the
implementation of its various services
and programs in 2011-2016 and beyond
with its battlecry“Sa Agri-Pinoy,
asenso'y tuloy-tuloy."

113. Duterte Administration
•Introduced Good Agricultural Practices
(GAP) in the DA.
•Good agricultural practice (GAP) are
specific methods which, when applied
to agriculture, create food for
consumers or further processing that is
safe and wholesome.

114. •GAPs -are practices that address
environmental, economic and social
sustainability for on-farm processes,
and result in safe and quality food and
non-food agricultural products.
•DA secretary –Emmanuel Piñol.

116. •Banana
Production in
the Philippines
as of 2018

118. •Banana production for the fourth quarter of 2018 was
accounted at 2.42 million metric tons,
increased by 0.6 percent from the previous year’s level
of 2.41 million metric tons.

119. •Davao Region had the highest production of 904.13
thousand metric tons or 37.3 percent of the total
banana production. Northern Mindanao followed with
492.25 thousand metric tons or 20.3 percent, while
SOCCSKSARGEN contributed 335.11 thousand
metric tons or 13.8 percent

120. •Of the total banana production, Cavendish variety
had the highest share during the period at 51.9
percent. Saba variety followed with 27.6 percent while
Lakatan variety together with other variety comprised
the remaining share of 20.5 percent

121. •Kalamansi
Production as
of 2018

122. •For the period October to December 2018, calamansi
production was estimated at 26.75 thousand metric
tons, lower by 4.6 percent compared with the
28.03 thousand metric tons during the same period of
2017.

123. •Among the regions, CALABARZON had the highest
production of 4.48 thousand metric tons
or 16.8 percent of the total production. This was
followed by Zamboanga Peninsula with 13.2 percent,
and Caraga with 12.8 percent

124. •Mango
Production as of
2018

126. •Pineapple
Production as of
2018

127. •Pineapple production during October to December
2018 posted an increment of 1.0 percent, reaching
706.46 thousand metric tons from 699.22 thousand
metric tons in the same period of the previous year.

128. •Almost two-thirds or 64.2 percent of total pineapple
production was from Northern Mindanao.
SOCCSKSARGEN came next with 30.0 percent share
to the total pineapple production while Bicol Region
contributed 2.1 percent

130. Volume of Production for Selected Fruit Crops, Philippines July-
September: 2017-2018 and October-December: 2017-2018P (In metric
tons)

131. Volume of Production for Banana by Region July-September: 2017-
2018 and October-December: 2017-2018P (In metric tons

132. Volume of Production for Calamansi by Region July-September: 2017-
2018 and October-December: 2017-2018P (In metric tons)

133. Volume of Production for Mango by Region July-September: 2017-
2018 and October-December: 2017-2018P (In metric tons)

134. The End
-aim high, top the board...
-Good Luck!

135. Crop Science Trivia
• Calcium oxalate –chemical substance that
causes itchiness in gabi
Sulfuric acid –chemical present in onion
Capsaicin–white crystalline compound that
causes hotness in some pepper varieties
• Solanine–glykoalkaloid chemical present
in potato tuber which causes greening when
exposed to sunlight

136. Momordicin–substance that causes bitter taste of ampalaya
Allicin–substance found in garlic; can heal common cold;
can reduce/improve blood pressure and cholesterol,
can be used to heal an-an and warts
Cyanogenic glycosides –chemical from cassava

137. FACTORS AFFECTING CROP
PRODUCTION
•Photosynthesis
•Respiration
•Transpiration
•Translocation and partitioning of
assimilates
•Mineral Nutrition
•Growth and development
•Plant movements
•Crop adaptation

138. 1. Photosynthesis
•Photosynthetic System
•a system that converts solar energy into
chemical energy
•plant dry matter analysis
•CO
2and H
2O are practically free while the
mineral elements have to be usually
purchased
•The product (grains, root, tubers) are
essentially net products of photosynthesis

139. •Photosynthetic Organ
•Leaf –chief site of photosynthesis
•Structural parts:
–upper and lower epidermis
–mesophyll cells
–vascular bundles

140. –Mesophyll sheaths:
–upper side –palisade parenchyma (regular-shaped
cells)
–lower side –spongy parenchyma (irregular shaped
cells)
–In some crops (corn), the mesophyll is
undifferentiated translocation of materials

141. Photosynthetic Organs

142. Photosynthetic Reaction
•Photosynthesis starts when a photon of light
strikes the chlorophyll molecule and excites
an electron, raising it to a high energy level
that makes it capable of transforming this
energy to other compounds in the
photosynthetic system

143. Photosynthesis
Photosynthesis

145. •Basic Processes during Photosynthesis
•Diffusion of CO2 from the air to the
reaction sites in the leaf
•Light reaction (photochemical reaction)
•Dark reaction (biochemical reaction)

146. Light Reaction
•Light energizes chlorophyll
•Produce high energy compounds, ATP and NADPH2
•Evolution of O2 through the photolysis of H2O and
photoelectron transport
•Involves 2 kinds of chlorophyll:
–chlorophyll a (bluish green) = 3

147. Dark Reaction
•Assimilation of CO2 production of CH2O
•Use of ATP and NADPH2 in the process
•Occurs in 3 pathways:
–Calvin-Benson or C3 Pathway
–Hatch and Slack or C4 Pathway
•Crassulacean Acid Metabolism (CAM) Pathway

151. DEFINITION OF TERMS
•Kranz anatomy. the special structure of leaves in C4
PLANTS (e.g. maize) where the tissue equivalent to
the spongy mesophyll cells is clustered in a ring
around the leaf veins, outside the bundle-sheath cells.
(The term 'Kranz' means wreath or ring in German)

152. •RuBisCo -Ribulose-1,5-bisphosphate
carboxylase/oxygenase, commonly known by
the abbreviations RuBisCO, RuBPCase, or
RuBPco, is an enzyme involved in the first
major step of carbon fixation, a process by
which atmospheric carbon dioxide is
converted by plants and other photosynthetic
organisms to energy-rich molecules.

153. •CO2 compensation Point -the (light) compensation
point is the amount of light intensity on the light curve
where the rate of photosynthesis exactly matches the
rate of respiration. ... In assimilation terms, at
compensation point, the net carbon dioxide
assimilation is zero.

154. Factors Affecting Photosynthesis
External factors
–Light = intensity, quality, duration
–CO2 concentration in atmosphere
–Temperature
–Moisture
–Dust
–Insect pest

155. Structural condition of leaves
–Number and distribution of stomata
–Abundance of leaf intercellular spaces

156. Organic/inorganic conditions
–Amount/distribution of chlorophyll and
enzymes
–Cell acidity
–Abundance of elements essential for the
synthesis of chlorophyll (e.g. Fe, Mg)

157. RESPIRATION
Significance
•plants need energy to build and maintain cells,
protoplasm
•main source of energy
Respiration Process
•a slow process taking place in the mitochondria
•involves enzymes

158. Mitochondrion

159. •Mitochondrion, membrane-boundorganellefound in
thecytoplasmof almost alleukaryoticcells(cells
with clearly defined nuclei), the primary function of
which is to generate large quantities of energy in the
form ofadenosine triphosphate(ATP).

160. •Mitochondria are typically round to oval in shape and
range in size from 0.5 to 10μm. In addition to
producing energy, mitochondria
storecalciumforcellsignaling activities, generate
heat, and mediate cell growth and death.

161. •The number of mitochondria per cell varies widely;
for example, in humans,erythrocytes(red blood cells)
do not contain any mitochondria, whereaslivercells
andmusclecells may contain hundreds or even
thousands.

162. •The only eukaryotic organism known to
lack mitochondria is the
oxymonadMonocercomonoidesspecies.
Mitochondria are unlike other cellular
organelles in that they have two
distinctmembranesand a unique genome
and reproduce bybinary fission; these
features indicate that mitochondria share an
evolutionary past withprokaryotes(single-
celled organisms).

163. •C
6H
12O
6+ 6O
26CO
2+ 6H
2O + 678
kcal/energy
•basically an oxidation process
(combustion/release energy in the form of heat)

164. Measure of Respiration
•Respiratory Quotient (RQ) = moles CO2 evolved
moles O2 absorbed
•if RQ = 1, glucose is being respired <1, some other
substances are respired (e.g. fats)

165. •Steps in Respiration
•Phosphorylation -formation of sugar
phosphates
•Glycolysis -breakdown of sugar into
pyruvate
•Kreb’s Cycle or tricarboxylic acid cycle
(TCA) -completes the oxidation of pyruvate
to CO
2Reducing potential is stored as
NADH and FADH2
•Phosphate Pentose Pathway (PPP) –aerobic
process

166. •Electron Transport System -where electron transport
takes place particularly in formation of H
2O -an
oxidation-reduction reaction energy trapped in the
process through conversion of low energy phosphates
into high energy phosphates

167. Factors Affecting Respiration
•Species
–Azotobacter chroococcum -2,000,000 æl
02/gmdry weight
–Arum maculatum -15,600-31,800 æl 02/gram
–Valencia orange -20 mgm C02/kgm/24 hours
–Ripe tomato -70 mgm C02/kgm/24 hours
–Part of the plant -generally, plant parts that are
highly protoplasmic and are actively involved in
growth or protein synthesis have higher
respiratory activity.

168. •Physiological state -dormant organs or organisms
respire less than those that are actively growing.
•Degree of hydration -tissues with higher moisture
content respire more than drier tissues such as those
in dry seeds.

169. •Temperature-between 00C-350C, the respiratory
rate increases at the rate or 2 to 2.5 times for every
100C rise in temperature (Q10 or temperature
coefficient is 2 or greater)
•Oxygen supply-with increasing 02, the aerobic
respiration become more dominant so that 02 uptake
and needs increases.
–

170. –The external oxygen concentration at
which fermentation is extinguished is
known as the extinction point.
–Light, salts, injury, biologically active
gases like ethylene-may increase
respiration.
–Inhibitors like cyanide and high C02-may
reduce or inhibit respiration.

173. TRANSPIRATION
•A process wherein plants use water through
evaporation in the form of gaseous water
diffusion driven by net radiation absorbed
by the leaf.

174. •Significance of Transpiration
•Transport and distribution of nutrients
and assimilates
•Dissipate plant’s heat load to maintain
favorable temperature for growth and
development
•In excess leads to plant desiccation 
conversion of starch to sugar and
proteins are hydrolyzed to amino acid

175. Two Stages of Transpiration
•1. Evaporation of water from cell surfaces
•dependent on the heat of vaporization= 539 cal/gram
•energy to convert water from liquid to gaseous state
w/o change in temperature

176. •2.Diffusion out of leaves through openings or
barriers
•vapor pressure gradient---driving forceof moisture
loss from surfaces
•magnitude of loss---resistance in the pathway due to
barriers such as cuticles and reduced opening of the
tomates

177. Types of Transpiration
•Loss of liquid water through the leaf
surface (hydathodes) Guttation
•Most of the water lost by plants is
through Transpiration(in 3 types)
•Cuticular transpiration –water loss
through epidermis covered by a cuticle.
About 5%-10%of the water lost from
plants may be lost by this pathway.

178. •Lenticular transpiration –water loss through the
lenticelsin tress without leaves, and in some fruits.
•Stomatal transpiration –water loss through the
stomata can account for more than 90% of the water
lost from plants.

179. Examples:
•The daily water lossof a large, well-
watered, tropical plant such as the
palm may run as high as 500 liters.
•A corn plantmay lose 3-4 liters/day
99%of the water absorbed by a corn
plant during its life cycle is lost in
transpiration
•A tree-size desert cactus loses less than
25 ml/day

180. Factors Affecting Transpiration
•Since most of the water lost from plants
occur through the stomata, factors that
would influence the opening and closure of
the stomata will invariably affect
transpiration
•Light intensity
•Carbon dioxide concentration
•Water content of the plant

181. Implications to Crop Production
•To sustain beneficial effects of transpiration, crop
should be:
–Given supplemental irrigation when needed
–Reduced competition from weeds
–Not fully exposed to winds –use of wind breaks
–Proper light management –based on crop light
requirement in relation to maintenance of heat load

183. TRANSLOCATION
•Significance of Translocation
•Absorption and transport of raw materials
used for photosynthesis
•Translocation of photosynthetic products to
areas of storage and consumption
•Tissues Involved in Translocation
•Xylem -water and solutes
•Phloem -photosyntates (sucrose)

184. •Principal Translocation System
•Water and solutes dissolved in itare transported from
roots to the other parts through non-living conduits--
-dead xylem vessels and intercellular spaces ---
apoplastApoplasticTransport

185. •Photosynthatesare transported in living
conduitslike the phloem vessels that
contain protoplasmic strands or
plasmodesmata---symplast
•Symplastic Transport

186. •Principal Translocation System
•Upward movement of solutionroots xylem 
stems uppermost leaves ---Transpirational Stream
•With transpiration as primary cause of this
movement, water columnduring rapid transpiration
is usually under tension

187. •Mechanisms of Translocation
•Movement of materials in living plants have
been observed to occur in different ways:
•Ordinary diffusion ---transports ions and
molecules slowly
•Cytoplasmic streaming---which transports
ions and molecules within the cytoplasm at
a considerably faster rate than diffusion

188. •Downward mass or bulk flow---movement
of materials from the upper portion of the
plant to the roots ---Munch pressure flow
hypothesis
•Other mechanisms may include
•activated diffusion and pumping, interface
diffusion and electroosmosis

189. Phloem Loading and Unloading
•1. Phloem Loading -the process whereby
carbohydrates enter the sieve tubes at the source. As a
result of phloem loading, a high. concentration of
sugar develops in phloem cells near the source.

190. •2. Phloem Unloading -Photoassimilate removal from
phloem and delivery to recipient sink cells (phloem
unloading) is the final step in photoassimilate
transport from source to sink.

192. MINERAL NUTRITION
•Background
•60 elementspresent in plant tissues
•92 naturally occurring elementswhen
supplied to plants in available forms -plants
may absorb them
•element may be present in plant tissue ---
but not necessarily essential
•importance of an element ---not proportion
to amount absorbed/uptake

193. •Criteria for Essentiality (Arnon and Stout, 1939)
•Positive requirement of the element for normal growth
or reproduction or to complete the plant's life cycle
•

194. •Function of the element cannot be replaced
by another element (i.e. the deficiency
symptom attributed to a particular element
can not be corrected by the addition of
another)
•Element has a direct or indirect function in
plant metabolism

195. •Nutrient Classification
•Macronutrients (N, P, K, S, Ca, & Mg)
•Major nutrients ---needed by plants in larger
quantities
•Components of proteins, nucleic acids and wide range
of smaller molecules

196. •Beneficial Plant Nutrients (Co, Al, Na, &
I)
•Elements which stimulate growth, but do not
fulfill Arnon's criteria of essentiality or
which are essential only for certain plant
species

197. •Functions of the Nutrient Elements:
Macronutrients
•Element/ Functions/ Available Form:
•1. N •Integral component of proteins
(enzymes) and nucleic acids, NH4+, NO3-
•2. P •Component of nucleic acids, phytin,
coenzymes, adenylases, •Regulatory function
of synthetase reactions, H2PO4-, HPO42-

198. •3. K •Osmoregulation,• Activator of certain
kinases, synthetases, lyases, •Required
for protein synthesis,K+
•4. S •Integral component of proteins,
sulfolipids, S-coenzymes, S-and Fe-S-
proteins, SO4 2-
•5. Ca •Pectates,•Regulatory protein
(calmodulin),•Regulates ion transport,
senescence, membrane permeability

199. •Activator of numerous enzymes,Ca2+
•6. Mg •Integral component of chlorophyll, Mg-ATP,
•Activator of phosphorylation, Rub-P
carboxylase,Mg2+

200. •Micronutrients:
•1. Fe -Fe-, Fe-S-proteins, cytochromes,
ferredoxins, Fe2+, Fe3+
•2. Mn -Possibly cis-diol-type borate
complexes with proteins
•Enzymatic regulation of growth and
development, BO33-
•3. Zn -Activator of carbonic anhydrase,
Alkalne phosphatas, hexokinase, Alcohol
dehydrogenase, Zn2+

201. •4. Cu-Activator of several oxidases, Activates
synthesis of lignin, Cu2+
•5. Mo -Component of nitrate reductase
•Essential for nitrogenase in bacteria for N2-fixation
related plants, MoO42-
•6. Cl -Activator of photosystem II
•Participates in e-transport in chloroplast, Cl-

202. Plant Nutrient Deficiency
Symptoms: Old leaves
(Symptom/Deficient Element)
•1. Nitrogen
•A. Older or lower leaves of plant
mostly affected; effects localized or
generalized.
•B. Effects mostly generalized over
whole plant; more or less drying or
firing of lower leaves; plant light or
dark green.

204. •2. Phosphorus
•Effects mostly localized; mottling or
chlorosis with or without spots of dead
tissue on lower leaves; little or no
drying up of lower leaves.
•Mottled or chlorotic leaves, typically
may redden, as with cotton, sometimes
with dead spots; tips and margins
turned or cupped upward, stalks
slender

206. •3. Magnesium
•CC. Mottled or chlorotic leaves with large or small
spots of dead tissue.
•4. Potassium
•D. Spots of dead tissue small, usually at tips and
between veins, more Marked at margins of leaves;
stalks slender

208. •5. Zinc
•Spots generalized, rapidly enlarging,
generally involving areas between veins and
eventually involving secondary and even
primary veins; leaves thick; stalks with
shortened internodes

210. Plant Nutrient Deficiency Symptoms:
Bud or Young Leaves
•1. Calcium
•Newer or bud leaves affected; symptoms localized.
•Terminal bud dies, following appearance of
distortions at tips or bases of young leaves

211. •C. Young leaves of terminal bud at first typically
hooked, finally dying back at tips and margins, so
that later growth is characterized by a cut-out
appearance at these points; stalk finally dies at
terminal bud

212. •3. Copper
•Terminal bud commonly remains alive; wilting or
chlorosis of younger bud leaves
•with or without spots of dead tissue; veins light or
dark green.

213. •Young leaves permanently wilted without spotting or
marked chlorosis; twig or stalk just below tip and
seedhead often unable to stand erect in later stages
when shortage is acute

214. •4. Manganese
•Spots of dead tissue scattered over the leaf; smallest
veins tend to remain green, producing a checkered or
reticulating effect

215. 4. Manganese
•Spots of dead tissue scattered over the leaf;
smallest veins tend to remain green,
producing a checkered or reticulating effect

216. •5. Sulfur
•Dead spots not commonly present;
chlorosis may or may not involve veins,
•making them light or dark green color.
•Young leaves with veins and tissues
light green in color

217. •6. Iron
•Young leaves chlorotic, principal veins
typically green; stalk short and slender, at
extreme terminal leaves may be completely
white

218. Growth and Development Related
Processes
•Growth
•Irreversible change accompanied by increase in size,
number, weight or mass

219. •Differentiation
•Outward sign of selective gene action, the
reflection of change in the cell's
biochemical repertoire (or program) as a
consequence of the release of information
encoded in one-dimensional sequences

220. •Organization
•Orientation and integration of differentiated cellsin
space together with regulated growth with the
consequent attainment of form and structure of the
complete organism.

221. Morphogenesis
Processconcernedwiththeshapingof
threedimensionalstructuresby
foldingandaggregationofone-
dimensionalgeneproducts,oraggregation
andredistributionofcells

222. •The molding of the whole into a definite
pattern which is morphogenesis should
be distinguished from differentiation, which
is essentially a process of developing
localized differences

223. Plant Growth and development
•Germination
•I. Germination Process
•A. Formation or Activation of Enzyme Systems
•Evidence for activation or de novo synthesis
during germination:
•Appearance of enzyme activity prior to and during
increased germination

224. •Use of protein synthesis inhibitors
•Incorporation of radioactive precursors into
proteins
•Immunological studies
•Molecular techniques

225. •During germination ---formation of enzyme system
can occur in several ways:
–From pre-existing enzymes which are active upon hydration
–Activation of pre-existing enzymes
–De novo synthesis of enzymes from pre-existing or de novo produced Mrna

226. •B. Metabolism of Storage Product and
Subsequent Transport
•Three types of chemical changes during
germination:
•Breakdown of reserve materials in seeds
•Transport of breakdown products (from one
part of the seed to another)

227. •Synthesis of new materials from breakdown products
like:
•Carbohydrates
•Lipids
•Proteins
•P-containing compounds

228. •C. Synthesis of new materials from
breakdown products like:
•Carbohydrates-typically broken down by
& ß amylases
–amylases -starch into variety of sugars such
as maltose, glucose
–ß amylases -oligosaccharides into maltose

229. –Lipids
–Lipid to fatty acids ---converted via ß oxidation to acetyl
CoA to TCA
–Also via oxidation ---peroxidative decarboxylation of
fatty acid coupled
•by CO2 formation

230. •Proteins
•Storage proteins are broken down
•Seeds contains several proteolytic enzymes present in dry
seeds/appear during germination

231. •P-containing compounds
•Main forms ---nucleic acid,
phospholipids, phosphate esters of
sugars, nucleotides, phytin
•Large decrease in phytin which make up
to 80 % of total phosphate in seeds -
phytin as storage pool
•Release of P from phytin by phosphatase
called phytase

232. •4. Transport of Digested Storage
Compound
•Once compounds reached their
destination, they are used for:
•Production of new enzymes
•Structural materials
•Regulatory compounds
•Plant growth substances
•Nucleic acids ( cell functions and
synthesis of new materials)

233. •II. Emergence of Radicle and Seedling
Growth
•Second burst of water uptake during
imbibition ---caused by decrease in
osmotic potential ---due to hydrolysis
of storage compounds
•Concurrent emergence of radicle ---
continuous supply of water and
nutrients for seedling growth

234. •Seedling development begins with cell division ---two
ends of embryonic axis---expansion of seedling
structures
–Plumule (shoot)
–Radicle (root

235. •III. Emergence of Radicle and Seedling
Growth
•Monocots ---endosperm; dicots ---
cotyledons
•Sharp decrease in RN once seedling breaks
through soil surface
•Water absorption increases -as new roots
are formed

236. •Epigeous germination
•hypocotyl elongates and brings cotyledons above
ground
•Hypogeous germination
•epicotyl emerges and the cotyledons remain below
soil surface

237. •Quiescence
•Condition where seed or bud is under
exogenous control such as water supply,
temperature and other environmental
conditions
•Rest
•Condition where seed or bud is under
endogenous control such as internal factors
which prevent growth even environmental
conditions are favorable
•

238. •Dormancy Terminology (Lang 1987)
•Ecodormancy
•Due to one or more unsuitable factors in the
environment ---non-specific effect (equivalent to
quiescence)

239. •Paradormancy
•Due to physical factors or biochemical
signals originating external to affected
structure for initial reaction
•e.g. in buds -apical dominance
•Endodormancy
•Regulated by physiological factors inside
the affected structure
•e.g. buds --rest period

240. •Categories of Seed Dormancy
•Primary Seed Dormancy
–Physical Dormancy
•seed coat dormancy
•seed coverings impervious to water
•acts as safety mechanism by preserving the seed in the dry state
•germination can be induced by disrupting the seed coat-->
imbibition

241. •seed coats are softened by:
–action of microorganism
–passing through digestive tracts
–mechanical abrasion
–alternate freezing and thawing
–fire

242. –Mechanical Dormancy
•Caused by seed enclosing structure ---being strong to permit
expansion of embryo even water can penetrate it
•Germination artificially induced by cracking the structure
covering the embryo or naturally by microorganisms

243. –Chemical Dormancy
•Caused by germination inhibitors ---accumulate in fruit seed
coverings during development
•Overcome by prolonged leaching/removal of seed coat

244. –Morphological Dormancy
•Occurs when seeds are shed from parent plant when their
embryos are not fully developed
•Embryos begin to enlarge after the seed imbibes water and before
germination begins

245. •Causes:
–rudimentary embryos-preembryos
embedded into massive endosperm
–underdeveloped embryo -torpedo shape
and fill up to I/2 the size of the seed
cavity

246. •overcomes by subjecting seeds to temp that
favors embryo enlargement and KNO3 and GA
treatment

247. –Physiological Dormancy
•General type of primary
dormancy in freshly harvested
seeds
•Controlled by endogenous growth
regulators and environmental
cues like light, temperature

248. •II. Secondary Seed Dormancy
–Safety mechanism for the seed-
--preventing germination if
other environmental
conditions are not favorable

249. –Conditions that promote SSD
are
•unfavorable temperature
•prolonged darkness
•prolonged white light
•prolonged red light
•water stress

250. –Overcome by
•chilling
•light
•PGR (GA)

251. •Bud Dormancy
•An adaptation in temperate woody plants --
-> cold Temperature
•Slow progress in this research

252. •Initiation, maintenance and release of
dormancy in buds involves complex
interaction of factors that are genetic,
chemical and environmental

253. •Temp & light are the two most important
environmental factors
•Moisture and nutrients control during initial stages
•Plants generally undergo cessation of plant growth
due to quiescence--prior to beginning of
physiological dormancy

254. •Once dormancy is broken --brief period
of quiescencefollowed by:
•Rehydration of bud leading to increase in
fresh weight
•Increased RN
•Formation/activation of enzyme system---
> breakdown of storage materials
•Growth of bud into shoots

255. •Senescence
•endogenously controlled deteriorative changes which
are natural causes of death of cells, tissues, organs,
organism; natural developmental process --->
terminal differentiation

256. •Changes During Senescence
•“ The ability to quantify specific regulating
components central to senescence is ideal”

257. •Due to lack of evidences, basis are:
•decrease in chlorophyll, total protein, PS (RUBP, PEP
carboxylases)
•changes in plant growth substances
•increase in membrane permeability
•abscission

258. •Flowering
•transition from vegetative to reproductive
development
•Stages:
•Flower initiation-internal physiological
change in the meristem ---precedes any
morphological change
•Indicating that a transition from
vegetative to reproductive development is
occurring

259. •Enhanced cell division in the central zone---
immediately below the apical part of the vegetative
meristem
•Divisions occuring ---> differentiation of
parenchyma cells which surround meristem --->
giving rise to flower primordia

260. •Flower formation
•visible initiation of flower parts
•Final stage
•flower development ---> differentiation
of flower structure including events
from flower formation to anthesis
(flowering).

261. •Plant Growth Regulators
•Plant Growth Regulators -control
growth, development and movement
•Internal and external signals that
regulate plant growth are mediated, at
least in part, by plant growth-
regulating substances, or hormones
(from the Greek word hormaein,
meaning "to excite").

262. •Auxins(cell elongation)
•Gibberellins(cell elongation + cell
division -translated into growth)
•Cytokinins(cell division + inhibits
senescence)
•Abscisic acid(abscission of leaves and
fruits + dormancy induction of buds
and seeds)
•Ethylene(promotes senescence,
epinasty, and fruit ripening)

263. •AUXIN
•Auxin increases the plasticity of plant cell
walls and is involved in stem elongation.
•Arpad Paál (1919) -Asymmetrical
placement of cut tips on coleoptiles
resulted in a bending of the coleoptile
away from the side onto which the tips
were placed (response mimicked the
response seen in phototropism).

264. •Frits Went (1926) determined auxin
enhanced cell elongation
•Discovered as substance associated with
phototropic response.
•Occurs in very low concentrations.
–Isolated from human urine, (40mg 33 gals
-1
)
–In coleoptiles (1g 20,000 tons
-1
)
•Differential response depending on dose.

265. •Auxin promotes activity of the vascular
cambium and vascular tissues.
–plays key role in fruit development
•Cell Elongation: Acid growth
hypothesis
–auxin works by causing responsive cells to
actively transport hydrogen ions from the
cytoplasm into the cell wall space
–Transport: Polar in nature
•Basipetal –tip to base
•Acropetal –base to tip

266. •Signal-transduction pathways in
plants
•Auxin interacts with calcium ions which
in turn calmodulin, a protein, which
regulates many processes in plants,
animals, and microbes.
•STP -A set of chemical reactions in a
cell that occurs when a molecule, such
as a hormone, attaches to a receptor on
the cell membrane.

267. •The pathway is actually a cascade of
biochemical reactions inside the cell
that eventually reach the target
molecule or reaction
•Synthetic auxins
–widely used in agriculture and horticulture
•prevent leaf abscission
•prevent fruit drop
•promote flowering and fruiting
•control weeds

268. •Additional responses to auxin
•abscission -loss of leaves
•flower initiation
•sex determination
•fruit development
•apical dominance

269. •Apical Dominance
•Lateral branch growth are inhibited near the shoot
apex, but less so farther from the tip.
•Apical dominance is disrupted in some plants by
removing the shoot tip, causing the plant to become
bushy.

270. •GIBERRELINS
•Discovered in association with bakanae or foolish
seedling disease of rice (Gibberella fujikuroi)

271. •Gibberellinsare named after the fungus Gibberella
fujikuroi which causes rice plants to grow abnormally
tall.
–synthesized in apical portions of stems and roots
–important effects on stem elongation
–in some cases, hastens seed germination

272. •Cell elongation.
–GA induces cellular division and
cellular elongation; auxin induces
cellular elongation alone.
–GA-stimulated elongation does not
involve the cell wall acidification
characteristic of auxin-induced
elongation

273. –Breaking of dormancy in buds and seeds.
–Seed Germination -Especially in cereal
grasses, like barley. Not necessarily as
critical in dicot seeds.

274. •Promotion of flowering.
•Gibberellins and Fruit Size
•Fruit Formation -"Thompson Seedless" grapes
grown in California are treated with GA to increase
size and decrease packing.

275. •Wild Radish –Rosette & Bolt
•Common Mullen –Rosette & Bolt
•Mobilization of reserves

276. CYTOKININS
•Discovery of cytokinin
•Gottlieb Haberlandin 1913 reported an
unknown compound that stimulated cellular
division.

277. •In the 1940s, Johannes van Overbeek, noted
that plant embryos grew faster when they were
supplied with coconut milk (liquid endosperm),
which is rich in nucleic acids.

278. •In 1964, the first naturally occurring cytokinin
was isolated from corn called zeatin. Zeatin
and zeatin riboside are found in coconut milk.
All cytokinins (artificial or natural) are
chemically similar to adenine.

279. •Cytokinins move nonpolarly in xylem,
phloem, and parenchyma cells.
•Cytokinins are found in angiosperms,
gymnosperms, mosses, and ferns. In
angiosperms, cytokinins are produced
in the roots, seeds, fruits, and young
leaves

280. Function of cytokinins
•Promotes cell division.
•Morphogenesis.
•Lateral bud development.
•Delay of senescence
•Cytokinins, in combination with auxin,
stimulate cell division and differentiation.

281. •Most cytokinin produced in root apical meristems
and transported throughout plant
•Inhibit formation of lateral roots, auxins promote
their formation

282. •Interaction of cytokinin and auxin in
tobacco callus (undifferentiated plant
cells) tissue
•Organogenesis: Cytokinins and auxin
affect organogenesis
•High cytokinin/auxin ratios favor the
formation of shoots
•Low cytokinin/auxin ratios favor the
formation of roots.

283. ABSCISSIC ACID (ABA)
•In 1940s, scientists started searching for hormones
that would inhibit growth and development, what
Hemberg called dormins.
•In the early 1960s, Philip Wareing confirmed that
application of a dormin to a bud would induce
dormancy.

284. •F.T. Addicott discovered that this substance
stimulated abscission of cotton fruit. he named this
substance abscisin. (Subsequent research showed that
ethylene and not abscisin controls abscission).
•Abscisin is made from carotenoids and moves
nonpolarly through plant tissue.
•

285. Functions of abscisic acid
•General growth inhibitor.
•Causes stomatal closure.
•Produced in response to stress.
•Produced chiefly in mature green
leaves and in fruits.

286. –suppresses bud growth and promotes
leaf senescence
–also plays important role in controlling
stomatal opening and closing

287. ETHYLENE
•Discovery of ethylene
•In the 1800s, it was recognized that street
lights that burned gas, could cause
neighboring plants to develop short, thick
stems and cause the leaves to fall off.

288. •In 1901, Dimitry Neljubow identified that a
byproduct of gas combustion was ethylene gas
and that this gas could affect plant growth.

289. •R. Gane showed that this same gas was
naturally produced by plants and that it caused
faster ripening of many fruits.
•Synthesis of ethylene is inhibited by carbon
dioxide and requires oxygen.

290. Functions of ethylene
•Gaseous in form and rapidly diffusing.
•Gas produced by one plant will affect
nearby plants.
•Fruit ripening.
•Epinasty –downward curvature of
leaves.
•Encourages senescence and abscission.

291. •Initiation of stem elongation and
bud development.
•Flowering -Ethylene inhibits
flowering in most species, but
promotes it in a few plants such as
pineapple, bromeliads, and mango.

292. •Sex Expression -Cucumber buds treated with
ethylene become carpellate (female) flowers,
whereas those treated with gibberellins become
staminate (male) flowers.

293. HOW PLANTS RESPOND TO
ENVIRONMENTAL STIMULI
Tropisms-plant growth toward or away from a
stimulus such as light or gravity.
Nastic Movements -response to environmental
stimuli that are independent of the direction of the
stimulus. Pre-determined response.

294. Tropic responses
Directional movements by growth in response
to a directional stimulus

295. 1. Phototropism
Phototropic responses involve bending of
growing stems toward light sources. Individual
leaves may also display phototrophic
responses. Auxin is most likely involved

296. 2. Gravitropism
•It is the response of a plant to the
earth’s gravitational field.
–present at germination
•auxins play primary role

297. 3. Thigmotropism
This is the directional growth response to
contact with an object, the tendrils.

298. 4. Seismonasty
•a nastic response resulting from contact or
mechanical shaking Mimosa pudica L.
(sensitive plant)

299. 5. Photomorphogenesis
Photomorphogenesis -
nondirectional, light-mediated
changes in plant growth and
development red light changes the
shape of phytochrome and can
trigger photomorphogenesis

300. 6. Nyctinasty
•The circadian rhythmic nastic
movement of higher plants in
response to the onset of darkness.
Examples are the closing of the
petals of a flower at dusk and the
sleep movements of the leaves of
many legumes.

301. Growth
the increase in plant biomass (dry matter) over
time.

302. DEVELOPMENT
•the progression of a plant through the
successive stages of its normal life cycle.

303. Vegetative
Establishment–seed germination,
emergence and, ultimately, independence of
seed reserves.
Vegetative growth –initiation, development
and expansion of leaves, stems and roots.

304. Reproductive
Floral initiation –the transition of stem apices
(growing points) from vegetative (producing leaf and
stem primordia [buds]) to reproductive (producing
inflorescence structures and floral primordia).

305. •Flowering and pollination (anthesis),
resulting in fertilized ovules which will develop
into seeds (grains).

306. Seed growth (grain filling)
to a maximum wet weight at physiological
maturity. • Seed (grain) maturation –grain
dries naturally to a moisture content suitable
for harvesting and storage.

307. Harvest ripeness–dry (12-14% moisture)
grain ready for harvest.