Placentation and fruits types.pdf

Placentation

1. Placentation:

Placenta is a ridge of tissue in the inner wall of the ovary
bearing one or more ovules; and the manner of distribution
of the placentae within the ovary is called placentation.
The placentae most frequently develop on the margins of
carpels either along their whole line of union called the
suture, or at their base or apex.
Types of Placentation: In the simple ovary (of one carpel)
there is one common type of placentation known as
marginal, and in the compound ovary placentation may be
axile, central, parietal, basal or superficial.
(1) Marginal: In marginal placentation the ovary is one-
chambered and the placenta develops along the junction of
the two margins of the carpel,


the ventral suture, as in pea, wild pea, gram, gold mohur,
Cassia, sensitive plant, etc. In Ranunculus the pistil is
apocarpous, and each ovary bears a single pendulous ovule
attached to the ventral suture.
(2) Axile: In the axile placentation the ovary is two to
many-chambered—usually as many as the number of
carpels—and the placentae bearing the ovules develop
from the central axis corresponding to the confluent
margins of carpels, and hence the name axile (lying in the
axis), as in potato, tomato, Petunia, China rose, lady’s finger,
hollyhock (Althaea), lemon, orange, etc. Three-chambered
ovary is common among monocotyledons, as in lily,
asphodel, onion, etc.


Dr. Sangekar Sarika
Yogeshwari Mahavidyalaya A.

2. (3) Central: In the central placentation the septa or
partition walls in the young ovary soon break down so that
the ovary becomes one-chambered and the placentae
bearing the ovules develop all round the central axis, as in
pink family, e.g. pink (Dianthus), Polycarpon, soap-wort
(Saponaria), etc. Remnants of partition walls may often be
seen in the mature ovary.
(4) Parietal: In the parietal placentation the ovary is one-
chambered, and the placentae bearing the ovules develop
on the inner wall of the ovary corresponding to the
confluent margins of carpels. There are as many placentae
as the number of carpels, as in papaw, poppy, prickly
poppy, orchids, etc. In mustard family, e.g., mustard, radish,
rape, etc., the placentation is also parietal but here the
ovary becomes two-chambered due to the development of
a false partition wall across the ovary from placenta to
placenta, and the seeds remain attached to a wiry
framework called the replum.
(3) Basal: In the basal placentation the ovary is unilocular
and the placenta develops directly on the thalamus, and
bears a single ovule at the base of the ovary. This is seen in
sunflower family, e.g. sunflower, marigold, Cosmos, etc.
(6) Superficial: In the superficial placentation the ovary is
multilocular

3. ,


Fruit.
Fruit is a developed and ripened ovary or ovaries together,
often, with adjacent floral organs and other plant parts.
Fruits range in complexity of their morphology from a
single carpel (e.g., legume) to a compound fruit (e.g.,
pineapple), where an entire inflorescence (including the
ovaries, floral parts, bracts, inflorescence axis, etc.)
converts into a single succulent mass. The fruit is the
product of the entire gynoecium and any floral parts
associated with the gynoecium in the fruiting stage.
Classification of Fruits
All the different kinds of fruits may be broadly classified
into three groups, viz.
simple,
aggregate and
multiple or composite.
common types are discussed under each group.

4. 1. Simple Fruits. When a single fruit develops from the
ovary (either of simple pistil or of syncarpous pistil) of
a flower with or without accessory parts, it is said to
be a simple fruit.
2. A simple fruit may be dry or fleshy. Dry fruits may
again be dehiscent or, indehiscent.
I. Dehiscent Or Capsular fruits:
(1) Legume or Pod: This is a dry, one-chambered fruit
developing from a simple pistil and dehiscing by both the
margins, e.g. pulses (pea, gram, lentil, etc.), bean, gold
mohur, Cassia, Mimosa, etc.


(2) Follicle: This is also a dry, one-chambered fruit like
the previous one, but it dehisces by one suture only.
Simple follicle is rare; it may sometimes be seen in madar
(Calotropis), blood flower (Asclepias), wax plant (Hoya),
Rauwolfia, etc. Usually follicles develop in an aggregate of
two, three, or many fruits.

5. 3) Siliqua: This is a dry, long, narrow, two-chambered fruit
developing from a bicarpellary pistil with two parietal
placentae. It dehisces from below upwards by both the
margins. The ovary is one-chambered at first, but soon it
becomes two-chambered owing to the development of a
false septum across a wiry framework, called replum, to
which the seeds remain attached, e.g. mustard, radish, etc.
A short, broad and flat siliqua, as in candytuft (Iberis), aiiscn
(Alyssum) and shepherd’s purse (Capsella), is otherwise
called a silicula.

(4) Capsule: This is a dry, one-to many-chambered fruit
developing from a syncarpous pistil, and dehiscing in
various ways. All dehiscent fruits developing from a
syncarpous pistil are commonly known as capsules, e.g.
cotton, lady’s finger, Datura, cock’s comb, poppy, etc.

6. II. Indehiscent Fruit

(1) Achene:An achene is a small, dry, one-seeded fruit
developing from a single carpel; but unlike the next one, the
pericarp of this fruit is free from the seed-coat, e.g. four
o’clock plant (Mirabilis), hogweed (Boerhaavid) and
buckwheat (Fagopyrum). Achenes, however, commonly
develop in an aggregate, as in rose, Clematis, Naraveha, etc.
(2) Caryopsis: This is a very small, dry, one-seeded fruit
developing from a simple (or syncarpous) pistil, with the
pericarp fused with the seed-coat, e.g. maize, rice, wheat,
bamboo, grass, etc.

(3) Cypsela: This is a dry, one-seeded fruit developing from
an inferior bicarpellary ovary, e.g. sunflower, marigold,
Cosmos, etc.
(4) Samara: This is a dry, indehiscent, one- or two-seeded,
winged fruit developing from a superior, bicarpellary or
tricarpellary ovary. In samara the wings, one or more,
always develop from the pericarp of the fruit, as in Hiptage
, ash (Fraxinus), yam, etc. Fruits of sal tree (Shorea), wood-
oil tree (Dipterocarpus), Hopea, etc., are also winged but in
them the wing are the dry, persistent sepals. A winged
fruit of this nature is called a samaroid.
(5) Nut :
This is a dry, one-seeded fruit developing from a superior
syncarpous pistil, with the pericarp hard and woody, e.g.
cashew-nut, marking nut, chestnut, oak, etc.

III. Splitting Or chizocarpic Fruit
(1) Lomentum: When the pod is constricted or partitioned
between the seeds into a number of one -seeded

7. compartments, it is called a lomentum, as in gum tree
(Acacia), nicker bean, sensitive plant (Mimosa), Indian
laburnum, (Cassia fistula), groundnut (Arachis), Indian
telegraph plant (Desmodium), etc.
(2) Cremocarp: This is a dry, two-chambered, inferior fruit
splitting into two indehiscent, one-seeded pieces, called
mericarps. Each mericarp remains attached to the forked
end of the axis (carpophore), as in coriander, anise or
fennel, cumin, carrot, etc.
(3) Double Samara : In maple (Acer), the fruit develops
from a superior, bicarpellary ovary, and when mature it
splits into two














(4) Regma: This is a dry, 3 to many chambered fruit
developing from a syncarpous pistil. It splits away from the
central axis into as many parts (cocci) as there are carpels,
each, part containing 1 or 2 seeds. Common examples are
castor, Euphorbia , Geranium, Jatropha etc.
Fleshy fruits:

8. (1) Drupe: This is a fleshy, one or more seeded fruit with
the pericarp differentiated into the outer skin or epicarp,
often fleshy or sometimes fibrous mesocarp, and hard and
stony endocarp, and hence this fruit is also known as stone-
fruit, e.g. mango, plum, coconut-palm, palmyra-palm,
country almond, etc.
(2) Bacca or Berry: This is a fleshy, superior (sometimes
inferior), usually many-seeded fruit, developing commonly
from a syncarpous pistil (rarelyfrom a single carpel) with
axile or parietal placentation, e.g. tomato, gooseberry,
grapes, banana, guava, papaw, etc. With the growth of the
fruit the seeds separate from the placentae and lie free in
the pulp. It is not infrequent to find a one-seeded berry, e.g.
date-palm. In Artabotrys berries develop in an aggregate.
















(3) Pepo: This is also a fleshy, many-seeded fruit like the
berry but it develops from all inferior, one-celled or
spuriously three celled, syncarpous pistil with parietal

9. placentation, e.g. gourd, cucumber, melon, water melon,
squash, etc. In pepo, the seeds, lying embedded in the pulp,
remain attached to the placentae.
(4) Pome: This is an inferior, two or more celled, fleshy,
syncarpous fruit surrounded by the thalamus. The fleshy
edible part is composed of the thalamus, while the actual
fruit lies within, e.g. apple and pear.
(5) Hesperidium: This is a superior, many celled fleshy
fruit with axile placentation. Here the endocarp projects
inwards forming distinct chambers, and the epicarp and the
mesocarp, fused together, form the separable skin or rind
of the fruit, e.g. orange, pummelo or shaddock, lemon etc.
2. Aggregate Fruits:
An aggregate fruit is a collection of simple fruits (or
fruitlets) developing from an apocarpous pistil
(freecarpels) of a flower. Since each free carpel develops
into a fruit there will be as many fruits as there are free
carpels in a flower. An aggregate of simple fruits borne by a
single flower is otherwise known as an ‘etaerio’, and. the
common forms of etaerios are: (1)) an etaerio of follicles ,
e.g. Michelia, madar (Calotropis), periwinkles (Vinca),
larkspur (Delphinium) etc.; (2) an etaerio of achenes , e.g.
rose, lotus, Clematis, .strawberry, Naravelia, etc.; (3) an
etaerio of drupes , e.g. raspberry (Rubus); and (4) an etaerio
of berries , e.g. custard-apple (Annona), Artabotrys , mast
tree (Polyathia), etc.
3. Multiple or Composite Fruits: A multiple or composite
fruit is that which develops from an inflorescence where
the flowers are crowded together and often fused with one
another.
(1)Sorosis: This is a multiple fruit developing from a spike
or spadix. The flowers fuse together by their succulent
sepals and at the same time the axis bearing them grows

10. and becomes fleshy or woody, and as a result the whole
inflorescence forms a compact mass; e.g. pineapple (A),
screwpine, jack-fruit and mulberry .


















(2) Syconus: The syconus develops from a hollow pear-
shaped, fleshy receptacle which encloses a number of
minute, male and female flowers. The receptacle grows,
becomes fleshy and forms the so-called fruit. It really
encloses a number of true fruits or achenes which develop
from the female flowers lying within the receptacle, as in
Ficus, (e.g. fig. banyan, peepul, etc.).
Q.3 : Explain in brief the Dispersal Strategies of seed
and fruit.
Ans : Flowering plants produce numerous seeds and fruits.
Some of the perennial plants produce seeds annually
during a specified period. If all the seeds and fruits

11. produced by a plant fall directly underneath its parent
plant, then the growing seeds and seedlings will cover all
the space and exhaust soil minerals and water. Under such
conditions, the seedlings cannot: grow into firm and well-
developed plants; and in due order a plant species may
grow well, the dispersal of their fruits are seeds is
absolutely essential, Seeds and fruits and provided with
vanous types of modifications which help them in
dispersal. In dehiscent fruits, dispersaltakes place after
their bursting while in indehiscent fruits, dispersal of their
fruits and seeds is absolutely essential. Seeds and fruits are
provided with various types of modifications which help
them in dispersal. In dehiscent fruits dispersal takes place
after their bursting while in indehiscent fruits, dispersal of
entire fruits is accomplished. The morphology of the
dispersing organ to a great extent is determined by the
environment.
1) Wind dispersal : Wind is the main medium for the
dispersal of a seeds and fruits. The following modifications
are noted in fruits and seeds which are dispersed through
wind.1) Seeds of orchids are very small, dry and dusty and
they are easily a way by wind.
2) Wings : Seeds and fruits develop wings which help in
dispersal.
a) Winged fruits : Fruits of Shorea, robusta have wings- the
modified calyx. In Hiptage, Acer, Dioscorea, Fraxinus (ash),
Terminalia myrocarpa, Hopea and Dipterocarpus, pericarp
is metamorphosed to wing-like structure.
b) Winged seeds : Seed coats of Bignonia. Cinchona,
Tacoma, Lagerstronia, Oroxylon, Stereospermim, Combritus
and Moringa are also minified to form wings.
Parachute mechanism :

12. Certain seeds and a few fruits have appendages which
accumulate air and become light to give buoyancy to the
seeds. The movement of such organs in the air is called
parachute mechanism.
a) Pappus : The fruits of Mikania, sunflower, dandelion
(Taraxacum officinal), Ageratum, Tridex and Sonchus of
family compositae are called as cypsella. Each fruit has
pappus i.e., hairy outgrowth or modified calyx in the form
of small hairs. The pappus is persistent in the fruit and
opens out in an umbrella-like fashion. When the fruit is
detached from the parent plant, the pappus acts like a
parachute and helps the fruit float in air and is carried away
to long distances. b) Coma : The seeds of Calotropis, bear
tuft of hairs known as coma. The coma acts like a parachute
and gives support to the seeds to float easily in air for
dispersal.
c) Hairy outgrowth : A group of hairs develop from the
inner-walls of the cotton seeds i.e., from the testa which
makes the seeds air-borne. Dispersal by water :
The plants which grow along the banks of rivers, sea-canals
and streams or directly in water disperse their fruits and
seeds by water currents. Such fruits and seeds are very light
and float on the surface of the water due to the presence of
spongy tissue containing air. The surface of these fruits is
usually smooth and ways or fibrous due to which fruits and
seeds are prevented from getting decayed. The fibrous fruit
of Coconut is carried to long distances on river or sea-coast
without causing any damage to the fruits. In coconut fruit,
the fibrous mesocarp accumulate air, becomes very light,
which helps in floating on water. The thalamus of
Nelumbiurn is conical and spongy and bears numerous
achenes embedded in it. A ripe fruit gets detached from the
mother, plant and falls on the surface of water and is carried

13. by water currents to long distances. Gradually, the spongy
thalamus decays and the seeds become free, which sink
down to water, settle in the mud and grow to form new
plants.









Dispersal by water: A-Lodoxia, B-Coconut, C-
Nilumbo

3) Dispersal by animals :
Many seeds and fruits are dispersed by animals, they
develop certain adaptivity to produce specific organs for
this purpose.
1) Organs for attachment : Various types of additional
organs are developed by plants of seeds for attachment to
animals.
a) Pointed organs : Many fruits are provided with curved
and pointedt hooks, barbs, spines, bristles, stiff hairs, etc.
On their body by mean of which they get attached to the
body surface or animals and clothes of human beings and
thus are carried away to long distance. The fruit of Urena,
Xanthiun (Cockle vur), Medicago and Martynia diandra
(tigera claw ) bear numerous curved hooks. Thi spikelets
of love thori (Chrysopogon) andi seeds of spea grass
(Aristida) have stiff hair pointing upwards. Pupalia fruit

14. are provided fruit, which enter the skin of animals and
clothes of humanL beings and are carried away from the
parent plant.
2} Sticky lands : In Plumbago and Boerhavia, the persistent
sepals, bear glandular hairs which easily stick to the body
of animals of clothes of human beings. Seeds watermelon,
muskmelon are also slightly adhesive) in nature. The fruits
of Cordia gharaf and Cordia obliqua grow in desert areas,
are very sticky in nature. Seeds of Aegle marmelos are also
sticky. Fruits of Achyranthes aspera are sticky due to their
scarious bracts and. perianths.









Hooked Fruits
Mechanical dispersal:
The dehiscence fruits by internal force is helpful in the
dispersal of seeds. This occurs due to the contraction of
moist walls on drying. The wall splits with a force and
seeds attached to it are thrown out. Such fruits are; called
as explosive. Many leguminous fruits like pea, bean and
gram burst L along both the sutures to disperse the seeds.
The ripe fruits of balsam, L when touched, burst
immediately. The valves roll-up inwards and the seeds 3
are-thrown out with are great force and scattered in

15. different direction. In Geranium, when the fruit ripes and
becomes dry, the styles curl-up carrying, the cocci at their
tips. The styles then open out with a jerk and the seeds;
are thrown away to some distance from the cocci. The
fruits of few plants t like Ruellia tuberosa,
Andrographispaniculata when burst, the two valves; eject
the seeds. The seeds have peculiar hook-like projection
called as ejaculatons or retinacula, developed from their
funicles, which become straight as soon as the fruit bursts
to eject the seeds.