Biology-Lecture on FLOWER by chanchal.ppt

biology

1. Lecture on flower
by
Dr Chanchal Kumar Biswas
Department of Botany

2. THE FLOWER
A flower is define as a
modified reproductive shoot
of determinant growth,
consisting either only stamens
(microsporophyll) or Carpel’s
(megasporophylls) or both and
may or may not be associated
with accessory parts like
sepal, petals to produce fruit
and seeds.

3. Different term related to flower.
CompleteFlower::Acomplete
flowerisaflowerthathasall
fourpartsoftheflower(sepals,
petals,androecium and
Gynoecium).
Incompleteflower:Acomplete
flowercontainsallfourorgans,
whileanincompletefloweris
missingatleastone.Abisexual
(or“perfect”)flowerhasboth
stamensandcarpels,anda
unisexual(or“imperfect”)flower
eitherlacksstamens(andis
calledcarpellate)orlacks
carpels(andiscalled
staminate).

4. Symmetry of flower
•Actinomorphic
(regular): Flowers that are
radially symmetrical so that they are
able to be bisected into similar
halves in more than one vertical
plane, forming mirror images.
•Zygomorphic flower
(irregular): Flowers that are
bilaterally symmetrical so that they
are able to be bisected into similar
halves in only one plane, forming
mirror images.

5. Cyclic(most of angiosperms): A flower whose parts are
arranged in a whorl. Cyclic flowers are characteristic of
most flowering plants, including those of the families
Liliaceae, Caryophyllaceae, and Solanaceae.
•Acyclic ( Eupomatia): A flowers whose parts are
arranged in spirals rather than in whorls, as in
magnoliales.
•spirocyclic flower( Nymphaeaceae):It is
flower where half of the members are
arranged spirally and half of members
arranged in whorl manner.

7. Pistillate and staminate flower
•Unisexual or
Imperfect flowers that
bear stamens only
are called staminate
flowersor male
flower.
•Unisexual or
Imperfect flowers that
bear pistils only are
called pistillate
flowers or female
flower.

8. •Monoeciousplants are those in which
both the staminate and pistillate flowers
are borne on the same plant. Cucerbita.
•Species in which the two imperfect flowers
are borne separately in different plants are
called dioecious. Borassus flabellifer.
•Some plant bear male, female and
bisexual flower are called polygamous
flower. Eg Litchi sinensis.

9. Perianth
•Perianth of a flower
•The perianth is the outer envelope enclosing a flower and is made
up of either:
•an outer calyx and inner corolla;
•a calyx or corolla; or
•calyx and corolla combined and undifferentiated from one another.
•The corollaof a flower is divided up into
petalswhereas the calyxis made up or
sepals.
–If the calyx and corolla are combined into
one undifferentiated unit, then the
individual parts are referred to as tepals.

11. Parts of typical flower
•A flower consist of an axis known as
thalamus, on which four different sets of floral
parts are inserted.
a.Thalamus: The thalamus is the receptacleor
terminal part of the axisof a flower. Some
times it is long , showing distinct internode.

12. Calyx:
•In many Plant species, the calyx consists of
green leaf-likestructures, the sepals, which
protect the delicate inner parts of the flower
while it is developing and prevent it from
desiccating. The sepals may be fused or free
and symmetrical or assymetrical. In some plant
families likeLiliaceae it is not possible to
distinguish between sepal and petals and these
structures are calledtepals.
•

13. Corolla
•In many species, the corolla which
consists of the whorl of petals, is the most
obvious part of the flower. Some flowers
have large, showy petals but in some
families such as the grasses the petals
have become very reduced. It is also free
or fused and termed as polypetalous and
gamopetalous.

14. AESTIVATION of floral parts.
It is the mode of arrangement of accessory floral
member ( sepal , petal & perianth ) with respect to one
another in a flower bud. These are following types.

15. •Valvate: In this type, the margin of sepals or
petals simply touch each other but not overlap.
Mimosaceae.
Twisted(contorted): In this case sepals or petals
are arranged in such way that their one margin
overlaps the margin of the next one and the other
margin is overlapped by margin of another.
Malvaceae
Imbricate: In this case out of five accessory
members one is purely internal, one is external
and other three partly internal and partly external.
E.g. Caesalppinaceae

16. Quincuncial: In this case out of five accessory
member two is purely internal, two are external
and one partly internal and partly external e.g.
Apocynaveae.
Vexillery: It is a type of imbricate aestivation,
here out of five petals the odd posterior one
(standard) is largest and outermost, it overlaps the
two lateral petals (wings) and the lateral petals
again in turn partly overlap the two smallest and
innermost petals (keel).

17. Androecium: Depending on the numbers
and arrangement of stamen, it is classified in
to following groups.
–Diplostemonous: stamens
occurs in two whorl. And
outer one is alternate with
petals and consequently
opposite to sepals. Cassia
fistula
–Obdiplostemonous: When
stamens of outer whorl are
opposite with petals and
consequently alternate to
sepals. Oxalis sp

18. •
–Isostemony: When all
stamens are in one whorl and
are equal to the number of
sepals and petals.
–Tetradynamous: Stamens are
six. Outer two are shorter and
inner four are longer or vice
versa (A2+4) Cruciferae
–Didynamous: Stamen four.
Two are long and two are
short. Labiatae

19. Union of stamen
The union of stamens takes place either among
themselves (cohesion) or with other whorls
(adhesion).
–Adhesion of stamens : Stamens may unite
with other floral whorls like Perianth, petals
or gynoecium. Based on the floral organ
involved in the union with stamens, the
adhesion may be of the following types :

20. Adhesion of stamens
•Epiphyllous :Stamens
unite with perianth. e.g.,
Asperagus.
•Epipetalous :Stamens
unite with petals. e.g.,
Datura.
•Gynandrous : Stamens
unite with gynoecium. It
is also called
gynandrium or
gynostegium. e.g.,
Calotropis.

21. Cohesion of Stamens
Usually three types of cohesion among stamens occur. They are
:
1. Adelphous: Anthers remain
free and filaments are united.
Adelphous condition can be
(a) Monoadelphous—United
to form 1 bundle, e.g.,
China rose
(b)Diadelphous—United to
form 2 bundles, e.g., Pea
(c)(c) Polyadelphous—
United into more than two
bundles, e.g., Lemon

22. 2. Syngenesious: Filaments
free and anthers united,
e.g., Sunflower.
3. Synandrous: Stamens
fused all through their
length,
e.g., Cucurbita

23. Attachment of anther to the
filament
•Innate or Basifixed: When the
filament is firmly attached to the
base of the anther. Solanumsp
•Adnate: When filament running
the whole length of the anther
from the base to apex. Michelia
sp
•Dorsifixed: When the filament
attached to the back of anther.
Bauhinia variegate.
•Versatile: Filament attached to
the back of anther at a point only
, so that the later can swing
freely. Graminae

24. Dehiscence pattern of Stamen
•(i)Porous: Pollens
released through pores,
e.g., Brinjal,
•Potato
•(ii)Longitudinal:
Pollens released
through the longitudinal
•slit of another lobes, e.g.,
China rose, Cotton

25. Gynoecium.
oGynoecium:Thegynoeciumorpistilisthefourth
essentialwhorloftheflowerandmaybemadeupof
oneormorecarpels(megasporophylls).
oAcarpelhasthreedistinctpart,namelyovary,style
andstigma.Thelowermostswollenfertilepartofthe
carpelistheovary.Itenclosesovules.Abovethe
ovaryelongatedthreadlikestructureattachedtothe
apexoftheovary,thestyle.Thestyleendwitha
round,stickystigma.
oAsterilepistilisknownpistillode.Thenumberof
carpelsinagynoeciumvaryindifferentflowers.
Accordinglythegynoeciummaybedescribedas
follows:

26. –Monocarpellary :It is a
ovary with a single carpel,
e.g., Bean.
–Bicarpellary :It is presence
of two carpels in a ovary,
e.g., Solanum.
–Tricarpellary :It is presence
of three carpels, e.g., Cocos.
–Tetracarpellary :It is
presence of four carpels,
e.g., Cotton.
•Pentacarpellary :It is presence
of five carpels, e.g., Hibiscus.
•Multicarpellary :It is presence
of many carpels, e.g., Annona.

27. Cohesion of carpel.
If number of carpels is more
than one, they may be
•(i)Apocarpous: Carpels
are free. Each carpel has
its own style and stigma,
e.g., Rose.
•(ii)Syncarpous: Carpels
are united, e.g., Lady’s
finger, Tomato

28. Theovaryenclosesonetomanychamberscalledthe
locules.Usuallythenumberofloculesinasyncarpous
ovarycorrespondstothenumberofcarpels.
Sometimes,thenumberofloculesmaybedoubled.
e.g.,inDatura,thegynoeciumisbicarpellary
syncarpouswithfourloculesintheovary.Basedonthe
numberoflocules,theovarymaybedescribedas
follows :
Unilocular:Ovarywithonelocule.e.g.,Dolichos.
Bilocular:Ovarywithtwolocules.e.g.,Solanum.
Trilocular:Ovarywiththreelocules.e.g.,Allium.
Tetralocular:Ovarywithfourlocules.e.g.,Datura.
Pentalocular:Ovarywithfivelocules.e.g.,Hibiscus.
Multilocular:Ovarywithmanylocules.e.g.,Abutilon.

29. Placentation
Placentationreferstothearrangementofovules
withintheovary.Ovulesareattachedtoovarian
wallsthroughspecialstructurescalledas
placenta.
Marginal:Theplacentaformsaridgealong
theventralsutureoftheovaryandthe
ovulesareborneonthisridge,e.g.,Pea
Axile:Theovaryispartitionedintoseveral
chambersorloculesandtheplacentaeare
bornealongtheseptaoftheovary,e.g.,
Tomato,Chinarose
Parietal:Theovulesdevelopontheinnerwall
oftheovaryoronperipheralpart.Ovary
unilocularbutinsomecasesbecomestwo
chamberedduetoformationofafalse
septum,e.g.,Mustard

30. (iv)Free central:
Ovules are borne
on the central axis and
septa are absent, e.g.,
Carnation, Chilly
(v)Basal: Placenta
develops at the base of
the ovary,
e.g. ,Sunflower.

31. Style
Thestalklikestructurepresentabovethe
ovaryiscalledthestyle.Thestylemaybe
long(Datura)orshort(grasses)orabsent
(Papaver).Inthefamilyumbelliferae
(Apiaceae)thebaseofthestyleisswollen
andformsastructurecalledstylopodium.
Therearethreetypesofstylesas
describedbelow:

32. Kinds of style
Terminalstyle:Ifthestyle
arisesfromterminalpartof
theovary,itiscalled
terminalstyle,e.g.,Datura,
HibiscusandSolanum.
Lateralstyle:Ifthestyle
arisesfromonesideofthe
ovary,itiscalledlateral
style,e.g.,mango.
Gynobasicstyle:Ifthestyle
arisesfromthebaseofthe
ovaryitiscalledgynobasic
style,e.g.,Ocimum,Salvia.

33. Stigma
The terminalpollen
receptiveportionofthe
styleiscalledthe
stigma.
Itreceptivepollengrain
during pollination.
Usuallythelobesofthe
stigmaequaltothe
numberofcarpels.
Thestigmamaybeunifid,
bifid,trifid,tetrafid,
pentafidormultifid.

34. •Capitate : Round
stigma. e.g., Hibiscus.
•Forked : Divided
stigma. e.g., Tridex.
•Feathery : Brush like
stigma. e.g., Grasses.

35. FLORAL FORMULA
•Oncethedescriptionoftheplantiscompleted,
majorcharactersoftheflowerarewrittenina
specialmethodwherefewsignsandlettersare
used.
•Thisformulaisusefulinknowingmajor
charactersofaflowerataglance.Inthismethod
charactersofbracts,symmetrysex,calyx,
corolla,(orparianth),androeciumand
gynoeciumaredenotedinthisorder.Someof
thecommonlyuseddenotationsaregiven
below.

37. •Bracts and Epicalyx;
Br……… Bracteate
Ebr……...Ebracteate
Brl………Bracteolate
E………...Epicalyx
•Symetry
…. Actinomorphic
or .Zygomorphic
•Sex;
…..Staminate flower
…..Pistillate flower
…. Hermaphrodite
•Calyx;
K…. Calyx
K4……Four free sepals
K(4) ….Four fused sepals
•Corolla;
C……Corolla
C4…..Four free petals
C(4)….Four fused petals
•Perianth;
P…….. Perianth
P5…….Five free tepals
P(5)……Five fused tepals
P3+3…..Six tepals in two
whorls

38. •Androecium;
A………Androecium
A5……..Five free stamens
A(5)……Five fused stamen.
A5+5…..Ten stamen in two
whorl of five each
A0…………Stamens absent.
A…………….Stamen
indefinite in number.

C A… .. Stamens
epipetalous

P A…… Staens epiphyllous
•Gynoecium;
G………..Gynoecium
G3……….three free carpels
G(3)………three fused
carpels.
G0……….. Carpels absent
G_(2)……..two fused carpel,
overy superior
G(3) ………Three fused
carpel, semi inferior overy.
G(2)……….Two fused
carpel, inferior overy.

41. Floral diagram
•Floral Diagram
•The floral diagram is a ideal ground plan of a
flower. It is a method in which many of the
characteristics of its parts and symmetry can be
expressed in a graphic form.

42. Insertion of floral leaves
It means the structure of thalamus and the consequent position and
insertion of calyx, corolla and androecium in relation to the pistil
•Hypogynous:
•A flower in which the
overy is superior and all
other floral organs are
situated below its level.
Michelia champaca

43. •Perigynous:
•Thethalamusisflatorconcaveandthefloral
organsarisingfromaroundtheovaryandnot
beneathit.Papilionaceae

44. •Epigynous:
•The thalamus is concave and the floral member
are arise above the pistil. E.g. Compositae

45. Insertion of floral leaves

46. Flower is Modified shoot
•Morphologically a flower is a modified
shoot. The elongated axis (internodes) of
a vegetative shoot is reduced into a
horizontal disc, the receptacle. Floral
leaves are arranged on the receptacle in
different whorls.
•By the Following fact it can be established
that the flower is modified shoot.

47. 1. Axis nature of the thalamus: Flower consists of a
thalamus or torus, which is very much like an axis in some
cases.
•a. The axis bears modified floral leaves such as
sepals, petals, stamens and carpels. Generally the
axis in a flower consist of short or suppressed
Internodes and nodes. But it is not the normal rule;
the axis is long in some flower e.g. Gynandropsis
gynandra ( Capparidaceae ), Passiflora suberosa(
Passifloraceae) etc. The internode of the thallamus
between corolla and androecium (andophore) and
between androecium and gynoecium (gynoephore)
become enlarged with same whorled arrangement of
stamens and carpels respectively.; so here thalamus
behaves like a axile.

48. •Gynandropsis
gynandra
•Passiflora superba

49. •b. Normally the growth of the thalamus is
checked by the carpels but in some the
thalamus has been found to undergo
further upward growth having green stem
and small foliage leaves beyond the
gynoecium, this phenomenon also support
that flower is a modified shoot. E.g. Rosa
sp, Pyrus spThis phenomenon is known
as monstrous development.

50. •c. In some cases the carpel bearing region
of the thalamus elongate like the stem
giving rise to an aggregate fruit. E.g.
Polyalthia longifolia Michalia champaca

51. 2. Leaf nature of floral member: This is evident
by many plant member Following are some
example.
a. In many cases the
sepal are leaf like
with veins and
petals like
pigments
e.g Mussanda frondosa

52. b. In some cases the floral leaves are both
verticillately and spirally arranged On long
thalamus but in majority of flowers the floral
phyllotaxy is whorled eg Michalia champaca
c. The leaf nature is also proved by the gradual
transition of sepals to petals and petals to
stamen and so on as in found in Nymphaea
sp

53. D. Carpel is also leafy in nature can
be proved by on examination of
single carpel of Pisum sativum
in which it is folded along its
midrib to form a chamber.

54. 3. Homology of floral buds
Floral buds like vegetative buds may be
metamorphosed bulbils e.g. viviparous
bulbils ofAgava sp. Development and
position of vegetative bud are also like
those of floral buds i.e. axillary and
terminal.