Myrmecophily : 4/27/2009 Myrmecophily Snails and slugs
accidentally pollinate
aroids
CHIROPTERIPHILY occurs in Bauhinia (camels foot, Kachnar) : 4/27/2009 CHIROPTERIPHILY occurs in Bauhinia (camels foot, Kachnar)
MALACOPHILY occurs in snake plant, Arisaema : 4/27/2009 MALACOPHILY occurs in snake plant, Arisaema
HYDROPHILY : 4/27/2009 HYDROPHILY None attractive small, inconspicuous plants
Very long pedicels
Every part of the flower with water proof waxy coating
Pollen grains small and light with water proof coat
Stigma waxy and sticky
There are two types of flowers.
Hypohydrogamous
Epihydrogamous
Types of hydrophilous plants : 4/27/2009 Types of hydrophilous plants Hypohydrogamous
Pollination inside water
Eg. Naias and Ceratophyllum
Epihydrogamous
Pollination above the waters surface Eg. Vallisnaria and Hydrilla
Pollination inside water E.g. Ceratophyllum : 4/27/2009 Pollination inside water E.g. Ceratophyllum
Pollination occurs above the waters surface E.g. Vallisnaria : 4/27/2009 Pollination occurs above the waters surface E.g. Vallisnaria
Slide 8 : 4/27/2009 Pollen grain Tube Cell Generative Cell Digests path through stigma, style, and ovary.
Locates micropyle of ovule.
Penetrates into embryo sac. Divides by mitosis to make two sperm.
Both join in syngamy events. Waterproofing prevents desiccation during pollen transfer. Recognition proteins cause allergic reactions.
Slide 9 : 4/27/2009 Pollen Grain Pollen Wall Generative Cell Tube
Cell Cytoplasm Nucleus Nucleolus Cytoplasm Nucleus Nucleolus Fate:
Digests Path to Egg
Locates Micropyle
Enters Embryo Sac
Is Burst to Release Sperm Fate:
Follows Path of Tube
Divides by Mitosis
Makes Two Sperm
Both Have Syngamy
DEVELOPMENT OF MALE GAMETOPHYTE : 4/27/2009 DEVELOPMENT OF MALE GAMETOPHYTE Male gametophyte is usually formed after
Pollen is discharged on stigma except in few cases.
Eg. Members of family Graminaceae show trinucleated pollen even before pollination
During development of gametophyte the pollen tube comes out of the germ-pore
The first to enter this tube is the TUBE NUCLEUS followed by the GENERATIVE NUCLEUS which after entry divides into TWO gametes mitotically.
This is raftered to SPERMATOGENESIS in PLANT
Slide 11 : 4/27/2009 Pollen grain deposited by vector on stigma Tube cell germinates through pollen wall Pollen tube digests pathway to egg
Attracted to source of hormones, Calcium, Boron
Chemotropism toward micropyle of ovule
Penetrates into embryo sac Generative cell divides to make two sperm cells. Tube nucleus Tube nucleus generative nucleus pollen tube Golgi
and
vesicles Synergids burst end of pollen tube.
Sperm released into embryo sac.
Syngamy events follow. Generative cell follows pathway of pollen tube.
Slide 12 : 4/27/2009 Pollen Tube Stigmatic papillae Pollen Grain -polyporate (with many round pores) Sagina nodosa (Caryophyllaceae)
Function of flower : 4/27/2009 Function of flower To attract pollinators with colorful petals, scent, nectar and pollen Carpel/
Slide 14 : 4/27/2009 MEGAGAMETOGENESIS During earlier stages, ovule is a mass of uniform cells made
up of NUCELLUS only
Nucellus is covered by single layered thick epidermis
during development, a hypodermal cell Becomes enlarged
called as ARCHESPORIUM
Epidermis on both sides of Archesporium starts dividing to
form inner integument of ovule
Archesporium gets enlarged called as MEGASPORE
MOTHER CELL which undergoes meiosis to form linear
row of FOUR Megaspores.
Slide 15 : 4/27/2009 Outer integument is also formed by now.
Angiospermic ovule is BITEGMIC
The integuments do NOT get fused on the
upper side leaving a pore called as MICROPHYLE
Of the linear row of FOUR megaspores the
upper THREE (towards micropyle) disappear
Slide 16 : 4/27/2009 The lower one that is left gets enlarged so
As to form gametophyte
In angiosperms, the development of
gametophyte is completely ENDOSPOROUS
In the typical Embryo sac (MONOSPORIC)
development, occurs from a SINGLE megaspore
The nucleus of megaspore divides THRICE
Mitotically forming 8 nuclei.
Four of them migrate to the upper pole and
Four to lower pole
Slide 17 : 4/27/2009 1 2
Slide 18 : 4/27/2009 Meiosis, 3 products Disintegrate leaving one megaspore 3 4 5 1st mitotic division 2nd mitotic Division
Slide 19 : 4/27/2009 One nucleus each from the two poles migrate to the center and fuse to from a SECONDARY NUCLEUS...the only DIPLOID STAGE OF EMBRYO SAC BEFORE FERTILIZATION.
Slide 20 : 4/27/2009 3rd Mitotic Division Female
Gametophyte
(embryo sac) Polar Nuclei
Types of embryosac : 4/27/2009 Types of embryosac Embryo sac can be classified into 3 types
Monosporic
Bisporic
Tetrasporic
1. MONOSPORIC : 4/27/2009 1. MONOSPORIC Develops from single Megaspore; also called as TYPICAL EMBRO SAC.
Eg. Polygonum
2. BISPORIC : 4/27/2009 2. BISPORIC Develops from two megaspores
If out of FOUR megaspores if only TWO
Disappear. Eg. Allium
3. TETRASPORIC : 4/27/2009 3. TETRASPORIC Develops from four megaspores
Megaspores where none disappear.
Eg. Peperomia, Adoxa
VARIATIONS IN EMBRYO SAC DEVELOPMENT : 4/27/2009 VARIATIONS IN EMBRYO SAC DEVELOPMENT There may be 4 or 16 nuclei in the embryo Sac instead of eight. E.g.
Oenothera (4) and Peperomia (16)
Embryo sac may not have any antipodal cell. Eg. Oenothera
Synergids may be ABSENT in egg apparatus.
In such cases, egg cell alone constitute the egg apparatus Eg. Plumbago & Peperomia have ONE synergid only.
Plumbago : 4/27/2009 Plumbago
Peperomia : 4/27/2009 Peperomia
VARIATIONS IN EMBRYO SAC DEVELOPMENT : 4/27/2009 VARIATIONS IN EMBRYO SAC DEVELOPMENT Secondary nucleus may be formed by ONE Nucleus (Oenothera); FOUR nuclei (Plumbago) and eight nuclei in peperomia
Ontogenetically 8 nucleate embryo sac is the MOST primitive and rest are derived By its modification.
FERTILIZATION : 4/27/2009 FERTILIZATION First observed by.....
E. STRASBURGER
It is also celled Syngamy Or Fecundation
SIPHONOGAMOUS= Gametes carried by pollen type tube
FERTILIZATION : 4/27/2009 FERTILIZATION Camerarius reported about sexual reproduction in plants
In most of the cases... Single pollen tube is formed from a single pollen…MONOSIPHONOUS
In Malvaceae and Cucurbitaceae many pollen tubes are formed from a single pollen..... POLYSIPHONOUS
Slide 31 : 4/27/2009 A single pollen tube can be branched which is characteristic of Gymnosperms but found in a primitive angiosperm family... Amentiferae
Growth of the pollen tube is due to
CHEMOTAXIS as sugary contents are released by the stigma
Pollen tube was first observed By AMICI
Longest pollen tube and styles silky are of maize (50cms).
Double Fertilization : 4/27/2009 Double Fertilization Double fertilization occurs: One sperm nucleus (1n) fertilizes the egg, producing a zygote (2n) ? which becomes the plant embryo inside the seed
Another sperm nucleus fuses with the polar nuclei, resulting in a triploid endosperm (3n)
Endosperm is a source of food for the young embryo. Endosperm
Slide 33 : 4/27/2009 Rhododendron maximum ovule ls disintegrate + sperm = endosperm + sperm = zygote burst pollen tube
release sperm
disintegrate
Slide 34 : 4/27/2009 Embryo Sac in Ovule Ovule Embryo Sac Antipodals Central Cell Egg Synergids Integument Funiculus Micropyle
Slide 35 : 4/27/2009 EMBRYOSAC Central Cell Egg Cell Syngamy Product = Endosperm 3N Syngamy Product = Zygote 2N
Slide 36 : 4/27/2009 After Syngamy, the Names are Changed… Egg becomes Zygote
Central cell becomes Endosperm
Ovule becomes Seed
Integument becomes Seed coat
Ovary wall becomes Fruit wall..
pericarp
Ovary becomes fruit
Slide 37 : 4/27/2009 Capsella shepherd’s purse seed
Anthophyta Life Cycle- heterosporous : 4/27/2009 Anthophyta Life Cycle- heterosporous
Slide 39 : 4/27/2009 END