Slide 1 : Presented by SEXUAL REPRODUCTION IN PLANTS Biswas Bio Institute Pvt. Ltd.
Penetration of pollen tube : Penetration of pollen tube On the basis of the movement or penetration of the pollen tube there a 3 different means of fertilization.
POROGAMY
CHALAZOGAMY
MESOGAMY
POROGAMY : POROGAMY In ORTHOTROPOUS & ANATROPOUS ovules, pollen tube enters the ovule through MICROPYLE
CHALOZOGAMY : CHALOZOGAMY First discovered in 1891 and is found in
Families : Casuarinaceae
Betulaceae
Fagaceae
Archichlamydae
The pollen tube enters the embryo sac after penetrating the chalazal region of the ovule.
Betula Competition tipsPlant with orthotropousovuleIt is only plant with ring bark : Betula Competition tipsPlant with orthotropousovuleIt is only plant with ring bark
MESOGAMY : MESOGAMY In family - Cucurbitaceae (Cucurbita)
The pollen tubes enters by piercing the
INTEGUMENTS.
Mechanism of SYNGAMY : Mechanism of SYNGAMY After penetrating nucellus, through the Micropyle or chalaza or integuments, the Pollen tube penetrates the embryo-sac and Then enters the egg Apparatus.
The pollen tube is guarded by synergids towards egg cell.
The pollen tube-tip bursts to release the Gametes.
The smaller gamete gets fused with egg cell to form zygote and the larger gamete gets fused with the diploid secondary nucleus to form the TRIPLOID NUCLEUS of the ENDOSPERM
Mechanism of SYNGAMY : Mechanism of SYNGAMY This is called as DOUBLE FERTILIZATION
This was first observed by NAWASCHIN and GUINGARD (1898) in the plants Lilium and Fritilaria
Lilium : Lilium
Fritallaria : Fritallaria
Double fertilization : Double fertilization
Double fertilization : Double fertilization
DEVELOPMENT OF ENDOSPERM AND EMBRYOGENESIS : DEVELOPMENT OF ENDOSPERM AND EMBRYOGENESIS All the structures of embryo sac, i.e.,
SYNERGIDS and ANTIPODALS
disappear except
ZYGOTE formed from egg cell and endosperm formed from secondary nucleus.
Angiosperm endosperm is distinct in being TRIPLOID tissue.
Types of Endosperm : Types of Endosperm Endosperm is classified into 3 types:
Nuclear
Cellular and
Helobial
1. NUCLEAR : 1. NUCLEAR Triploid nucleus of endosperm keeps on dividing forming large number of free nuclei.
E.g. Coconut milk (Cocos nucifera).... liquid endosperm
In some cases, central cavity remain vacuolated even in mature seed and nuclei migrate to periphery. E.g. Palm