post fertilization changes
TRANSCRIPT
POST FERTILIZATION CHANGES
DEVELOPMENT OF ENDOSPERM
Endosperm is the nutr it ive t issue for nourishment of developed embryo.
In some angiosperm, the product of second fert i l izat ion or tr ip le fusion is PEN.
I t develops into endosperm.
In some cases i t is absent such seeds are cal led non endospermic or ex-albuminous seeds eg. pea, bean, grams etc.
In other angiosperm, endosperm persists in mature seeds and i t support the growth of embryo, such seeds are cal led endospermic or a lbuminous seeds eg. Sunfl ower, castor, coconut, maize etc
DEPEND ON THE MODE OF DEVELOPMENT
Endosperm
Nuclear endoperm
Cellular endosperm
Helobial endosper
m
TYPE OF ENDOSPERM
DEVELOPMENT OF EMBRYO
FORMATION OF SEEDS AND FRUITS Simaltaneously with the development of embryo and
endosperm, ovary enlarges in size.
Sepals, petals, stamens, style and stigma fall off and ovary changes into fruit.
Ovary wall change into pericarp (fruit wall).
Pericarp initially is green and on ripening become orange, red, purple, yellow etc.
Each ovule in ovary also enlarge, outer integument become thick and hard outer seed coat, called testa .
Inner integument become thin, inner seed coat, called tegmen.
PARTHENOCARPY
Mostly, the fruits are formed after fertilization but there are some species in which fruits develop without fertilization.
This is called parthenocarpy and such fruits are called parthenocarpic fruits eg. Banana.
APOMIXIS AND POLYEMBRYONY
Seeds are the product of fertilization.
In some spices of grasses seeds are produce without fertilization.
This is called apomixis and such seed is called apomictic seeds.
Some nucellar cell near embryo sac start dividing and develop many embryo this is called polyembryony.
SIGNIFICANCE OF SEED
The distribution and dominance of angiosperms on earth is due to the seeds.
Success of seeds as propogule is due to many characters such as –
1. Dormancy 2. Viability3. Reserve food4. Protective coat 5. Dispersal 6. Edible fruits