A) DESCRIBE THE PROCESS OF FERTILIZATION IN FLOWERING PLANT. (15 MKS) B) STATE THE CHANGES THAT TAKE PLACE IN A FLOWER AFTER FERTILIZATION. (5 MKS)

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a) Describe the process of fertilization in flowering plant.  (15mks)

Ø  Pollen grains stick to the stigma surface;  surface of the stigma produces a chemical substances; which stimulates the pollen grain to produce a pollen tube; the pollen tube germinates;
Ø  The pollen tube grows down into the tissues of the style from which it derives nutrients;
Ø  The generative nucleus divides giving rise to two male nuclei;
Ø  The embryosac has eight nuclei; 2 synergids ; egg cell ; two polar nuclei ; three antipodal cells;
Ø  When the pollen tube reaches the micropyle the vegetative nucleus/pollen tube nucleus in the tip of the pollen tube degenerates/disintegrates ;
Ø  One male nucleus fuses with  eggs cell; and forms a zygote; which develops into embryo;
Ø  The other male nucleus fuses with two polar nuclei ; to form triploid nucleus; which develops into endosperm;
Ø  The process involves double  fertilization;

b) State the changes that take place in a flower after fertilization. (5 mks) 
structures and what they change into:
Ø  Interguments of ovule – seed  coat / testa
Ø  Zygote – embryo ;
Ø  Triploid nucleus – endosperm ;
Ø  Ovary wall – pericarp;
Ø  Ovary  - fruit;
Ø  Ovule – seed
Ø  Any other  part/style/petal/calyx/stamen/corolla/stigma – dry/falls off;

5mks

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