a) Describe the process of fertilization in flowering plant. (15mks) b) State the changes that take place in a flower after fertilization. (5mks)
a) Describe the process of fertilization in flowering plant. (15mks)
5mks
- Pollen grains stick to the stigma surface; surface of the stigma produces a chemical substance ; which stimulates the pollen grain to produce a pollen tube // germinate;
- The pollen tube grows down ( into the tissues of the style from which it derives nutrients;
- The generative nucleus divides to give rise to two male nuclei; and embryo sac has eight nuclei; 2 synergids ; one egg cell ; two polar nuclei ; three antipodal cells;
- When the pollen tube reaches the micropyle the vegetative nucleus // pollen tube nucleus in the pollen tube degenerates// disintegrates ; one male nucleus fuses with egg cell ovum ; and forms a zygote; which develops into embryo;
- The other male nucleus fuses with two polar nuclei ; to form triploid nucleus, primary endosperm; which develops into endosperm; the process involves double fertilization;
- Outer integument of the ovule develop into testa
- Inner integument of the ovule develop into tegmen
- Zygote – embryo ;
- Triploid primary endosperm nucleus – Secondary endosperm ;
- Ovary wall – pericarp;
- Ovary - fruit;
- Ovule – seed
- Any other part // style / petal / calyx / stamen // corolla // stigma – dry // falls off;
5mks
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