a) Describe the process of fertilization in flowering plant. (15mks) b) State the changes that take place in a flower after fertilization. (5mks)

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a) Describe the process of fertilization in flowering plant. (15mks)
  • 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;
b) Changes in flower after fertilizationOuter integuments of ovule – testa
  • 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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