questions based on reproduction in plants and lower forms of life.

Asked by vshrikanth | 3rd Dec, 2010, 07:37: PM

Expert Answer:

 
Dear student,
After pollination, each compatible pollen grain adhering to the stigma sends through the style a pollen tube which carries two male gametes (sperm) to the ovule, where the egg and other cell nuclei are housed in the embryo sac. One sperm  unites with the egg cell (n) to produce a zygote  (2n) which becomes the embryo. The second sperm (n) unites with the diploid fusion nucleus (2n) to form the triploid endosperm (3n), the energy source for the developing embryo. This process is known as double fertilization.

 

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As a result of fertilisation, the following changes are observed in a flower:

  1. Within two to three days after fertilization, the pistil begins to elongate and swell to accommodate the enlarging ovules.
  2. The sepals and petals wither and drop off, having completed their functions(In some, the sepals persist in the fruit, e.g., Solanum.
  3. A diploid zygote is formed and develops into an embryo which is the future plant.
  4.  The triploid endosperm tissue serves as a source of nutrition for the developing embryo.
  5. The ovule becomes seed.
  6.  The ovary becomes fruit.
  7. The antipodals and synnergids disintegrate before, during or immediately after fertilisation in most of the plants.
  8. The outer and inner integuments of ovule become the testa (seed coat) of the seed.  

  

 
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Answered by  | 4th Dec, 2010, 08:15: AM

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