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Sexual Reproduction in Flowering Plants — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYSexual Reproduction in Flowering Plants3 Marks
Question
What does an interaction between pollen grain and its compatible stigma result in, after pollination? List two steps in sequence that follow after the process.
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Answer

Events in pollen-pistil interaction:
  1. A compatible pollen grain starts its germination on the stigma.
  2. The intine grows out through one of the germ pores to form a pollen tube; the contents of the pollen grain move into the pollen tube.
  3. In those species, where the pollen grains are shed at the two-celled stage, the generative cell divides to form two male gametes.
  4. The pollen tube grows through the tissues of style and stigma and reaches the ovary.
  5. It enters the ovule through the micropyle and then enters the embryo sac through the filiform apparatus of one of the synergids.
  6. All these events, from the deposition of pollen grains on the stigma till the entry of pollen tube into the ovule, are collectively called pollen-pistil interaction.
The two events that follow this are:
  1. Syngamy, i.e., fusion of male and female gametes to form a zygote.
  2. Triple fusion, i.e., fusion of two polar nuclei (secondary nucleus) and a male gamete, to form the primary endosperm nucleus (PEN).

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