Q.Give a concise account on the steps involved in fertilization of an angiosperm plant.

Step 1. Fertilization begins with pollen-pistil interaction: a compatible pollen grain lands on the receptive stigma, hydrates, and germinates to form a pollen tube, whose growth is confined to its tip.

Step 2. The pollen tube then grows down through the style - over glandular transmitting-tissue cells in a hollow style, or through the intercellular spaces of transmitting tissue in a solid style - guided by chemotropic substances.

Step 3. On reaching the ovary, the tube enters the ovule by porogamy (through the micropyle, the commonest route), chalazogamy (through the chalaza) or mesogamy (through the integument), often guided in by an obturator.

Step 4. The tube always enters the embryo sac at the micropylar end, directly into one of the two synergids, where a terminal pore releases the two male gametes, the vegetative nucleus and cytoplasm; the tube nucleus then disorganises. …

List the sequence of pollen-tube growth events followed by the two simultaneous fusion events (syngamy and triple f …

• Omitting the pollen-tube's entry route options (porogamy/chalazogamy/mesogamy) or forgetting that both male gametes are used - one in syngamy and one in triple …