Question

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Which of the following scenarios could prevent a short-day plant from flowering?

flashes of red light during the day

flashes of red light during the night

flashes of far-red light during the night

a shorter period of daylight

. a longer period of darkness.

An S₂ pollen grain lands on the stigma of a plant with the genotype S₁S₂. This species has a gametophytic self-incompatibility system. Which of the following events will occur?

RNAse will prevent the growing tube cell from reaching an egg

Material will block the S2 pollen grain, preventing the absorption of water

An embryo will result

Answer 1

1. Short day flowering plants are the plants that grow in longer darkness and shorter day light requirement. If the short day plants are interrupted by the light during the night time then they cannot grow and produce flowers. The far red light acts as darkness for the short day plants and hence it flowers in the presence of far red light. Hence the answer to this question is:

Flashes of red light during the night.

2. Gametophytic self incompatibility is a system where the gametes formed by the female parent either S1 or S2 will only fertilise or fuse with pollen grains other than S1 or S2 alleles. Hence the S2 pollen grain cannot fertilise the egg with the genotype S1S2. The mechanism which stops this fusion is called as the RNAse mechanism whereby the pollen tube growth is stopped by the RNase produced by the female stigma which cleaves the rRNA of the pollen grain which inhibits translation and thereby the pollen tube elongation due to inhibition of protein synthesis. Hence the answer to this question is : RNAse will prevent the growing tube cell from reaching an egg.

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