1
Question
Pollen grains are able to withstand extremes of temperature and desiccation because their exine is composed of
Pollen grains are able to withstand extremes of temperature and desiccation because their exine is composed of
Open in App
Solution
The correct option is C Sporopollenin
The pollen grain is the immature male gametophyte that precociously develops into mature male gametophyte through micro gametogenesis. Meiosis in microspore mother cell forms four haploid microspores which are initially covered with a common wall of callose (β 1,3-glucan). Microspore matures into pollen grain which is a uni-nucleate cell with the two-layered cell wall. The exine is the outer covering of pollen grain which is highly sculptured with sporopollenin; a chemically inert polymer of carotenoid ester which is highly resistant to degradation by any enzyme, as known so far. It can withstand extremes of temperature and desiccation. Cutin is an insoluble heterogenous lipid-polymer of long chain substituted aliphatic acids which are main constituent of cuticles and serves as the waterproof substance to reduce water loss; it does not withstand extremes of temperatures and is not present in exine. Suberin is a waterproofing waxy substance which restricts the water movement to reduce the risk of embolism caused by wear and tear damage to leaf/petiole. It is not a constituent of exine. Thus, the correct answer is option C.
The pollen grain is the immature male gametophyte that precociously develops into mature male gametophyte through micro gametogenesis. Meiosis in microspore mother cell forms four haploid microspores which are initially covered with a common wall of callose (β 1,3-glucan). Microspore matures into pollen grain which is a uni-nucleate cell with the two-layered cell wall. The exine is the outer covering of pollen grain which is highly sculptured with sporopollenin; a chemically inert polymer of carotenoid ester which is highly resistant to degradation by any enzyme, as known so far. It can withstand extremes of temperature and desiccation. Cutin is an insoluble heterogenous lipid-polymer of long chain substituted aliphatic acids which are main constituent of cuticles and serves as the waterproof substance to reduce water loss; it does not withstand extremes of temperatures and is not present in exine. Suberin is a waterproofing waxy substance which restricts the water movement to reduce the risk of embolism caused by wear and tear damage to leaf/petiole. It is not a constituent of exine. Thus, the correct answer is option C.
Suggest Corrections
0
Similar questions
View More
Join BYJU'S Learning Program
Explore more
Join BYJU'S Learning Program
