Learning Outcomes Review 40.4 Seasonal changes, such as reduction in temperature

Question

Learning Outcomes Review 40.4 Seasonal changes, such as reduction in temperature, light, and water availability, may lead to plant dormancy; in deciduous trees, leaf abscission is part of entering dormancy. Seed dormancy prevents germination until growth conditions are optimal. At low temperatures, lipids in membranes begin to solidify and ice crystals may form in tissues; at high temperatures, proteins denature. Auxi the b More th was th the pla stems sure occur of auxin though reason why is it advantageous for broadleaf trees to drop leaves in autumn, when they must grow them again in spring?

Explanation / Answer

It is advantageous for broadleaf plants to shed leaves in autumn and grow them again in spring because of

i. The photosynthetic efficiency of pigments in the leaf is decreased over time. So, they have to be replaced.

ii. Accumulation of harmful metabolites

iii. Sometimes older leaves may become positioned at a location that they can no longer obtain sunlight due to the overlaying leaves.

iv. Many plants enter into a dormant state to protect themselves from the harsh environmental conditions which can damage plant tissues. Hence, required nutrients are sequestered from the leaves and the remaining leaf is shed.

v. The plant needs constant production of new leaves at new locations. Having older leaves with low efficiency increases transpiration rate.

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