Answer 4 questions: Answer 4 questions: 1. When plants are grown under dry condi

Question

Answer 4 questions:

Answer 4 questions: 1. When plants are grown under dry conditions (low water availability), there is an increase in the allocation of carbon to the production of roots at the expense of leaves. How would this shift in allocation influence the plant^?s leaf area ratio (LAR)? 2. Nitrogen availability can directly influence the rate of net photosynthesis. Assuming no change ja the allocation of carbon or leaf morphology, how would an increase in the rate of net photosynthesis resulting from an increase in nitrogen availability influence relative growth rate? Which component of RGR would be influenced by the increase in net photosynthesis? 3. Which has greater surface area or volume ratio 4. What benefits does an organism hve being small over large?

Explanation / Answer

Answer1. Plants under extremely dry conditions have great water using efficiency. They have higher rate of carbon uptake per unit water transpired. C4 plants best explains the water use efficiency under xerophytic conditions. C4 plants have very low concentration of CO2 in mesophyll cells which creates a steep concentration gradient between internal and external environment (air) of plant leaves.

Plants under xerophytic conditions shows low conductance of water through stomata, it increase the water use efficiency. In C4 plants or plants under xerophytic conditions the allocation of carbon is more to the roots at the expense of leaves. It leads to high development and production of roots which increases the accessibility of roots to soil water. Reduces carbon uptake and less stomatal activity results in less development of leaves thus plant’s leaf area ratio (LAR) is much less in xerophytic plants. In extreme hot places leaves gets converted into spines also.

Answer 2.         Relative growth rate (RGR) = Leaf area ratio (LAR) X Net assimilation rate (NAR)

LAR is the product of specific leaf area (SLA) and leaf mass ratio (LMR). Net assimilation rate is the production of dry mass per unit leaf area. High concentration of nitrogen increases the total dry weight of plant, leaf area and dry weight of leaf. It also influenced the rate of photosynthesis in plants.

Factor of RGR influenced by high rate of photosynthesis from high nitrogen supply is net assimilation rate i.e. NAR.

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