38. As a specialized form of root, pneumatophores are utilized primarily by plan

Question

38. As a specialized form of root, pneumatophores are utilized primarily by plants which a. grow on steep hillsides or in very loose soil. b. store large quantities of phototsynthetic products in their roots as starch c. need to "hold on" to vertical surfaces like a wall for support during growth. d. often find themselves in soils that are very low in oxygen. 39. Plant root hairs find it difficult to take up positively charged nutrient a. positively charged ions will increase t he pH of the inside of the root too greatly ions because b. positively charged ions are washed away too easily when it rains. c. there charged ions. d. such ions usually bind strongly to soil particles are no molecular channels in the root hair cells that will allow passage of positively 40. In satisfying the water needs of a plant, water moves up through xylem due to whereas it moves through root cortex cells due to a. gradients in solute potential; molecular water pumps in epidermal cells. b. action of proton pumps; action of plasmodesmata e. solute potential gradients; pressure potential gradients d. cohesion and surface tension forces; diffusion gradients 41. The role of leghemoglobin in the roots of nitrogen-fixing plants is to: a. deliver oxygen to metabolically active nitrogen fixing nodules. b. provide the additional oxygen needed by Rhizobium and other nitrogen-fixing bacteria. c. to deliver nitrogen fixed by the bacteria to other parts of the plant. d. maintain a low oxygen environment for the nitrogenase enzyme in nitrogen-fixing bacteria.

Explanation / Answer

38. C

39. A

40. D
Transpiration is the loss of water from the plant through evaporation at the leaf surface. It is the main driver of water movement in the xylem. It leads to cohesion of water molecules to each other.

41. D
Leghemoglobin has a high affinity for oxygen, about ten times higher than of human hemoglobin. This allows an oxygen concentration that is low enough to allow nitrogenase to function

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