31. In the spring, you pass by a rocky outcrop that is dripping with water and c

Question

31. In the spring, you pass by a rocky outcrop that is dripping with water and covered with a carpet of short green plants. In the summer, you notice that water is no longer dripping off the rock, and the plants appear brittle and dry. In the fall, the rock is again wet, and the plants now appear soft and green. These plants are most likely to be: A) angiosperms. B) gymnosperms. C) algae. D) bryophytes. 32. Assuming the stomata are open to the same degree, the rate of transpiration should on a rainy day compared with a sunny day because the H20 inside the leaf concentration gradient would change with it now compared to outside of the leaf ! A) decrease; lower B) decrease; higher C) increase; lower D) increase; higher 33. When stomata are open and a plant is transpiring normally, water moves from the soil into the root xylem. Which of the following is NOT involved in this water transport? A) ATP driven pumps move water in the roots. B) Water moves without any work by the plant. C) Water moves via a force generated by partial dehydration of cell walls in leaves. D) Water movement is ultimately driven by evaporation from the shoot. 34. Which of the following statements are true about sugar transport through the phloem? A) Sugar enters the xylem by active transport. B) Water enters the phloem by osmosis to assist in bulk transport of sugars. Water enters the phloem by active transport to assist in bulk transport of sugars. Water returns to the xylem by active transport.

Explanation / Answer

31. Angiosperms and gymnosperms are both non-carpeting plants. While angiosperms are flowering plants, gymnosperms are distinctly identified from the naked seed morphology. Algae are microscopic plants/organisms and they are not really plants. Bryophytes do not produce flowers or seeds and can grow where vascularized plants cannot because they do not depend on roots for an uptake of nutrients from soil. Bryophytes can also survive on rocks and bare soil. Therefore, your answer is (d)

32. Transpiration of water from the leaves happens under the driving force of water concentration gradient between the (inside of) leaf and the surrounding air. On a rainy day the water content of the surrounding air as well as of leaf would increase, hence water gradient between the leaf and air would decrease. Therefore, your answer is (b)

33. Water moves from soil into the root xylem under the influence of force generated by partial dehydration of cell walls in leaf, which in turn is driven by the evaporation from the shoot. This also means that in this movement of water there is no work done by plant itself and hence there is no contribution of ATP driven pumps. Therefore, your answer is (a)

34. Sugars molecules at the sources (i.e. leaves) are moved into the phloem cells through the active transport from source to sink, while the water moves by passive transport under the influence of osmosis to assist in bulk transport of sugars. However, water returns from xylem by active transport of pressure gradient. Therefore, your answers are your answers are (a), (b), and (d).

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