Advantages of tracheids over vessels for long-distance transport to great heights include:
I. Adhesive forces are proportionally greater in narrower cylinders than in wider cylinders.
II. The smaller the diameter of the xylem, the more likely cavitation will occur.
III. Cohesive forces are greater in narrow tubes than in wide tubes of the same height.
1. Only I and II
2. Only I and III
3. Only II and III
4. I, II and III

All the following regarding the cohesion-tension model are true except:
1. Water movement is driven by transpiration.
2. The water potential of atmospheric air is more positive than that for xylem.
3. Cohesion represents the tendency for water molecules to stick together by hydrogen bonds.
4. The physical forces in the capillary-sized xylem cells make it easier to overcome gravity.

A poison that blocks proton pumps would not directly affect:
1. photosynthesis.
2. phloem loading.
3. xylem transport.
4. cellular respiration.

Guard cells:
1. have endoplasmic reticulum that store potassium ions.
2. accumulate ${\mathrm{K}}^{+}$ and close the stomata.
3. prevent mineral loss through stomata.
4. help balance the photosynthesis-transpiration compromise

Which of the following does not enter the plant through roots?
1. carbon dioxide
2. nitrogen
3. potassium
4. water

Wilting of leaves causes decline in photosynthesis because:
1. chloroplasts in wilted leaves cannot photosynthesize.
2. ${\mathrm{CO}}_2$ accumulation in the leaves inhibits Calvin cycle enzymes.
3. of lack of water for photolysis.
4. closure of stomata prevents entry of ${\mathrm{CO}}_2$ entry into the leaf.

Substances travelling via the symplast move from cell-to-cell through:
1. membrane proteins.
2. phospholipid channels.
3. tonoplast.
4. plasmodesmata.

What happens to the tensile strength of fluid column with a decrease in the diameter of a tracheid?
1. It increases.
2. It decreases.
3. It approaches zero.
4. It approaches infinity.

The pace at which transpiration takes place is primarily due to:
1. proton pumps.
2. phloem diameter sphincters.
3. cell wall expansion
4. guard cell dilation.

The most important problem faced by most plants during flooding is:
1. inability to receive sunlight
2. leaching of nutrients
3. damage to the root system
4. oxygen deprivation