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

Normally, the fastest delivery of water and minerals to the leaves of a tree is most likely to happen on a:
1. cool, dry day
2. warm, dry day
3. warm, humid day
4. very hot, dry, windy day

A decrease in potassium in the guard cells and surrounding epidermal cells would not lead to:
1. a decrease in photosynthesis.
2. a reduced uptake of water by roots.
3. closure of stomata.
4. a decrease in leaf temperatures.