The hormone that helps plants respond to drought is a. auxin. b. abscisic acid. c. cytokinin. d. ethylene.

Charles and Francis Darwin discovered that a. auxin is responsible for phototropic curvature. b. red light is most effective in shoot phototropism. c. light destroys auxin. d. light is perceived by the tips of coleoptiles.

How may a plant respond to severe heat stress? a. by reorienting leaves to increase evaporative cooling b. by creating air tubes for ventilation c. by producing heat-shock proteins, which may protect the plant's proteins from denaturing d. by increasing the proportion of unsaturated fatty acids in cell membranes, reducing their fluidity

The signaling molecule for flowering might be released earlier than usual in a long-day plant exposed to flashes of a. far-red light during the night. b. red light during the night. c. red light followed by far-red light during the night. d. far-red light during the day.

If a long-day plant has a critical night length of 9 hours, which 24-hour cycle would prevent flowering? a. 16 hours light/8 hours dark b. 14 hours light/10 hours dark c. 4 hours light/8 hours dark/4 hours light/8 hours dark d. 8 hours light/8 hours dark/light flash/8 hours dark

A plant mutant that shows normal gravitropic bending but does not store starch in its plastids would require a reevaluation of the role of          in gravitropism. a. auxin b. calcium c. statoliths d. differential growth

DRAW IT Indicate the response to each condition by drawing a straight seedling or one with the triple response.