3 An increase in auxin concentrations causes A. a decrease in stem curvature B an increase in stem curvat D. an elongation of cumber roots 4 A decrease in 2. 4-D will cause A a decrease in cotyledon siz B an increase in cotyledon size D. a decrease in stem cu 5 An increase in gibberellic will cause A. a decrease in cotyledon size B an increase in cotyledon size C. an elongation of roots D. a decrease in stem curvature 6 What is a major function of auxi A. controls the abscission of leaves B promotes stem elongation C absorbs light and affects seed germination D a component of proteins 7 How would gibberellic acid be beneficial to plants? A. By suppressing lateral buds, the plant will not have too many leaves to block each other's availability to light B. By hastening the ripening of fruit, the plant's seeds will be dispersed sooner C. By promoting leaf senescence, the plant can save energy by reabsorbing photosynthetically D. By increasing stem and internode elongation the plant will be able to grow taller and gain 8 What plant hormones stimulate cell division in the presence of auxin, promote chloroplast development and bud formation, and delay leaf aging? A. abscisic acid B. cytokinins C. gibberellins D. ethyl 9对IAA浓度最敏感的植物器官是 A.芽 B.叶 根 D.茎 10果实催熟可选用下列激素中的 B. KI C.乙烯 D. ABA l1生长素类的主要功能是 A.诱导器官分化 B.加速细胞生长 C.促进衰老 D.加速成熟D. a micronutrient 3 An increase in auxin concentrations causes _____. A. a decrease in stem curvature B. an increase in stem curvature C. an enlargement of cotyledons D. an elongation of cucumber roots 4 A decrease in 2,4-D will cause ____. A. a decrease in cotyledon size B. an increase in cotyledon size C. an elongation of roots D. a decrease in stem curvature 5 An increase in gibberellic acid will cause ____. A. a decrease in cotyledon size B. an increase in cotyledon size C. an elongation of roots D. a decrease in stem curvature 6 What is a major function of auxin? A. controls the abscission of leaves B. promotes stem elongation C. absorbs light and affects seed germination D. a component of proteins 7 How would gibberellic acid be beneficial to plants? A. By suppressing lateral buds, the plant will not have too many leaves to block each other's availability to light. B. By hastening the ripening of fruit, the plant's seeds will be dispersed sooner. C. By promoting leaf senescence, the plant can save energy by reabsorbing photosynthetically important molecules. D. By increasing stem and internode elongation, the plant will be able to grow taller and gain access to light. 8 What plant hormones stimulate cell division in the presence of auxin, promote chloroplast development and bud formation, and delay leaf aging? A. abscisic acid B. cytokinins C. gibberellins D. ethylene 9 对 IAA 浓度最敏感的植物器官是________ A. 芽 B. 叶 C. 根 D. 茎 10 果实催熟可选用下列激素中的________ A. GA B. KT C. 乙烯 D. ABA 11 生长素类的主要功能是________ A. 诱导器官分化 B. 加速细胞生长 C. 促进衰老 D. 加速成熟