下列关于生长素的叙述中，正确的是（）。
- A.顶芽和幼茎中生长素浓度一般保持在促进生长的范围
- B.促进同种植物扦插枝条生根效果相同的生长素浓度是相同的
- C.促进果实发育所需的生长素主要来自顶芽
- D.顶端优势中侧芽由于生长素浓度过低而不能生长
正确答案及解析
正确答案
解析
用一定浓度生长素类似物浸泡枝条下端，不久长出大量的根，但同种植物的扦插枝条本身芽的数目可能不同，生根效果可能不相同，B错误。种子发育过程中，能产生大量的生长素，种子发育过程产生的生长素能促进果实的发育，所以促进果实发育所需的生长素主要来自发育的种子，C错误。当植物表现出顶端优势时，顶芽优先生长，其产生的生长素向下运输，导致靠近顶芽的侧芽所含生长素的浓度偏高，从而侧芽生长被抑制，D错误。
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