图甲表示胚芽鞘受到单侧光的照射，图乙表示不同浓度生长素溶液对胚芽鞘切段生长的影响，如果图甲中b处的生长素浓度为m，则a处的生长素浓度x的范围值为（ ）。
- A.n<x<i
- B.m<x<n
- C.m<x<i
- D.x>i
正确答案及解析
正确答案
解析
甲图为胚芽鞘，给予右侧单侧光照射，在单侧光的作用下，胚芽鞘尖端的生长素发生横向运输，所以a侧生长素浓度高于b侧；乙图表示不同浓度生长素溶液切去尖端的胚芽鞘生长的影响，i浓度之前的浓度都是促进生长；i浓度既不促进，也不抑制；i浓度之后的浓度都起抑制作用。在单侧光的作用下，生长素向背光侧横向运输，导致向光侧生长素浓度小于背光一侧，所以x>m。根据向光性导致胚芽鞘向光弯曲生长则a侧的生长速度大于b侧，则a侧的生长素浓度应小于n即x
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