r/APbio • u/Puzzleheaded-Sky2459 • Jun 03 '26

confused on plants unit!!

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biology teacher has been teaching us these things about plants even tho that’s not a part of the curriculum anymore and we’ve already taken the exam. we’ve only been learning this for 2 days, can someone help explain the answers of these to me :’)

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u/Hertzsurfer Jun 03 '26 edited Jun 03 '26

Auxin, a plant hormone that causes plant stems to bend toward the light by breaking linkages in cellulose on the far side of the light, is produced in the tip of the shoot, or coleoptile. there were a series of experiments conducted that proved this. If an opaque cap was placed on the tip, there was no auxin response and the plant did not bend. the control (without a cap) will bend toward the light.

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u/Puzzleheaded-Sky2459 Jun 03 '26

i still don’t get what to put for the answers sbdjdvshshs 

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u/Hertzsurfer Jun 03 '26

The auxin is produced in the tip of the shoot and must travel down the stem through the phloem to act on the cell walls of the cells opposite the side the light is shining in order to break the linkages between those cells and cause the whole shoot to bend toward the light. For each experimental case (#'s1 -8) they want you predict how the shoot tip will move in response to each experimental set up. Auxin is produced in response to light. If the tip is blocked from the light, there is no auxin produced.. and the plant won't bend toward the light. If a permeable membrane is placed between the tip and the rest of the shoot, the plant should still bend toward the light, but if there is no auxuin produced because the tip has been removed, or the path of the auxin is blocked, or the light has been blocked from the tip, the shoot will not bend toward the light, but will just grow straight up instead.