# Another basic plant question.

**URL:** <https://boards.straightdope.com/t/another-basic-plant-question/659539>\
**Category:** Factual Questions\
**Created:** [May 28, 2013, 1:40pm UTC](https://boards.straightdope.com/t/another-basic-plant-question/659539 "2013-05-28T13:40:43Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![dauerbach](https://avatars.discourse-cdn.com/v4/letter/d/c2a13f/32.png) [@dauerbach](https://boards.straightdope.com/u/dauerbach)\
**Post date:** [May 28, 2013, 1:40pm UTC](https://boards.straightdope.com/t/another-basic-plant-question/659539/1 "2013-05-28T13:40:43Z")

</div>

How do plants know that they have been injured. I am fairly sure they have no nervous system. If I prune a branch the leaf pair just below the cut will very rapidly start growing into new plant. What kind of feedback system does a plant have that allows it to know I have removed some of it?

---

<div class="post-metadata">

**Author:** ![kayaker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayaker/32/441_2.png) [@kayaker](https://boards.straightdope.com/u/kayaker)\
**Post date:** [May 28, 2013, 1:57pm UTC](https://boards.straightdope.com/t/another-basic-plant-question/659539/2 "2013-05-28T13:57:18Z")

</div>

> [@dauerbach](#):
>
> How do plants know that they have been injured. I am fairly sure they have no nervous system. If I prune a branch the leaf pair just below the cut will very rapidly start growing into new plant. What kind of feedback system does a plant have that allows it to know I have removed some of it?

The apical meristem (end of he branch you pruned) produces chemicals that suppress branching. Removing that tissue leads to loss of suppression.

Been a long time since Botany class, maybe someone can explain it better.

---

<div class="post-metadata">

**Author:** ![dauerbach](https://avatars.discourse-cdn.com/v4/letter/d/c2a13f/32.png) [@dauerbach](https://boards.straightdope.com/u/dauerbach)\
**Post date:** [May 28, 2013, 1:58pm UTC](https://boards.straightdope.com/t/another-basic-plant-question/659539/3 "2013-05-28T13:58:48Z")

</div>

So a negative feedback loop. That makes perfect sense.

Could a positive feedback loop even exist?

---

<div class="post-metadata">

**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\
**Post date:** [May 28, 2013, 2:18pm UTC](https://boards.straightdope.com/t/another-basic-plant-question/659539/4 "2013-05-28T14:18:35Z")

</div>

plants look for light, water, climbing plants look (in a seeking sense) for support.

a plant might have other reactions to insect damage and increase its insect deterrent chemicals.

---

<div class="post-metadata">

**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\
**Post date:** [May 28, 2013, 9:50pm UTC](https://boards.straightdope.com/t/another-basic-plant-question/659539/5 "2013-05-28T21:50:03Z")

</div>

> [@dauerbach](#):
>
> So a negative feedback loop. That makes perfect sense.

It’s not a feedback loop, it’s just basic humoural suppression. If the cells are supplied with chemical X, they remain dormant. If they don’t, they begin to divide. No feedback, and no loop.

> [@](#):
>
> Could a positive feedback loop even exist?

Positive response to damage can, and does, occur. The cells at the site of the injury release a whole slew of chemicals that aid in sealing the wound, including initiating callus growth. In most plants the callus itself will produce buds if no other tissue is capable of doing so.

---

<div class="post-metadata">

**Author:** ![Anaglyph](https://avatars.discourse-cdn.com/v4/letter/a/ed8c4c/32.png) [@Anaglyph](https://boards.straightdope.com/u/Anaglyph)\
**Post date:** [May 29, 2013, 3:47pm UTC](https://boards.straightdope.com/t/another-basic-plant-question/659539/6 "2013-05-29T15:47:15Z")

</div>

Upon injury, plants can release volatile compounds that elicit responses not only in neighboring cells, but also in neighboring plants.

e.g. Plant Signal Behav. 2012 February 1; 7(2): 222–226.  
doi: 10.4161/psb.18765  
PMCID: PMC3405699  
[Plant communication: Mediated by individual or blended VOCs?](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3405699/)  
Hirokazu Ueda, 1 Yukio Kikuta, 2 and Kazuhiko Matsuda 1 ,\*