MadSci Network: Botany
Query:

Re: How does a plant vine 'know' how to wrap around something?

Date: Fri Mar 19 17:59:13 1999
Posted By: Hurley Shepherd, Agricultural Research, USDA Southern Regional Center
Area of science: Botany
ID: 916472843.Bt
Message:

Plants have evolved ways to get what they need without being able to move 
about.  Generally this is done by growing in the direction of a desired 
nutrient or condition.  This growth toward (or away from) something is 
called a "tropism".  You may have heard of phototropism (shoots growing 
toward light) or gravitropism (roots growing toward gravity, shoots 
growing away from gravity).  The process by which vines wrap around 
something for support is called "thigmotropism", growth stimulated by 
touch or contact.  

Like the other tropisms, it is the result of a stimulation of growth in a 
specific region of the plant.  As in phototropism, where the growth is 
faster on the side away from the light, in thigmotropism, the growth is 
faster on the side away from the contact, thus causing the stem to bend in 
that direction (toward the contact).  If you think about it you will see 
how this will cause the plant to bend toward the source of contact.  Since 
it can't (usually) go through the contact, it will grow around it, 
continually curving as long as the contact is maintained.

As to exactly how this increased growth rate is achieved, in most tropisms 
the plant growth hormone "auxin" is implicated and thought to accumulate 
on the side where increased growing is to take place.  How does the auxin 
know to go there?  Not much work has been done on thigmotropism, but 
scientists are looking at these questions, and seem to be finding 
involvement of calcium ions and/or calmodulin (a protein found in many 
animal and plant systems which controls developmental processes) or 
derivatives of fatty acids inducing the response.  Is that what causes the 
auxin to accumulate?  Don't know yet.  This is an area which bears 
watching.

You can find out more about auxins and tropisms in a Plant Physiology 
textbook (I use one by Taiz and Zeiger) or in a Botany textbook and in 
some general biology texts.

For the truly serious about the physiology of all this (and you need a 
serious library also):
Blechert, S; Bockelmann, C; Fusslein, M; Von Schrader, T; Stelmach, B;  
Structure-activity analyses reveal the existence of two separate groups of 
active octadecanoids in elicitation of the tendril-coiling response of 
Bryonia dioica Jacq.   
PLANTA, 207: (3) 470-479 JAN 1999 

Authors: Liss, H; Bockelmann, C; Werner, N; Fromm, H; Weiler, EW Title: 
Identification and purification of the calcium-regulated Ca2+-ATPase from 
the endoplasmic reticulum of a higher plant mechanoreceptor organ
Source: PHYSIOLOGIA PLANTARUM, 102: (4) 561-572 APR 1998




Current Queue | Current Queue for Botany | Botany archives

Try the links in the MadSci Library for more information on Botany.



MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci


MadSci Network, webadmin@www.madsci.org
© 1995-1999. All rights reserved.