MadSci Network: Botany

Re: Why is leaf senescence important to the overall survival of a plant?

Date: Mon Jan 7 20:23:33 2002
Posted By: David Hershey, Faculty, Botany, NA
Area of science: Botany
ID: 1010413427.Bt

In general terms, leaf senescence is a way for a deciduous plant to prepare for 
winter and recycle some of the valuable and often scarce mineral nutrients, 
such as nitrogen and phosphorus. Leaf senescence is also a way to to get rid of 
old and photosynthetically less efficient leaves in both deciduous and 
evergreen plants.

Leaf senescence is considered a genetically programmed process and is an area 
of considerable recent research. The hormones ethylene and cytokinin are 
involved in regulation of senescence. Cytokinin applied to leaves delays 
senescence. Various enzymes are also involved.  One important process in leaf 
senescence is the formation of an abscission zone which seals off the vascular 
connections and allows the leaf to be shed. This is important to prevent 
disease-causing microbes from entering and the vascular connections from 

The development of fall leaf colors is a very noticable change that occurs 
because chlorophyll synthesis stops and the current chlorophyll degrades 
thereby revealing yellow carotenoids in chloroplasts that were there all along. 
Anthocyanins are formed in vacuoles in some leaves giving reds and purple 
shades. Anthocyanin formation in fall leaves is promoted by dry, sunny days and 
cool, dry nights. Spectacular fall leaf colors are a multi-billion dollar 
tourist attraction that may help prevent some forests from being logged. There 
are several ideas for the development of anthocyanins including their acting as 
a sunscreen, to attract animals that disperse seeds, protect from freeze 
damage, or prevent water stress.


Leaf sensecence: Physiology and molecular biology

Leaf Senescence Web Search

Leaf Abscission

Leaf Abscission Web Search

Chemistry of Autumn Colors

Possible Functions of Red Fall Leaf Color

Fall Leaf Colors Web Search

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