MadSci Network: Botany

Re: how/why do shade leaves grow bigger than sun leaves in a tree

Date: Sun Oct 10 14:13:51 2004
Posted By: David Hershey, Faculty, Botany, NA
Area of science: Botany
ID: 1093695796.Bt

Sorry for the delay in answering.

Sun leaves are also usually thicker with a better developed palisade layer, a 
thicker cuticle and contain more chlorophyll per unit area than shade leaves. 
Most of the differences seem to be triggered by light but more water stress in 
sun versus shade might have an effect on cuticle development and leaf 

Plants have several pigments that they use to sense light level. For example, 
plants have several  phytochrome pigments that allows the plant to determine 
whether it is in light, shade or dark based on the relative amount of red and 
far-red light it receives. In sun, there is a lot of red and little far-red, 
so a high R/FR ratio. In shade, there is just the opposite, little red and 
lots of far-red, so low R/FR ratio. The plant response to shade is to elongate 
its growing stems and expand its growing leaves. This may be beneficial 
because taller stems may carry the leaves above surrounding plants and out of 
the shade. As you mentioned, increased leaf area increases light interception.

Botanists have been studying the genes that are affected by phytochromes. See 
the first website for a discussion. It gets very complicated when looking at 
all the genes and the proteins they code for.

Changes in plant shape due to light is termed photomorphogenesis, which is a 
good search word. Also, try putting "shade leaf" or "sun leaf" in parentheses 
when searching with or other search engine to give more hits. There 
seem to be many websites discussing sun leaves and shade leaves.



Photomorphogenesis lecture

Sun leaf versus shade leaf

Developmental Plasticity in Oak Leaves

The shade avoidance syndrome: multiple responses mediated by multiple 

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,
© 1995-2003. All rights reserved.