Discovered: Why leaves fall off trees

Ever wondered why leaves fall off trees in fall? Well, the secret actually lies in cellular mechanism, says a new study.  

Researchers have found that trees use an elaborate cellular mechanism to part company from their leaves, which act as "solar cells" in the summer but become superfluous in the darker winter months.  

According to them, at the base of each leaf is a special layer called the abscission zone. When the time comes in autumn to shed a leaf, cells in this layer begin to swell, slowing the transport of nutrients between the tree and leaf.  

And, once the abscission zone has been blocked, a tear line forms and moves downwards, until eventually the leaf is blown away or falls off -- a protective layer seals the wound thereby preventing water evaporating and bugs getting in, 'The Daily Telegraph' reported.  

 

In fact, the discovery into how trees take on their winter aspect follows a study explaining the bright colours of autumn foliage.  

And, in their new study, the researchers at Missouri University has revealed that the genetic pathway that controls abscission in the plant species Arabidopsis thaliana, a little weed that's the favourite experimental subject of scientists.  

According to them, a pathway of genes is involved in the process of abscission in Arabidopsis using a combination of molecular genetics and imagine techniques.  

"Several different genes are involved in the process. Instead of looking at individual genes or proteins, we looked at an entire network at once to see how the difference genes work together in abscission," lead researcher Prof John Walker was quoted as saying.  

The findings are published in the 'Proceedings of the National Academy of Sciences' journal.