Smart defence mechanisms against
browsing
Date: September 12, 2016
Source: German Centre for
Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig
In spring, the young, delicate
shoots in the forest light up, bright and May green. The buds and shoots are
the future of the forests as they allow young trees to grow. The problem for
the trees is: Roe deer like to eat them, and especially their buds. With a bit
of luck, the young, gnawed saplings will only take a few more years to grow
than their non-bitten conspecifics. In the worst case, they will become stunted
trees, or they will have to give up their fight for survival after a number of
years. In this respect, roe deer can cause a great deal of damage and hinder
the regeneration of many deciduous tree species.
In order to protect themselves
against roe deer browsing, trees purposely put up a fight. By studying young
beeches (Fagus sylvatica) and maples (Acer pseudoplatanus), biologists from the
Leipzig University and the German Centre for Integrative Biodiversity Research
(iDiv) have now found out that trees are able to recognise precisely whether a
branch or bud has been purposefully nibbled off by a roe deer -- or just
randomly torn off by a storm or other mechanical disturbance. The saliva of the
animals gives them the signal. If a deer feeds on a tree and leaves its saliva
behind, the tree will increase its production of salicylic acid. This hormone,
in turn, signals to the plant to increase the production of specific tannins.
It is known for some of these substances that they influence the feeding
behaviour of roe deer, with the result that the deer lose their appetite for
the shoots and buds. In addition, the saplings increase their concentrations of
other plant hormones, growth hormones in particular. These hormones enhance the
growth of the remaining buds to compensate for the lost ones.
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