Just like with people, strong sunshine can also lead to plants becoming burnt. They react with bright spots (chlorosis) on the leaves. In worse cases, leaf cells die off (necrosis) or the affected leaves are shed. The consequence for the farmer is lower yields, since the plant has a smaller leaf surface available for photosynthesis, thus reducing the production of biomass.
A good supply of the nutrient magnesium protects plants against sunburn. As the central atom of chlorophyll and with other functions, magnesium participates in the smooth functioning of photosynthesis. If the plant lacks magnesium and is simultaneously exposed to bright sunshine, photosynthesis is disrupted. Reactive oxygen species (e.g. free radicals) arise, which damage the leaf cells.
Our diagram of the month shows this effect using the example of bean plants. The photo comes from a testing facility of Prof. Ismail Cakmak at Sabanci University in Istanbul/Turkey with which K+S KALI GmbH cooperates in research.
In the experiment, part of the bean plants is well supplied with magnesium, the other part is poorly supplied. In the case of both groups, the leaves are partly shaded with a filter, and partly exposed to UV radiation. The plant in the photo is poorly supplied with magnesium and shows the symptoms of sunburn in the unshaded leaf areas. Plants well supplied with magnesium suffered no sunburn in Prof. Cakmak’s experiment. They can tolerate light stress without any problems.
Magnesium has a number of other important functions in the plant, as well as in the nutrition of animals and people. These relationships will be examined in more detail at a scientific symposium in Göttingen on 8 and 9 May 2012. It is being organised by the Institute of Applied Plant Nutrition (IAPN), an institute at the Georg-August University of Göttingen sponsored by K+S KALI GmbH.
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