Reaction of savanna plants from Botswana on UV-B radiation

Author： Ernst W.H.O. van de Staaij J.W.M. Nelissen H.J.M.

ISSN： 1385-0237

Source： Vegetatio, Vol.128, Iss.1-2, 1997-01, pp. : 163-170

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Abstract

The annual savanna grasses Chloris virgata (C_4) and Tragus berteronianus (C_3) and the tree Acacia tortilis were exposed in a greenhouse to elevated UV-B radiation (16.8 kJ m^{ -2} d^{-1}UV-B\rm _{Be}) and to no UV-B and grown on a poor and a rich soil for one life-cycle (grasses) and one growing season (Acacia). UV-B radiation had no effect on biomass production and caryopses mass of both annual grasses. The longevity of the cotyledons of A. tortilis was shortened by 4 to 10 days under enhanced UV-B radiation, which also hampered the translocation of Fe, Mg and Mn from the cotyledons to the seedling and the retranslocation of Mn on both soil types and that of P on fertile soil out of senescent leaves. At the end of the growth period (190 days after germination), photosynthesis of UV-B radiated leaves of A. tortilis was significantly decreased and supported the tendency of decreased biomass of UV-B radiated plants. It is concluded that from the investigated savanna species the grasses are relatively well adapted to increased UV-B due to their actual exposure to high UV-B radiation under Botswana conditions, whereas saplings of A. tortilis are more sensitive to UV-B radiation.