REGREENING OF DESICCATED LEAVES OF THE POIKILOCHLOROPHYLLOUS XEROPHYTA-SCABRIDA UPON REHYDRATION

The poikilochlorophyllous and desiccation tolerance nature of the leaves of the monocotyledonous Xerophyta scabrida and the physiological recovery of the air-dried leaves upon rehydration after a long-term desiccation is described in this paper. Water uptake through the leaf surface upon rehydration was found to be of prime importance for recovery. Field observations in the natural habitat showed that at the onset of the rainy season water uptake through the leaf surface preceded the development of new adventitious roots. In dry leaves carotenoids were found as the only photosynthetic pigments. Upon rehydration de novo chlorophyll and carotenoid synthesis began just before the leaves reached their maximum water content and specific leaf area. The accumulation of chlorophylls and carotenoids was found to rise very fast and maximum content was reached about 72 hours after rehydration. The values of the chlorophyll fluorescence ratio, F690/F735, and of the fluorescence intensities at 690nm and at 730nm (both at maximum Fm and steady-state fluorescence Fs) continuously decreased from the begin of regreening until reaching maximum chlorophyll content after 3 days. The fluorescence ratio F690/F735 proved to be a very suitable non-destructive diagnostic method to monitor the chlorophyll content during regreening of the poikilochlorophyllous leaves of X. scabrida upon rehydration.