Trade-off between leaf turnover and biochemical responses related to drought tolerance in desert woody plants

We describe differences in leaf photo-protection mechanisms in a group of arid adapted C3 and C4 shrubs that differ in their leaf life-span and compared these mechanisms to known differences in drought tolerance. The experiments were carried out in the field with fourteen woody species native to the Hexi Corridor region, northwestern China. We assessed water status, chlorophyll content, antioxidant enzymes activity, and solute content. We found that differences in photo-protection mechanism among species were not a consequence of differences in photosynthetic pathway, but they were related to leaf life-span. Further, we found evidence that supports the concept of a trade-off between leaf turnover and photo-protective mechanism: species with a longer leaf life-span (leaves with low turnover rate) had higher values of enzymatic (POD and CAT) and no-enzymatic (Chl a, Chl b, Car, and soluble sugars-SS) compounds, than species with a shorter life-span (high turnover rate). These different photoprotective strategies are in accordance with known differences in morphological and physiological leaf attributes that allow for rapid acquisition resources (i.e. acquisitive type) or permit conservation of resources within well protected tissues (i.e. conservative type).