Photosynthetic performance and water use efficiency of the fern Cheilanthes persica

Morphological, anatomical and physiological frond traits of Cheilanthes per sica (Bory) Mett. ex Kuhn were studied to analyze its adaptive strategy. Me an frond life span is about 340 d. Mature fronds are characterized by 91 g m(-2) areal dry mass (ADM) and 217 g m(-2) succulence. The reduction of fro nd water content in July (dehydration phase) caused a 51 % decrease in fron d surface area (SA). Fronds were dry in August (desiccation phase); neverth eless, in September they showed an increased SA (rehydration phase). Chloro phyll (Chl) a/b ratio, above 3, and the well developed palisade parenchyma (two layers, total thickness of 103.9 mu m) are typical for sun leaves. Chi and carotenoid contents and net photosynthetic rate (P-N) increased during frond development until the highest values in April-May (maturity phase). When mean air temperature reached 31.3 degrees C, stomatal conductance (g(s )) decreased by 34 % and P-N by 33 %. The high pigment contents can dissipa te the excess of radiant energy, particularly under unfavourable conditions , when P-N is low. Rather high P-N was found during the rehydration stage. The pronounced decline of mesophyll activity during the declining phase was confirmed by the lowest P-N.