The contribution of leaf life span to sexual dimorphism in deciduous and evergreen Pistacia species under Mediterranean conditions

Gender differentiation may be quite different between species with different strategies to cope with environmental stresses. In this study, we tested the hypothesis that sexual dimorphism is stronger in plant species under summer drought stresses and long leaf longevity. For that, we selected two Mediterranean dioecious species: the winter-deciduous Pistacia atlantica Desf. from Iran and the evergreen-sclerophyllous Pistacia lentiscus L. from Portugal. Our results indicated that there were no morphological differences between genders except for leaf mass-per-area (LMA) in P. lentiscus, where females displayed higher values than males. Leaves from female P. lentiscus presented a higher C/N ratio and lower carbon isotope composition (delta C-13), which is related with higher stomatal conductance during photosynthesis; whereas males had higher nitrogen concentration and more enriched leaf delta C-13 values. Pistacia atlantica, which experiences a shorter growing season, did not show any sexual dimorphism. Accordingly to our initial hypothesis, environmental conditions with the particular stressful conditions and leaf life strategy play a crucial role in gender dimorphism, both in physiological and morphological responses. Thus, a long longevity of P. lentiscus leaves was crucial for the observation of differences in gender-related physiological differences.