Abstract
Sex-related differences in the response of dioecious plants to abiotic stress have been poorly studied to date. This work explored to what extent sex may affect plant stress responses in Pistacia lentiscus L. (Anacardiaceae), a tree well adapted to Mediterranean climatic conditions. It was hypothesized that a greater reproductive effort in females may increase oxidative stress in leaves, particularly when plants are exposed to abiotic stress. Measurements of oxidative stress markers throughout the year revealed increased lipid peroxidation in females, but only during the winter. Enhanced lipid peroxidation in females was associated with reduced photoprotection, as indicated by reduced tocopherol levels and nonphotochemical quenching (NPQ) of chlorophyll fluorescence. Enhanced lipid peroxidation in females was also observed at predawn, which was associated with increased lipoxygenase activity and reduced cytokinin levels. An analysis of the differences between reproductive (R) and nonreproductive (NR) shoots showed an enhanced photoprotective capacity in R shoots compared to NR shoots in females. This capacity was characterized by an increased NPQ and a better antioxidant protection (increased carotenoid and tocopherol levels per unit of chlorophyll) in R compared to NR shoots. It is concluded that (i) females exhibit higher lipid peroxidation in leaves than males, but only during the winter (when sex-related differences in reproductive effort are the highest), (ii) this is associated with a lower photoprotective capacity at midday, as well as enhanced lipoxygenase activity and reduced cytokinin levels at predawn, and (iii) photoprotection capacity is higher in R relative to NR shoots in females.
Highlights
Studies on dimorphism between sexes in dioecious plants have shown differential reproductive traits in males and females and significant differences in vegetative traits generally associated with a greater reproductive effort in females (Barrett and Hough, 2013)
This capacity was characterized by an increased nonphotochemical quenching (NPQ) and a better antioxidant protection in R compared to NR shoots
These studies show that females are more sensitive than males to drought stress in terms of productivity and leaf gas exchange, females of Pistacia lentiscus showing reduced CO2 assimilation rates and photosystem II (PSII) efficiency compared to males
Summary
Studies on dimorphism between sexes in dioecious plants have shown differential reproductive traits in males and females and significant differences in vegetative traits generally associated with a greater reproductive effort in females (Barrett and Hough, 2013). More studies are needed to better understand the consequences of sex dimorphism in the adaptation of plants to environmental stresses. This information can provide helpful insights into better understanding the biology of dioecious plants and help to improve management practices in their natural habitat
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