Photochemistry differs between male and female Juniperus communis L. independently of nutritional availability

Juniperus communis males are better adapted than females to changing, seasonal environmental conditions due to their higher photosynthetic capacity and the higher concentration of photosynthetic pigments in their needles. Males cope with ROS more efficiently than females having greater carotenoids concentration in needles. In dioecious woody plants, females often exhibit greater reproductive effort than male plants and as a result, they can be more vulnerable to different stressors. We hypothesized that female plants of J. communis L. could have a lower photochemical capacity and a higher level of antioxidant enzyme activity and that these differences between males and females would be more pronounced under conditions where nutrient availability is limited. We also assume that additional stressors connected with different seasons would increase those differences. Male and female plants of J. communis growing in fertilized or non-fertilized soils were used to test this hypothesis. The effect of fertilization and sex on photochemical parameters derived from chlorophyll a fluorescence light curves, and on the concentrations of photosynthetic pigments in needles, was determined in different seasons within 2 years. To assess the tolerance of male and female plants to the nutrient deficit, antioxidant enzyme activity, and the level of reactive oxygen species (ROS) were determined. Results revealed sex-related differences in photochemical parameters, level of antioxidant enzyme activity, H2O2 levels, the concentration of photosynthetic pigments, and in the leaf mass-to-area ratio. This indicates that J. communis males could be better adapted than females to changing, seasonal environmental conditions due to their higher photosynthetic capacity, as reflected by their higher ETRmax, and a higher concentration of photosynthetic pigments in their needles. The sex-related differences concerning photosynthetic capacity and stress response found in our study are constitutive traits of each sex and are genetically based as they occurred independently of fertilization.