Secondary sexual dimorphism traits under abiotic stress in dioecious species: The case of Amaranthus palmeri

The evolution of secondary sex-specific traits of dioecious species under abiotic stress conditions has received limited research, especially in the case of Amaranthus palmeri, a fast adapting and highly competing plant. Here, we have examined the interactive effects of abiotic stress on mineral accumulation, chlorophyll a and b content, and the operating capacity of Photosystem II (PSII) in both male and female A. palmeri plants grown under three different intensities (150, 450 and 1300 mol photons m-2 s-1) of white light, and under N, K or P deficiency. Mineral profiling of the leaves and stems (with inflorescence) highlighted intra- and intersexual differences in their accumulation pattern and mineral associations. Chlorophyll a and b content was different between the male and the female plants, being lower in the latter, at high light intensity, especially as the flowering progressed, or when they were under K or P deficient condition. Further, the chlorophyll a/b ratio was lower at the higher light intensity in the female, over that in the male, plants. Chlorophyll fluorescence parameters, i.e., steady state (FS) and maximum (FM) fluorescence increased under high light intensity, whereas the PSII operating efficiency ({Phi}PSII) decreased in the female plants, indicating reduced PSII capacity. Sex-specific differences in A. palmeri showed a differential response to stressful conditions because of differences in their ontogeny and physiology, and possibly due to the cost of reproduction. We suggest that the breeding system of dioecious species has weaknesses that can be used for the ecological management of dioecious weed species.