Variations in growth response and cadmium accumulation of different gender Morus alba seedlings to combined treatments of Cd and acid rain

Abstract

To investigate sex-specific adaptive responses and cadmium accumulation of Morus alba seedlings, we analyzed growth parameters, photosynthetic capacity and chlorophyll fluorescence parameters, and Cd accumulation and allocation of Qiangsang 1 (female) and Nongsang 14 (male) under different treatments [cadmium (Cd, 100 mg·kg-1), acid rain (AR, pH 3.0) and their combinations (Cd+AR)]. When exposed to Cd stress alone, females showed higher cadmium content in root, stem and leaf than males. The root, stem and total biomass, and maximum net photosynthetic rate (Amax) of males were significantly decreased, while those of females (except Amax) showed no significant changes. Cd had no effect on maximal photochemical efficiency (Fv/Fm), photochemical quenching coefficient (qP), non-photochemical quenching coefficient (qN) in both sexes. When exposed to Cd+AR stress, the total biomass and Amax of males and females decreased. Compared to Cd stress alone, the cadmium content in root and leaf of females significantly increased while those of males did not under Cd+AR. In addition, Cd+AR stress had no effect on Fv/Fm and qP, but significantly increased qN in both sexes. Our results suggested that females had greater tolerance than males when exposed to Cd stress alone in short term. Acid rain would decrease the tolerance of females to Cd stress, which might attribute to the enhanced absorption and accumulation of cadmium.