不同性别桑树幼苗对镉与酸雨复合处理的生长响应及镉积累差异

为研究不同性别桑树在镉(Cd)与酸雨(AR)复合处理条件下的生长与镉积累差异,本试验以‘强桑1号’(雌株)和‘农桑14号’(雄株)两种不同性别桑树为材料,研究重金属镉(100 mg·kg^-1干土)和模拟酸雨(pH 3.0)处理下,两者生物量积累和分配、最大净光合速率(A_max)和叶绿素荧光参数,以及Cd积累与分配的差异.试验共设置无Cd和AR(对照)、单独Cd、单独AR、Cd+AR复合4个处理.结果表明:单独Cd处理虽然显著增加了雌株和雄株根茎叶中Cd含量,而且雌株各部分Cd含量显著高于雄株,但是只有雄株根、茎和总生物量、最大净光合速率显著下降,而雌株除了A_max显著下降外,各部分生物量积累下降均不显著,且两者的最大光化学效率(F_v/F_m)、光化学淬灭系数(q_P)和非光化学淬灭系数(q_N)均未发生显著变化.复合处理下,雄株和雌株的总生物量、A_max均显著降低,与单独镉处理相比,雌株根和叶中的Cd含量显著升高,但雄株没有明显变化,两者的F_v/F_m、q_P没有显著变化,但q_N均显著降低.短时间处理下桑树雌株对单独镉胁迫的耐受性高于雄株,但是酸雨的加入会降低雌株对镉的耐受性,可能是因为酸雨促进雌株根系对镉的吸收,并导致叶片积累了更多的镉.

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

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 (A_max) of males were significantly decreased, while those of females (except A_max) showed no significant changes. Cd had no effect on maximal photochemical efficiency (F_v/F_m), photochemical quenching coefficient (q_P), non-photochemical quenching coefficient (q_N) in both sexes. When exposed to Cd+AR stress, the total biomass and A_max 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 F_v/F_m and q_P, but significantly increased q_N 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.