The responses of plant growth, chlorophyll fluorescence and light energy allocation in leaves of Sorghum bicolorXS. sudanense and Sorghum sudanense (Piper) Stapf seedlings to drought stress were in-vestigated. Results showed that plant height, root length and total biomass of S. bicolorXS. sudanense were significantly higher than that of S. sudanense (Piper) Stapf. Relative water content (RWC) in above-ground S. bicolorXS. sudanense under drought stress was higher than that of S. sudanense (Piper) Stapf. . The activity and opening proportion of PS[[ reaction centers and electron transport rate (ETR) in leaves of both plants were reduced under drought stresS. Under severe drought stress, ETR in leaves of S. bicolorX S. sudanense maintained higher than that of S. sudanense (Piper) Stapf to alleviate photoinhibition. The proportion of light energy used to quantum yield of PSII photochemistry (ΦPSⅡ) and xanthophyll-mediated thermal dissipation (ΦNpq) decreased under drought. But, under severe drought stress,ΦPSn and Φnpq in leaves of S. bicolorX S. sudanense seedlings were much higher than that of S. sudanense (Piper) Stapf. Quantum yield used to thermal dissipation in non-functional PSH (Φnf) in leaves of S. bicolorXS. sudane-nse was lower than that of S. sudanense (Piper) Stapf. Thermal dissipation by xanthophyll cycle played an important role in photoprotection of S. sudanense (Piper) Stapf under severe drought condition to ensure physiological function of PS II reaction centers and alleviate photoinhibition.%研究了高丹草(Sorghum bicolor×S.sudanense)和苏丹草(Sorghum sudanense (Piper) Stapf.)的生长特性、叶片叶绿素荧光特性及激发能的分配对干旱的响应.结果表明:高丹草的株高、根系长度和干物质积累等明显优于苏丹草,干旱下高丹草地上部相对含水率高于苏丹草.干旱降低了2种牧草叶片的PSⅡ反应中心活性和反应中心开放程度,电子传递速率降低,但高丹草叶片在重度干旱下的电子传递速率高于苏丹草,光抑制程度明显低于苏丹草.干旱下2种牧草叶片的PSⅡ反应中心吸收的光能用于光化学反应的量子产额(ΦPSⅡ)和依赖于叶黄素循环的能量耗散的量子产额(ΦNPQ)所占比例呈现降低趋势,但重度干旱下高丹草叶片的ΦPSⅡ和ΦNPQ明显高于苏丹草,而PSⅡ反应中心的热耗散量子产额(ΦNF)所占比例低于苏丹草,说明高丹草叶片在重度干旱下叶片以叶黄素循环为主的光保护机制在防御光破坏方面发挥着重要作用,从而保证了PSⅡ反应中心的正常生理功能,减轻了高丹草在重度干旱下的光抑制程度.
展开▼
