遮阴和紫外辐射对凤眼莲株型与光合作用的影响

Effects of Shading and UV-B Treatments on Plant Type and Photosynthesis of Eichhornia crassipes

采用室外培养,单因子设计,设置紫外辐射(UV-B 100 μW/cm2)、遮阴(光强为自然光的70%)和全自然光3个处理,测定凤眼莲(Eichhornia crassipes)30d处理前后生长势和光合参数的变化。结果表明:(1)凤眼莲是对光因子高度敏感的植物,不同光环境下株型不同;与全自然光处理材料相比,遮阴后增加了叶柄的长度;紫外辐射后则缩短叶柄,紧凑株型,并增加根长;(2)凤眼莲生长势的高低不仅与叶片的受光状况密切相关,而且与其光合能力的发挥也有关;在低光强下,通过提高叶片的叶倾角,增大气孔导度(Gs),从而增加净光合速率(Pn)来补偿光强不足造成物质累积的减少;在紫外辐射条件下,通过降低群体的受光能力,降低Gs和蒸腾速率(Tr),以下调Pn缓解紫外辐射对植株的伤害。(3)在凤眼莲的人工种养工程中采取两步法,即前期增加光强,后期覆盖遮阳网,可显著增加其干物质的累积。

With single-factor experiment designed, the growth potential and photosynthetic parameters of Eichhornia crassipes before and after the treatments were measured outdoors in Nanjing under the treatments of ultraviolet radiation （UV-B 100 μW/cm2）, shading （light intensity： 70% of natural light）, and natural light for 30 d. The research indicated that （1） E.crassipes is a plant species of highly light sensitivity, plant type variable with different luminous environment. Compared with natural light treatment, petiole length of E.crassipes under shading treatment increased, but petiole length decreased under UV radiation, with plant type compact and root length extending. （2） The growth potential of E.crassipes was highly related to light intensity photosynthetic capacity. With light intensity lower, reduction of matter accumulation caused by insufficient light intensity was compensated by increasing MLIA, enhancing stomatic conductance （Gs）, thus increasing net photosynthesis rate （Pn）. Under UV radiation, UV radiation damage to the plants was alleviated by reducing light-absorbing capacity of E.crassipes, consequently decreasing transpiration rate （Tr）, stomatic conductance （Gs） and net photosynthesis rate （Pn）. （3） Two-step approach is to be applied in the artificial culture of E.crassipes, and dry matter accumulation can be significantly increased by increasing light intensity at early stage, and by covering sunshade screen at later stage.