三峡库区岸生植物秋华柳对水淹的光合和生长响应

RESPONSE TO SIMULATED FLOODING OF PHOTOSYNTHESIS AND GROWTH OF RIPARIAN PLANT SALIX VARIEGATA IN THE THREE GORGES RESERVOIR REGION OF CHINA

为阐明三峡库区岸生植物秋华柳(Salix variegata)对水淹的耐受机制,模拟三峡库区消落带水淹发生的情况,研究了在不同水淹时间和水淹深度处理下秋华柳的光合和生长特性。实验设置了对照(不进行水淹,常规供水管理)、水淹根部(植株置于水中,植株地下部分被淹没)、水下0.5 m(植株置于水中,植株顶部在水面下0.5 m)和水下2 m(植株置于水中,植株顶部在水面下2 m)4个不同的水淹深度和0、10、20、40、60和90 d 6个不同的水淹时间处理,并测定了在不同水淹时间和水淹深度处理下秋华柳的光合作用、叶绿素荧光和生长。研究结果发现:随着水淹时间的延长,对照和水淹根部植株都具有高的净光合速率、表观量子效率和羧化效率。水淹40 d后,相同水淹深度处理秋华柳植株的净光合速率显著高于耐水湿环境的垂柳(Salix babylonica)(p<0.05)。水淹90 d后,全淹处理植株的光合能力较对照有显著的下降(p<0.05),对照、水下0.5 m和水下2 m植株的净光合速率分别为13.2、10.1和8.05μmol.m-2·s-1,同时全淹植株PSII的最大光化学效率也有一定程度的下降,显著低于对照和水淹根部处理的植株(p<0.05)。水淹40、60和90 d后,全淹植株的胞间CO2浓度都高于对照和水淹根部植株。随着水淹时间的增加,水淹根部植株不定根数量不断增加,而全淹植株只有极少量的不定根产生。水淹根部植株的主茎长的增量、分枝数的增量、主茎新生叶片数、根生物量的积累和总生物量的积累都高于全淹植株,全淹植株在水淹过程中,其主茎长、分枝数、主茎新叶数、根生物量和总生物量都有增加,同时其凋落叶片较多。水淹90 d后,秋华柳植株的存活率为100%。研究结果表明,秋华柳在经过较长时间的水淹后,表现出较强的光合和生长适应性,可以考虑将秋华柳列为三峡库区消落带植被构建的物种之一。

Aims The aim was to reveal the effects of flooding on photosynthesis and growth of the riparian plant Salix variegata for revegetation of riparian areas in Three Gorges Reservoir Region. Methods Four flooding treatments were applied to the plants： no flooding, belowground submergence and whole plant submergence to water depths of 0.5 and 2 m. Net photosynthetic rate, apparent quantum yield, carboxylation efficiency, intercellular CO2 concentration and maximal photochemical efficiency of PSII （ Fv/ Fm） were determined at 0, 40, 60 and 90 d. The numbers of adventitious roots were determined at 6, 15, 25 and 32 d. Increase of stem length, increase of number of shoots, number of newly grown leaves on stem, number of shed leaves on stem, increase of root biomass and increase of plant biomass were determined at 10, 20, 40, 60 and 90 d. Important findings Control and belowground-submerged plants maintained high net photosynthetic rate, apparent quantum yield and carboxylation efficiency during inundation. At 40 d, the net photosynthetic rate of S. variegata was significantly higher than that in the waterlogging-tolerant species S. babylonica （p 〈 0.05）. At 60 and 90 d, the photosynthetic capacity and Fv/Fm of wholly submerged plants decreased significantly as compared with that of the control and belowground-submerged plants （p 〈 0.05）, but the plants could still maintain high photosynthetic capacity. At 40, 60 and 90 d, the intercellular CO2 concentration of wholly submerged plants was higher than that of the control and belowground-submerged plants. At 32 d, many adventitious roots were developed in belowground-submerged plants, while the wholly submerged plants had few adventitious roots. The belowground-submerged plants had greater increase in stem length, number of shoots, and newly generated leaves on stem, root biomass and total plant biomass than wholly submerged plants. During the flooding period, the stem length, number of shoots, and newly generated leaves on stem, root biomass and total plant biomass of wholly submerged plants increased, and the number of shed leaves of wholly submerged plants was higher than that of the control and belowground-submerged plants. At 90 d, all below- ground-submerged and wholly submerged S. variegata were alive. Therefore, S. variegata has high photosynthetic capacity and growth adaptability over inundation of 90 d and is a promising species for revegetation of the riparian zone in the Three Gorges Reservoir Region .