香根草形态性状和光合特性对三峡库区消落带水陆生境变化的响应

基于定位观测,研究三峡库区消落带淹水区和未淹区香根草的形态性状、生物量、光合参数和资源利用效率,并对其适应机制进行讨论。结果显示:(1)香根草可以在消落带每年淹水期4个月左右、淹水深度小于9m的海拔区段存活。(2)淹水区香根草的地上部分多数形态性状指标较未淹区有所降低,降低幅度随香根草露出水面恢复生长的时间长短而异。(3)淹水区香根草总生物量、地上部分生物量分别减少10.58%、48.46%,而根径、根系长度、根系数量、根幅、地下生物量以及地下/地上生物量的比值分别提高12.50%、24.13%、19.09%、78.46%、30.04%、151.71%;同期香根草的蒸腾速率、气孔导度和胞间CO2浓度分别减少20.75%、9.19%和10.04%,而净光合速率、水分利用效率、表观CO2利用效率分别提高7.23%、36.47%和63.64%。研究表明,加速根系分蘖和生长、增加叶片长度和地下生物量,降低植株高度、减少蒸腾、提高水分和CO2利用效率是香根草对三峡库区消落带水陆生境变化的适应对策。

Form Traits and Photosynthesis Characteristics of Vetiveria zizanioides Response to Flooding-drying Habitat Changes in the Hydro-fluctuation Belts of the Three Gorges Reservoir

Based on located monitoring,morphological characteristics,biomass,photosynthesis and resource utilization of Vetiveria zizanioides at flooded and non-flooded areas were studied on the hydro-fluctuation belts in the Three Gorges Reservoir and the adaptation mechanism was discussed.The results showed that:(1)V.zizanioides can still live within 4 months of yearly flooding at the maximum depth of 9 m.(2)Compared with the V.zizanioides at the non-flooded area,most of the aboveground morphological characteristics of V.zizanioides at the flooded area decreased and the margin varied as the time of restore growth varied.(3)The total biomass,aboveground biomass,T_r,G_s,C_i decreased by 10.58%,48.46%,20.75%,9.19% and 10.04%,respectively,and root diameter,root length,root number,root spread range,underground biomass,underground and aboveground biomass ratio,P_n,WUE and CUE increased by 12.50%,24.13%,19.09%,78.46%,30.04%,151.71%,7.23%,36.47% and 63.64%,respectively.Increasing root tillering and growth,leaf length,underground biomass and underground biomass allocation and improving water and CO₂ utilization while decreasing plant height and transpiration improving were the adaptation strategy of V.zizanioides in the Three Gorges Reservoir to flooding-drying habitat changes.