水淹持续胁迫对湿地松光合特性及生理生化的影响

目的 分析三峡库区消落带经历冬季水淹持续胁迫后对幼苗针叶光合特性以及生理生化的影响，揭示其变化规律，为消落带分区段监测和治理及植被恢复提供重要的科学依据。 方法 本研究以2年生湿地松幼苗为试验材料，研究了经历夏季干旱后，通过人为设置对照组、根淹组和全淹组等来模拟长达5个月的冬季水淹持续胁迫对幼苗针叶光合特性以及生理生化的影响。 结果 表明：经历夏季干旱胁迫45 d后，随着水淹时间增加，根淹组1和全淹组2植物的净光合速率（Pn）呈现出“下降-平缓”的趋势，但根淹组3和全淹组4植株的Pn处于一直下降趋势，且60 d后的Pn低于前者，水淹150 d后，湿地松的Pn分别比初始值下降30.9%、33.0%、51.9%和62.3%；同时，水淹显著降低了针叶气孔导度（Gs）和蒸腾速率（Tr）。通过比较Ci和Ls（气孔限制值）的关系得出：湿地松Pn下降前期主要由气孔因素决定，而后期则大多由非气孔因素决定。根淹组植株可溶性蛋白含量在淹水阶段大多与对照组植株差异不明显；全淹组的湿地松针叶内可溶性蛋白含量在淹水初期（水淹前60 d）出现了显著的增加，而在水淹后期逐渐下降。水淹45~60 d时，湿地松针叶内的超氧化物歧化酶（SOD）活性显著高于对照。不同淹水处理下，湿地松在水淹前30 d内丙二醛（MDA）含量均与对照组相比差异不显著，但水淹60 d后，湿地松针叶中的MDA含量显著增加并逐渐稳定在一定水平。 结论 这些研究结果对未来消落带适生物种选择以及植被恢复与重建具有重要的参考价值。

Effects of Continuous Flooding Stress on Photosynthetic Characteristics and Physiological and Biochemical Characteristics of Pinus elliottii

Objective To study the effects of continuous flooding on leaf photosynthetic characteristics and physiological and biochemical characteristics of young plant. Method The Zigui section of the Three Gorges Reservoir riparian zone is affected by the water level operation of winter storage and summer discharge, forming a "drought-flooding-drought" water level fluctuation model, which makes the ecological environment of the riparian zone facing severe challenges. In this study, two-year-old Pinus elliottii seedlings were divided into six groups (including two control groups) with different initial drought and then flooding treatments and to study the effects of a simulated five-month winter flooding stress on photosynthetic characteristics and physiological and biochemical characteristics of seedling leaves after 45 days of drought stress. Result The results showed that with the increase of flooding time, the net photosynthetic rate of Group 1 (initially under mild drought stress and then root-flooded) and Group 2 (initially under mild drought stress and then full-flooded) showed a "decline-gentle" trend, but the net photosynthetic rate of Group 3 (initially under moderate drought stress and then root-flooded) and Group 4 (initially under moderate drought stress and then full-flooded) showed a downward trend. After 60 days, the net photosynthetic rate was lower than that of the former. After 150 days of flooding, the net photosynthetic rate of P. elliottii decreased by 30.9%, 33.0%, 51.9% and 62.3% respectively compared with the original values. Meanwhile, water flooding significantly reduced the stomatal conductance and transpiration rate. By comparing the relationship between Ci and Ls, it is concluded that the decrease of net photosynthetic rate of P. elliottii was mainly determined by stomatal factors in the early stage, and non-stomatal factors in the later stage. The content of soluble protein in root-flooded groups was mostly not significantly different from that in the control group during the flooding stage, while the content of soluble protein in leaves of P. elliottii in full-flooded group increased significantly at the early stage (60 days before flooding), but decreased gradually at the later stage. At 45 to 60 days of flooding, the activity of SOD in P. elliottii needles were significantly higher than those in the control group. The MDA content of P. elliottii leaves in different flooding conditions was not significantly different from that of the control groups within 30 days before flooding, but after 60 days of flooding, the MDA content of P. elliottii leaves increased significantly and gradually stabilized to a certain level. Conclusion These results can provide reference for the selection of suitable species and vegetation restoration and reconstruction in Three Gorges Reservoir riparian zone.