中国科学院海岸带环境过程与生态修复重点实验室知识库

研究四倍体和二倍体金银花叶片光合作用对盐胁迫的响应，特别是盐胁迫对PSⅠ和PSⅡ性能以及协调性的影响，比较盐胁迫下叶片光合特性的差异，分析盐胁迫对叶片Na+、Cl-和丙二醛含量以及叶片生物量的影响，揭示不同倍性金银花耐盐胁迫的能力，为盐碱地栽培品种的选择提供参考。【方法】选用四倍体和二倍体金银花为试验材料，采用叶绿素荧光快速诱导动力学曲线和820 nm 光反射曲线同步测定技术，结合气体交换参数，研究中度（150 mmol·L-1 NaCl）和重度（300 mmol·L-1 NaCl）盐胁迫对四倍体和二倍体金银花叶片光合作用和光合机构的影响。金银花植株定植于装有石英砂的塑料盆中，Hoagland 营养液培养。营养液中加入NaCl 用于盐处理，每天递增50 mmol·L-1 到达处理浓度（150 和300 mmol·L-1），处理持续15 d。以不加入NaCl的营养液培养对照植株。盐处理过程中选取枝条中部全展的叶片用于指标测定。【结果】中度盐胁迫下，四倍体和二倍体金银花叶片光合速率、气孔导度和胞间CO2 浓度显著降低，但四倍体下降幅度小于二倍体，说明中度盐胁迫下光合速率的降低是由气孔限制引起的，四倍体叶片光合作用受气孔限制程度较小。重度盐胁迫下，四倍体和二倍体金银花叶片光合速率也显著降低，但四倍体下降幅度小于二倍体，能维持较高的光合活性。重度盐胁迫7 d后，二倍体金银花叶片Rubisco 酶的活化状态和羧化效率显著降低，诱发PSⅡ光抑制，降低向PSⅠ电子传递的量子产额。因此，PSⅠ的还原受到抑制，820 nm 光反射曲线应该显示PSⅠ氧化幅度增加。但结果相反，PSⅠ氧化幅度却显著降低。重度盐胁迫下，二倍体金银花叶片PSⅠ也发生了光抑制，不能有效推动电子向PSⅠ受体侧传递，抑制了PSⅠ的氧化，而PSⅠ光抑制程度高于PSⅡ，导致PSⅠ氧化幅度显著降低，破坏了PSⅡ与PSⅠ的协调性。重度盐胁迫15 d 后，四倍体金银花叶片Rubisco 酶活化状态和羧化效率显著下降，但下降幅度小于二倍体金银花，PSⅡ和PSⅠ的性能未受显著影响，维持了PSⅡ和PSⅠ的协调性。因此，相对于二倍体，四倍体金银花叶片在重度盐胁迫下也具有较高的光合活性。盐胁迫15 d 后，二倍体金银花叶片Na+、Cl-和丙二醛含量显著增加，整株叶片干重显著降低，其变化幅度大于四倍体金银花，说明四倍体金银花受离子毒害的影响较轻，这可能是其在盐胁迫下维持较高光合性能的原因。【结论】盐胁迫下，四倍体金银花叶片能维持较高的气孔导度和Rubisco 酶的活化状态，保持了PSⅡ和PSⅠ的协调性，因而具有较高的光合活性，能够积累较多的生物量。因此，四倍体金银花耐盐胁迫的能力强于二倍体，更适于盐碱地栽培。

In order to provide a reference for cultivar selection of saline land, leaf photosynthetic responses to salt stress in diploid and tetraploid honeysuckle, especially the effects of salt stress on PSⅠand PSⅡperformance and coordination were studied, the difference in leaf photosynthetic characters under salt stress was compared and the effects of salt stress on leaf Na+, Cland malondialdehyde contents and the leaf biomass were analyzed so that revealed salt tolerance of the honeysuckle with different ploidies.【Method】Tetraploid and diploid honeysuckle plants were used as experimental materials to study the effects of moderate (150 mmol·L-1 NaCl) and severe (300 mmol·L-1 NaCl) salt stress on photosynthesis and photosynthetic apparatus by simultaneously analyzing chlorophyll a fluorescence transient and light reflection at 820 nm as well as gas exchange parameters. Honeysuckle plants were planted in plastic pots filled with quartz sand and cultured with Hoagland nutrient solution. NaCl was added to nutrient solution incrementally by 50 mmol·L-1 step per day to provide final concentrations of 150 and 300 mmol·L-1 for salt treatment, and the treatment lasted for 15 days. The control plants were cultured with nutrient solution without adding NaCl. During salt treatment, expanded leaves from the middle of a shoot were sampled for measuring parameters.【Result】Under moderate salt stress, leaf photosynthetic rate, stomatal conductance and intercellular CO2 concentration were significantly decreased in diploid and tetraploid honeysuckle, and the decrease was lower in the tetraploid, indicating less stomatal inhibition on photosynthesis. Under severe salt stress, leaf photosynthetic rate was also significantly decreased in diploid and tetraploid honeysuckle, and the tetraploid could maintain higher photosynthetic activity than the diploid due to the lower decrease in leaf photosynthetic rate. After 7 days of severe salt stress, leaf carboxylation rate and Rubisco activation state were significantly decreased in diploid honeysuckle. PSⅡphotoinhibition was induced, resulting in the decline of quantum yield of electron transport to PSⅠ. Therefore, PSⅠreduction was inhibited, and the increased PSⅠoxidation should be observed in the 820 nm reflection transient. On the contrary, PSⅠoxidation was significantly decreased. Under severe salt stress, PSⅠphotoinhibition also occurred in the leaves of diploid honeysuckle, which could not effectively drive electrons to its acceptor side and then inhibited PSⅠoxidation. The significant decrease of PSⅠoxidation resulted from the greater photoinhibition in PSⅠthan PSⅡ, and the coordination between PSⅡand PSⅠwas destroyed. After 15 days of severe salt stress, leaf carboxylation rate and activation state of Rubisco enzyme were significantly decreased in tetraploid honeysuckle, and the decrease was lower than that in diploid honeysuckle. The capacity of PSⅡand PSⅠwas not significantly affected, and their coordination was maintained in tetraploid honeysuckle under severe salt stress. Thus, tetraploid honeysuckle also had higher leaf photosynthetic activity than the diploid upon severe salt stress. After salt stress for 15 days, leaf Na+, Cl- and malondialdehyde contents were significantly increased in diploid honeysuckle, whereas leaf dry weight per plant was significantly reduced, and the change amplitude was greater than that in tetraploid honeysuckle, indicating lower leaf ionic toxicity in the tetraploid, which might be responsible for maintaining higher photosynthetic capacity under salt stress.【Conclusion】Under salt stress, tetraploid honeysuckle possesses higher leaf photosynthetic activity in terms of greater leaf stomatal conductance, higher Rubisco activation state and normal PSⅡ and PSⅠcoordination, and then could accumulate greater biomass. Therefore, tetraploid honeysuckle has stronger salt tolerance and is more suitable for cultivation in saline land.