Meng Changjun, Liu Xiao, Chai Yongfu, Xu Jinshi, Yue Ming
Key Laboratory of Resource Biology and Biotechnology in Western China, Northwest University, Xi'an, Shaanxi, China.
College of Biology and Environmental Engineering, Xi'an University, Xi'an, Shaanxi, China.
PeerJ. 2019 Jan 8;7:e5933. doi: 10.7717/peerj.5933. eCollection 2019.
In the case of tall trees in the field or in rugged terrain where an instrument cannot be placed operationally, beveling is a popular method used to measure photosynthesis. However, some studies and our own research have shown that net photosynthesis values measured are generally significantly lower than values measured .
To develop a more accurate and applicable method for determination of photosynthesis, we evaluated five different methods for preparing detached tree branches to measure photosynthesis and gas exchange (beveling, cracking, splitting, girdling, and immersion in salicylic acid solution). Ten common tree-species were used.
By comparing light response curves and water-status data, we found that (1) it is possible, to some extent, to substitute measurement of photosynthetic characteristics of tree species for measurement, provided a suitable treatment is employed; (2) the beveling method is likely to underestimate photosynthetic potential of some trees; (3) after cracking application, most detached branches effectively continued to absorb water; and (4) measurements obtained using detached tree-branches processed by the cracking method were closer to those obtained in intact trees; (5) some tree species () appeared to be particularly sensitive to the cracking method, and their maximum net photosynthesis rate ( ) was significantly less than the value ( < 0.05).
Our findings provide a methodological support for comprehensive and accurate measurement of plant functional traits. The use of the cracking method contributes to feasibility and reliability of the measurement of photosynthetic parameters in tall trees, thus providing more accurate photosynthetic parameters for the analysis of trade-off strategies at the leaf level.
对于野外高大树木或地形崎岖无法实际放置仪器的情况，斜面切割是一种常用的光合作用测量方法。然而，一些研究以及我们自己的研究表明，所测得的净光合作用值通常明显低于[实际]测量值。
为开发一种更准确且适用的光合作用测定方法，我们评估了五种不同的离体树枝制备方法以测量光合作用和气体交换（斜面切割、劈裂、纵切、环剥以及浸泡在水杨酸溶液中）。使用了十种常见树种。
通过比较光响应曲线和水分状况数据，我们发现：（1）只要采用合适的处理方法，在一定程度上可以用离体树种的光合特性测量替代[整株树的]测量；（2）斜面切割法可能会低估某些树木的光合潜力；（3）采用劈裂处理后，大多数离体树枝能有效持续吸水；（4）使用劈裂法处理的离体树枝所获得的测量结果更接近完整树木的测量结果；（5）一些树种（[具体树种未给出]）似乎对劈裂法特别敏感，其最大净光合速率（[具体参数未给出]）显著低于[完整树木的]值（<0.05）。
我们的研究结果为全面准确测量植物功能性状提供了方法学支持。劈裂法的应用有助于高大树木光合参数测量的可行性和可靠性，从而为叶片水平权衡策略分析提供更准确的光合参数。
