Jin Chuan, Zha Tianshan, Bourque Charles P-A, Jia Xin, Tian Yun, Liu Peng, Li Xinhao, Liu Xinyue, Guo Xiaonan, Xu Mingze, Kang Xiaoyu, Guo Zifan, Wang Ning
Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, China.
Key Laboratory for Soil and Water Conservation, State Forestry and Grassland Administration, Beijing Forestry University, Beijing, China.
Front Plant Sci. 2022 Nov 3;13:1057943. doi: 10.3389/fpls.2022.1057943. eCollection 2022.
Acclimation strategies in xerophytic plants to stressed environmental conditions vary with temporal scales. Our understanding of environmentally-induced variation in photosystem II (PSII) processes as a function of temporal scales is limited, as most studies have thus far been based on short-term, laboratory-controlled experiments. In a study of PSII processes, we acquired near-continuous, field-based measurements of PSII-energy partitioning in a dominant desert-shrub species, namely , over a six-year period from 2012-2017. Continuous-wavelet transformation (CWT) and wavelet coherence analyses (WTC) were employed to examine the role of environmental variables in controlling the variation in the three main PSII-energy allocation pathways, i.e., photochemical efficiency and regulated and non-regulated thermal dissipation, i.e., , , and , respectively, across a time-frequency domain from hours to years. Convergent cross mapping (CCM) was subsequently used to isolate cause-and-effect interactions in PSII-energy partitioning response. The CWT method revealed that the three PSII-energy allocation pathways all had distinct daily periodicities, oscillating abruptly at intermediate timescales from days to weeks. On a diurnal scale, WTC revealed that all three pathways were influenced by photosynthetically active radiation (), air temperature ( ), and vapor pressure deficit (). By comparing associated time lags for the three forms of energy partitioning at diurnal scales, revealed that the sensitivity of response was more acutely influenced by , declining thereafter with the other environmental variables, such that the order of influence was greatest for , followed by , and then soil water content (. PSII-energy partitioning on a seasonal scale, in contrast, displayed greater variability among the different environmental variables, e.g., and being more predisposed to changes in , and to changes in . CCM confirmed the causal relationship between pairings of PSII-energy allocation pathways, according to shrub phenology. is shown to have an innate ability to (i) repair damaged PSII-photochemical apparatus (maximum quantum yield of PSII photochemistry, with / > 0.78), and (ii) acclimatize to excessive , dry-air conditions, and prolonged drought. is relatively sensitive to extreme temperature and exhibits photoinhibition.
旱生植物对胁迫环境条件的适应策略随时间尺度而变化。我们对作为时间尺度函数的光系统II（PSII）过程中环境诱导变化的理解有限，因为迄今为止大多数研究都基于短期的实验室控制实验。在一项关于PSII过程的研究中，我们在2012年至2017年的六年期间，对一种优势沙漠灌木物种（即 ）的PSII能量分配进行了近乎连续的实地测量。采用连续小波变换（CWT）和小波相干分析（WTC）来研究环境变量在控制PSII能量分配的三个主要途径变化中的作用，即光化学效率以及调节性和非调节性热耗散，分别为 、 和 ，跨越从小时到年的时频域。随后使用收敛交叉映射（CCM）来分离PSII能量分配响应中的因果相互作用。CWT方法表明，PSII能量分配的三个途径都有明显的每日周期性，在从几天到几周的中间时间尺度上突然振荡。在日尺度上，WTC表明所有三个途径都受到光合有效辐射（ ）、气温（ ）和水汽压亏缺（ ）的影响。通过比较日尺度上三种能量分配形式的相关时间滞后，发现响应的敏感性受 影响更强烈，此后随其他环境变量下降，因此影响顺序为 最大，其次是 ，然后是土壤含水量（ ）。相比之下，季节性尺度上的PSII能量分配在不同环境变量之间表现出更大的变异性，例如 和 更容易受到 变化的影响，而 则受 变化的影响。CCM根据灌木物候证实了PSII能量分配途径配对之间的因果关系。结果表明， 具有天生的能力：（i）修复受损的PSII光化学装置（PSII光化学的最大量子产率， / > 0.78），以及（ii）适应过量的 、干燥空气条件和长期干旱。 对极端温度相对敏感，并表现出光抑制作用。
