![]() ![]() Consequently, understanding how dryland plants can cope with their harsh surroundings is of great importance to land managers and ecologists worldwide.Īs a basis for maintaining energy and material flows in ecosystems, plant photosynthesis is particularly susceptible to environmental fluctuations, especially when representing extreme departures from favorable conditions ( Schurr et al., 2006 Rodríguez-Calcerrada et al., 2008 Kalaji et al., 2012). ![]() Consequently, plants in drylands (arid and semiarid lands) are frequently exposed to environmental stressors, triggered by excessive solar radiation, extreme temperature, drought, and other climatic anomalies ( Jia et al., 2014 Tominaga et al., 2014). ordosica is relatively sensitive to extreme temperature and exhibits photoinhibition.ĭrylands, which make up almost half the earth’s continental area, have been expanding at an alarming rate as regional-to-global climate continues to deteriorate and human activity increases ( Huang et al., 2017 Li et al., 2021). ordosica is shown to have an innate ability to (i) repair damaged PSII-photochemical apparatus (maximum quantum yield of PSII photochemistry, with F v/ F m > 0.78), and (ii) acclimatize to excessive PAR, dry-air conditions, and prolonged drought. CCM confirmed the causal relationship between pairings of PSII-energy allocation pathways, according to shrub phenology. PSII-energy partitioning on a seasonal scale, in contrast, displayed greater variability among the different environmental variables, e.g., Φ PSII and Φ NO being more predisposed to changes in T a, and Φ NPQ to changes in VPD. 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 PAR, declining thereafter with the other environmental variables, such that the order of influence was greatest for T a, followed by VPD, and then soil water content ( SWC). On a diurnal scale, WTC revealed that all three pathways were influenced by photosynthetically active radiation ( PAR), air temperature ( T a), and vapor pressure deficit ( VPD). ![]() 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. Convergent cross mapping (CCM) was subsequently used to isolate cause-and-effect interactions in PSII-energy partitioning response. 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., Φ PSII, Φ NPQ, and Φ NO, respectively, across a time-frequency domain from hours to years. In a study of PSII processes, we acquired near-continuous, field-based measurements of PSII-energy partitioning in a dominant desert-shrub species, namely Artemisia ordosica, over a six-year period from 2012–2017. 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. Acclimation strategies in xerophytic plants to stressed environmental conditions vary with temporal scales.
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