Abstract
Responses of plants exposed to drought and rewatering have been well documented; however, little is known concerning strategies of psammophyte to drought and rewatering under different soil nutrient regimes. For this study, Pennisetum centrasiaticum under two soil nutrient regimes was subjected to progressive drought and subsequent rewatering. Soil water status, gas exchange characteristics, chlorophyll a fluorescence characteristics as well as biomass traits were measured to investigate ecophysiological responses. Net photosynthesis rate (P n), stomatal conductance (g s), water use efficiency, maximum quantum efficiency of photosynthesis system II (PSII, F V/F M), electron transport flux per cross section (ET0/CS0), and performance index on cross section basis (PICS) were suppressed during drought periods for both nutrient regimes. Meanwhile, leaf intercellular CO2 concentration (C i ), minimal fluorescence intensity (F 0), and dissipated energy flux per cross section (DI0/CS0) increased. Reversible downregulation of PSII photochemistry and enhanced thermal dissipation of excess excitation energy (DI0/CS0) contributed to enhanced photo-protection in drought-stressed plants. Thus, the results indicate that P. centrasiaticum is capable of withstanding and surviving extreme drought events, and the recovery pattern of stressed P. centrasiaticum under both nutrient regimes was similar. However, fertilization increased the biomass and the variation in gas exchange and chlorophyll a fluorescence characteristics during drought periods. Additionally, fertilization accelerated the process of drought and aggravated stress under extreme drought events. Thus, the fertilization strategy used in P. centrasiaticum restoration should be carefully selected—fertilization may not always be beneficial.
Highlights
Water and nutrients are critical resources for plant life and associated physiological processes
Photosynthetic performance and biomass traits during drought stress and recovery Withholding water for 17 and 11 days resulted in a successive limitation of water availability under both nutrient regimes in P. centrasiaticum (Fig. 2)
Following soil water content during the drought periods, leaf photosynthesis rate (Pn) declined in parallel with gs after drought stress for both unfertilized and fertilized P. centrasiaticum (Fig. 3)
Summary
Water and nutrients are critical resources for plant life and associated physiological processes. The supply of water and nutrients in arid and semi-arid ecosystems usually is so low that plants repeatedly suffer from water and nutrient deficiency (Chen et al 2005; Miyashita et al 2005). Desertification processes usually result in significant decreases in soil nutrient levels (Zhou et al 2008; Zhao et al 2009). Water is the crucial limiting factor for plant recruitment, photosynthesis, growth, and net ecosystem productivity in arid ecosystems. It is known that vegetative growth of stressed plants can recover after rewatering (Galle et al 2007; Luo et al 2011), suggesting a reversibility of physiological changes generated by water
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