ALBERT

Description: As a brassinosteroid (BR), 24-epibrassinolide (24-epiBL) has been widely used to enhance the resistance of plants to multiple stresses, including salinity. Black locust (Robinia pseudoacacia L.) is a common species in degraded soils. In the current study, plants were pretreated with three levels of 24-epiBL (0.21, 0.62, or 1.04 µM) by either soaking seeds during the germination phase (Sew), foliar spraying (Spw), or root dipping (Diw) at the age of 6 months. The plants were exposed to salt stress (100 and 200 mM NaCl) via automatic drip-feeding (water content ~40%) for 45 days after each treatment. Increased salinity resulted in a decrease in net photosynthesis rate (Pn), stomatal conductance (Gs), intercellular:ambient CO2 concentration ratio (Ci/Ca), water-use efficiency (WUEi), and maximum quantum yield of photosystem II (PSII) (Fv/Fm). Non-photochemical quenching (NPQ) and thermal dissipation (Hd) were elevated under stress, which accompanied the reduction in the membrane steady index (MSI), water content (RWC), and pigment concentration (Chl a, Chl b, and Chl). Indicators of oxidative stress (i.e., malondialdehyde (MDA) and antioxidant enzymes (peroxidase (POD) and superoxide dismutase (SOD)) in leaves and Na+ content in chloroplasts increased accompanied by a reduction in chloroplastid K+ and Ca2+. At 200 mM NaCl, the chloroplast and thylakoid ultrastructures were severely disrupted. Exogenous 24-epiBL improved MSI, RWC, K+, and Ca2+ content, reduced Na+ levels, maintained chloroplast and thylakoid membrane structures, and enhanced the antioxidant ability in leaves. 24-epiBL also substantially alleviated stress-induced limitations of photosynthetic ability, reflected by elevated chlorophyll fluorescence, pigment levels, and Pn. The positive effects of alleviating salt stress in R. pseudoacacia seedlings in terms of treatment application was Diw 〉 Sew 〉 Spw, and the most positive impacts were seen with 1.04 µM 24-epiBL. These results provide diverse choice for 24-epiBL usage to defend against NaCl stress of a plant.

Description: The “Water-Energy-Food Nexus” is one of the present research hotspots in the field of sustainable development. Water resources are the key factors that limit local human survival and socioeconomic development in arid areas, and the water footprint is an important indicator for measuring sustainable development. In this study, the structural dynamics and complex relationships of the water-energy-food system in arid areas were analyzed from the perspective of the water footprint, and the risk characteristics were evaluated. The results show that: (1) Agriculture products and livestock products account for the largest water footprints (〉90%), which is much higher than the water footprints of energy consumption (〈5%). From the water footprint type, the blue water footprint (〉50%) 〉 the grey water footprint (20%–30%) 〉 the green water footprint (〈20%). (2) Since 2000, especially after 2005, while energy consumption drove rapid economic growth, it also led to the rapid expansion of the water footprint in the Manas River Basin. By 2015, the water deficit was relatively serious, with the surface water resource deficit reaching 16.21 × 108 m3. (3) The water-energy risk coupling degree of the water-energy-food system in this basin is comparatively significant, which means that it is facing the dual pressures of internal water shortage and external energy dependence, and it is vulnerable to global warming and fluctuations in the international and domestic energy markets. Thus, it is necessary to adjust the industrial structure through macroeconomic regulation and control, developing new energy sources, reducing the coupling degree of system risks, and achieving sustainable development.