Several recent studies have shown that citric acid/citrate (CA) can confer abiotic stress tolerance to plants. Exogenous CA application leads to improved growth and yield in crop plants under various abiotic stress conditions. Improved physiological outcomes are associated with higher photosynthetic rates, reduced reactive oxygen species, and better osmoregulation. Application of CA also induces antioxidant defense systems, promotes increased chlorophyll content, and affects secondary metabolism to limit plant growth restrictions under stress. In particular, CA has a major impact on relieving heavy metal stress by promoting precipitation, chelation, and sequestration of metal ions. This review summarizes the mechanisms that mediate CA-regulated changes in plants, primarily CA’s involvement in the control of physiological and molecular processes in plants under abiotic stress conditions. We also review genetic engineering strategies for CA-mediated abiotic stress tolerance. Finally, we propose a model to explain how CA’s position in complex metabolic networks involving the biosynthesis of phytohormones, amino acids, signaling molecules, and other secondary metabolites could explain some of its abiotic stress-ameliorating properties. This review summarizes our current understanding of CA-mediated abiotic stress tolerance and highlights areas where additional research is needed.

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Anthropogenic modification of aquatic systems has diverse impacts on food web interactions and ecosystem states. To reverse the adverse effects of modified freshwater flow, adequate management of discharge is required, especially due to higher water requirements and abstractions for human use. Here, we look at the effects of anthropogenically controlled freshwater flow regimes on the planktonic food web of a Ramsar listed coastal lagoon that is under recovery from degradation. Our results show shifts in water quality and plankton community interactions associated to changes in water flow. These shifts in food web interactions represent modifications in habitat complexity and water quality. At high flow, phytoplankton-zooplankton interactions dominate the food web. Conversely, at low flow, bacteria, viruses and nano/picoplankton interactions are more dominant, with a substantial switch of the food web towards heterotrophy. This switch can be associated with excess organic matter loading, decomposition of dead organisms, and synergistic and antagonistic interactions. We suggest that a lower variability in flow amplitude could be beneficial for the long-term sustaining of water quality and food web interactions, while improving the ecosystem health of systems facing similar stresses as the Coorong.

An experiment was conducted at the Bangladesh Agricultural University, Mymensingh during 2008-2009 and 2009-2010 to investigate the impacts of irrigation by saline water (7 dS m 1) at different growth stages of wheat (Triticum aestivum L.). Irrigations at crown root initiation (CRI) (T 1 ) or booting (T 2 ) or flowering (T 3 ) or grain filling (T 4 ) stage by saline water but at other growth stages by fresh water, and irrigation at all growth stages by fresh water (T 5 , control) were applied. Wheat was cultivated in two consecutive years (2008 -2010) under four irrigations and with recommended fertilizer doses. Irrigation water having salinity of 7 dS m 1 did not significantly influence plant height, spike density, spikelets per spike, 1000-grain weight, grain yield, biomass yield and harvest index. The observed diminutive variations among the treatments reflected only non harmful impacts of salinity. Irrigation water salinity, however, significantly reduced spike length and grains per spike in most cases in the first year only. Treatment T 4 producing, on an average over two years, the lowest grain yield (30% less compared to T 5 ), grains per spike, spike length and spikelets per spike revealed that the grain filling stage of wheat was the most sensitive to irrigation water salinity. Although application of one of four irrigations by water of salinity 7 dS m 1 did not impart significant effect on wheat production, it was beneficial to avoid such irrigation at the grain filling stage.

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