Abiotic stresses trigger premature leaf senescence by affecting some endogenous factors, which is an important limitation for plant growth and grain yield. Among these endogenous factors that regulate leaf senescence, abscisic acid (ABA) works as a link between the oxidase damage of cellular structure and signal molecules responding to abiotic stress during leaf senescence. Considering the importance of ABA, we collect the latest findings related to ABA biosynthesis, ABA signaling, and its inhibitory effect on chloroplast structure destruction, chlorophyll (Chl) degradation, and photosynthesis reduction. Post-translational changes in leaf senescence end with the exhaustion of nutrients, yellowing of leaves, and death of senescent tissues. In this article, we review the literature on the ABA-inducing leaf senescence mechanism in rice and Arabidopsis starting from ABA synthesis, transport, signaling receptors, and catabolism. We also predict the future outcomes of investigations related to other plants. Before changes in translation occur, ABA signaling that mediates the expression of NYC, bZIP, and WRKY transcription factors (TFs) has been investigated to explain the inducing effect on senescence-associated genes. Various factors related to calcium signaling, reactive oxygen species (ROS) production, and protein degradation are elaborated, and research gaps and potential prospects are presented. Examples of gene mutation conferring the delay or induction of leaf senescence are also described, and they may be helpful in understanding the inhibitory effect of abiotic stresses and effective measures to tolerate, minimize, or resist their inducing effect on leaf senescence.

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Photosynthesis is a very important metabolic pathway for plant growth and crop yield. This report investigated the effect of the herbicide imazethapyr on photosynthesis in the Arabidopsis thaliana pnsB3 mutant (a defect in the NDH pathway) and pgr5 mutant (a defect in the PGR5 pathway) to determine which cyclic electron transport chain (CET) of the NDH and PGR5 pathways is more important for protecting the photosynthetic system under herbicide stress. The results showed that 20 μg/L imazethapyr markedly inhibited the growth of the three ecotypes of A. thaliana and produced more anthocyanins and reactive oxygen species (ROS), particularly in the pgr5 mutant. The chlorophyll fluorescence results showed that PSII was severely damaged in the pgr5 mutant. Additionally, the CET was significantly stimulated to protect the photosynthetic system from light damage in Wt and the pnsB3 mutant but not the pgr5 mutant. The real-time PCR analysis indicated that imazethapyr treatment considerably decreased the transcript levels of most photosynthesis-related genes in the three treated groups. Several genes in the PGR5 pathway were significantly induced in the pnsB3 mutant, but no genes in the NDH pathway were induced in the pgr5 mutant. The gene transcription analysis showed that the pgr5 mutant cannot compensate for the deficit in the PGR5 pathway by stimulating the NDH pathway, whereas the pnsB3 mutant can compensate for the deficit in the CET cycle by regulating the PGR5 pathway. The iTRAQ analyses also showed that the photosynthesis system, glycolysis, and TCA cycle suffered the most severe damage in the pgr5 mutant. All of these results showed that the PGR5 pathway is more critical for electron transfer around PSI than the NDH pathway to resist herbicide stress.

Ambient temperature and nitrogen (N) fertilizer are two of the most important factors that affect rice grain quality. However, less information has been available on the interactive effect of N fertilizer and ambient temperature on grain quality under stressful high temperature (HT). In this article, the effects of panicle N fertilizer, ambient temperature, and their interaction on starch composition, particle size distribution of starch granules, starch physicochemical properties, and storage protein accumulation in milled grains were investigated to clarify the potential role of panicle N fertilizer topdressing in regulating rice grain quality under stressful HT by using a two-factor experiment of three N levels in combination with two temperature regimes. Results showed that appropriate application of panicle N fertilizer could attenuate the adverse effect of HT during grain filling on milling quality and chalky occurrence to some extent, particularly for the effective alleviation of HT-induced decrease in milling quality. However, the topdressing of panicle N fertilizer tended to enhance starch gelatinization enthalpy (ΔH) and its setback viscosity in HT-ripening grains, with the simultaneous decrements in the number and surface area proportions of smaller starch granules under the higher N fertilizer in combination with HT exposure. The effects of higher nitrogen fertilizer and HT exposure on total protein content and gluten composition of grains were additively increased. Hence, the topdressing of panicle N fertilizer exacerbated HT-induced deterioration in cooking and eating quality, rather than alleviating the negative impact of HT exposure on the palatability of cooked rice.