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Nickel (Ni) plays an important role in nitrogen metabolism and biological nitrogen fixation in legume plants. Recent studies have demonstrated the beneficial effects of Ni fertilization on soybean nodulation and crop yield; however, the physiological mechanism regulating Rhizobia chemotaxis is not understood. This study aimed to investigate the effects of Ni fertilization on urease activity, flavonoid profile, nodulation, ureide metabolism and its impact on plant growth and yield. We tested fertilization with three Ni doses (0.0, 1.5, and 3.0 mg kg−1) and two soybean genotypes (commercial soybean (TMG 2158) and urease-null (eu3- a), which is a near-isogenic line (NIL), cultivated under greenhouse conditions. Ni fertilization decreased nitrate reductase activity of the NIL and increased the activity for TMG 2158 plants. Ni increased urease activity, breaking down urea into ammonia in the leaves. Ni enhanced daidzein and genistein in roots and nodulation mainly for TMG 2158 plants. There was a positive correlation between daidzein, nodulation, ureides and seed yield in response to Ni fertilization, only to the genotype TMG 2158. These results suggest that Ni plays a role in flavonoids metabolism (mainly daidzein) inducing chemotaxis between soybean plants and rhizobia boosting nodulation and ureide metabolism. Enhanced biological nitrogen fixation induced by Ni fertilization promoted higher nodulation generating more organic nitrogen available to soybean plants resulting in a higher number of pods per plant and seed yield. This study showed important information on how Ni modulates nodulation to increase the yield of commercial soybean plants. • Ni increase nodulation of soybean plants. • Ni enhance biological nitrogen fixation by increased ureides in soybean plants. • Ni fertilization enhanced flavonoid profile mainly daidzein in roots of soybean plants. • Ni increased plant growth and yield of soybean plants. [ABSTRACT FROM AUTHOR]

Plant leaf senescence is regulated by complicated signaling network involving endogenous and environmental factors. Appropriate leaf senescence processing plays important roles in plant growth and stress response and contributes to crop production. The regulatory mechanism of leaf senescence has been widely investigated but still remains elusive. Here we identified the rice transcription factor OsDERF8 as the positive regulator of leaf senescence. Overexpression of OsDERF8 resulted in shortened reproductive stage and earlier leaf senescence, as well as lower grain yield. The knockout lines of OsDERF8 exhibited the "stay-green" phenotype and higher grain yield per plant. Dark induced senescence assays confirmed the function of OsDERF8 in senescence regulation. The leaves of OsDERF8 knockout lines showed less sensitivity to dark treatment with slighter chloroplast damage. OsDERF8 knockout mutants also exhibited less sensitivity to jasmonate (JA) treatment with higher chlorophyll accumulation and less root inhibition. Transcriptomic analysis and promoter-luciferase assays indicated that OsDERF8 regulated multiple senescence related genes, plant hormone related genes and photosynthesis genes. Taken together, OsDERF8 positively regulates rice leaf senescence through JA signaling and might be used for molecular breeding to increase grain yield. • OsDERF8 is identified as the positive regulator of leaf senescence. • Knockout of OsDERF8 resulted in "stay-green" phenotype and higher grain yield per plant. • OsDERF8 is involved in JA signaling and regulates multiple singling genes. [ABSTRACT FROM AUTHOR]

Low availability of zinc (Zn) in soil can limit plant growth and yields. In soils with elevated nickel (Ni) concentrations, which can be due to anthropogenic and geogenic sources, Zn uptake by plants may be inhibited due to competition between the two elements. Here we used a hydroponic system to investigate short-term effects of a wide range of Ni concentrations on Zn uptake and translocation in two spring wheat cultivars at two different levels of Zn supply. Seedlings of the Zn efficient cultivar Back Cross Rushan and the Zn inefficient cultivar Kavir were grown for three weeks in Zn and Ni free nutrient solution and then exposed for two days to either 0, 1, 2, 10, 20, or 40 μM Ni and either 400 nM or 2 μM Zn, before they were harvested. Increasing Ni had no influence on Zn uptake by Kavir at the low Zn level and even slightly enhanced it in Back Cross Rushan, which means that competition by Ni for uptake sites was irrelevant and suggests that Zn uptake was governed by a highly selective uptake system under these conditions. At the high Zn level, Ni had contrasting effects on the uptake of Zn in the two cultivars: Increasing Ni led to a strong increase in Zn uptake in Kavir as opposed to a slight decrease in Back Cross Rushan. The difference indicates that the two cultivars strongly differ in their low-affinity Zn uptake systems. Also the fraction of Zn translocated to the shoots differed between the two cultivars at high Zn supply, while they were very similar at the low Zn level. A strong decrease with increasing Ni solution concentration was observed in Kavir at the high Zn level, whereas there was little Ni dependence of root-to-shoot translocation in Back Cross Rushan. The findings suggest that differences in root Zn compartmentalization may be involved in the different Zn efficiencies of the cultivars. [ABSTRACT FROM AUTHOR]

Salinity stress can be detrimental to the growth and yield of plants. The adverse effects of salinity can be ameliorated with the application of plant growth-promoting endophytic bacteria (PGPEB). The concomitant beneficial effects of exogenous jasmonic acid (JA) in synergism with PGPEB have been well-established; however, its physiological responses under salinity stress have least been understood. In initial screening, PGPEB ( Sphingomonas sp. LK11) was grown with or without JA and sodium chloride. LK11 did not significantly compromise its growth and physiological processes such as biosynthesis of cell wall-related amino acids (aspartate, glutamate, and alanine) during JA treatment under salinity stress. This improved growth performance during salinity stress was mainly due to the expression of glutathione-related genes in LK11 genome. PGPEB counteracting salinity stress can be vital trait to improve crop’s growth and tolerance. In plant-microbe interaction, the interplay of JA and LK11 and their synergistic effects on the growth of wild-type Solanum pimpinellifolium and non-isogenic mutant ( Got-3 ) plants under salinity stress were assessed. Combined LK11-JA applications significantly improved the shoot/root growth in both wild-type and Got-3 tomato plants with or without salinity stress. Combined treatment of LK11-JA responded well to salinity stress by significantly regulating glutathione contents in wild-type and Got-3 plants. Endogenous stress-responsive abscisic acid contents were significantly low in sole and combined LK11-JA applications during salinity as compared to sole saline conditions in both types of plants. Relatively high levels of salicylic acid (SA) and low levels of JA showed the impaired stress tolerance and growth with/without salinity stress in Got-3 plants. In contrast, wild-type plants showed relatively higher JA and lower SA levels in response to combined LK11-JA treatments under salinity stress. These findings indicate that combination of PGPEB and JA is not essentially harmful to plants; however, both can reprogramme crop plant responses to overcome the adverse effects of salinity stress. [ABSTRACT FROM AUTHOR]

Enhanced photosynthesis and biomass have been achieved in C 3 plants by over-expressing NADP dependent malate dehydrogenase (SmNADP-mdh), a C 4 pathway gene from Suaeda monoica. Over-expression of the SmNADP-mdh improved seed germination, seedling growth and accumulation of pigments, sugar, starch and C H N S elements in transgenic tobacco under in vitro conditions. Transgenic tobacco exhibited higher NADP-MDH activity, membrane stability index, photosynthesis efficiency, improved stomatal conductance, carboxylation efficiency, photosystem II (PSII) operating efficiency, electron transfer rate, photochemical quenching and better accumulation of sugar and starch at elevated (1200 ppm) CO 2 (eCO 2). Chlorophyll a fluorescence analysis showed improved pool size, electron transfer, water-splitting activity, photosynthetic performance indexes and efficient working of PSII at eCO 2 in transgenic tobacco over-expressing SmNADP-mdh. The higher expression of antioxidant defence genes indicated better scavenging and lesser accumulation of ROS at eCO 2. Results suggest the potential of a single-cell C 4 halophytic NADP-mdh gene in the development of smart agriculture to improve the photosynthetic efficiency and biomass yield in C 3 plants. • The SmNADP-mdh transgenic tobacco exhibited higher NADP-mdh activity. • SmNADP-mdh gene improved seed germination and seedling growth. • Transgenic tobacco exhibited higher sugar contents under in vitro conditions. • Transgenic tobacco showed higher photosynthesis and carboxylation efficiency. • Transgenic tobacco showed higher contents of pigments and sugar at eCO 2. [ABSTRACT FROM AUTHOR]

Diurnal cycles of photosynthesis and water use in field-grown soybean ( Glycine max ) are tied to light intensity and vapor pressure deficit (VPD). At high mid-day VPD, transpiration rates can lead to a decline in leaf water potential (Ψ leaf ) if leaf hydraulic conductance ( K leaf ) is insufficient to supply water to intercellular airspaces in pace with demand. K leaf is determined by leaf xylem conductivity to water, as well as extra-xylem pathways that are likely mediated by aquaporin water transport proteins. When transpiration demand exceeds the maximum capacity of K leaf to supply water, high tension in the water column can cause cavitation in xylem, and these emboli-blocked xylem vessels reduce water transport and thus lower K leaf . Stomatal conductance typically remains high at mid-day for soybean, suggesting either a mid-day increase in K leaf or that photosynthesis may be maintained at the cost of leaf water status, indicative of an anisohydric water management strategy in soybean. This study examined diurnal fluctuations in K leaf and Ψ leaf , showing a mid-day depression in K leaf in a pattern closely reflecting that of Ψ leaf , indicating that K leaf depression is the result of cavitation in leaf xylem. The diurnal depression of K leaf was not prevented by growth at elevated [CO 2 ], which lowered stomatal conductance. Diurnal transcription patterns of aquaporin genes showed that a total of 34 genes belonging to 4 aquaporin families were expressed in soybean leaves, of which 22 were differentially expressed between at least two time points. These data suggest that mid-day K leaf depression was driven primarily by cavitation at increasing xylem water tensions, but that aquaporins are also likely involved in diurnal regulation of soybean leaf water status. It is further concluded that because soybean photosynthesis is typically sustained at mid-day, K leaf even at the depressed level was in excess of that needed to sustain a stomatal conductance sufficient to prevent depression of photosynthesis in soybean. [ABSTRACT FROM AUTHOR]

• Vegetation spectroscopy was used to evaluate pomegranate/ozone interaction. • Spectral signatures accurately discriminated cultivars and ozone treatments. • Spectral models accurately estimated leaf traits related to oxidative stress. • Leaf traits derived from spectra showed a lower O 3 -tolerance of Wonderful cultivar. Techniques to monitor oxidative stress pre-visually are essential to optimize plant management. Here, we investigated the capability of hyperspectral reflectance (350−2500 nm) to characterize responses of two pomegranate cultivars (Parfianka and Wonderful) under ozone (O 3) episodes at a gradient of concentrations (50, 100 and 200 ppb for 5 h). Analyzing spectral signatures collected rapidly and non-destructively from asymptomatic leaves, we accurately discriminated the two cultivars, as well as controls from plants exposed to O 3 , in particular those under the higher oxidative stress (i.e. 200 ppb). These discriminations were especially accurate in Wonderful at the end of the exposure (5 h from the beginning of exposure; FBE), and at 24 h FBE. Furthermore, using a partial least squares regression (PLSR) approach, we constructed predictive spectral models to estimate from spectra an array of commonly used physiological and biochemical leaf traits related to plant/oxidative stress interaction (photosynthesis, lipid peroxidation, enzymatic and non-enzymatic antioxidants). Most traits were relatively well predicted by spectroscopic models (model goodness-of fit for validation, R2 : 0.77−0.50). Finally, variations of spectra-derived vegetation indices and leaf traits derived from spectra confirmed the lower O 3 -tolerance of the Wonderful cultivar, when exposed to 200 ppb. Overall, the present study shows that the proposed spectroscopic approach can rapidly and non-destructively assess early oxidative stress conditions in plants, and consequently it can help in increasing plant yield and quality. Limitations of the approach are also presented and discussed. [ABSTRACT FROM AUTHOR]

• Cold stress alters morpho-physiological and biochemical processes in plants. • Transcription factors regulate plant development and response towards cold stress. • Different transcription factors regulate cluster of cold responsive gene expression. • Focused research is required for development of resilient plants towards cold stress. Abiotic stresses including low temperature severely affect plant yield and productivity throughout the globe. Low-temperature sensing and signalling is a complex process and significantly alter morphological, physiological, and biochemical processes in plants. To make the plant tolerant towards cold stress, it is a prerequisite to explore the regulatory hubs involved in the intricate networks of cold stress perception, signalling, and response in plants. In recent years, several transcriptional factors have been identified and characterized from different plant species that regulate plant growth, development, and response towards cold stress. Besides, the existence of cross-talk between different transcription factors and plant response towards cold stress has been recognized. In this review, an overview of the current understanding of sensing, signalling, and transcriptional regulation of cold stress has been provided. The review presents the current understanding of the different transcription factors involved in regulating the cluster of the cold-response pathway. Additionally, it reckons that new insights and focus research are required for developing resilient plant species towards low temperature for achieving agricultural sustainability and ensuring food security in the coming years. [ABSTRACT FROM AUTHOR]

• Blueberry plants exhibit a remarkable photosynthetic plasticity that is able to protect fruit yield at up to 50 % defoliation. • Photosynthetic increase following defoliation is driven by stomatal, photochemical and biochemical processes. • Understanding the mechanisms driving photosynthetic adaptation could lead to the development of novel breeding targets to enhance crop yield. In some growing environments blueberry (Vaccimium corymbosum L.) yields exhibit excessive annual variation associated with poor photosynthetic performance. The purpose of this study was to determine how photosynthesis may be affected by demand and to define the mechanisms underpinning photosynthetic plasticity. Manipulation of source-sink ratios revealed that yields were maintained following 50 % defoliation. This was associated with an adaptive increase in photosynthetic capacity mediated via changes in stomatal physiology, photosynthetic electron transport and CO 2 assimilation. Transcripts encoding enzymes of the Calvin-Benson cycle including the Rubisco large subunit, Rubisco activase, phosphoribulokinase and plastid-localised glyceraldehyde phosphate dehydrogenase 3 were more abundant in leaves from partially defoliated plants relative to control plants. Short-term 13CO 2 labelling experiments suggested that partial defoliation did not incur an assimilation penalty although the accumulation of sugars and starch in some organs was reduced. Metabolite profiles of leaves from partially defoliated plants exhibited some differences from those of control leaves, however, no changes in the diurnal content of leaf sugar and starch were observed between treatments. The data highlights the mechanisms by which blueberry leaves adapt to increased demand and demonstrate that photosynthetic plasticity can compensate for significant loss of the photosynthetic area. [ABSTRACT FROM AUTHOR]