Nitric oxide secures reproductive efficiency in heat-stressed lentil (Lens culinaris Medik.) plants by enhancing the photosynthetic ability to improve yield traits.

Rising temperatures, globally and locally, would be detrimental for cool- and summer-season food legumes, such as lentil (Lens culinaris Medik.). Lentil is highly sensitive to supra-optimal temperatures (> 30 °C), particularly during reproductive growth, resulting in flower and pod losses. Thus, suitable strategies are needed to introduce heat tolerance in this legume. Here, we evaluated the efficacy of nitric oxide (NO)-applied as foliar treatment of 1 mM sodium nitroprusside (SNP), twice (one day before final exposure to high temperature, and again five days later)-on heat-stressed (32/20 °C) lentil genotypes, differing in heat sensitivity. As a result of heat stress, endogenous NO increased significantly in heat-tolerant genotypes (46-62% in leaves and 66-68% in anthers, relative to the respective controls), while it decreased in heat-sensitive (HS) genotypes (27-30% in leaves and 28-33% in anthers, relative to the respective controls). Foliar supplementation with SNP markedly increased endogenous NO in leaves and anthers of both the control and heat-treated plants. Heat stress significantly accelerated phenology, damaged membranes, chlorophyll, chlorophyll fluorescence, cellular viability, and decreased leaf water status, carbon fixing and assimilating ability, less so in plants treated with SNP. Heat stress plus SNP significantly improved carbon fixation (as RuBisCo activity) and assimilation ability, (as sucrose concentration (in leaves and anthers), sucrose synthase and vacuolar acid invertase activity, reducing sugars), as well as osmolyte accumulation (proline and glycine betaine) in leaves and anthers. Moreover, SNP-treated plants had significantly less oxidative damage-measured as malondialdehyde and hydrogen peroxide concentrations-in leaves and anthers, relative to the respective control. Reproductive function-assessed as pollen grain germination and viability, stigma receptivity, and ovular viability-decreased markedly in plants exposed to heat stress alone, more so in HS genotypes, but increased significantly with SNP treatment as a consequence of improved leaf and anther function, to significantly increase the pod and seed numbers in heat-stressed lentil plants, relative to heat-stress alone.

Heat Priming of Lentil (Lens culinaris Medik.) Seeds and Foliar Treatment with γ-Aminobutyric Acid (GABA), Confers Protection to Reproductive Function and Yield Traits under High-Temperature Stress Environments.

Gradually increasing temperatures at global and local scales are causing heat stress for cool and summer-season food legumes, such as lentil (Lens culinaris Medik.), which is highly susceptible to heat stress, especially during its reproductive stages of development. Hence, suitable strategies are needed to develop heat tolerance in this legume. In the present study, we tested the effectiveness of heat priming (HPr; 6 h at 35 °C) the lentil seeds and a foliar treatment of γ-aminobutyric acid (GABA; 1 mM; applied twice at different times), singly or in combination (HPr+GABA), under heat stress (32/20 °C) in two heat-tolerant (HT; IG2507, IG3263) and two heat-sensitive (HS; IG2821, IG2849) genotypes to mitigate heat stress. The three treatments significantly reduced heat injury to leaves and flowers, particularly when applied in combination, including leaf damage assessed as membrane injury, cellular oxidizing ability, leaf water status, and stomatal conductance. The combined HPr+GABA treatment significantly improved the photosynthetic function, measured as photosynthetic efficiency, chlorophyll concentration, and sucrose synthesis; and significantly reduced the oxidative damage, which was associated with a marked up-regulation in the activities of enzymatic antioxidants. The combined treatment also facilitated the synthesis of osmolytes, such as proline and glycine betaine, by upregulating the expression of their biosynthesizing enzymes (pyrroline-5-carboxylate synthase; betaine aldehyde dehydrogenase) under heat stress. The HPr+GABA treatment caused a considerable enhancement in endogenous levels of GABA in leaves, more so in the two heat-sensitive genotypes. The reproductive function, measured as germination and viability of pollen grains, receptivity of stigma, and viability of ovules, was significantly improved with combined treatment, resulting in enhanced pod number (21-23% in HT and 35-38% in HS genotypes, compared to heat stress alone) and seed yield per plant (22-24% in HT and 37-40% in HS genotypes, in comparison to heat stress alone). The combined treatment (HPr+GABA) was more effective and pronounced in heat-sensitive than heat-tolerant genotypes for all the traits tested. This study offers a potential solution for tackling and protecting heat stress injury in lentil plants.

Novel derivatives of plant monomeric phenolics: act as inhibitors of bacterial cell-to-cell communication.

The aim of the present study was to synthesize novel active Anti-Quorum sensing derivatives from secondary metabolites viz. Gallic acid, Protocatechuic acid and Vanillic acid present in the plant Bergenia ciliata. Efficacy of all synthesized derivatives have been evaluated on the formation of bacterial biofilm and inhibition of cell-to-cell communication. Anti-Quorum Sensing activity and biofilm formation of all synthesized compounds was measured on biomonitor strain Chrobacterium violaceum, ATCC 12472 using standard paper disk-diffusion assay and quantification of violacein pigment. Among all derivatives, five derivatives 3,4,5-Trihydroxy-benzoic acid methyl ester (9a), 3,4-Dihydroxy-benzoic acid methyl ester (10a), 3,4,5-Tris-(2,4-dichloro-benzyloxy)-benzoic acid methyl ester (12), 3,4,5-Tris-(2,5-dichloro-benzyloxy)-benzoic acid methyl ester (13) and 4-(2,4-Dichloro-benzyloxy)-3-methoxy-benzoic acid methyl ester (15) has shown Anti-Quorum Sensing activity by inhibiting violacein pigment production and biofilm formation without interfering with its growth. The inhibitory effects in violacein pigment production were: positive control (C-30) 72%, (9a), (10a) 47.2%, (12) 27.3%, (13) 40.1% and (15) 22.7% at the concentration of 1 mg/mL and biofilm percent inhibition were found (C-30) 64% (9a) 46.2%, (10a) 40.3%, (12) 18.4%, (13) 35.2%, and (15) 17.3% when compared with the untreated control. Results reveal that synthesized derivatives seem to be good compounds for inhibition and formation of biofilm and AHL-mediated Quorum-sensing mechanism. The present article highlights the importance of derivatives derived from secondary metabolites as potent drug for biofilm formation and inhibition of cell-to-cell communication.

Influence of drought and heat stress, applied independently or in combination during seed development, on qualitative and quantitative aspects of seeds of lentil (Lens culinaris Medikus) genotypes, differing in drought sensitivity.

Terminal droughts, along with high temperatures, are becoming more frequent to strongly influence the seed development in cool-season pulses like lentil. In the present study, the lentil plants growing outdoors under natural environment were subjected to following treatments at the time of seed filling till maturity: (a) 28/23 °C day/night temperature as controls; (b) drought stressed, plants maintained at 50% field capacity, under the same growth conditions as in a; (c) heat stressed, 33/28 °C day/night temperature, under the same growth conditions as in a; and (d) drought + heat stressed, plants at 50% field capacity, 33/28 °C day/night temperature, under the same growth conditions as in (a). Both heat and drought resulted in marked reduction in the rate and duration of seed filling to decrease the final seed size; drought resulted in more damage than heat stress; combined stresses accentuated the damage to seed starch, storage proteins and their fractions, minerals, and several amino acids. Comparison of a drought-tolerant and a drought-sensitive genotype indicated the former type showed significantly less damage to various components of seeds, under drought as well as heat stress suggesting a cross tolerance, which was linked to its (drought tolerant) better capacity to retain more water in leaves and hence more photo-assimilation ability, compared with drought-sensitive genotype.

Impact of heat stress during seed filling on seed quality and seed yield in lentil (Lens culinaris Medikus) genotypes.

BACKGROUND: Lentil, a cool-season food legume, is highly sensitive to high temperatures, which drastically reduce biomass and seed yield. The effects of heat stress on qualitative and quantitative aspects of seeds are not yet known. RESULTS: In this study, we assessed the effects of high temperatures on quantitative and qualitative aspects of seeds in a heat-tolerant (HT; FLIP2009) and heat-sensitive (HS; IG4242) genotypes in a controlled environment. Initially, the plants were raised in a natural, outdoor environment (22/10 °C mean day/night temperature, 1350 µmol m-2 s-1 light intensity, 60-65% relative humidity) from November to mid-February until 50% flowering (114-115 days after sowing). After that, one set of plants was maintained in a controlled environment (28/23 °C, as mean day and night temperature, 500 µmol m-2 s-1 light intensity, 60-65% relative humidity;control) and one set was exposed to heat stress (33/28 °C, as mean day and night temperature, 500 µmol m-2 s-1 light intensity, 60-65% relative humidity), where they remained until maturity. Compared to control, heat stress reduced the seed growth rate by 30-44% and the seed-filling duration by 5.5-8.1 days, which ultimately reduced the seed yield by 38-58% and individual seed weights by 20-39%. Heat stress significantly damaged cell membranes and reduced chlorophyll concentration and fluorescence, and the photosynthetic rate, which was associated with a significant reduction in relative leaf water content. The proximate analysis of seed reserves showed that heat stress reduced starch (25-43%), protein (26-41%) and fat (39-57%) content, and increased total sugars (36-68%), relative to the controls. Heat stress also inhibited the accumulation of storage proteins including albumins, globulins, prolamins and glutelins (22-42%). Most of the amino acids decreased significantly under heat stress in comparison to control, whereas some, such as proline, followed by glycine, alanine, isoleucine, leucine and lysine, increased. Heat stress reduced Ca (13-28%), Fe (17-52%), P (10-54%), K (12.4-28.3%) and Zn (36-59%) content in seeds, compared to the controls. CONCLUSIONS: High temperatures during seed filling are detrimental for seed yield and quality components in lentil genotypes, with severe impacts on heat-sensitive genotypes. © 2018 Society of Chemical Industry.