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A variety of environmental issues are affecting crops all across the world, but rising temperatures are posing the greatest threat. High temperature has been found to drastically inhibit seedling emergence and cause leaf necrosis at the seedling stage, which results in poor plant stand and significantly decreased yields. Polyamines (PAs) are positively charged, low-molecular-weight aliphatic nitrogenous bases present in all living organisms and are involved in various biological processes in plant growth and development, including senescence and response to different abiotic stresses. Putrescine (Put) functions as a master growth regulator that promotes optimal plant development and greater stress tolerance. Here, the current study aimed to elucidate how Put (1 mM) functions in reducing the negative impacts of high temperature on four varieties of Brassica juncea (RH-1707, RH-1708, RH-1566 and RH-1999-42). Exposure of plants to high temperature resulted in decrease in growth parameters, chlorophyll content and relative water content. Simultaneously, increases were found in antioxidant enzymes, electrolyte leakage, lipid peroxidation, hydrogen peroxide content and stomatal density. High temperature more significantly affected varieties RH-1707 and RH-1708, while RH-1566 and RH-1999-42 showed lesser effects. Exogenous application of Put mitigated the negative impacts of high temperature by enhancing growth, chlorophyll content, relative water content and antioxidant enzyme activities and, simultaneously, it reduces oxidative damage and stomatal density. This study specifies that varieties RH-1707 and RH-1708 are sensitive whereas RH-1566 and RH-1999-42 are tolerant of high temperature and provides an insight into the effectiveness of Put in mitigating the effects of high temperature to a significant extent in B. juncea seedlings. [ABSTRACT FROM AUTHOR]

The present study identified inverse relationships between nickel (Ni) levels and growth, photosynthesis and physio-biochemical attributes, but increasing levels of Ni stress enhanced methylglyoxal, electrolyte leakage, hydrogen peroxide, and lipid peroxidation content. Exogenous application of salicylic acid (SA) (10−5 M) ameliorated the ill-effects of Ni by restoring growth, photosynthesis and physio-biochemical attributes and increasing the activities of enzymes associated with antioxidant systems, especially the ascorbate–glutathione (AsA–GSH) cycle and glyoxalase system. In addition, SA application to Ni-stressed plants had an additive effect on the activities of the ascorbate and glutathione pools, and the AsA–GSH cycle enzymes (ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase), superoxide dismutase, catalase, glutathione S-transferase, and osmolyte biosynthesis). This trend also follows in glyoxalase system viz. glyoxalase I and glyoxalase II enzymes. Nevertheless, exogenous SA supplementation restored mineral nutrient contents. Principal component analysis showed that growth, photosynthesis, and mineral nutrient parameters were positively correlated with each other and negatively correlated with antioxidant enzymes and oxidative stress biomarkers. Hence, SA is an alternative compound with potential application in the phytoremediation of Ni. Image 1 • Salicylic acid (SA) ameliorated the nickel (Ni) oxidative stress. • SA modulated physio-biochemical attributes. • SA triggered up-regulation of antioxidant defense and glyoxalase systems. • SA improved growth and photosynthesis in mustard plants. [ABSTRACT FROM AUTHOR]

Biological effects of extracts obtained from the seaweeds Hormophysa cuneiformis (J.F.Gmelin) P.C.Silva and Actinotrichia fragilis (Forsskål) Bùrgesen were investigated using wheat for the improvement of growth and amelioration of the negative effects of soil salinity. Exposure of plants to salt stress resulted in an overall decrease in growth, chlorophyll a and b, carotenoids and soluble sugars, as well as nutrient uptake (i.e., K, Ca and Mg) and K+/Na+ ratio. At the same time, increases were found in proline, total free amino acids, phenolic compounds, malondialdehyde (MDA), Na+ ions, as well as the activities of peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD). Priming wheat seeds with H. cuneiformis and A. fragilis extracts mitigated the negative impacts of salinity by enhancing growth and all the above attributes except MDA and Na+. Treatments with H. cuneiformis or A. fragilis extracts resulted in an increased intensity of the polypeptide bands with 200, 159, 120, 40, and 22 KDa which were already apparent in the control. A. fragilis showed higher effectiveness than H. cuneiformis extracts under both control and stressed regimes. Our results highlight "biofertilizer" properties of two seaweeds and furnish mechanistic insight into their salinity-improvement action, which is pertinent for both applied and basic research. [ABSTRACT FROM AUTHOR]