Effect of foliar application of potassium fertilizers on soybean plants under salinity stress

Accumulation of lead (Pb) in agricultural soils has become a major factor for reduced crop yields and poses serious threats to humans consuming agricultural products. The present study investigated the effects of KNO3 seed priming (0 and 0.5% KNO3 ) on growth of maize (Zea mays L.) seedlings exposed to Pb toxicity (0, 1300 and 2550 mg kg-1 Pb).; Results: Pb exposure markedly reduced the growth of maize seedlings and resulted in higher Pb accumulation in roots than shoots. Pretreatment of seeds with KNO3 significantly improved the germination percentage and increased physiological indices. A stimulating effect of KNO3 seed priming was also observed on pigments (chlorophyll a, b, total chlorophyll and carotenoid contents) of Pb-stressed plants. Low translocation of Pb from roots to shoots caused an increased accumulation of total free amino acids and higher activities of catalase, peroxidase, superoxide dismutase and ascorbate peroxidase in roots as compared to shoot, which were further enhanced by exogenous KNO3 supply to prevent Pb toxicity.; Conclusion: Maize accumulates more Pb in roots than shoot at early growth stages. Priming of seeds with KNO3 prevents Pb toxicity, which may be exploited to improve seedling establishment in crop species grown under Pb contaminated soils. © 2017 Society of Chemical Industry.; © 2017 Society of Chemical Industry.

Seed priming with KNO3 mediates biochemical processes to inhibit lead toxicity in maize (Zea mays L.).

The agricultural sustainability concept considers higher food production combating biotic and abiotic stresses, socio-economic well-being, and environmental conservation. On the contrary, global warming-led climatic changes have appalling consequences on agriculture, generating shifting rainfall patterns, high temperature, CO2, drought, etc., prompting abiotic stress conditions for plants. Such stresses abandon the plants to thrive, demoting food productivity and ultimately hampering food security. Though environmental issues are natural and cannot be regulated, plants can still be enabled to endure these abnormal abiotic conditions, reinforcing the stress resilience in an eco-friendly fashion by incorporating fungal endophytes. Endophytic fungi are a group of subtle, non-pathogenic microorganisms establishing a mutualistic association with diverse plant species. Their varied association with the host plant under dynamic environments boosts the endogenic tolerance mechanism of the host plant against various stresses via overall modulations of local and systemic mechanisms accompanied by higher antioxidants secretion, ample enough to scavenge Reactive Oxygen Species (ROS) hence, coping over-expression of defensive redox regulatory system of host plant as an aversion to stressed condition. They are also reported to ameliorate plants toward biotic stress mitigation and elevate phytohormone levels forging them worthy enough to be used as biocontrol agents and as biofertilizers against various pathogens, promoting crop improvement and soil improvement, respectively. This review summarizes the present-day conception of the endophytic fungi, their diversity in various crops, and the molecular mechanism behind abiotic and biotic resistance prompting climate-resilient aided sustainable agriculture.

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Fungal Endophytes to Combat Biotic and Abiotic Stresses for Climate-Smart and Sustainable Agriculture

Secondary metabolites, which have an important role in regulating plants’ relationship with the environment, are affected by soil pollution. Thus, it is important to describe the mechanism in which lemon balm’s (Melissa officinalis L. subsp. officinalis) secondary metabolite accumulation is affected by Cadmium (Cd) stress. For this purpose, lemon balms seedlings that were grown in a controlled environment were exposed to increasing Cd stress and the relationship of lemon balm’s growth and development with EO (essential oil) accumulation were investigated. Morphological, anatomical and physiological parameters of plants’ that were exposed to Cd significantly decreased in parallel with increasing Cd concentration. Impairments in growth and development of lemon balm due to increasing Cd concentrations also affected EO accumulation. However, this destructive effect was most evident on EO accumulation amongst all investigated parameters. Furthermore, amount of EO decreased by 97%, at the highest concentration. In conclusion, Cd might have damaged both the EO producing mechanism and the structures that produce EO by inhibiting plant growth. Therefore it is important to reveal the responses of all parameters which affect EO production of medicinal plants under various stress conditions.

Effects of cadmium-induced stress on essential oil production, morphology and physiology of lemon balm (Melissa officinalis L., Lamiaceae)

The present study was conducted in view of the alarming increase in the concentration of various heavy metals like nickel, copper, lead, cadmium, and arsenic etc., in the soils globally. Little attention has been paid towards the deleterious effect of these heavy metals particularly nickel (Ni) on the performance of pharmaceutically exigent essential oil-bearing crops like menthol mint (Mentha arvensis L.). Menthol mint, a dominant essential oil-producing aromatic plant, is widely cultivated in Uttar Pradesh (India) and has wide applications in pharmaceutical industry. Nickel, an essential micronutrient and a main component of the plant enzyme urease, has vital role in plants and is required in very low amounts for normal growth and functioning of plants. In this study, Ni was applied in the form of NiCl2 with various concentrations of 20, 40, 60, 80, and 100 mg kg−1 Ni of soil and one set was kept as control. Interestingly, Ni at 20 mg kg−1 of soil significantly enhanced all the parameters studied, including constituents of essential oil, particularly menthone and menthyl acetate content. However, a significant reduction was observed in most of the parameters studied with increasing concentrations of Ni. The growth (plant height, fresh and dry weights and herbage yield), biochemical (photosynthetic pigments, chlorophyll fluorescence and carbonic anhydrase activity), and quality parameters (content of essential oil & its active constituents) exhibited a significant reduction over 20 mg kg−1 of soil. However, the activities of enzymatic antioxidants, such as superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX), and the level of proline (PRO) were enhanced at the higher concentrations of Ni. Thus, the present study confirms that Ni applied at 20 mg kg−1 of soil proved beneficial dose, whereas 100 mg kg−1 of soil produced toxic response for the overall growth and development of the mint crop.

Alterations in photosynthetic pigments, antioxidant machinery, essential oil constituents and growth of menthol mint (Mentha arvensis L.) upon nickel exposure

This investigation was carried out to study the effect of foliar application of K as potassium nitrate (KNO3) ability to mitigate the negative impacts of salinity on coriander (Coriander sativum L.) plants. In a greenhouse condition we used three levels of NaCl (0, 40 and 80 mM) applied to the growth medium and three levels of K as KNO3 (0, 50 and 100 mM) adjusted two times as a foliar spray on the plants. Salt stress affected adversely the growth rate, relative content of leaf water, the plant contents of protein and chlorophyll, attributes of gas exchange containing net CO2 assimilation rate, transpiration rate, stomatal conductance and substomatal CO2 concentration, essential oil content and leaf K+, Mg2+, P, Ca2+, N as well as Na+/K+ ratio, while it enhanced the electrolyte leakage, the plant contents of proline and Na+. It can be concluded that the tested parameters were generally positively affected by the foliar application of the KNO3 under saline and control conditions. Supplied with KNO3 treatment significantly showed better tolerance towards salinity. This can be explained by the positive effects of all external KNO3 application on the membrane permeability, photosynthetic activities, relative water content and nutrients balance and concentration under salinity stress conditions.

Al-Adl Hassan

Papers

Foliar application of potassium nitrate affects the growth and photosynthesis in coriander (Coriander sativum L.) plants under salinity