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To minimize the damaging effects of stresses, plant growth regulators (PGRs) are widely used to sustain the plant life under stress-prone environments. So, a study was carried out to evaluate the response of two canola (Brassica napus L.) cultivars, Dunkeld and Cyclone, to foliar-applied two potential PGRs, nitric oxide (NO) and 5-aminolevulinic acid, under water deficit conditions. In this study, the levels of NO and ALA used were 0.02 and 0.895 mM, respectively. Plants of both canola cultivars were subjected to control (100% field capacity) and water deficit (60% field capacity). Drought stress significantly decreased growth, chlorophyll pigments, relative water contents (RWC), and soluble proteins, while it increased relative membrane permeability (RMP), proline, glycinebetaine (GB), malondialdehyde (MDA), total phenolics, and activities of catalase (CAT) and peroxidase (POD) enzymes in both cultivars. Foliar application of PGRs improved growth, chlorophyll a, GB, total phenolics, CAT activity, and total soluble proteins, while it decreased RMP, MDA, and POD activity in both canola cultivars. Other physio-biochemical attributes such as chlorophyll b, RWC, hydrogen peroxide (HO) and proline contents as well as superoxide dismutase (SOD) activity remained unaffected due to application of PGRs. So, the results of the present study suggest that exogenous application of NO and ALA could be useful to enhance the drought tolerance of canola plants by up-regulating the oxidative defense system, osmoprotectant accumulation, and minimizing the lipid peroxidation.

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The effectiveness of exogenous application of K in ameliorating the adverse effects of waterlogging on cotton plants was assessed under greenhouse conditions. Forty-day-old plants were subjected to continuous flooding for 1 week and then K (60 kg ha–1) was applied either as soil application, foliar spray, or in combination. The waterlogging treatment significantly reduced plant height and fresh and dry biomass, photosynthetic pigments, gas exchange parameters and nutrient accumulation (N, K+, Ca2+) in stem, root and leaves of cotton plants, Although Mg2+ content in roots increased significantly due to waterlogging, it was not affected in stem or leaves. In contrast, Mn2+ and Fe2+ contents generally increased under waterlogged conditions. All water relation parameters were also significantly influenced by waterlogging stress. Waterlogged plants supplemented with K showed a significant improvement in growth, photosynthetic pigments and photosynthetic capacity. Potassium supplementation also improved nutrient uptake of waterlogged plants and resulted in significantly higher accumulation of K+, Ca2+, N, Mn2+ and Fe2+ than those plants not supplied with K. Although all modes of K application were effective in mitigating the inhibitory effects of waterlogging, the combined application through soil + foliar spray yielded the best results and the foliar application (alone) being the least effective.

In this study, water-soaked seeds of sunflower were exposed to He-Ne laser irradiation of different energies to determine whether or not He-Ne laser irradiation caused changes to seed thermodynamic and germination parameters as well as effects on the activities of germination enzymes. The experiment comprised four energy levels: 0 (control), 100, 300 and 500mJ of laser energy and each treatment replicated four times arranged in a completely randomized design. The experimentation was performed under the greenhouse conditions in the net-house of the Department of Botany, University of Agriculture, Faisalabad. The seed thermodynamic parameters were calculated according to seed germination thermograms determined with a calorimeter at 25.8°C for 72h. Various thermodynamic parameters of seed (ΔH, (ΔS)(e), (ΔS)(c), (ΔS)(e) /Δt and (ΔS)(c) /Δt) were affected significantly due to presowing laser treatment. Significant changes in seed germination parameters and enzyme activities were observed in seeds treated with He-Ne laser. The He-Ne laser seed treatment resulted in increased activities of amylase and protease. These results indicate that the low power continuous wave He-Ne laser light seed treatment has considerable biological effects on seed metabolism. This seed treatment technique can be potentially employed to enhance agricultural productivity.

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