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A greenhouse experiment was conducted to examine the alleviating role of thiourea (TU) on antioxidants and some vital physiological attributes in salt-stressed plants of two maize cultivars. The maize cv. DK 5783 performed better than cv. Apex 836 in an initial experiment. Of the six TU levels used in the initial experiment, 400 and 500 mg L-1 were chosen for subsequent studies. The two cultivars were subjected to saline stress (100 mM NaCl) and two levels of TU were applied presowing or as foliage spray. Salt stress suppressed total biomass, maximum fluorescence yield (Fv/Fm), chlorophyll, and leaf water potential (Ψw), but it increased proline, hydrogen peroxide (H2O2), malondialdehyde (MDA), leaf osmolality (LO), membrane permeability (MP), and antioxidant enzymes. Exogenous TU application resulted in considerable increases in the dry weight of salt sensitive and tolerant cultivars (38% and 35%, respectively). TU partially improved the salt tolerance of maize plants; it reduced Na+ but increased N, K+, Ca2+, and P in the maize plants under saline regimes. TU regulated the growth of maize plants under stress conditions by reducing MP, MDA, and H2O2 levels, and altering activities of antioxidant enzymes as well as increasing photosynthetic pigments under a saline regime. [ABSTRACT FROM AUTHOR]

Interactive effects of silicon (Si) and high boron (B) on growth and yield of tomato (Lycopercison esculentum cv. ‘191 F1’) plants were studied. Treatments were: 1) control (B1), normal nutrient solution including 0.5 mg L−1 B (boron), 2) B1 +Si treatment: 0.5 mg L−1 boron plus 2 mM Si, 3) B2 treatment: 3.5 mg L−1 B, 4) B2 +Si treatment: 3.5 mg L−1 B plus 2 mM Si, 5) B3 treatment: 6.5 mg L−1 B, and 6) B3 +Si: 6.5 mg L−1 B plus 2 mM Si. High B reduced dry matter, fruit yield and chlorophyll (Chl) in tomato plants compared to the control treatment, but increased the proline accumulation. Supplementary Si overcame the deleterious effects of high B on plant dry matter, fruit yield and chlorophyll concentrations. High B treatments increased the activities of superoxide dismutase (SOD; EC 1.15.1.1), peroxidase (POD; EC. 1.11.1.7) and polyphenol oxidase (PPO; EC 1.10.3.1). However, supplementary Si in the nutrient solution containing high B reduced SOD and PPO activities in leaves, but POD activity remained unchanged. These data suggest that excess B-induced oxidative stress and alterations in the antioxidant enzymes. Boron (B) concentrations increased in leaves and roots in the elevated B treatment as compared to the control treatment. Concentrations of calcium (Ca) and potassium (K) were significantly lower in the leaves of plants grown at high B than those in the control plants. Supplementing the nutrient solution containing high B with 2 mM Si increased both nutrients in the leaves. These results indicate that supplementary Si can mitigate the adverse effects of high B on fruit yield and whole plant biomass in tomato plants. [ABSTRACT FROM PUBLISHER]

Abstract: The effect of supplementary phosphorus on growth and yield of tomato (Lycopersicon esculentum cv. Target F1) plants grown at high boron was investigated. The results showed that high B reduced dry matter, fruit yield and chlorophyll content. High B plus 0.5 or 1mM P increased plant dry matter, fruit yield and chlorophyll concentrations as compared to high B treatments only. Membrane permeability was not increased significantly due to high B application. In the leaves of plants grown at high boron treatments, superoxide dismutase (SOD), peroxidase (POD) and polyphenol oxidase (PPO) levels were increased. However, supplementary P to nutrient solution containing high B reduced the activities of the earlier mentioned enzymes in leaves but their levels were still higher than those at the control treatments. The study revealed that B status affects the activities of some antioxidant enzymes examined. Boron (B) concentrations increased in leaves and roots in the highest external B treatment as compared to the control treatment. Concentrations of Ca, P and K were significantly lower in the leaves of plants grown at high B than those in the control plants. Supplemented nutrient solution containing high B with 0.5 or 1mM P increased the tissue concentrations of nutrients. These results indicate that supplementary P can mitigate the adverse effects of high B on fruit yield and growth in tomato plants. [Copyright &y& Elsevier]