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This study evaluated the effect of the plant growth regulator trinexapac-ethyl on chemical composition and physiological quality of wheat seeds produced under fertilization for high yield potential. The experiment was performed under completely randomized design with five treatments (0; 200; 400; 600; 800 mL ha-1 of the commercial product Moddus ®) and four repetitions. The plant growth regulator was applied at elongation via foliar spraying. Seeds were harvested at the end of crop cycle. Variables evaluated were 1000 seeds weight, germination and first count of germination, speed of germination index, seedling dry matter, electrical conductivity, accelerated ageing and the contents of total soluble sugars, starch, amino acids and proteins. The first count of germination increased until the higher dose. Electrical conductivity after three hours of imbibition reduced at the doses of 600 mL ha-1 and 800 mL ha-1 , indicating greater seed physiological quality. Starch showed a trend of increase until the dose of 448 mL ha-1 ; amino acids until the dose of 243 mL ha-1 and protein until the dose of 417 mL ha-1. The content of total soluble sugars decreased with the increasing dose of the plant growth regulator. Therefore, wheat seeds produced from plants in which trinexapac-ethyl is applied present higher vigor and greater contents of starch, protein and amino acids, but lower content of total soluble sugars. Our results demonstrate that trinexapac-ethyl can be used for wheat management in seed production fields in the recommended dose (400 mL ha-1) with benefits in seed quality and composition.

Iron toxicity is a major challenge faced by plants in hypoxic soils; however, the consequences of such combined stress for soybean (Glycine max) remain to be determined. Here we assessed the physiological responses of soybean plants exposed to hypoxia and a high concentration of iron. Soil-grown plants cultivated in a greenhouse until the vegetative stage were transferred to a hydroponic system containing nutrient solution and subjected to two oxygen conditions (normoxia (6.2 mg L -1 ) and hypoxia (0.33 mg L -1 )) and two iron concentrations (Fe-EDTA) (0.09 and 1.8 mM) for 72 h. During hypoxia, high concentrations of iron in the nutrient solution resulted in increased iron accumulation in roots and leaves. Under this condition, the concentrations of zinc, nitrogen, potassium, and calcium decreased in the roots, while the concentration of nitrogen and magnesium decreased in the leaves. Additionally, during hypoxia, the higher concentration of iron led to an increase in the activity of the antioxidant enzymes in roots and leaves, while decreased the levels of the photosynthetic pigments, leaf gas exchange, and plant growth. In conclusion, high iron concentration in the root medium results in a considerably more severe damage condition to soybean plants under hypoxia compared to plants grown under low iron availability.

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