Physiological and biochemical role of nickel in nodulation and biological nitrogen fixation in Vigna unguiculata L. Walp.

Studies on the role of nickel (Ni) in photosynthetic and antioxidant metabolism, as well as in flavonoid synthesis and biological fixation nitrogen in cowpea crop are scarce. The aim of this study was to elucidate the role of Ni in metabolism, photosynthesis and nodulation of cowpea plants. A completely randomized experiment was performed in greenhouse, with cowpea plants cultivated under 0, 0.5, 1, 2, or 3 mg kg-1 Ni, as Ni sulfate. In the study the following parameters were evaluated: activity of urease, nitrate reductase, superoxide dismutase, catalase and ascorbate peroxidase; concentration of urea, n-compounds, photosynthetic pigments, flavonoids, H2O2 and MDA; estimative of gas exchange, and biomass as plants, yield and weight of 100 seeds. At whole-plant level, Ni affected root biomass, number of seeds per pot, and yield, increasing it at 0.5 mg kg-1 and leading to inhibition at 2-3 mg kg-1 (e.g. number of seeds per pot and nodulation). The whole-plant level enhancement by 0.5 mg Ni kg-1 occurred along with increased photosynthetic pigments, photosynthesis, ureides, and catalase, and decreased hydrogen peroxide concentration. This study presents fundamental new insights regarding Ni effect on N metabolism, and nodulation that can be helpful to increase cowpea yield. Considering the increasing population and its demand for staple food, these results contribute to the enhancement of agricultural techniques that increase crop productivity and help to maintain human food security.

Selenium increases photosynthetic capacity, daidzein biosynthesis, nodulation and yield of peanuts plants (Arachis hypogaea L.).

This study aimed to investigate the roles of selenium (Se) application on the profile of photosynthetic pigments, oxidant metabolism, flavonoids biosynthesis, nodulation, and its relation to agronomic traits of peanut plants. Two independent experiments were carried out: one conducted in soil and the other in a nutrient solution. When the plants reached the V2 growth stage, five Se doses (0, 7.5, 15, 30, and 45 µg kg-1) and four Se concentrations (0, 5, 10, and 15 µmol L-1) were supplied as sodium selenate. The concentration of photosynthetic pigments, activity of antioxidant enzymes and the concentration of total sugars in peanut leaves increased in response to Se fertilization. In addition, Se improves nitrogen assimilation efficiency by increasing nitrate reductase activity which results in a higher concentration of ureides, amino acids and proteins. Se increases the synthesis of daidzein and genistein in the root, resulting in a greater number of nodules and concentration and transport of ureides to the leaves. Se-treated plants showed greater growth, biomass accumulation in shoots and roots, yield and Se concentration in leaves and grains. Our results contribute to food security and also to increase knowledge about the effects of Se on physiology, biochemistry and biological nitrogen fixation in legume plants.

Can the application of low doses of paraquat induce the hormesis effect in upland rice?

This study aimed to verify the effects of the application of paraquat low doses on the agronomic traits of upland rice in two different application modes. The treatments consisted of a combination of 6 low doses of the paraquat (0; 20; 40; 60; 80 and 120 g a.i. ha-1) and 2 application modes of low doses a) single application performed between active tillering and floral differentiation b) application split into four applications, the first being carried out at the beginning of active tillering, the second being carried out between active tillering and floral differentiation, the third application carried out after floral differentiation and the fourth application carried out after flowering with 25% of the dose in each application. The application of low doses of paraquat does not promote the hormesis effect of upland rice. The increase in the frequency of the plant to the herbicide caused by the splitting of applications negatively affected the plant height, number of spikelets per panicle, yield, leaf nitrogen and sulfur as the low doses levels were increased. On the other hand, there is no influence of paraquat low doses levels when single applied to the agronomic traits of upland rice.

Tecnologic Development on Pleurotus Cultivation: Specific Practices Used in Brazil

HIGHLIGHTS P. ostreatus and P. sapidus are the most productive species under the evaluated conditions. Different growing systems are suitable for the production of P. ostreatus var. Florida. Temperature control level affects differently the P. ostreatus var. Florida isolates. Environmental and strain factors affect yield and production parameters of P. ostreatus var. Florida.

Abstract In Brazil, Pleurotus is the most important mushroom produced especially P. ostreatus var. Florida. In this country as in many others, the great potential for mushroom cultivation remains unexplored. Therefore, it is very important to develop new studies that allow optimizing its production. The aims of the manuscript were: i) to evaluate the productivity of six different species of Pleurotus (P. citrinopileatus; P. djamor; P. ostreatus; P. ostreatus var. Florida; P. pulmonarius; P. sapidus); ii) to measure the effect of three different environmental conditions during cultivation of three isolates of P. ostreatus var. Florida. As results, P. ostreatus and P. sapidus were the most productive isolates under the evaluated conditions. Different environments produced variable effects according to the P. ostreatus var. Florida isolates, being possible to observe a highly plastic strain (POF 02/18), a highly sensitive strain (POF 03/18) and a strain with variable responses (POF 01/18).