Plant mineral nutrition and Tanzania guinea grass tolerance to stress caused by metals

Abstract

Brazil has about 196 million hectares of grasslands, equivalent to 71% of the country's agricultural area and 23% of the country. The vast majority of pasture areas are occupied by tropical forage grasses and one of the most used species is Panicum maximum, and tanzania guinea grass is one of the largely planted cultivars of this species. The fact that Tanzania guinea grass have high agricultural importance is due to the genetic aspects of such grass, which provide high hardiness and ability to tolerate environments with adverse conditions. This characteristic led this research group to identify other potential uses for this grass, facing the phytoremediation of metals, as such grass features the prerequisites of remediation plants, such as rapid regrowth, accelerated growth (mainly in tropical conditions), large biomass accumulation, large absorption of mineral elements and tolerance to some toxic elements. Soil contamination by metals is widespread environmental problem and the amount of areas contaminated by metals has been growing worldwide in recent years, with a strong impact on the human health, since the metals can enter the food chain. In this proposal five sub-projects are grouped into a broader project, maintaining a unique approach to address mineral nutrition of grasses versus tolerance to stress caused by metals. The objective in this research project is to evaluate the effects of nutrient supply as N (nitrate and ammonium forms), K and S in alleviating the stress induced by the metals Ba, Cd, Cr, Cu and Zn in tanzania guinea grass grown in nutrient solution. Each subproject is designed in factorial, as nutrient rates x metal rates, set in randomized block design, with six replications. The basis for the preparation of nutrient solutions is that of Hoagland and Arnon, and the evaluations are established for two periods of plant growth. Three experimental replications will be used in the production and nutritional evaluations, while the other three will serve in the metabolic determinations. The evaluations will be: visual observations, SPAD readings, photosynthetic activity, morphogenesis and plant dry mass production, concentration and accumulation of nutrients and metals involved in each subproject, as well as the oxidative stress indicators (MDA and H2O2), activities of the enzymes of the antioxidant system (catalase, ascorbate peroxidase, glutathione reductase, guaiacol peroxidase and superoxide dismutase). In particular cases, the enzyme activities (nitrate reductase and gluthamine synthase) and / or concentration of organic compounds (such as amino acids and / or di- and polyamines) related to the nutrient metabolism will also be determined. The statistical analysis will be performed using the SAS software. (AU)