Anatomia foliar de dois genótipos de milho submetidas à seca e sua influência no crescimento e nas trocas gasosas

Abstract

Maize (Zea mays L.) is the primary cultivated cereal in the world, and its production is facing significant challenges due to drought increase in the frequency and intensity. In this context, plants present a range of morphophysiological modifications for the resistance to drought. Thus, more studies are needed to identify genotypes that are more resistant to water deficiency due to climatic changes, aiming at the discovery of morphophysiological modifications mediating tolerance or sensitive (avoidance) responses to drought. The objective of this study was to evaluate the morphophysiological changes of leaves of two maize genotypes DKB 390 (Tolerant) and BRS 1010 (Sensitive) in the vegetative stage under water deficit, which contribute to the identification of tolerance or sensitivity (avoidance) to drought. The experiment was carried out using two contrasting maize genotypes in relation to dry resistance, designed in a 2x2 factorial scheme. It was composed of two maize genotypes (DKB 390 tolerant and BRS 1010 sensitive) and two irrigation systems: irrigated plants (PI) and plants under water deficiency (PDH). The plants were grown in a greenhouse at 25 ± 2 °C. Plants under water deficiency were maintained at 30% of the field capacity, and irrigated treatments were maintained at 100% of the field capacity, in the experimental period of 30 days. After the experimental period, growth, gas exchange, and quantitative anatomical analysis were performed. The water deficit reduced plant growth, decreased the leaf water potential, and reduced vascular tissue in both genotypes. The genotype BRS 1010, which is considered sensitive, invested in drought avoidance mechanism due to its sensitivity, through morphophysiological modifications, improving the ability in water use efficiency by reduction in perspiration, stomatal conductance, increase in density (stomatal resistance), and higher root/shoot ratio. The DKB 390 genotype, which is considered drought tolerant, invested mainly in tolerance mechanisms, through its normal physiological activities even under conditions of water deficit. Moreover, there was the maintenance of the cellular turgor at the level of aerial part for maintenance of the cells, which did not lead to photoinhibition and leaf damage.