Leaf application of chitosan and physiological evaluation of maize hybrids contrasting for drought tolerance under water restriction

ABSTRACT

Abstract It is a fact that the regions that cultivate the most maize crop do not have fully adequate technologies to measure productivity losses caused by irregularities in water availability. The objective of this study was to evaluate the physiological characteristics of maize hybrids tolerant (DKB 390) and sensitive (BRS 1030) to drought, at V5 growth stage and under water restriction, in order to understand the mechanisms involved in the induction of tolerance to drought by chitosan in contrasting maize genotypes. Plants were cultivated in pots at a greenhouse, and chitosan 100 ppm was applied by leaf spraying. The water restriction was imposed for 10 days and then leaf gaseous exchange and chlorophyll fluorescence were evaluated. The tolerant hybrid (DKB 390) showed higher photosynthesis, stomatal conductance, carboxylation efficiency, electron transport rate, and non-photochemical quenching when chitosan was used. Plants from tolerant genotype treated with chitosan were more tolerant to water stress because there were more responsive to the biopolymer.

RESUMO

Resumo As regiões que cultivam milho como cultura principal ainda não possuem tecnologias adequadas para mensurar as perdas na produtividade decorrentes na disponibilidade irregular de água. O objetivo desse estudo foi avaliar as características fisiológicas de híbridos de milho tolerante (DKB 390) e sensível (BRS1030) à seca, no estádio de crescimento V5 e sob restrição hídrica, para compreender os mecanismos envolvidos na indução de tolerância à seca pela quitosana em genótipos contrastantes. As plantas foram cultivadas vasos na casa de vegetação e a quitosana 100 ppm foi aplicada por pulverização foliar. A restrição hídrica durou 10 dias e foram avaliadas as trocas gasosas e a fluorescência da clorofila. O híbrido tolerante (DKB 390) apresentou maior fotossíntese, condutância estomática, eficiência de carboxilação, taxa de transporte de elétrons e quenching não fotoquímico quando aplicada a quitosana. As plantas do genótipo tolerante tratadas com quitosana foram mais tolerantes ao déficit hídrico porque foram mais responsivas ao biopolímero.