Corn root morphoanatomy at different development stages and yield under water stress

Abstract

-The objective of this work was to characterize the morphoanatomy of roots and the yield traits of two corn hybrids contrasting for drought tolerance (DKB 390, tolerant; and BRS 1030, sensitive), at different stages of development. Water deficit was imposed for ten days, in a greenhouse, at three growth stages: V5, VT, and R3. These treatments were combined to generate cumulative stress during the plant cycle, as: V5VT, V5R3, VTR3, and V5VTR3. The following were analyzed: root anatomy; proportion of aerenchyma in the cortex; metaxylem number and diameter; phloem thickness; as well as morphological characteristics, such as root length, volume, and surface area, specific root length, length of fine roots, grain yield, and ear length and diameter. Development stage affected the responses to stress: DKB 390 showed the best performance for root morphoanatomy and yield traits, under drought stress, at the reproductive stages, mainly R3, and in the treatments with cumulative stress, especially V5VTR3; whereas BRS 1030 presented higher means for the studied parameters, mainly at the V5 and VT stages, but did not show a higher grain yield under water stress. The greater tolerance of the DKB 390 hybrid to water deficit is probably linked with a memory of pre-exposure to water stress at different growth stages.Index terms: Zea mays, aerenchyma, drought, endoderm, specific root length, WinRhizo. Morfoanatomia radicular em diferentes estádios de desenvolvimento e produtividade do milho sob estresse hídricoResumo -O objetivo deste trabalho foi caracterizar a morfoanatomia radicular e os atributos de rendimento de dois híbridos de milho contrastantes quanto à seca (DKB 390, tolerante; e BRS 1030, sensível), em diferentes estádios de desenvolvimento. A deficiência hídrica foi imposta por dez dias, em casa de vegetação, em três estádios de desenvolvimento: V5, VT e R3. Esses tratamentos foram combinados para gerar estresses acumulativos durante o ciclo da planta, como: V5VT, V5R3, VTR3 e V5VTR3. Foram analisados: anatomia radicular; proporção de aerênquima no cortex; número e diâmetro de metaxilema; espessura do floema; bem como características morfológicas, como comprimento, volume e área de superfície radicular, comprimento específico das raízes, comprimento de raízes finas, rendimento de grãos, e comprimento e diâmetro da espiga. O estádio de desenvolvimento influenciou as respostas ao estresse: DKB 390 apresentou o melhor desempenho quanto à morfoanatomia radicular e aos atributos de rendimento, quando submetido a estresse hídrico, nos estádios reprodutivos, sobretudo em R3, e nos tratamentos acumulativos de estresse, principalmente no V5VTR3; enquanto BRS 1030 apresentou as maiores médias para os parâmetros estudados, principalmente nos estádios V5 e VT, mas não apresentou maior rendimento de grãos sob estresse hídrico. A maior tolerância do híbrido DKB 390 ao estresse hídrico provavelmente relaciona-se à memória de exposição prévia ao estresse hídrico em diferentes estádios de desenvolvimento.Termos para indexação...

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

“…In addition, the stressed chitosan-treated DKB 390 showed significantly higher average mean than BRS 1030 at the same condition. Souza et al (2016) evaluated these two maize hybrids under water stress and observed that the BRS 1030 sensitive hybrid had a more advantageous root system for water absorption (volume, root length) at V5 stage than the tolerant hybrid DKB 390. In advanced stages an inversion of root architecture occurred among hybrids.…”

“…Two maize (Zea mays L.) hybrids with contrasting drought tolerance were used: DKB 390 (tolerant) from Dekalb and BRS 1030 (sensitive) from the Embrapa Breeding Program (Souza et al, 2013a(Souza et al, , 2016. The experiment was conducted in a greenhouse of the Federal University of Alfenas, located in Alfenas, MG (altitude 818 m, latitude 21º25 'South, longitude 45º58' West).…”

“…However, few studies focused on physiological characteristics such as leaf gaseous exchange and chlorophyll fluorescence (Martins et al, 2018). The genotype, growth stage, time of application, concentration and composition of biopolymers must be considered for improving plant responses to these molecules (Dutta et al, 2004;Zargar et al, 2015;Souza et al, 2016). Thus, despite the induction of drought tolerance in maize by chitosan, drought-resistant genotypes may respond differently to chitosan application, as observed for other substances (Ali and Ashraf, 2011;Souza et al, 2013a).…”

“…Drought is limiting in three stages of maize cycle: V5, with five fully expanded leaves; VT, at tasseling; and R3 during grain filling. The drought occurrence in the initial V5 can reduces the productive potential since floral differentiation occurs at this phase (Magalhães and Durães, 2008;Souza et al, 2016;Yan et al, 2016). Nevertheless, in a scenario of climate change, the irregular water availability for the plants in the initial stages of development becomes increasingly evident, with dry periods in rainy seasons.…”

Drought-Tolerant Maize Genotypes Invest in Root System and Maintain High Harvest Index During Water Stress

“…In fact, Souza et al (2016) working with droughttolerant genotypes of maize observed that plants with a better development of root system exhibit higher values of water potential under drought conditions.…”