Foliar application of potassium nitrate induces tolerance to water deficit in pre-flowering sorghum plants

Roniel Geraldo Ávila,Eder Marcos Da Silva,Aldo Max Custódio,Paulo César Magalhães,Amauri Alves De Alvarenga,Adriano Jakelaitis,Thiago Corrêa De Souza,Caroline Oliveira Dos Reis

doi:10.4025/actasciagron.v44i1.53069

Abstract

The objective of this study was to evaluate the the ability of foliar application of potassium nitrate (KNO3) to induce water deficit tolerance in sorghum plants (Sorghum bicolor cv. P898012) subjected to water deficit at pre-flowering. The experiment was conducted under greenhouse conditions with 4 treatments: field capacity (FC), water deficit (WD), field capacity + KNO3 (FC + KNO3), and water deficit + KNO3 (WD + KNO3). Two foliar applications of 3% (m/v) KNO3 were made, the first on day zero of stress and the second on the fifth day. All analyses were performed after 12 days of stress (end of stress). Foliar application of KNO3 to irrigated plants led to increases in relative chlorophyll content, photosynthetic rate, stomatal conductance, transpiration, and carboxylation efficiency. It also induced increases in leaf concentrations of P, Mg, S, Cu, and Fe, in addition to height growth. Under water deficit conditions, plants treated with KNO3 presented higher relative chlorophyll content, leaf area, photosynthetic rate, stomatal conductance, transpiration, carboxylation efficiency, and higher levels of P, K, Mg, S, Cu, and Fe than those not treated with KNO3. The morphometry of the root system was not altered by the treatments. In addition, plants treated with KNO3 under water deficit conditions showed higher growth and a grain yield 32.2% higher than those that did not receive KNO3. These results demonstrated that KNO3 applied to the leaves induced water deficit tolerance in sorghum plants subjected to severe water stress at pre-flowering.

Highlights

After 12 days of treatment, all plants that were under water deficit (WD) presented a reduction in leaf water potential in relation to those that remained with irrigation at the field capacity level (FC), regardless of the treatment (Figure 1A)
KNO3 induced an increase in the chlorophyll biosynthesis of the plants at FC and guaranteed the maintenance of the plants under WD since, under FC, plants treated with KNO3 had higher chlorophyll indices than those not treated
Among the plants that were under stress conditions, those treated with KNO3, presented a higher relative chlorophyll content and had values of this variable similar to those that were under FC

Summary

Introduction

The major challenge for this half of the century is to produce more food with reduced water resources (Foley et al, 2011); this will generate selection pressure, requiring crops that are highly adapted to water deficit. Among these food crops, sorghum (Sorghum bicolor Moench L.), which originated in tropical Africa and is a food source for more than 500 million people in 98 countries, is a cereal with great adaptation to drought, when compared to other crops (Pennisi, 2009). Due to the poor rainfall distribution, studies and techniques that search for tolerant genotypes are necessary because sorghum shows good tolerance to water deficit, losses due to water stress recur (Elhag & Zhang, 2018)

Objectives

Methods

Results