Gas exchange in yellow passion fruit under irrigation water salinity and nitrogen fertilization

José A C Wanderley,Carlos A V De Azevedo,Fagner N Ferreira,Mailson A Cordão,Marcos E B Brito,Robson F De Lima

doi:10.1590/1807-1929/agriambi.v26n2p135-141

Abstract

ABSTRACT The objective of this study was to evaluate the gas exchange of ‘Redondo Amarelo’ passion fruit seedlings under the mitigating action of nitrogen fertilization on the salinity of irrigation water. The experiment was carried out in a greenhouse of the Universidade Federal de Campina Grande (CCTA-UFCG), Campus of Pombal, PB, Brazil, The experimental design was in randomized blocks, split plots, comprising five irrigation water electrical conductivities (plot) (ECw) (0.3; 1.0; 1.7; 2.4 and 3.1 dS m-1) and five doses of nitrogen (subplot) (60; 80; 100; 120 and 140% of 300 mg of N dm-3), in five blocks. Plants were grown in pots (Citropote JKS®) with volume of 3.780 mL, filled with soil, bovine manure, wood shavings in a proportion of 2:1:0.5 (mass basis), respectively. Water with salinity levels was applied in the period from 40 to 85 days after sowing. The internal CO2 concentration, transpiration, stomatal conductance and photosynthesis were measured at 55 and 70 days after sowing. There was an attenuating effect of nitrogen doses at irrigation water electrical conductivities of 1.7 and 2.4 dS m-1 on photosynthesis at 55 DAS. Irrigation water salinity reduces most of the variables evaluated, especially at the highest level studied (3.1 dS m-1).

Highlights

Among the species with production potential in the Brazilian semi-arid region, yellow passion fruit (Passiflora edulis Sims f. flavicarpa Deg.) stands out
Based on the analysis of variance, there was a significant effect of the interaction between irrigation water salinity and nitrogen doses (Table 3) on the gas exchange variables Ci, A, water use efficiency (WUEi) and carboxylation efficiency (CEi) at 55 days after sowing (DAS), whereas transpiration (E) was significantly affected by the individual factors salinity and nitrogen doses, and stomatal conductance was not significantly affected by any of the factors
Significant effect of N levels on Ci values was observed only under irrigation with 2.4 dS m-1 water and a quadratic regression model fitted to the values, with the lowest concentration recorded at 55 DAS, at N dose of 250.58 mg dm-3 of soil (105.87% of the recommendation) with 249.00 mmol of CO2 m-2

Summary

Introduction

Among the species with production potential in the Brazilian semi-arid region, yellow passion fruit (Passiflora edulis Sims f. flavicarpa Deg.) stands out. Among the species with production potential in the Brazilian semi-arid region, yellow passion fruit The Northeast region faces problems with the excess of salts in the irrigation water, compromising the formation and establishment of seedlings and their production (Moura et al, 2017). The excess of salts in the soil solution reduces the osmotic potential, compromising growth and production (Islam et al, 2017). High levels of toxic ions interfere with physiological activity by reducing the rates of transpiration, photosynthesis and internal CO2 concentration (Gong et al, 2018). Silva Neta et al (2020) observed a reduction in photosynthesis, stomatal conductance and transpiration rates in passion fruit seedlings irrigated using water with salinity above 0.3 dS m-1

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