Nitric Oxide as an Attenuator of Ecophysiological Changes in Corn (Zea mays L.) Plants Submitted to Copper Toxicity

Ana Ecidia De Araújo Brito,Cândido Ferreira De Oliveira Neto,Diana Jhulia Palheta De Sousa,Joze Melisa Nunes De Freitas,Jessica Suellen Silva Teixeira,Gerson Diego Pamplona De Albuquerque,Ricardo Shigueru Okumura,Evelyn Fátima Lima De Souza,Gabriel Ito Dos Santos Teixeira

doi:10.5296/jas.v8i4.18157

Abstract

The aim of this work was to evaluate the attenuating effect of the nitric oxide donor (sodium nitroprusside-NPS) on the ecophysiological responses of corn plants (Zea mays L.) submitted to copper toxicity. The corn seeds of the K9606 VIP3 variety were soaked for 48 hours in Germitest with solution containing treatment with sodium nitroprusside Na2 [Fe (CN) 5 NO] 2H2O (0, 200 and 300µM), sodium ferrocyanide Na4Fe (CN) 6 ( 300, 100 and 0 µM) respectively and deionized water (control), sown in buckets with 15 kg of soil incubated for 50 days containing copper concentrations CuSO4.5H2O (0, 60 and 200 mg kg-1). The design consisted of randomized blocks with 12 treatments and 4 repetitions, making a total of 48 plants. in ecophysiological variables: height, leaf area and number of leaves, stem diameter increased by 32, 66% and 11.29% in the treatments with 60 mg kg-1 of copper and 200 mg kg-1 of copper, respectively. There was no effect of treatments on the chlorophyll content measured by the SPAD index and gas exchange. The chlorophyll a fluorescence variables indicate that the concentration of 200 mg kg-1 of copper caused damage to the structure of the PS II reaction center complexes and indicate a slightly protective effect of nitric oxide-NO present in sodium nitroprusside and cyanide present in sodium ferrocyanide, reflecting a smooth functioning of the maximum activity of photosystem II and the electron transport chain.

Highlights

Corn is a fundamental product for Brazilian agriculture, grown in all regions of the country, being the second crop with the highest grain production in the national territory with a large share in exports (USDA, 2019), being the most produced and consumed cereal in the country (Contini et al, 2019), with national average productivity of 5,719 kg ha-1 and 5,682 kg ha-1 in the off-season (CONAB, 2020).Abiotic stresses are the main environmental problems that negatively influence plant growth and development (Dresselhaus and Hückelhoven 2018)
Corn seeds of the K9606 VIP3 variety were soaked for 48 hours in Germitest paper with a solution containing treatment with sodium nitroprusside Na 2 [Fe (CN) 5 nitric oxide (NO)] 2H 2 O (0, 200 and 300μM), sodium ferrocyanide Na 4 Fe (CN) 6 (300, 100 and 0 μM) respectively and deionized water, sown in buckets with 15 kg of soil incubated for 50 days containing copper concentrations CuSO 4 .5H 2 O (0, 60 and 200 mg kg -1)
There was no interaction between the dosages of sodium nitroprusside (SPL) and sodium ferrocyanide (FCS) with copper concentrations or the isolated effect of treatments (Table 1)

Summary

Introduction

Corn is a fundamental product for Brazilian agriculture, grown in all regions of the country, being the second crop with the highest grain production in the national territory with a large share in exports (USDA, 2019), being the most produced and consumed cereal in the country (Contini et al, 2019), with national average productivity of 5,719 kg ha-1 and 5,682 kg ha-1 in the off-season (CONAB, 2020).Abiotic stresses are the main environmental problems that negatively influence plant growth and development (Dresselhaus and Hückelhoven 2018). The phytotoxic effect of heavy metals can be characterized by a decrease in the total phytomass of the plants, in lengths of the aerial part and root and a decrease in the concentration of chlorophyll (Pinto, 2017). The increase in agricultural production raised the need for adding inputs, increasing the levels of heavy metals in soils (Komárek et al, 2010; Ali et al, 2013; Sarwar et al, 2017). Copper (Cu) is classified as a heavy metal, it is considered an essential element in plants (Yruela , 2009), which can become toxic in high concentrations (Rodrigues et al, 2016), causing disturbances in the structure of proteins and inhibition of cell stretching (Yruela , 2013). The excess of Cu can cause damage to the photosynthetic apparatus (González- mendoza et al, 2013), and alterations in photosynthesis can represent the physiological state of the plant (Kalaji et al, 2016)

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