Nitrate: ammonium nutrition alleviates detrimental effects of salinity by enhancing photosystem II efficiency in sorghum plants

Rafael De S Miranda,Natanael S Freitas,Enéas Gomes-Filho,José T Prisco,Rosilene O Mesquita

doi:10.1590/1807-1929/agriambi.v18nsupps8-s12

Rafael De S Miranda, Natanael S Freitas + Show 3 more

Open Access

https://doi.org/10.1590/1807-1929/agriambi.v18nsupps8-s12

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Abstract

ABSTRACT This study was carried out to evaluate if replacement of nitrate (NO3-) by ammonium (NH4+) in the growth medium prevents the damage in the photosystem II (PSII) efficiency and degradation of photosynthetic pigments caused by saline stress in sorghum plants. Sorghum bicolor plants were cultivated in nutrient solutions containing different NO3-:NH4+ ratios (100:0, 75:25, 50:50, 25:75 and 0:100) at a final concentration of 5.0 mM. Salinity was imposed by adding NaCl at 75 mM in the growth medium; and the analysis were performed after ten days of salt stress. The most striking effects of nitrogen regime were observed in plants supplied with equal amounts of NO3-: NH4+ (50:50). Under salt stress, 50:50-grown plants displayed an increase in the photosystem II maximum efficiency (Fv/Fm), which was associated with a lower non-photochemical quenching (NPQ). The superior performance of salt-stressed plants grown in 50:50 ratio was indicated by a higher effective quantum yield of PSII (ΦPSII) and electron transport rate (ETR), as well as increased chlorophyll b and anthocyanins. In conclusion, nitrogen nutrition with same amounts of nitrate and ammonium avoids the degradation of photosynthetic pigments and allows higher PSII efficiency in salt-stressed sorghum plants.

Highlights

Salinity is one of the most severe factors limiting plant growth and yield
This study was carried out to evaluate if replacement of nitrate (NO3-) by ammonium (NH4+) in the growth medium prevents the damage in the photosystem II (PSII) efficiency and degradation of photosynthetic pigments caused by saline stress in sorghum plants
Nitrogen nutrition with same amounts of nitrate and ammonium avoids the degradation of photosynthetic pigments and allows higher

Summary

Introduction

Salinity is one of the most severe factors limiting plant growth and yield. Photosynthesis is a physiological process closely related to crop productivity. Decline of photosynthetic capacity commonly occurs in salt stressed plants, but the underlying mechanisms are complex and remain unclear (Saleem et al, 2011). Photosystem II (PSII) plays an important role in plant photosynthesis, and it often operates abnormally under environmental stress (Havaux, 1992; Baker, 2008). Over-reduction because of electron excess on thylakoid membranes is frequently related under salinity (Szepesi et al, 2005; Aragão et al, 2012). In order to avoid or minimize photo-damage, photo-inhibition and oxidative stress, the plants can deploy several mechanisms such as photorespiration, heat dissipation and the xanthophyll cycle.

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