Changes in Photo-Protective Energy Dissipation of Photosystem II in Response to Beneficial Bacteria Consortium in Durum Wheat under Drought and Salinity Stresses

Mohammad Yaghoubi Khanghahi,Sabrina Strafella,Carmine Crecchio

doi:10.3390/app10155031

Mohammad Yaghoubi Khanghahi, Sabrina Strafella + Show 1 more

Open Access

https://doi.org/10.3390/app10155031

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Abstract

The present research aimed at evaluating the harmless dissipation of excess excitation energy by durum wheat (Triticum durum Desf.) leaves in response to the application of a bacterial consortium consisting of four plant growth-promoting bacteria (PGPB). Three pot experiments were carried out under non-stress, drought (at 40% field capacity), and salinity (150 mM NaCl) conditions. The results showed that drought and salinity affected photo-protective energy dissipation of photosystem II (PSII) increasing the rate of non-photochemical chlorophyll fluorescence quenching (NPQ (non-photochemical quenching) and qCN (complete non-photochemical quenching)), as well as decreasing the total quenching of chlorophyll fluorescence (qTQ), total quenching of variable chlorophyll fluorescence (qTV) and the ratio of the quantum yield of actual PSII photochemistry, in light-adapted state to the quantum yield of the constitutive non-regulatory NPQ (PQ rate). Our results also indicated that the PGPB inoculants can mitigate the adverse impacts of stresses on leaves, especially the saline one, in comparison with the non-fertilized (control) treatment, by increasing the fraction of light absorbed by the PSII antenna, PQ ratio, qTQ, and qTV. In the light of findings, our beneficial bacterial strains showed the potential in reducing reliance on traditional chemical fertilizers, in particular in saline soil, by improving the grain yield and regulating the amount of excitation energy.

Highlights

Durum wheat (Triticum durum Desf.) is a very important worldwide food crop widely cultivated all over the Mediterranean basin, where it often suffers from multiple and coincident environmental stresses such as drought and salinity [1,2,3]
The fraction of light absorbed by photosystem II (PSII) that is used in photochemistry (P) increased by the fertilizer application in all non-stress, drought, and salinity conditions, while inversely, the fraction of absorbed light dissipated thermally, including the quantum yield of thermal dissipation in the dark-adapted state (L) and quantum yield of thermal dissipation in the light-adapted state (D), decreased or remained unchanged by the application of plant growth-promoting bacteria (PGPB) inoculation and chemical fertilization
P: the fraction of light absorbed by PSII that is used in photochemistry; L: Quantum yield of thermal dissipation in the dark-adapted state; D: Quantum yield of thermal dissipation in the light-adapted state; Non-photochemical quenching (NPQ): non-photochemical quenching coefficient; qCN: Complete non-photochemical quenching of ChlF; qTV: Total quenching of variable ChlF; qTQ: Total quenching of

Summary

Introduction

Durum wheat (Triticum durum Desf.) is a very important worldwide food crop widely cultivated all over the Mediterranean basin, where it often suffers from multiple and coincident environmental stresses such as drought and salinity [1,2,3]. There are two photo-protection mechanisms for dissipating the excess of light energy absorbed by chlorophyll molecules including re-emitting as light-chlorophyll fluorescence (~2–5% of the absorbed energy) and dissipating as heat (~15–18%), which otherwise may result in the production of harmful molecular species like singlet oxygen [5,6]. These two mechanisms, along with photosynthesis pathway (as a consumer of ~80% of assimilated energy), occur in a competitive way, so that any increase in the efficiency of one will decrease the yield of the other two [7,8].

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