Synergism between calcium nitrate applications and fungal endophytes to increase sugar concentration in Festuca sinensis under cold stress.

Lianyu Zhou,Richard D Johnson,Chunjie Li,James F White

doi:10.7717/peerj.10568

Abstract

Epichloë endophytes have been shown to increase tolerance to biotic and abiotic stresses in many cool-season grasses. We investigated the impact of endophyte infection of Festuca sinensis, on root metabolic activity, photosynthetic pigments, leaf relative water content (RWC) and soluble carbohydrates in a field experiment carried out during chilling and irrigation with Ca(NO3)2. A highly significant (P < 0.001) correlation for Epichloë endophytes was observed for root metabolic activity. Ca(NO3)2 affected very significantly root metabolic activity and total chlorophyll (P < 0.001). Low temperature led to highly significant (P < 0.001) reductions in root metabolic activity, RWC, total chlorophyll, chlorophyll a/b ratio, and carotenoid contents. In addition, the fructose concentrations of shoots were greater on the 14th day than on the 28th day and before treatment, whilst the glucose concentration of roots was much higher on the 28th day than before and after 14 days treatment. Moreover, our results indicated that the addition of calcium nitrate contributed to higher levels of total chlorophylls, soluble sugars, sucrose, fructose or glucose in the shoots and roots in both E+ and E- plants during long periods of chilling. These results suggest that Epichloë endophyte infection and/or exogenous calcium nitrate can confer better tolerance to cold stress.

Highlights

Low temperature is one of the main abiotic stresses that retards growth and development of many plants (Nayyar, Bains & Kumar, 2005)
Significant (P < 0.001) effects of Epichloë endophyte, calcium nitrate treatment, or treatment time were found on root metabolic activity of F. sinensis
In this study we compared the changes in physiological performance and soluble sugar concentrations in 5-month-old F. sinensis E+ and E- plants when supplied with exogenous chlorophyll a (Ca)(NO3)2 to elucidate the mechanism of plant survival during cold winter conditions

Summary

Introduction

Low temperature is one of the main abiotic stresses that retards growth and development of many plants (Nayyar, Bains & Kumar, 2005). Exogenous calcium has been demonstrated to confer protection against cold stress by alleviating chlorophyll and carotenoid degradation (Schaberg et al, 2011; Feng et al, 2010), increasing antioxidant enzyme activity, increasing root metabolic activity (Li, Gao & Liu, 2011; Feng et al, 2010; Liu et al, 2012), and enhancing sugar contents (Halman et al, 2008; Hawley et al, 2006). Cold stress promotes endogenous Ca2+ level in leaves and roots, exogenous application of Ca2+ increased endogenous Ca2+ content under control and cold conditions (Shi et al, 2014)

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