Enhancement of Drought Tolerance in Trifoliate Orange by Mycorrhiza: Changes in Root Sucrose and Proline Metabolisms

Fei Zhang,Qiu-Dan Ni,Jia-Dong He,Ying-Ning Zou,Qiang-Sheng Wu

doi:10.15835/nbha46110983

Abstract

Sucrose and proline metabolisms are often associated with drought tolerance of plants. This study was conducted to investigate the effects of two arbuscular mycorrhizal fungi (AMF) species (Funneliformis mosseae and Paraglomus occultum) on root biomass, lateral root number, root sucrose and proline metabolisms in trifoliate orange (Poncirus trifoliata) seedlings under well-watered (WW) or drought stress (DS). All the AMF treatments significantly increased root dry weight, taproot length, and the number of lateral roots in 1st, 2nd, and 3rd class under WW and DS. Mycorrhizal seedlings conferred considerably higher fructose and glucose concentrations but lower sucrose accumulation, regardless of soil water status. Under DS, F. mosseae treatment significantly increased root sucrose synthase (SS, degradative direction) and sucrose phosphate synthase (SPS) activity but deceased root acid invertase (AI) and neutral invertase (NI) activity, and P. occultum inoculation markedly increased root AI, NI, SS, and SPS activities. AMF treatments led to a lower proline accumulation in roots, in company with lower activities of Δ1-pyrroline-5-carboxylate synthetase (P5CS), δ-ornithine aminotransferase (OAT), Δ1-pyrroline-5-carboxylate reductase (P5CR), and proline dehydrogenase (ProDH) in roots. It appears that the AM symbiosis induced greater root development and sucrose and proline metabolisms to adapt DS.

Highlights

Arbuscular mycorrhizal fungi (AMF), a kind of beneficial soil microorganism, can form mycorrhizal association with ~80% of land’s plant species
Mycorrhizal colonization and root performance Drought stress (DS) treatment significantly reduced root colonization by 41% under F. mosseae conditions and by 30% under P. occultum conditions, respectively, as compared with WW treatment (Table 1)
Root sucrose concentrations were notably higher under non-AMF condition than under F. mosseae and P. occultum conditions, regardless of WW or DS, except a nonsignificant difference between non-AMF and F. mosseae under WW (Fig. 1c)

Summary

Introduction

Arbuscular mycorrhizal fungi (AMF), a kind of beneficial soil microorganism, can form mycorrhizal association with ~80% of land’s plant species. Mycorrhizal symbiosis can help the host plant to absorb water and mineral nutrients from the soil to the fungal partner, and AMF get as many as 20% of photosynthetic carbon of the host plant (Parniske, 2008). Such AM symbiosis is a key component in resisting drought stress in various economic crops, including pepper (Davies, 2002), macadamia (Yooyongwech et al, 2013), citrus (Huang et al, 2014), and so on.

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