Mycorrhizal Inoculation Modulates Root Morphology and Root Phytohormone Responses in Trifoliate Orange under Drought Stress

Jin Liu,Yingning Zou,Cha Guo,Jiadong He,Zili Chen

doi:10.9755/ejfa.2015-11-1044

Jin Liu, Yingning Zou + Show 3 more

Open Access

https://doi.org/10.9755/ejfa.2015-11-1044

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Abstract

Phytohormones can be responsible for activating tolerance responses of drought stress (DS). The present study was done to evaluate the effects of an arbuscular mycorrhizal fungus (AMF), Funneliformis mosseae, on root morphology and root phytohormones levels in trifoliate orange (Poncirus trifoliata) seedlings exposed to well-watered (WW, 75% of maximum water holding capacity) and drought stress (55% of maximum water holding capacity). The six-week DS treatment strongly restricted root mycorrhizal colonization by 27.7%. The DS treatment caused the decrease of total plant biomass and root morphological traits, but the AMF inoculation significantly increased total plant biomass and root total length, projected area, surface area, average diameter, volume, and number of 1st, 2nd, and 3rd lateral root under WW and DS conditions. AMF plants exhibited significantly higher leaf water potential than non-AMF plants exposed to WW and DS. AMF colonization notably regulated the changes in root phytohormone levels: the increase of indole-3-acetic acid (IAA), abscisic acid (ABA), methyl jasmonate (MeJA), and zeatin riboside (ZR) levels under WW condition, and the increase of IAA, ABA, MeJA, ZR, and brassinosteroids (BRs) concentrations under DS conditions. These results concluded that AMF enhanced drought tolerance in trifoliate orange through modulation of root phytohormones and root morphology.

Highlights

Soil drought stress (DS) is one of the important abiotic stresses, strongly limiting crop growth and yield (Nazar et al, 2015)
The experiment consisted of soil water treatments (DS and WW) and arbuscular mycorrizal fungi (AMF) treatments (+AMF and -AMF), which are WW+AMF, WW-AMF, DS+AMF, and DS-AMF, Root Arbuscular mycorrhiza (AM) colonization In this study, there was not root mycorrhizal colonization in the non-AMF treated plants
The DS treatment significantly decreased root colonization by 27.7%, as compared with the WW treatment. Such reduction in root AM colonization by the DS may be due to relatively lower germination of AMF spores, lower carbohydrate supply from the host plant (Wu et al, 2013), and the decrease of root exudates (Fagbola et al, 2001)

Summary

Introduction

Soil drought stress (DS) is one of the important abiotic stresses, strongly limiting crop growth and yield (Nazar et al, 2015). Roots are directly in touch with soil moisture changes, and the damage of plant to drought is firstly in roots. Since plant root is the most crucial organ for water and nutrient absorption, root morphological and physiological responses to DS are an important adaptation to drought (Shan et al, 2015). Evaluating the changes of root physiology and morphology under DS seems to be very important. AM develops well extraradical mycelium spread in the soil around the root to absorb nutrient elements and water from the soil to the fungal partner (Johnson and Gibert, 2015; Zhang et al, 2015).

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