Mycorrhizal Fungi Regulate Root Responses and Leaf Physiological Activities in Trifoliate Orange

Plant responses to mycorrhization are mediated through secretion of certain signal molecules deposited in mycorrhizosphere in response to environmental stimuli. Responses of four arbuscular mycorrhizal fungi (AMF), namely Claroideoglomus etunicatum, Diversispora versiformis, Funneliformis mosseae, and Rhizoglomus intraradices on root morphology, lateral root (LR) number, and leaf carbohydrates, nitric oxide (NO), and calmodulin (CaM) changes were studied using trifoliate orange. Inoculation response of D. versiformis, F. mosseae, and R. intraradices registered significantly higher plant growth performance (plant height, stem diameter, leaf number, and shoot and root biomass), root morphological traits (total length, projected area, surface area, and volume), and LR number (first-, second-, third-, and forth-order), compared to un-inoculated response. Higher concentrations of CaM, NO, glucose, and fructose and lower sucrose level in leaves were observed in AMF-seedlings than in non-AMF seedlings. Correlation studies further revealed, root morphological traits and LR numbers were significantly negatively correlated with sucrose whereas positively correlated with glucose, fructose, NO, and CaM level in leaves. These results suggested, AMF-induced root modification is routed through sucrose cleavage and partly through changes in NO and CaM.