Effect of arbuscular mycorrhizal fungi (AMF) and water stress on growth, phenolic compounds, glandular hairs, and yield of essential oil in basil (Ocimum gratissimum L)

Abstract

Background: Water stress is one of the most adverse conditions that may affect growth, and synthesis of essential oils in aromatic and medicinal plants. To overcome these climatic conditions, mycorrhiza is an adaptation strategy developed by plants to help them cope with these adverse conditions. For this purpose, we studied the influence of mycorrhizal fungi (Glomus intraradices) and water stress on the growth of basil plants (Ocimum gratissimum L), the yield of essential oils, and the abundance of glandular hairs. Results: The analyses show that AMF increases the yield of oils with a maximum recorded in stressed mycorrhizal plants (0.33%) and the lowest in non-stressed non-mycorrhizal plants (0.22%). The contents of total phenolic compounds increase in non-mycorrhizal plants under stress (104% in leaves and 97% in the roots) unlike the mycorrhiza which did not stimulate the synthesis of these compounds, Moreover, the contents of chlorophyll pigments decrease with the application of stress in non-mycorrhizal plants (53%) and increase in mycorrhizal plants. The proline contents increased significantly with the application of water stress; this increase is more pronounced in non-mycorrhizal plants than mycorrhizal plants. Conclusions: Water stress limits the growth and leads to a decrease in morphological parameters, this reduction is accompanied by a synthesis of several molecules in particular proline and phenolic compounds, However, the AMF stimulates growth, and drives the water status in plants at an optimal level, thus confirming the role of mycorrhizal symbiosis in plant defense against biotic and abiotic stress.