Effect of arbuscular mycorrhizal fungi and water stress on ultrastructural change of glandular hairs and essential oil compositions in Ocimum gratissimum

Abstract

Abstract Background The objective of this work is to study the influence of arbuscal mycorrhizal fungi (Glomus intraradices) and water stress on the ultrastructural change of basil glandular hair and also on the essential oil synthesis, especially on the isomerization of the two main compounds methyl chavicol and trans-anethole. Results The results of this study show that mycorrhization increases the yield of essential oils, with a maximum recorded in mycorrhizal stressed plants (0.33%) and a minimum among non-mycorrhizal unstressed plants (0.22%). Oxygenated monoterpenes represent the main family of essential oils. Furthermore, the chemical composition of these essential oils changed under the condition in which the plant is. However, the main compound methyl chavicol was found to be at maximum concentration (93%) in mycorrhizal stressed plants and minimum in non-mycorrhizal stressed plants (84%). Contrariwise, its isomer trans-anethole reached the maximum (8%) among non-mycorrhizal non-stressed plants and minimum (2%) in non-mycorrhizal stressed plants. Conclusion Ocimum gratissimum L. leaves showed the presence of two types of peltate glands: the first one with 4 secreting cells and the second with 8 secreting cells. The diameter of these glands changed with the hydric state of plants; in the absence of mycorrhization, stress causes a decrease in the extracellular cavity diameter of glandular trichomes and their deflation which would cause a concentration of essential oil in the glands. Graphical abstract Effect of arbuscular mycorrhizal fungi and water stress on essential oil yield and compositions by the change in some endogenous plant growth regulators and glandular hairs morphology and density in Ocimum gratissimum

Keywords

• AMF
• Glomus intraradices
• m-Chavicol
• t-Anethole
• Glandular trichomes
• Water stress