Abstract
BackgroundThe 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.ResultsThe 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.ConclusionOcimum 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 abstractEffect 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
Highlights
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 on the essential oil synthesis, especially on the isomerization of the two main compounds methyl chavicol and trans-anethole
The glandular trichome morphology is largely influenced by mycorrhizal and the hydric state of plant; the observations made in this study have demonstrated the existence of two types of peltate glands according to their shape: inflated glands and deflated glands
Our results show that water stress causes a slight increase in essential oil yield; this increase may be a result of the activation of certain enzymes involved in the synthesis of some secondary metabolites implicated in defense
Summary
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 on the essential oil synthesis, especially on the isomerization of the two main compounds methyl chavicol and trans-anethole. Water stress causes significant changes in essential oil yield and composition in several aromatic plants [26]. In Ocimum basilicum plant, water stress increases the essential oil yield and the levels of major compounds (linalool and methyl chavicol) [14]. Solinas et al [30] confirmed that water stress strongly affected the secondary metabolism of plants in a general way and essential oils in a specific way. In our previous work performed on Ocimum gratissimum L. plants, Hazzoumi et al [10] have confirmed that water stress may slightly increase the essential oil yield to an average of 10%
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