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.

Background Higher absorption and translocation of sodium (Na) and chlorine (Cl) ions in plant tissue can lead to serious physiological and biochemical changes. However, salicylic acid (SA) is a natural signaling molecule responsible for the induction of environmental stress tolerance in plants. Spraying SA could provide protection against several types of stress such as salinity. This study aimed to show the influence of SA spraying (0.5 and 1 mM) on the damaging effects of NaCl toxicity (150 mM) in Salvia officinalis L. plants. Results The results showed that salinity strongly inhibited the growth of aerial and root parts and this inhibition was accompanied by a significant decrease in the production of chlorophyll pigments (by 63%). There was also a significant accumulation of Na, mainly in the roots. This accumulation of Na+ ions was accompanied by a decrease of calcium (Ca), potassium (K) and phosphorus (P) concentrations. However, SA mainly at 0.5 mM, greatly improved plant growth, essential oils and chlorophyll pigments synthesis. Besides, SA led to a decrease in Na content and an improvement in Ca, K and P content in the leaves and roots. Salt stress decreased the essential oil yield from 1.2% (control) to 0.4% (NaCl). Furthermore, gas chromatography–mass spectrometry analysis of essential oils exhibited that the 1,8-cineol, α-thujone, and camphor were identified as the main components of essential oils under all treatments. However, we noted in stressed plant treated or not with SA the appearance of the new majority compound thujanone. Salt stress decreased the major compounds content. SA spray under stress condition increased the content of major compounds compared to stressed plants untreated with SA. The histological study in scanning electron microscopy showed the peltate glands density decreased strongly under NaCl toxicity. However, SA application on stressed plants increased peltate glands density. On the other hand, the glands of stressed plants often show certain anomalies in the morphology: the first anomaly observed was the presence of glandular structures characterized by deformations in the form of small protuberances located on the head of the gland. The second, a less common abnormality is the morphological change in certain glands that change from a spherical to an ovoid shape. On another hand, all these anomalies were not detected in stressed plants sprayed with SA. Therefore, the absence of these anomalies under the effect of SA showed the repairing effect of this growth regulator. Conclusion The findings of the present work suggest that spraying of SA may be useful for improving the plant growth in NaCl-contaminated areas.

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.

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The accumulation of essential oils in plants is generally limited to specialized secretory structures, namely, glandular trichomes (hairs) which are multicellular epidermal glands, found in some families such as Lamiaceae, Asteraceae, and Solanaceae, and which secrete terpenes in an extracellular cavity at the apex of the trichome. Storage of terpenoids in these structures can also be used to limit the risk of toxicity to the plant itself. The morphology of these structures varies according to the conditions of irrigation and also according to the toxicity of intracuticular contents and can be changed with the phenology of the plant. The secretory glands of aromatic plants come in different shapes and sizes, in order to ensure a specific function. This function consists mainly in the protection of different plant organs and the attraction of pollinators. Some scientist classified these glands into peltate hairs and capitate hairs, based on morphological criteria; however, others classified them into short-term glands and long-term glands, based on the mode of secretion. Short-term glands are glands that secrete rapidly to protect young organs. The long-term glands are glands in which the secretory substance accumulates gradually in the subcuticular space and play a role in the protection of mature organs such as the flower, as well as in pollination. According to this definition, he inferred that the capitate hairs are the short-term glands, while the peltate hairs are long-term glands. The difference between these two types of glands consists several aspects like structure, mode of secretion, and timing of secretion. In this object, this chapter includes some microscopic observation to glandular hairs and their combination with mode of secretion, nature of contents, and phenology of plant to give a good comprehension and classification.

During the extraction, a portion of oil remains trapped inside the cells and its release requires the degradation of the walls and cell membranes, especially when the fruits have not reached a maximum maturity which is likely to cause an optimal embrittlement of the parietal structures and cell membrane. This can be done by specific enzymes necessary for the degradation of various cellular barriers. Three different enzyme treatments proteolytic, pectolytic or both are applied on the Moroccan Picholine olives from veraison to maturity of the fruit. The effect of these treatments is evaluated by olive oil diffusion, its phenolic content (PC) and cellular embrittlement determination of olives during ripening. The pectolytic activities lead to a significant increase in both the oil extractability (76 % at veraison and 14 % at maturity) and the PC (up to 50 % of gain compared to the control at veraison and 27 % at maturity). The proteolytic activities applied alone have no significant effect on the extractability and the polyphenols levels of oils. Furthermore, when these proteolytic activities are added in combination with the pectolytic activities, the oil extractability is doubled at veraison and its flowing up to 99 % at maturity that barely 84 % in the control in addition to a richness of polyphenols which can reach 84 % more compared to the control. This increase in polyphenols wealth is probably due to the degradation of cell walls, cellular and vacuolar membranes by enzyme activities releasing PCs that were previously associated with these structures in the drupe.

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