Contribution to the Substrate Effect Study on the Morpho-Physiological Behaviour of Origanum Majorana l. Under Salt Stress

In Morocco, the process of soil salinisation affects significant areas of the agricultural regions. The aim of this study is to evaluate the substrate influence on the morpho-physiological response of Origanum (Origanum majorana L.) under salt stress (NaCl). To establish a classification of salt stress tolerance thresholds, which is an essential criterion for selecting species to include in a development program for areas impacted by salinity. Oregano was planted in plastic pots measuring 9 cm in diameter and 11 cm in height. Arenosols, sea sand, and vertisols were the substrates utilized in this study. The plants in the pots were watered with 40 ml of sodium chloride solution every 3 days, at concentrations of 6, 9, and 12 g.l−1, along with a control group that did not receive any salt. The parameters that were measured in this study included the length of the plant's aboveground and belowground parts, the root volume, as well as the water content (WC) and soluble sugar content (SS). Each treatment was replicated 10 times. Another experiment was carried out to explore the drainage percentage impact on plant growth. The study involved using pots filled with sea sand and placing them in a vegetable garden with plastic film underneath to restrict drainage. According to the results, the saline treatments had a more significant impact (P = 0.002) on root morphological parameters compared to aerial morphological parameters. Plant cuttings grown in Vertisols showed a slight reduction in growth compared to those planted in arenosols. This is attributed to the effect of salt on the physiological characteristics of the plants, which led to a considerable decline in their water content (P = 0.017). Moreover, there was a significant rise (P = 0.001) in soluble sugar content. These parameters become more pronounced with higher salt concentrations and longer treatment durations. When comparing the three substrates, it can be inferred that under salt stress, arenosol presents optimal characteristics for oregano germination. The depressive effect of salt stress is observed above 6 g.l−1.