In nature, plants are often exposed to a multitude of environmental constraints that severely limit crop productivity. Water deficit is one of the factors that most affects agricultural production. The aim of this work is to evaluate the effect of water deficit on morphology, development, nutritional behavior, as well as chlorophyll fluorescence and certain important metabolic parameters (soluble sugars, organic acids, starch, carotenoid, and vitamin C) of the cultivated tomato (Solanum lycopersicum cv Plovdiv). In this study, the water supply was reduced by 60% compared to control conditions. The conditions of water deficit showed that the size of the different organs (leaves, fruits) was reduced. A reduction in the number, width, and length of the leaves, respectively, 9%, 36%, and 37%, then the leaf surface was also observed. Reduction of fluorescence (Fo, Fm, and Fv) and total index performance were among the other symptoms of plants with water deficiency. For fruit, we observed a significant decrease in diameter, fresh weight, and moisture content during the cell division period, the cell expansion period, and the fruit ripening period. In contrast, the composition of the Plovdiv fruit changed only during cell division and expansion phase. On the other hand, the water deficit induces an increase in the total carotenoid and vitamin C content of the fruits.. Besides, water deficit induced a reduction of fruit size, moisture content, and production dry matter during different phases of development. Decrease levels of soluble sugars and organic acid but increase in vitamin C and carotenoid content.

Ziziphus lotus (L.) Lam. (Rhamnaceae) and Rhus tripartitum or Sumac (Anacardiaceae) are two indigenous species from arid and semiarid regions of Tunisia, characterized by a severe climate where dry seasons are very long. The combined action of anthropogenic factors and climate in arid regions caused a gradual threat of plant assets. In this context, an experimental study of the effects of water stress (0 to −1 MPa) on seeds has identified the water requirements germinal stage of both species. The results showed that both species were able to germinate at relatively low water potentials. However, beyond −0.6 MPa, germination was completely inhibited for R. tripartitum, when it reached for another 50% for Z. lotus. Increasing the concentration of PEG 6000 progressively inhibited germination in both species. Only Z. lotus could be considered tolerant of water stress, because, to −1 MPa, seeds germinated with a rate of 17%. It resulted in that the species Z. lotus presented an adaptive capacity to aridity much greater than that observed for R. tripartitum.

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The present study belongs to the program of biodiversity conservation inside BouHedma national Park. Among the plant species in this park, Rhus tripartita (Ucria) Grande, Anacardiaceae, has several interests. Drought tolerance of R. tripartita seedlings subject to different levels of water stress: T (100% FC; 50% FC (S1); 25% FC (S2) and severe (S3) (No watering) based on photosynthetic gas exchange, chlorophyll content and biochemical analysis (soluble sugars and proline) was examined. A highly significant decrease was recorded in photosynthetic gas exchanges, in particular the stomatal conductance which has been diminished to zero with the intensity of water stress (S3). Similarly, leaf transpiration and photosynthetic assimilation are highly affected. These changes were accompanied by a reduction in chlorophyll pigment content (Cha and total chlorophyll content) and stabilization of Chb content. In contrary to that, the water stress induced an accumulation of organic solutes (soluble sugars and proline) in leaves and roots of young plants.