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Tuberisation under salt stress of potato vitroplants (Solanum tuberosum L.). In Chott-Mariem (Tunisia), potato plants of Claustar variety, regenerated in vitro from a salt-adapted cal (3 g.l-1 of NaCl) and cultivated in presence of NaCl concentration of 4 g.l-1 have tuberised. These adapted plants were as outstanding as plants regenerated from a control cal and irrigated with NaCl-free water, relating to the number of tubers per plant and the average fresh weight of tuber. However, tubers of NaCladapted plants have shown a reduction in diameter and bud number, and they were affected by a deep fissuring when grown under irrigation with saline water. These results suggest that increasing the level of organic matter above 1 % in soil can be recommended in order to overcome such abnormalities, caused by salinity and saline water use (3 to 4 g.l-1 of NaCl) in the Sahel region (Mahdia, Monastir and Sousse).

In Tunisia, olive tree is traditionally propagated using ovules that delays fruiting period. Using herbaceous cutting allows shortening juvenile period and enhancing productivity. The present study aims to understand the hydraulic characteristics of the conducting system of the olive-tree as related to plant material origin. Experiments were carried out within an olive grove "Chemlali", 17 years old conducted in rain-fed conditions on sandy soil in the arid region of Souassi, Gouvernorate of Mahdia (center-east Tunisia) receiving an average rainfall of 250 mm per year. Olive trees were propagated either by ovules or herbaceous cuttings and planted at 14m x 14m (51 trees/ha). Comparative study was made using parameters of water status (wood density and wood relative water contents) and anatomical observations (conducting vessels, hydraulic diameter, surface of the lumen and theoretical hydraulic conductivity). The dynamic of water use by olive shoots was also studied on both olive plant types under plastic house conditions. Results showed that conducting system characteristics of olive trees issued from herbaceous cuttings permitted a good adaptation to water stress. Those of trees issued from traditional propagating method allowed, relatively, more water loss and less water absorption. [ABSTRACT FROM AUTHOR]