Physiological and Biochemical Behaviour of Gleditsia triacanthos L. Young Seedlings Under Drought Stress Conditions

Drought affects a wide part of the world and constitutes one of the most important limiting factors for growth and development of vegetation cover. Plants evolved several physiological and biochemical mechanisms to cope with biotic and abiotic stresses. Gleditsia L. (Fabaceae) is a small genus of typically spiny trees native to America, Asia, and Africa. Among this genus Gleditsia triacanthos L. belongs to drought-tolerant species and could be a long-term solution for reforestation of dry land areas. The aim of our work is to study the impact water stress on G. triacanthos plants at early stage of development. After six weeks of culture, water stress was imposed during 19 days. A gradual dehydration of the soil caused a progressive drop in the relative water content (RWC) down to 60.54 +/- 2.06% at the end of treatment. On the other hand, G. triacanthos young seedlings show an important osmotic adjustment by an early accumulation of proline. The phenylpropanoids metabolism was also affected by water stress where a significant increase in total polyphenols, total flavonoids and anthocyanin concentrations was recorded. These compounds could play a dual role both in osmoregulation mechanism and antioxidant system. G. triacanthos stressed plants appear to protect its photosystems by increasing carotenoids rate and maintain a stable Chl a/b ratio despite a substantial decrease in chlorophyll pigments (Chl a+b) content.