Abstract
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.
Highlights
The natural environment of plants is composed of a complex set of abiotic stresses and biotic stresses
Leaf water status G. triacanthos foliar Relative Water Content (Fig. 1) of control seedlings was almost constant during 19 days of the experiment around 90.43 ± 2.57%, because the amount of water lost in the process transpiration from leaves seems to be quickly recovered from the regularly watered soil through the roots
We observed a decline in chlorophyll photosynthetic pigments (Chl a+b) in stressed plants, from 18.71 ± 0.62 mg g-1 DW in the first day of experiment to 2.16 ± 0.26 mg g-1 DW on the 19th day of stress
Summary
The natural environment of plants is composed of a complex set of abiotic stresses and biotic stresses. Drought, defined as the occurrence of a substantial water deficit in the soil or in the atmosphere, is an alarming constraint to crop productivity and yield stability worldwide It is the leading environmental stress in world agriculture, causing losses in crop yield probably exceeding losses from all other causes combined. Plants have evolved mechanisms to cope with the stress; such adaptive mechanisms are the results of a multitude of morpho-anatomical, physiological, biochemical, and molecular changes. Among those adaptations, osmoregulation is the most common physiological one, which takes place by reducing cellular water potential and allowing the maintenance of the turgor of the plant under stress. This adjustment involves the accumulation of compatible osmoprotectants such as sugars, nitrogen compounds and compounds derived from
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