Changes in henna (Lawsonia inermis L.) morphological traits under different deficit irrigations in the southern Tunisia

Henna plant belongs to continental oases where water shortage constitutes the essential limiting factors of its agricultural production. Lawsonia inermis L. (Lytraceae) is often exposed to severe drought stress in Gabes; a Tunisian arid region. The present study was carried out to evaluate the impact of water stress on the morphology of Tunisian henna plants. Thus, an experiment of four months was carried out under greenhouse at the Institute of Arid Region in Medenine, Tunisia. Henna was exposed to three different irrigation regimes, whereby the plants where irrigated to field capacity (control, T0), 50% of the control (moderate stress, T1) and 25% of the control (severe deficit irrigation, T2). Results showed that, leaf area (LA), leaf number and stem length of henna, decreased in response to the studied stress. The effect of water stress was clearly observed on those parameters. Moderate drought (T1) did not damage henna morphology, and the plants grew better than without water limitation (T0). Furthermore, the water stress-typical responses were shown as time and severity dependent in all the measured parameters. Indeed, lowest water availability treatment (T2) induced significant decrease in total number of leaves, as well as reductions in LA. Under this severe water stress (T2); LA was reduced by 65.79%, compared to control, at 60 days after the initiation of the bioassay. Stem length decreased significantly in the most severe water stress, this reduction was about 44%. Globally, we conclude that henna plant growth decreased progressively to long-term water limitation

Cadmium stress tolerance in plants: a key role of endogenous and exogenous salicylic acid

Cadmium (Cd) has become one of the major metal stresses which pose a serious threat to plants and animals. In this context, endogenous and exogenous salicylic acid (SA) could play an important role in mitigating the uptake of the Cd ions and providing immunity to plants against the heavy metal stress. SA enhances the resistance capacity of contaminated plants, which, however, depends on the metal concentration and the duration of the treatment. Moreover, SA is considered as a promising signal molecule for improving the efficiency of phytoremediation, and, consequently, growing of safe crops in metal polluted areas. The recent developments in the probable mechanisms by which SA could enhance the tolerance of plants to heavy metals and how it could have an effect on phytoremediation of Cd from contaminated soils are discussed

Cellular and signaling mechanisms supporting cadmium tolerance in salicylic acid treated seedlings

This review spotlights on recent indications that recognizes potential cellular mechanisms that may be involved in the tolerance of salicylic acid (SA)-treated seedlings to the presence of cadmium (Cd) in their environment. It appears probable that SA stimulates signaling systems implicated in plant defense-related actions against Cd-induced oxidative stress. These include mechanisms that reduce uptake of metals into the cytosol by extracellular chelation through extruded ligands and binding onto cell-wall constituents. Cellular chelation of metals in the cytosol by a range of ligands (peptides, phytochelatins (PCs)), or increased efflux from the cytosol out of the cell or into sequestering compartments are also key mechanisms improving tolerance. Free-radical scavenging capacities through the activity of antioxidant enzymes or production of peptides and PCs add another line of defense against the toxic effect of Cd. The SA signaling events can be attributed to the extracellular SA perception model in which reactions between SA and apoplastic proteins result in acute oxidative burst under Cd stress