Abstract
Climatic change, ecosystem imbalance, and soil salinization and desertification are serious obstacles to the restoration of degraded landscapes. Halophyte cultivation could constitute a way of mitigating these problems. Frankenia pulverulenta is used in the remediation and revegetation of areas affected by salinity and as an ornamental plant on saline soils since it can tolerate salt concentrations up to 200 mM NaCl. To increase saline tolerance, different plant growth regulators (auxins, cytokinins, gibberellins, spermidine, and salicylic acid) were tested in hydroponic conditions before the addition of NaCl (300 mM). At 52 days, growth, proline, saline excretion, free polyamines, and ethylene were determined under both saline and non-saline conditions. All growth regulators improved growth in the salt-free pretreatment; however, under conditions of salinity, pretreatment with spermidine (0.5 mM) and then salicylic acid (0.5 mM) were efficient at reversing the inhibitory effect of salt and improved saline excretion in F. pulverulenta. A strong positive correlation of polyamines and proline, and a negative correlation with ethylene, indicate that pretreatments that increase endogenous polyamine content and osmolytes are the most effective in improving salt tolerance of F. pulverulenta and could be used in the technical guidance of the cultivation of this halophyte.
Highlights
Climate change, intensive agriculture, and the poor quality of irrigation water have provoked the degradation, salinization, and desertification of soils, and led to a loss of agriculture areas, lower crop yields and imbalances in ecosystems [1,2]
All plant growth regulators (PGRs) increased the dry weight of the stem + leaves (SLDW)
All PGRs increased the dry weight of the stem + leaves (SLDW) and roots (RDW)
Summary
Climate change (i.e., irregular rainfall and extreme temperatures), intensive agriculture, and the poor quality of irrigation water have provoked the degradation, salinization, and desertification of soils, and led to a loss of agriculture areas, lower crop yields and imbalances in ecosystems [1,2]. Halophytes possess different strategies such as seed heteromorphism, dormancy, seed bank dynamics, and the ability to recover seed germination after exposure to high salinity and so improve the chances of seedling survival in diverse habitats [4,5] These plants have morphological (succulence, salt glands, trichomes or bladders), physiological, and bioquimic attributes (high K+ /Na+ selectivity, Na+ compartmentalization that prevents ionic toxicity, osmolyte synthesis favoring osmotic adjustment, xanthophyll cycle involved in the dissipation of excess excitation energy in the PSII antenna as heat, protecting the photosynthetic machinery, water use efficiency, activation of antioxidant systems (enzymatic and non-enzymatic) to mitigate oxidative damage, and plant growth regulators that modulate transcription and translation, up-regulating antioxidants and osmolytes) that allow them to thrive under adverse conditions [6,7,8]. In terms of abiotic stress tolerance, they delay leaf senescence, control stomata conductance, regulate antioxidant enzymes, and act as signal molecules [9,10,11]
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