Constitutive and Adaptive Traits of Environmental Stress Tolerance in the Threatened Halophyte Limonium angustebracteatum Erben (Plumbaginaceae)

Utilization of halophytes in saline agriculture and restoration of contaminated salinized soils from genes to ecosystem: Suaeda salsa as an example

Halophytes can be used to screen genes for breeding salt-tolerant crops and are of great value in the restoration of salinized or contaminated soils. However, the potential of halophytes in improving saline soils remains limited. In this paper, based on the latest research progress, we use Suaeda salsa L. as an example to evaluate the value of halophytes in developing saline agriculture including: 1) some defined salt-resistance genes and high-affinity nitrate transporter genes in the species for breeding salt-tolerance and nitrogen efficiency crops; 2) the value of S. salsa and microorganisms from S. salsa in remediation of heavy metal contaminated and organic polluted saline soils; and 3) the capacity to remove salts from soils and the application of the species. In conclusion, S. salsa has high value as a candidate to explore the theoretical base and practical application for utilizing halophytes to improve salinized soils from genes to ecosystem.

Wild Halophytes: Tools for Understanding Salt Tolerance Mechanisms of Plants and for Adapting Agriculture to Climate Change

Halophytes, wild plants adapted to highly saline natural environments, represent extremely useful-and, at present, underutilised-experimental systems with which to investigate the mechanisms of salt tolerance in plants at the anatomical, physiological, biochemical and molecular levels. They can also provide biotechnological tools for the genetic improvement of salt tolerance in our conventional crops, such as salt tolerance genes or salt-induced promoters. Furthermore, halophytes may constitute the basis of sustainable 'saline agriculture' through commercial cultivation after some breeding to improve agronomic traits. All these issues are relevant in the present context of climate emergency, as soil salinity is-together with drought-the most critical environmental factor in reducing crop yield worldwide. In fact, climate change represents the most serious challenge for agricultural production and food security in the near future. Several of the topics mentioned above-mainly referring to basic studies on salt tolerance mechanisms-are addressed in the articles published within this Special Issue.

Effect of Recurrent Salt and Drought Stress Treatments on the Endangered Halophyte Limonium angustebracteatum Erben

Limonium angustebracteatum is an endemic halophyte from the Spanish Mediterranean coastal salt marshes. To investigate this species' ability to cope with recurrent drought and salt stress, one-year-old plants were subjected to two salt stress treatments (watering with 0.5 and 1 M NaCl solutions), one water stress treatment (complete irrigation withholding), or watered with non-saline water for the control, across three phases: first stress (30 days), recovery from both stresses (15 days), and second stress (15 days). Growth and biochemical parameters were determined after each period. The plants showed high salt tolerance but were sensitive to water deficit, as shown by the decrease in leaf fresh weight and water content, root water content, and photosynthetic pigments levels in response to the first water stress; then, they were restored to the respective control values upon recovery. Salt tolerance was partly based on the accumulation of Na+, Cl- and Ca2+ in the roots and predominantly in the leaves; ion levels also decreased to control values during recovery. Organic osmolytes (proline and total soluble sugars), oxidative stress markers (malondialdehyde and H2O2), and antioxidant compounds (total phenolic compounds and flavonoids) increased by various degrees under the first salt and water stress treatments, and declined after recovery. The analysed variables increased again, but generally to a lesser extent, during the second stress phase, suggesting the occurrence of stress acclimation acquired by the activation of defence mechanisms during the first stress period.