Halophytes, plants that survive to reproduce in environments where the salt concentration is around 200 mM NaCl or more, constitute about 1% of the worlds flora. Some halophytes show optimal growth in saline conditions; others grow optimally in the absence of salt. However, the tolerance of all halophytes to salinity relies on controlled uptake and compartmentalization of Na+, K+ and Cl- and the synthesis of organic compatible solutes, even where salt glands are operative. Although there is evidence that different species may utilize different transporters in their accumulation of Na+, in general little is known of the proteins and regulatory networks involved. Consequently, it is not yet possible to assign molecular mechanisms to apparent differences in rates of Na+ and Cl- uptake, in root-to-shoot transport (xylem loading and retrieval), or in net selectivity for K+ over Na+. At the cellular level, H+-ATPases in the plasma membrane and tonoplast, as well as the tonoplast H+-PPiase, provide the transmembrane proton motive force used by various secondary transporters. The widespread occurrence, taxonomically, of halophytes and the general paucity of information on the molecular regulation of tolerance mechanisms persuade us that research should be concentrated on a number of model species that are representative of the various mechanisms that might be involved in tolerance.

Salinity tolerance in halophytes

Diversity, distribution and roles of osmoprotective compounds accumulated in halophytes under abiotic stress

In vegetables, tolerance to drought can be improved by grafting commercial varieties onto drought tolerant rootstocks. Grafting has emerged as a tool that copes with drought stress. In previous results, the A25 pepper rootstock accession showed good tolerance to drought in fruit production terms compared with non grafted plants and other rootstocks. The aim of this work was to study if short-term exposure to drought grafted plants using A25 as a rootstock would show tolerance to drought now. To fulfill this objective, some physiological processes involved in roots (rootstock) and leaves (scion) of grafted pepper plants were analyzed. Pepper plants not grafted (A), self-grafted (A/A) and grafted onto a tolerant pepper rootstock A25 (A/A25) were grown under severe water stress induced by PEG addition (-0.55 MPa) or under control conditions for 7 days in hydroponic pure solution. According to our results, water stress severity was alleviated by using the A25 rootstock in grafted plants (A/A25), which indicated that mechanisms stimulated by roots are essential to withstand stress. A/A25 had a bigger root biomass compared with plants A and A/A that resulted in better water absorption, water retention capacity and a sustained CO2 assimilation rate. Consequently, plants A/A25 had a better carbon balance, supported by greater nitrate reductase activity located mainly in leaves. In the non grafted and self-grafted plants, the photosynthesis rate lowered due to stomatal closure, which limited transpiration. Consequently, part of NO3- uptake was reduced in roots. This condition limited water uptake and CO2 fixation in plants A and A/A under drought stress, and accelerated oxidative damage by producing reactive oxygen species (ROS) and H2O2, which were higher highest in their leaves, indicating great sensitivity to drought stress and induced membrane lipid peroxidation. However, drought deleterious effects were slightly marked in plants A than in A/A. To conclude, the A25 rootstock protects the scion against oxidative stress, which is provoked by drought, and shows better C and N balances that enabled the biomass to be maintained under water stress for short-term exposure, with higher yields in the field.

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Pepper Rootstock and Scion Physiological Responses Under Drought Stress.

Influence of biological, environmental and technical factors on phenolic content and antioxidant activities of Tunisian halophytes.

Using euhalophytes to understand salt tolerance and to develop saline agriculture: Suaeda salsa as a promising model

Clustering of halophytes from an inland salt marsh in Turkey according to their ability to accumulate sodium and nitrogenous osmolytes

In this study, Na+, Cl–, K+, Ca2+, chlorophyll and proline levels and the rate of lipid peroxidation level in terms of malondialdehyde (MDA), were investigated in tissues of 15 different tomato cultivars in salt tolerance. As a material, 15 different tomato genotypes were used during a 28-day period and 150 mmol NaCl was applied in sand culture. While one of tomato genotypes was a wild type belonging to Lycopersicum peruvianum, the others were local genotypes belonging to Lycopersicum esculentum L. Better NaCl-stress tolerance in salt-tolerant cultivars as compared to salt-sensitive cultivars observed during the present investigation might be due to restriction of Na+ accumulation and ability to maintain high K+/Na+ ratio in tissue. The chlorophyll level decreased more in salt-sensitive than in salt-resistant cultivars, whereas proline level increased more in salt-sensitive than in salt-resistant cultivars. The exposure to NaCl induced a significant increase in MDA level in both salt-resistant and salt-sensitive cultivars; yet, MDA level was higher in salt-sensitive cultivars. As a result, exclusion or inclusion of Na+, Cl–, K+ and Ca2+ MDA levels, chlorophyll and proline levels may play a key protective role against stress and these features can be used as identifiers for tolerance to salt.

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Salt resistance of tomato species grown in sand culture.

The effects of cold-shock treatment of Capsicum annuum L. buds at 4iC for 48 or 96 h, and the addition of 0.25% activated charcoal on embryo formation were examined. Murashige and Skoog (MS) basal nutrient medium was supplemented with combinations of 4 mg l -1 naphthalene acetic acid (NAA) and 1 mg l -1 benzyladenine (BA) or 1 mg l -1 NAA and 4 mg l -1 BA, together with 0.8% (w/v) agar and 3% (w/v) sucrose. The highest number of embryos was obtained from the control anthers which were not subject to cold treatments and were cultured on MS medium containing 4 mg l -1 NAA and 1 mg l -1 BA and activated charcoal. The mean androgenetic embryo production was found to be about 12.5%. The addition of growth regulators and activated charcoal had a greater effect than a cold pretreatment on embryo formation in pepper anther culture. On the other hand, the developmental stages of the microspores of this pepper genotype were investigated. Cytological studies were performed using the acetocarmine squash and paraffin methods. The bud size and morphological characteristics of the buds and anthers were defined and the microspore stages were determined. The buds 5 mm in diameter and 7 mm in length were determined to contain microspores at the uninucleate and 1 st pollen mitosis stages. At this stage, the length of corolla was about the same as or slightly greater than that of the calyx.

https://journals.tubitak.gov.tr/botany/issues/bot-02-26-3/bot-26-3-2-0011-5.pdf

The Effects of Cold Treatment and Charcoal on the In Vitro Androgenesis of Pepper (Capsicum annuum L.)

The effects of salinity on the growth, relative water content (RWC), chlorophyll content, inorganic ions, proline accumulation, lipid peroxidation and antioxidant enzymes, superoxide dismutase (SOD), ascorbate peroxidase (APOX), and catalase (CAT) of 3 cucumber (Cucumis sativus L.) cultivars (Cengelkoy, Anadolu F1, and Beith Alpha) were investigated. Cucumber cultivars were grown in perlite culture and irrigated with half-strength Hoagland nutrient solution for a period of 35 days under controlled conditions. After this period, seedlings were treated with 150 mM NaCl solution and the plants were harvested on day 7 and day 14 of salt treatment. The fresh and dry weights, RWC, inorganic ions, total chlorophyll, proline and malondialdehyde (MDA) content, and SOD, CAT, and APOX activities were determined. In general, the applied salinity affected all of the considered parameters depending on the duration of salt treatment and the cultivars analyzed. Proline content also increased with salinity, but accumulation of proline was lower in Cengelkoy than in the other cultivars. The results suggest that the protection mechanism against oxidative damage due to induced activity of antioxidant enzymes may be better in Cengelkoy than in Beith Alpha or Anadolu F1. The higher K+ concentrations, RWC, total chlorophyll content, and SOD, CAT, and APOX activities, together with the lower MDA, proline content, and Na+ and Cl- concentrations detected in Cengelkoy might make this cultivar more salt-tolerant than Beith Alpha or Anadolu F1.

/pdf/physiological-and-antioxidant-response-of-three-cultivars-of-1o4ktm14m9.pdf

Physiological and antioxidant response of three cultivars of cucumber (Cucumis sativus L.) to salinity

The levels of inorganic (Na + , K + , Ca +2 , Mg +2 , Cl - ) and organic (proline, carbohydrates) osmolytes and quaternary ammonium compounds were measured in 3 endemic Limonium Mill. species (L. lilacinum (Boiss. & Bal.) Wagenitz, L. iconicum (Boiss. & Heldr.) Kuntze, and L. anatolicum Hedge) of Lake Tuz in central Anatolia, Turkey. Samples were collected between May and October from plants growing in their natural habitats. Soil samples also were taken from the plant root zone at the time of plant sampling. The results of pH, electrical conductivity (EC) values, and mineral composition in the soil showed seasonal changes. The highest EC and soil Na + concentrations were found in the autumn. The seasonal changes in the osmolyte concentrations of plants were found to be dependent on soil properties such as EC, anions, and cations. The investigated plants exhibit different abilities to accumulate proline, inorganic ions, soluble carbohydrates, and quaternary ammonium compounds. Proline, ion, and carbohydrate concentrations were found to be negatively related to EC, Na + , and Cl - values of soil. These results show us that each species has its own adaptation mechanism to survive in saline soil. The findings of this investigation are the first reported results based on for these 3 endemic species of Limonium located at Lake Tuz, Turkey.

https://journals.tubitak.gov.tr/botany/issues/bot-13-37-3/bot-37-3-5-1112-8.pdf

Rukiye Tipirdamaz

Papers

Clustering of halophytes from an inland salt marsh in Turkey according to their ability to accumulate sodium and nitrogenous osmolytes

Salt resistance of tomato species grown in sand culture.

The Effects of Cold Treatment and Charcoal on the In Vitro Androgenesis of Pepper (Capsicum annuum L.)

Physiological and antioxidant response of three cultivars of cucumber (Cucumis sativus L.) to salinity

Seasonal changes of inorganic and organic osmolyte content in three endemic Limonium species of Lake Tuz (Turkey)