Responses of Selected C3 and C4 Halophytes to Elevated CO2 Concentration under Salinity (original) (raw)
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Salinity is one of the major problems facing agricultural production worldwide , particularly in arid and semiarid environments. Unfortunately, most major economic crops (glycophytes) cannot tolerate saline conditions, even at low concentrations (<40 mM NaCl). Halophytes are tolerant of high salinities, up to 200 mM NaCl. Therefore, there is increased interest in the production of new cultivars that have the potential to produce higher yields under saline conditions. There is also research interest in understanding the various strategies, including salt tolerance and salt avoidance, that halophytes use to adapt to saline conditions, besides conventional habits like accumulation of compatible solutes and polyamine production. Additionally , halophytes use a number of complicated mechanisms to grow and reproduce under such harsh conditions, such as regulating ion concentrations in cells, exuding excessive salt from plant tissues, and eliminating salts via glands and hairs to keep salt concentrations in leaves and shoots below a certain threshold. Some halophytes produce high leaf/stem succulence or accumulate excessive salt in old leaves. Other species use ion accumulation and control plant growth to cope with salinity. In this chapter we discuss the classification and distribution of halophytes and their potential role as resources for humankind (food, oil, forage, and biofuel). Glycophyte growth is affected by high salinity, which can lead to plant death. Therefore, glycophytes use various strategies to enhance growth under salinity stress, such as producing salt-tolerant genotypes and using different mechanisms-like excretion of salt ions and salt sequestration-to improve growth and productivity. Salinity stress reduces glycophyte growth due to its negative effects on the metabolism and phytohormone levels, such as cytokinin and gibberellic acid. In addition, high salt levels have an adverse effect on water relations and disturb the nutritional balance in plant cells.
2021
A significant increase in atmospheric CO2 concentration and associated climate aridization and soil salinity are factors affecting the growth, development, productivity, and stress responses of plants. In this study, the effect of ambient (400 ppm) and elevated (800 ppm) CO2 concentrations were evaluated on the C4 xero-halophyte Kochia prostrata treated with moderate salinity (200 mM NaCl) and polyethylene glycol (PEG)-induced osmotic stress. Our results indicated that plants grown at elevated CO2 concentration had different responses to osmotic stress and salinity. The synergistic effect of elevated CO2 and osmotic stress increased proline accumulation, but elevated CO2 did not mitigate the negative effects of osmotic stress on dark respiration intensity and photosystem II (PSII) efficiency. This indicates a stressful state, which is accompanied by a decrease in the efficiency of light reactions of photosynthesis and significant dissipative respiratory losses, thereby resulting in ...
Salt Adaptation Mechanisms of Halophytes: Improvement of Salt Tolerance in Crop Plants
Elucidation of Abiotic Stress Signaling in Plants, 2015
Soil salinity is one of the most serious environmental factors that affect crop productivity worldwide. Inevitable global climate change leading to rise in sea water level would exacerbate degradation of irrigation systems and contamination of ground water resources, which render conventional agricultural practices impossible due to the sensitivity of most crops to salinity. Breeding for development of salt-tolerant crop plants has been a major challenge due to the complexity and multigenic control of salt tolerance traits. Halophytes are capable of surviving and thriving under salt at concentrations as high as 5 g/L, by maintaining negative water potential. Physiological and molecular studies have suggested that halophytes, unlike glycophytes, have evolved mechanisms, such as ion homeostasis through ion extrusion and compartmentalization, osmotic adjustments, and antioxidant production for adaptation to salinity. Employment of integrated approaches involving different omics tools would amplify our understanding of the biology of stress response networks in the halophytes. Translation of the knowledge and resources generated from halophyte relatives of crop plants through functional genomics will lead to the development of new breeds of crops that are suitable for saline agriculture.
Journal of Experimental Botany, 2008
This study investigated the interaction of NaCl-salinity and elevated atmospheric CO 2 concentration on gas exchange, leaf pigment composition, and leaf ultrastructure of the potential cash crop halophyte Aster tripolium. The plants were irrigated with five different salinity levels (0, 25, 50, 75, 100% seawater salinity) under ambient and elevated (520 ppm) CO 2 . Under saline conditions (ambient CO 2 ) stomatal and mesophyll resistance increased, leading to a significant decrease in photosynthesis and water use efficiency (WUE) and to an increase in oxidative stress. The latter was indicated by dilations of the thylakoid membranes and an increase in superoxide dismutase (SOD) activity. Oxidative stress could be counteracted by thicker epidermal cell walls of the leaves, a thicker cuticle, a reduced chlorophyll content, an increase in the chlorophyll a/b ratio and a transient decline of the photosynthetic efficiency. Elevated CO 2 led to a significant increase in photosynthesis and WUE. The improved water and energy supply was used to increase the investment in mechanisms reducing water loss and oxidative stress (thicker cell walls and cuticles, a higher chlorophyll and carotenoid content, higher SOD activity), resulting in more intact thylakoids. As these mechanisms can improve survival under salinity, A. tripolium seems to be a promising cash crop halophyte which can help in desalinizing and reclaiming degraded land.
Catrina Journal , 2023
Salinity stress poses a significant challenge to plant growth and agricultural productivity worldwide. However, certain plant species, known as halophytes, have evolved remarkable adaptive mechanisms to thrive in high salinity environments. Understanding the physiological and molecular mechanisms underlying the salt tolerance of halophytes holds great potential for enhancing salinity tolerance in non-halophytic crop plants. This review aims to explore the adaptive strategies employed by halophytes to cope with salinity stress and their implications for improving plant salinity tolerance. Physiological adaptations of halophytes include mechanisms to regulate ion homeostasis, maintain osmotic balance, and minimize water loss under high salinity conditions. These adaptations involve the accumulation of compatible solutes, such as proline and glycine betaine, as well as the compartmentalization of toxic ions in vacuoles. Halophytes also exhibit efficient antioxidant systems to counteract oxidative stress induced by salt accumulation. At the molecular level, halophytes employ a range of genetic and epigenetic mechanisms to regulate gene expression and enhance salt tolerance. These mechanisms include the activation of stress-responsive transcription factors, modulation of ion transporters and channels, and epigenetic modifications that alter chromatin structure and gene expression patterns. Recent advancements in molecular techniques, such as transcriptomics and proteomics, have provided valuable insights into the complex regulatory networks involved in halophyte salt tolerance. Harnessing the knowledge gained from halophyte adaptation mechanisms can offer promising prospects for improving the salinity tolerance of economically important crop plants. Genetic engineering and breeding approaches can be employed to introduce or enhance the expression of key salt tolerance genes in non-halophytic species. Additionally, the identification and utilization of halophytederived salt tolerance traits through conventional breeding strategies hold great potential for developing salt-tolerant crop varieties. Therefore, the investigation of halophytes' physiological and molecular mechanisms of salt tolerance provides valuable insights into the intricate strategies employed by plants to adapt and thrive in high salinity environments. The knowledge gained from these studies can be harnessed to enhance the salinity tolerance of non-halophytic crop plants, thereby contributing to sustainable agriculture in salinity-affected regions.
Functional Plant Biology, 2013
Salinity is one of the major abiotic stress factors that drastically reduces agricultural productivity. In natural environments salinity often occurs together with other stresses such as dehydration, light stress or high temperature. Plants cope with ionic stress, dehydration and osmotic stress caused by high salinity through a variety of mechanisms at different levels involving physiological, biochemical and molecular processes. Halophytic plants exist successfully in stressful saline environments, but most of the terrestrial plants including all crop plants are glycophytes with varying levels of salt tolerance. An array of physiological, structural and biochemical adaptations in halophytes make them suitable models to study the molecular mechanisms associated with salinity tolerance. Comparative analysis of plants that differ in their abilities to tolerate salinity will aid in better understanding the phenomenon of salinity tolerance. The halophyte Thellungiella salsuginea has bee...
Growth and photosynthetic responses to salinity in an extreme halophyte, Sarcocornia fruticosa
Physiologia Plantarum, 2006
Sarcocornia fruticosa (L.) A.J. Scott is found in coastal marshes of south-west Spain, growing under a very wide range of interstitial soil salinity from 10 mM up to nearly 1000 mM. A glasshouse experiment was designed to investigate the effect of this range of salinities on the morphology and the photosynthetic apparatus of S. fruticosa by measuring growth rate, photosynthetic and non-photosynthetic area, atrophy of distal branch ends, water status, chlorophyll fluorescence parameters, gas exchange and photosynthetic pigment concentrations. The long-term effects of salinity on the growth of S. fruticosa were mainly determined by the extent of photosynthetic area rather than the variations in net photosynthetic rate. Photosynthetic area was reduced at 1030 mM as a result of a decrease in the length of the photosynthetic portions. This was induced by fewer internodes and, at salinities lower than 510 mM, smaller internode diameter. Net photosynthetic rate increased as the quantum efficiency of photosystem II decreased in the different salinity treatments, which means that the plant could be increasing photorespiration and/or using cyclic electron transport as additional photoprotective mechanisms. The recorded drop in net photosynthetic rate at higher salinities appeared to be due to a reduction in stomatal conductance. The results indicate that S. fruticosa is capable of tolerating very high and continued exposure to salt, showing its greatest growth rate at 510 mM NaCl.
Responses of Halophytes to Salt Stress
Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca: Horticulture, 2007
Halophytes. plants naturally adapted to conditions of high salinity in the soil. have been the subject of many different studies but. paradoxically. not so much to investigate the mechanisms of salt tolerance at the biochemical and molecular level. Halophytes can be considered important. but underutilised. genetic resources for the identification of salt tolerance determinants. We present here a brief summary of the initial results of our ongoing. multidisciplinary studies on the general responses to salt stress in halophytes of the genera Plantago and Juncus. focusing on the effect of NaCl on seed germination. vegetative growth. reproductive development. and on the accumulation of mono and divalent cations and putative osmolytes in the aerial part of the plants
Adaptive Mechanisms of Halophytes and Their Potential in Improving Salinity Tolerance in Plants
International Journal of Molecular Sciences
Soil salinization, which is aggravated by climate change and inappropriate anthropogenic activities, has emerged as a serious environmental problem, threatening sustainable agriculture and future food security. Although there has been considerable progress in developing crop varieties by introducing salt tolerance-associated traits, most crop cultivars grown in saline soils still exhibit a decline in yield, necessitating the search for alternatives. Halophytes, with their intrinsic salt tolerance characteristics, are known to have great potential in rehabilitating salt-contaminated soils to support plant growth in saline soils by employing various strategies, including phytoremediation. In addition, the recent identification and characterization of salt tolerance-related genes encoding signaling components from halophytes, which are naturally grown under high salinity, have paved the way for the development of transgenic crops with improved salt tolerance. In this review, we aim to ...