Volume 5 Special Issue 2 2011
Proceedings of the European COST action FA0901
How to reference: Muscolo A, Sidari M, Panuccio MR, Santonoceto C, Orsini F, De Pascale S (2011) Plant Responses in Saline and Arid Environments: An Overview. In: Muscolo A, Flowers TJ (Eds) Proceedings of the European COST action FA0901. The European Journal of Plant Science and Biotechnology 5 (Special Issue 2), 1-11
Dipartimento di Gestione dei Sistemi Agrari e Forestali, Facoltà di Agraria
Università "Mediterranea" di Reggio Calabria, Italy
Timothy J. Flowers
Sussex University, UK
CONTENTS AND ABSTRACTS
Adele Muscolo, Maria Sidari, Maria Rosaria Panuccio, Carmelo Santonoceto , Francesco Orsini, Stefania De Pascale (Italy) Plant Responses in Saline and Arid Environments: An Overview (pp 1-11)
Invited Review: Salinity is the most serious threat to agriculture and to the environment in many parts of the world. It is estimated that over 6% of the world’s land is affected by either salinity or sodicity. Using saline lands for conventional agriculture requires either improving the soil or enhancing the salt tolerance limit of field crops, the majority of which cannot survive with the levels of average soil salinity prevailing in the fields. Plants exposed to salt stress undergo changes in their environment. The ability of plants to tolerate salt is determined by multiple biochemical pathways that facilitate retention and/or acquisition of water, protect chloroplast functions, and maintain ion homeostasis. Essential pathways include the synthesis of osmotically active metabolites, specific proteins and certain free radical scavenging enzymes that control ions and water flux and support scavenging of oxygen radicals or chaperones. The ability of plants to detoxify radicals under conditions of salt stress is probably the most critical requirement. Many salt-tolerant species accumulate metabolites which play crucial dual roles as osmoprotectants and as radical scavengers. In this paper, plant responses to salinity stress are reviewed with emphasis on physiological and biochemical mechanisms of salt tolerance. Understanding the biochemical and physiological plant responses to salinity may favour the identification of new salt-tolerant cultivars or species and it provides a framework to identify breeding targets for improving salt tolerance. This review may help in interdisciplinary studies to assess the ecological significance of salt stress.
Marius-Nicuşor Grigore (Romania/Spain), Monica Boscaiu, Oscar Vicente (Spain) Assessment of the Relevance of Osmolyte Biosynthesis for Salt Tolerance of Halophytes under Natural Conditions (pp 12-19)
Invited Review: The study of the mechanisms of response to salt stress is one of the most active research topics in plant biology, not only due to its unquestionable academic interest but also because of its economic implications, since high soil salinity is – together with drought – one of the major causes of reduction of crop yields worldwide. These studies have shown a series of basic mechanisms of response to abiotic stress, which include, among others, the synthesis and accumulation in the cytoplasm of ‘compatible solutes’ or osmolytes, used for osmotic balance and as ‘osmoprotectants’. Today, there is overwhelming evidence that osmolyte, and especially proline accumulation, represents a general and reliable biochemical marker for salt stress. However, and despite the large amount of data available regarding this response mechanism, our knowledge of the importance of osmolyte biosynthesis for salt tolerance of any given species under natural conditions, is still very limited. This is partly due, in our opinion, to the approaches commonly used in these studies, which rely on experiments performed with salt-sensitive plants (glycophytes) – instead of halophytes, plants naturally adapted to high soil salinities – under artificial laboratory or greenhouse conditions. In this review, we describe and comment on data supporting these ideas, and point out that extreme caution should be taken when assessing the biological relevance of laboratory results.
Brahim Lotmani, Lalia Fatarna, Abdallah Berkani (Algeria), Jacques Rabier, Pascale Prudent, Isabelle Laffont-Schwob (France) Selection of Algerian Populations of the Mediterranean Saltbush, Atriplex halimus, Tolerant to High Concentrations of Lead, Zinc, and Copper for Phytostabilization of Heavy Metal-Contaminated Soils (pp 20-26)
Original Research Paper: We investigated the effect of three heavy-metal-rich media (Pb, Zn and Cu) on germination and growth of three Algerian populations (Kharouba, Debdaba and El Mactae) of Atriplex halimus L. Four concentrations of metals (0, 250, 500 and 1000 ppm) were applied to test the tolerance and metal accumulation of the populations grown in a greenhouse. Germination rates were not decreased by heavy metal treatment. Among the three populations, growth of Kharouba was the least affected, regardless of the metal present as confirmed by the tolerance indices. Atriplex from Kharouba originated from a contaminated site that may have lead to a better metal tolerance for this population. All three populations showed good metal sorption capabilities in root tissues. Maximal metal accumulation in aerial parts was obtained for Debdaba population with a mean of 30.9, 1.1 and 257 ppm of Cu, Pb and Zn accumulation, respectively. However, metal concentrations were below the level of US Domestic Animal Metal Toxicity Limits and the three A. halimus populations, appeared to be good candidates for a phytostabilization strategy without threat to grazing animals.
Uwe Schleiff (Germany), Adele Muscolo (Italy) Fresh Look at Plant Salt Tolerance as Affected by Dynamics at the Soil/Root-Interface Using Leek and Rape as Model Crops (pp 27-32)
Free Sample [PDF]
Original Research Paper: In the past decades crop salt tolerance research focussed mainly on two important aspects: (a) study of the effects of vertical salt distribution in the rooted soil layer on crop salt tolerance, which is applied to manage crop growth on saline soils, (b) and to understand biochemical and physiological effects of salinity on plants at cell, tissue, organ and whole plant level as basic information to develop more salt tolerant plants. Unfortunately most biochemical and physiological findings were little relevant to improve plant growth under saline soils conditions. The objective of this paper is to point out an aspect that was rarely considered in the past decades, it is the effect of the transpiration driven lateral salt distribution around roots on crop salt tolerance. It is supposed that root morphology is a most important feature, which affects the process of salt accumulation around roots and thus water uptake from saline soils. Shoot transpiration causes a much steeper increase of soil solution salinity around roots forming small rhizocylinder volumes (e.g. onions, leek) as compared to roots forming larger rhizocylinder volumes (e.g. rape). Consequently root morphology affects conditions for root water uptake from saline soils and crop salt tolerance. At the beginning of the experimental phase, when soil water salinity was relatively low (total soil water potential Ψt about -0.1 to -0.2 MPa in the low saline treatment and -0.3 to -0.4 MPa in the moderately saline treatment), water uptake rate by roots of rape was 300 to 400% higher as compared to leek roots. Leek roots nearly ceased water uptake, when Ψt has dropped to -0.9 to -1.0 MPa, but water uptake by rape roots was still significant. A concept for future research is presented.
Kamel Hessini (Tunisia), Cristina Cruz (Portugal), Mhemmed Gandour, Ahmed Debez (Tunisia), Hans-Werner Koyro, Bernhard Huchzermeyer (Germany), Chedly Abdelly (Tunisia) Ammonium Nutrition Improves Salt Tolerance of Spartina alterniflora (pp 33-36)
Original Research Paper: The effects of inorganic nitrogen (N) form on biomass allocation, photosynthesis, osmotic adjustment, and cell wall elasticity of Spartina alterniflora were studied in a greenhouse under natural light and with sandy soil in the presence or absence of 500 mM NaCl. Under non saline conditions ammonium nutrition enhanced dry matter production and leaf area by ca. 50% in comparison to nitrate-fed plants. Under saline conditions the enhancement was more pronounced. NH4+ nutrition improved photosynthesis, transpiration, and stomatal conductance, suggesting that S. alterniflora prefers ammonium as a nitrogen source. The addition of 500 mol.m−3 NaCl significantly affected plant growth in both nitrate and mixed media, but had no impact when ammonium was supplied alone, suggesting a considerable advantage of NH4+ nutrition under saline conditions. As a whole, ammonium treatment seems to improve salt tolerance of S. alterniflora by decreasing the energetic cost, needed for osmotic adjustment and cell wall elasticity, to growth.
Agnieszka Piernik, Piotr Hulisz (Poland) Soil-plant Relations in Inland Natural and Anthropogenic Saline Habitats (pp 37-43)
Original Research Paper: Three types of saline habitats were investigated in central Poland: natural saline grasslands, anthropogenic saline meadows next to the waste ponds of two soda factories and halophytic vegetation along brine pipelines. In total 76 phytosociological relevés and soil samples (0-25 cm) in each plot were taken. After discriminant analysis (CVA) including all measured soil properties high pH values were identified as significant for pipeline habitats, high ECe values together with high Ca2+ concentrations (and the highest Ca2+/Na+ ratio) for the waste pond areas and finally relatively high K+ concentrations as characteristic for natural stands. Canonical Correspondence Analysis (CCA) of all species and environmental data demonstrated that in species-environment relations model ECe linked to waste pond areas, K+ characteristic for natural habitats and Ntot together with organic matter were significant. Vegetation of the natural habitats differed significantly from the vegetation of waste pond and pipeline areas. More species were frequent in the natural habitats, both halophytes and glycophytes, than in the waste ponds and brine pipelines. There were no significant differences in vegetation between waste ponds and pipelines stands. For the two anthropogenic habitats, the presence of obligatory halophytes Salicornia europaea, Aster tripolium, Atriplex prostrata and Spergularia marina was typical. Considering community distribution the results of discriminant analysis identified natural stands as significantly different from the two other categories with more frequent Scirpus maritimus community and a Glaux maritima-Potentilla anserina-Agrostis stolonifera and Triglochin maritima communities. Salicornia europaea, Puccinellia distans-Salicornia europaea, Puccinellia distans and Atriplex prostrata communities were typical for anthropogenic stands. Differences between the two anthropogenic habitats were not reflected well by differences in species and community distribution.
Tibor Tóth, András Szabó (Hungary) Larger Gradients of Abiotic Factors Result in More Vegetative Zones in Salt-Affected Habitats (pp 44-47)
Research Note: Data of 11 transects were collected from the literature in order to find an answer to the question: what is the most important factor that determines the number of zones in a transect? From collected data on transect length, elevation, soil salinity and soil pH, the gradients of these parameters were calculated between the highs and lows of the transects. The number of vegetative zones per unit transect length showed a very strong correlation (significant at 0.01 level) with every studied gradient. The strongest correlation was shown by the pH gradient with r = 0.991, because of the toxicity of sodium carbonate, being responsible for the high pH values in the affected soils. Although the studied database is rather heterogeneous, the tendencies are very clear. For a comparison of the effect of separate abiotic factors on the number of vegetative zones per unit transect length, more detailed analysis with a larger number of transects (with similar length and elevation) is necessary.
Amram Eshel, Israel Oren, Chingiz Alekperov, Tamar Eilam, Aviah Zilberstein (Israel) Biomass Production by Desert Halophytes: Alleviating the Pressure on the Scarce Resources of Arable Soil and Fresh Water (pp 48-53)
Research Note: The utilization of plants for mitigating carbon dioxide accumulation in the atmosphere in Clean Development Mechanism (CDM) projects and biofuel production causes a severe burden on the limited sources of arable land and fresh water. This research is aimed at finding alternative plant types for biomass and biofuel production among desert halophytes. Such plants have the advantages of being naturally adapted to grow under the harsh desert conditions, on non-arable soils irrigated with reclaimed sewage or other types of brackish water. Exceptionally fast growing salt-resistant genotypes were identified among native populations of Tamarix of Israel. These may serve for future CDM projects and short-rotation forestry for biomass production. Another plant that originated from East Africa, Euphorbia tirucalli was also shown to be able to grow under desert conditions and saline water irrigation. This plant has been named in the literature as a potential source of biofuel.
Munir Ozturk, Bengu Turkyilmaz (Turkey), Salih Gucel (Cyprus), Aykut Guvensen (Turkey) Proline Accumulation in Some Coastal Zone Plants of the Aegean Region of Turkey (pp 54-56)
Research Note: In this study, the proline contents of ecophysiologically different plants were determined on a seasonal basis. The plant species investigated were Cakile maritima, Medicago marina, Pancratium maritimum and Suaeda prostrata (psammophyte-from sand dunes); Arthrocnemum fruticosum,Halimione portulacoides, Halocnemum strobilaceum, Limonium bellidifolium and Salicornia europaea (halophytes-from saline habitats). The results showed that proline content in all taxa was highest in autumn and lowest in spring. The accummulation in general was higher in halophytes (0.104 ± 0.004 μmol g-1 (f.m.) to 55.138 ± 6.138 μmol g-1 (f.m.)), as compared to psammophytes (0.242 ± 0.118 μmol g-1 (f.m.) to 38.307 ± 1.455 μmol g-1 (f.m.)). This can be attributed to both salinity and water stress in the halophytes, and water stress alone in the psammophytes.
Carla Cassaniti, Daniela Romano (Italy) The Use of Halophytes for Mediterranean Landscaping (pp 57-63)
Research Note: A study was carried out to identify some halophytes that naturally grow in the Mediterranean area, which could be utilized for ornamental purposes. The current investigation, based also on previous literature, showed about 172 suitable species in 30 families and 86 botanical genera. The Chenopodiaceae was found to be the largest family with 34 species. Within the genera, the most represented were Limonium and Atriplex (17 and 14 species, respectively). The most common life form was the herbaceous perennial (49%), the hydrohalophyte the most widespread habitat (about 40%). The characteristic lack of showy flowers in most of these halophytes, suggests the opportunity of using them to provide green areas with aesthetic features. The tolerance to saline environments allows these plants to be used in landscape restoration. Prostrate species such as Carpobrotus edulis, Mesembryanthemum crystallinum and M. nodiflorum seem to be of particular value not only for the spectacular blooming but also for their utilization such as groundcover. Future studies should be carried out in order to improve halophyte use with appropriate protocols for cultivation.
Pasquale Martiniello (Italy), Jaime A. Teixeira da Silva (Japan) Physiological and Bioagronomical Aspects Involved in Growth and Yield Components of Cultivated Forage Species in Mediterranean Environments: A Review (pp 64-98)
Free Sample [PDF]
Review: This review provides an updated perspective on the effect of agronomic management and weather conditions on biological pathways in the organs of plants used for herbage seed production. Biochemical pathways from seedling to herbage harvest or seed production in forage crop species are emphasized. The review reports the effect of weather conditions and agronomic practices on physiological processes in plants growing during forage and seed yield production in Mediterranean or Mediterranean-like environments. When the available scientific information is not adequate to explain the physiological aspects involved in plant development, experimental results on forage crops or related species in environments close to the weather condition of a Mediterranean climate have been used. Plant breeding progress of the agronomic characteristics seed and herbage production achieved in annual and perennial forage crop varieties included in the Italian register of the EU catalogue, in the last 10 years, is scant in comparison to those of other cultivated crops. The genetic gain in forage crop varieties for herbage production over this period has been 4% in herbage against 13.0% in cereal grain crops while no breeding progress has occurred for seed production and seed yield components. Knowledge of the effect of agronomic management and weather conditions on physiological processes in plant organs during the growing cycle of herbage and seed production is useful to develop a breeding strategy able to endow the biochemical requisites to better exploit harsh weather conditions.