Nutritional management and physiological responses of Atriplex nummularia Lindl. on the improvement of phytoextraction in salt-affected soil.

Soil salinity is a significant abiotic stress and poses risks to environmental sustainability. Thus, the improvement of the time for recovering the salt-affect soil is crucial for the phytoextraction process using halophytes plants, especially regarding on nutritional management. We evaluated the responses of Atriplex nummularia Lindl. to nitrogen (N) and phosphorus (P) under different salinity levels. The treatments comprised doses of N (N1 = 80 kg ha-1) and P (P1 = 60 kg ha-1): (1) without N and P (N0P0) (control); (2) with N and without P (N1P0); (3) without N and with P (N0P1); and (4) with N and P (N1P1) and five levels of electrical conductivity from irrigation water: 0.08, 1.7, 4.8, 8.6, and 12.5 dS m-1. The. We evaluated dry biomass of leaves, stems, and roots 93 days after transplantation. We also assessed the leaf and osmotic water potential, the osmotic adjustment, and the nutrient contents (N, P, Na, and K). N application increased 22.3, 17.8, and 32.8% the leaf biomass, stem biomass, and osmotic adjustment, respectively; and consequently, boosts Na extraction in 27.8%. Thus, the time of the phytoextraction process can be improved with N fertilizer at a rate of 80 kg ha-1.

Very few studies have investigated the nutrient dynamics responses in Atriplex species in salt-affected soils; thus, this study represents a novelty. We tested the management of nitrogen (N) and phosphate (P) fertilizers to increase crop yield and optimize the phytoextraction process in salt-affected soils. We believe our results contribute to the improvement of the knowledge of this relevant topic, mainly in terms of the recovery of areas degraded by salinity. There is a paucity of studies associating salinity and nutritional management of soils worldwide.

Photosynthetic acclamatory response of Panicum antidotale Retz. populations to root zone desiccation stress

Abstract Growth of plants is severely reduced due to water stress by affecting photosynthesis including photosystem II (PSII) activity and electron transport. This study emphasised on comparative and priority targeted changes in PSII activity due to progressive drought in seven populations of Panicum antidotale (P. antidotale) collected from Cholistan Desert and non-Cholistan regions. Tillers of equal growth of seven populations of P. antidotale grown in plastic pots filled with soil were subjected progressive drought by withholding water irrigation for three weeks. Progressive drought reduced the soil moisture content, leaf relative water content, photosynthetic pigments and fresh and dry biomass of shoots in all seven populations. Populations from Dingarh Fort, Dingarh Grassland and Haiderwali had higher growth than those of other populations. Cholistani populations especially in Dingarh Grassland and Haiderwali had greater ability of osmotic adjustment as reflected by osmotic potential and greater accumulation of total soluble proteins. Maximum H2O2 under water stress was observed in populations from Muzaffargarh and Khanewal but these were intermediate in MDA content. Under water stress, populations from Muzaffargarh and Dingarh Fort had greater K+ accumulation in their leaves. During progressive drought, non-Cholistani populations showed complete leaf rolling after 23 days of drought, and these populations could not withstand with more water stress condition while Cholistani populations tolerated more water stress condition for 31 days. Moreover, progressive drought caused PSII damages after 19 days and it became severe after 23 days in non-Cholistani populations of P. antidotale than in Cholistani populations.

Resumo O crescimento das plantas é severamente reduzido devido ao estresse hídrico, afetando a fotossíntese, incluindo a atividade do fotossistema II (PSII) e o transporte de elétrons. Este estudo enfatizou as mudanças comparativas e prioritárias na atividade do PSII devido à seca progressiva em sete populações de Panicum antidotale (P. antidotale) coletadas no Deserto do Cholistão e regiões fora do Cholistão. Perfilhos de igual crescimento de sete populações de P. antidotale cultivadas em vasos de plástico cheios de solo foram submetidos à seca progressiva, retendo a irrigação com água por três semanas. A seca progressiva reduziu o teor de umidade do solo, teor de água relativo nas folhas, pigmentos fotossintéticos e biomassa fresca e seca dos brotos em todas as sete populações. Populações de Dingarh Fort, Dingarh Grassland e Haiderwali tiveram maior crescimento do que as de outras populações. As populações de Cholistani, especialmente em Dingarh Grassland e Haiderwali, apresentaram maior capacidade de ajuste osmótico, refletido pelo potencial osmótico e maior acúmulo de proteínas solúveis totais. H2O2 máximo sob estresse hídrico foi observado em populações de Muzaffargarh e Khanewal, mas estas foram intermediárias no conteúdo de MDA. Sob estresse hídrico, as populações de Muzaffargarh e Dingarh Fort tiveram maior acúmulo de K+ em suas folhas. Durante a seca progressiva, as populações não cholistanesas mostraram rolagem completa das folhas após 23 dias de seca, e essas populações não conseguiram suportar mais condições de estresse hídrico, enquanto as populações cholistani toleraram mais condições de estresse hídrico por 31 dias. Além disso, a seca progressiva causou danos ao PSII após 19 dias e tornou-se severa após 23 dias em populações não cholistanesas de P. antidotale do que em populações cholistanesas.

Photosynthetic acclamatory response of Panicum antidotale Retz. populations to root zone desiccation stress / Reação fotossintética aclamatória de Panicum antidotale Retz. populações submetidas ao estresse da dessecação da zona radicular

Abstract Growth of plants is severely reduced due to water stress by affecting photosynthesis including photosystem II (PSII) activity and electron transport. This study emphasised on comparative and priority targeted changes in PSII activity due to progressive drought in seven populations of Panicum antidotale (P. antidotale) collected from Cholistan Desert and non-Cholistan regions. Tillers of equal growth of seven populations of P. antidotale grown in plastic pots filled with soil were subjected progressive drought by withholding water irrigation for three weeks. Progressive drought reduced the soil moisture content, leaf relative water content, photosynthetic pigments and fresh and dry biomass of shoots in all seven populations. Populations from Dingarh Fort, Dingarh Grassland and Haiderwali had higher growth than those of other populations. Cholistani populations especially in Dingarh Grassland and Haiderwali had greater ability of osmotic adjustment as reflected by osmotic potential and greater accumulation of total soluble proteins. Maximum H2O2 under water stress was observed in populations from Muzaffargarh and Khanewal but these were intermediate in MDA content. Under water stress, populations from Muzaffargarh and Dingarh Fort had greater K+ accumulation in their leaves. During progressive drought, non-Cholistani populations showed complete leaf rolling after 23 days of drought, and these populations could not withstand with more water stress condition while Cholistani populations tolerated more water stress condition for 31 days. Moreover, progressive drought caused PSII damages after 19 days and it became severe after 23 days in non-Cholistani populations of P. antidotale than in Cholistani populations.

Resumo O crescimento das plantas é severamente reduzido devido ao estresse hídrico, afetando a fotossíntese, incluindo a atividade do fotossistema II (PSII) e o transporte de elétrons. Este estudo enfatizou as mudanças comparativas e prioritárias na atividade do PSII devido à seca progressiva em sete populações de Panicum antidotale (P. antidotale) coletadas no Deserto do Cholistão e regiões fora do Cholistão. Perfilhos de igual crescimento de sete populações de P. antidotale cultivadas em vasos de plástico cheios de solo foram submetidos à seca progressiva, retendo a irrigação com água por três semanas. A seca progressiva reduziu o teor de umidade do solo, teor de água relativo nas folhas, pigmentos fotossintéticos e biomassa fresca e seca dos brotos em todas as sete populações. Populações de Dingarh Fort, Dingarh Grassland e Haiderwali tiveram maior crescimento do que as de outras populações. As populações de Cholistani, especialmente em Dingarh Grassland e Haiderwali, apresentaram maior capacidade de ajuste osmótico, refletido pelo potencial osmótico e maior acúmulo de proteínas solúveis totais. H2O2 máximo sob estresse hídrico foi observado em populações de Muzaffargarh e Khanewal, mas estas foram intermediárias no conteúdo de MDA. Sob estresse hídrico, as populações de Muzaffargarh e Dingarh Fort tiveram maior acúmulo de K+ em suas folhas. Durante a seca progressiva, as populações não cholistanesas mostraram rolagem completa das folhas após 23 dias de seca, e essas populações não conseguiram suportar mais condições de estresse hídrico, enquanto as populações cholistani toleraram mais condições de estresse hídrico por 31 dias. Além disso, a seca progressiva causou danos ao PSII após 19 dias e tornou-se severa após 23 dias em populações não cholistanesas de P. antidotale do que em populações cholistanesas.

Seed Priming with Glass Waste Microparticles and Red Light Irradiation Mitigates Thermal and Water Stresses in Seedlings of Moringa oleifera.

The association between population increase and the exploitation of natural resources and climate change influences the demand for food, especially in semi-arid regions, highlighting the need for technologies that could provide cultivated species with better adaptation to agroecosystems. Additionally, developing cultivation technologies that employ waste materials is highly desirable for sustainable development. From this perspective, this study aimed to evaluate whether seed priming with glass waste microparticles used as a silicon source under red light irradiation mitigates the effects of thermal and water stress on seedlings of Moringa oleifera. The experimental design was set up in randomized blocks using a 2 × 2 × 2 factorial arrangement consisting of seed priming (NSP-no seed priming, and SPSi-seed priming with glass microparticles under red light irradiation), soil water replenishment (W50-50%, and W100-100% of crop evapotranspiration-ETc), and temperature change (TC30°-30 °C day/25 °C night and TC40°-40 °C day/35 °C night). Seed priming with glass microparticles under red light irradiation mitigated the effects of thermal and water stress on seedlings of Moringa oleifera seedlings through the homeostasis of gas exchange, leaf water status, osmotic adjustment, and the antioxidant mechanism.

Metabolic changes associated with differential salt tolerance in sorghum genotypes.

MAIN CONCLUSION: Accumulation of specific metabolites, mainly γ-aminobutyric acid, polyamines, and proline, was essential to homeostasis regulation and differential salt tolerance in sorghum genotypes. Salinity is severe abiotic stress that limits plant growth and development in arid and semi-arid regions. Survival to abiotic stresses depends on metabolic and sometimes even morphological adjustments. We measured the growth parameters, water relations, the content of ions (Na+, K+, Cl-), compatible solutes [some free amino acids (FAAs) including γ-aminobutyric acid (GABA) and proline and soluble carbohydrates) and polyamines (PAs), the activity of PAs metabolism enzymes, and metabolomic profile in plants after 14 days of salt stress treatment. These analyses were to evaluate the influence of metabolomic responses of sorghum genotypes exhibiting sensitivity (CSF18) or tolerance (CSF20) to salinity on plant growth. The salinity promoted growth reductions and induced increases in Na+ and Cl- content and decreases in K+ content. The water status and osmotic potential (Ψo) were reduced by salt stress, but to minimize damage, especially in the CSF20, the osmolytes and PAs contributed to the osmotic adjustment. The results showed that salinity induced an increase in putrescine (Put) in the sensitive genotype. However, it raised spermidine (Spd), spermine (Spm), and cadaverine (Cad) in the tolerant genotype. In addition, the regulation of polyamine oxidase can be related to Spm and GABA biosynthesis. Differential metabolic changes to salt tolerance include metabolites associated with tricarboxylic acid (TCA) cycle intermediates and the metabolisms of sugars, FAAs, and PAs.

Characterization of Trehalose-6-phosphate Synthase and Trehalose-6-phosphate Phosphatase Genes and Analysis of its Differential Expression in Maize (Zea mays) Seedlings under Drought Stress.

Maize is the most important crop around the world and it is highly sensitive to abiotic stress caused by drought, excessive salinity, and extreme temperature. In plants, trehalose has been widely studied for its role in plant adaptation to different abiotic stresses such as drought, high and low temperature, and osmotic stress. Thus, the aim of this work was to clone and characterize at molecular level the trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP) genes from maize and to evaluate its differential expression in maize seedlings under drought stress. To carry out this, resistant and susceptible maize lines were subjected to drought stress during 72 h. Two full-length cDNAs of TPS and one of TPP were cloned and sequenced. Then, TPS and TPP amino acid sequences were aligned with their homologs from different species, showing highly conserved domains and the same catalytic sites. Relative expression of both genes was evaluated by RT-qPCR at different time points. The expression pattern showed significant induction after 0.5 h in resistant lines and after two to four hours in susceptible plants, showing their participation in drought stress response.

Identification of Factors Linked to Higher Water-Deficit Stress Tolerance in Amaranthus hypochondriacus Compared to Other Grain Amaranths and A. hybridus, Their Shared Ancestor.

Water deficit stress (WDS)-tolerance in grain amaranths (Amaranthus hypochondriacus, A. cruentus and A. caudatus), and A. hybridus, their presumed shared ancestor, was examined. A. hypochondriacus was the most WDS-tolerant species, a trait that correlated with an enhanced osmotic adjustment (OA), a stronger expression of abscisic acid (ABA) marker genes and a more robust sugar starvation response (SSR). Superior OA was supported by higher basal hexose (Hex) levels and high Hex/sucrose (Suc) ratios in A. hypochondriacus roots, which were further increased during WDS. This coincided with increased invertase, amylase and sucrose synthase activities and a strong depletion of the starch reserves in leaves and roots. The OA was complemented by the higher accumulation of proline, raffinose, and other probable raffinose-family oligosaccharides of unknown structure in leaves and/or roots. The latter coincided with a stronger expression of Galactinol synthase 1 and Raffinose synthase in leaves. Increased SnRK1 activity and expression levels of the class II AhTPS9 and AhTPS11 trehalose phosphate synthase genes, recognized as part of the SSR network in Arabidopsis, were induced in roots of stressed A. hypochondriacus. It is concluded that these physiological modifications improved WDS in A. hypochondriacus by raising its water use efficiency.

Phytohormone profiling in relation to osmotic adjustment in NaCl-treated plants of the halophyte tomato wild relative species Solanum chilense comparatively to the cultivated glycophyte Solanum lycopersicum.

A holistic approach was used to investigate the hormonal profile in relation with osmotic adjustment under salinity in Solanum lycopersicum and its halophyte wild relative Solanum chilense. Plants were subjected to 125mM NaCl for 7days. Solanum chilense displayed a contrasting behaviour comparatively to S. lycopersicum, not only for mineral nutrition, but also regarding the modalities of osmotic adjustment and phytohormonal profiling. The extent of osmotic adjustment was higher in S. chilense than in S. lycopersicum. Ions K+ and Na+ were the major contributors of osmotic adjustment in S. chilense, accounting respectively for 47 and 60% of osmotic potential. In contrast the contributions of proline and soluble sugars remained marginal for the two species although salt-induced accumulation of proline was higher in S. lycopersicum than in S. chilense. Both species also differed for their hormonal status under salinity and concentrations of most hormonal compounds were higher in S. chilense than in S. lycopersicum. Interestingly, salicylic acid, ethylene and cytokinins were positively correlated with osmotic potential in S. chilense under salinity while these hormones were negatively correlated with osmotic adjustment in S. lycopersicum. Our results suggested that the capacity to use inorganic ions as osmotica may improve salt resistance in S.chilense and that phytohormones could be involved in this process.

Productivity and drought tolerance of cassava cultivars in the Coastal Tablelands of Northeastern Brazil / Produtividade e tolerância à deficiência hídrica de cultivares de mandioca nos Tabuleiros Costeiros do Nordeste

ABSTRACT: Ten cassava cultivars were grown in the field and evaluated to identify the most adapted to the Coastal Tablelands of northeast Brazil. The cultivars showed differences in proline and chlorophyll contents, plant height, number of leaves and branches, canopy area and root production, however they did not differ on photosynthetic rates. Cultivars 'Tianguá' and '9783-13' presented lower root yield, whereas 'BRS Tapioqueira' and 'Irará' had the highest root yield. Few leaves coupled with the highest water use efficiency for CO2 assimilation was found in 'BRS Kiriris' in contrast to 'BRS Jarina' and '9783-13'. 'BRS Caipira' had high proline content in both Umbaúba and Frei Paulo areas, traits usually associated to drought tolerance, that contribute to the adaptation. It is also important to consider that cultivar 'BRS Caipira' was the first to present increase in chlorophyll content after extended period of drought, that indicates a faster recovery after dry season. Furthermore, the results indicated that the most adapted cultivars for cultivation in this area are 'Irará', 'BRS Tapioqueira', 'BRS Kiriris' and 'BRS Caipira'.

RESUMO: Dez cultivares de mandioca foram cultivadas no campo e avaliadas para identificar a mais adaptada aos Tabuleiros Costeiros do Nordeste do Brasil. As cultivares apresentaram diferenças nos teores de prolina e clorofila, altura, número de folhas e ramos, área de copa e produção de raízes, no entanto, não diferiram quanto às taxas fotossintéticas. As cultivares 'Tianguá' e '9783-13' apresentaram menor rendimento de raízes e 'BRS Tapioqueira' e 'Irará' maior rendimento. Poucas folhas e maior eficiência no uso da água para a assimilação de CO2 foi verificado em 'BRS Kiriris', em contraste com 'BRS Jarina' e '9783-13'. 'BRS Caipira' teve alto teor de prolina em Umbaúba e em Frei Paulo, características geralmente associadas à tolerância à seca, que contribuem para adaptação. Também é importante considerar que a cultivar 'BRS Caipira' foi a primeira a apresentar aumento no teor de clorofila após longo período de seca, o que indica recuperação mais rápida após período seco. Além disso, os resultados indicam que as cultivares mais adaptadas ao cultivo nessa área são 'Irará', 'BRS Tapioqueira', 'BRS Kiriris' e 'BRS Caipira'.

Productivity and drought tolerance of cassava cultivars in the Coastal Tablelands of Northeastern Brazil / Produtividade e tolerância à deficiência hídrica de cultivares de mandioca nos Tabuleiros Costeiros do Nordeste

Ten cassava cultivars were grown in the field and evaluated to identify the most adapted to the Coastal Tablelands of northeast Brazil. The cultivars showed differences in proline and chlorophyll contents, plant height, number of leaves and branches, canopy area and root production, however they did not differ on photosynthetic rates. Cultivars 'Tianguá' and '9783-13' presented lower root yield, whereas 'BRS Tapioqueira' and 'Irará' had the highest root yield. Few leaves coupled with the highest water use efficiency for CO2 assimilation was found in 'BRS Kiriris' in contrast to 'BRS Jarina' and '9783-13'. 'BRS Caipira' had high proline content in both Umbaúba and Frei Paulo areas, traits usually associated to drought tolerance, that contribute to the adaptation. It is also important to consider that cultivar 'BRS Caipira' was the first to present increase in chlorophyll content after extended period of drought, that indicates a faster recovery after dry season. Furthermore, the results indicated that the most adapted cultivars for cultivation in this area are 'Irará', 'BRS Tapioqueira', 'BRS Kiriris' and 'BRS Caipira'.(AU)

Dez cultivares de mandioca foram cultivadas no campo e avaliadas para identificar a mais adaptada aos Tabuleiros Costeiros do Nordeste do Brasil. As cultivares apresentaram diferenças nos teores de prolina e clorofila, altura, número de folhas e ramos, área de copa e produção de raízes, no entanto, não diferiram quanto às taxas fotossintéticas. As cultivares 'Tianguá' e '9783-13' apresentaram menor rendimento de raízes e 'BRS Tapioqueira' e 'Irará' maior rendimento. Poucas folhas e maior eficiência no uso da água para a assimilação de CO2 foi verificado em 'BRS Kiriris', em contraste com 'BRS Jarina' e '9783-13'. 'BRS Caipira' teve alto teor de prolina em Umbaúba e em Frei Paulo, características geralmente associadas à tolerância à seca, que contribuem para adaptação. Também é importante considerar que a cultivar 'BRS Caipira' foi a primeira a apresentar aumento no teor de clorofila após longo período de seca, o que indica recuperação mais rápida após período seco. Além disso, os resultados indicam que as cultivares mais adaptadas ao cultivo nessa área são 'Irará', 'BRS Tapioqueira', 'BRS Kiriris' e 'BRS Caipira'.(AU)

Effects of Arbuscular Mycorrhiza on Osmotic Adjustment and Photosynthetic Physiology of Maize Seedlings in Black Soils Region of Northeast China

ABSTRACT To investigate the effect of arbuscular mycorrhiza fungi on maize growth, osmoregulation substances and photosynthetic physiology, a popular maize variety ZD 958 was measured under potted condition. Arbuscular mycorrhiza (AM) symbiosis promoted plant growth, and enhanced plant height, leaf length, mean leaf width and dry weight. Higher soluble sugar and protein, but lower proline concentrations were detected in AM seedlings than corresponding non-AM seedlings. Quantum yield of PSII photochemistry and potential photochemical efficiency increased by arbuscular mycorrhiza fungi, meanwhile, AM plants had lower primary fluorescence but higher maximal fluorescence and variable fluorescence than non-AM plants. AM enhanced apparent quantum efficiency, maximum net photosynthetic rate, dark respiration rate and light saturation point, but reduced light compensation point. The conclusion was that, after the seedling inoculated with Glomus. tortuosum, AM symbioses could protect cell from being hurt through regulating substances related to osmotic adjustment, besides, the efficiency of light utilization, the capacity of using low light and the capacity of fitting and using high light were all increased by AM symbiosis.

Effects of water deficit on radicle apex elongation and solute accumulation in Zea mays L.

In this study, we examined the effects of water deficit on the elongation of radicles of maize seedlings and on the accumulation of solutes in the radicle apices of two maize varieties: VS-22 (tolerant) and AMCCG-2 (susceptible). Sections of radicle corresponding to the first 2 mm of the primary roots were marked with black ink, and the seedlings were allowed to grow for 24, 48, and 72 h in polyvinyl chloride (PVC) tubes filled with vermiculite at three different water potentials (Ψ(w), -0.03, -1.0, and -1.5 MPa). The radicle elongation, sugar accumulation, and proline accumulation were determined after each of the growth periods specified above. The Ψ(w) of the substrate affected the dynamics of primary root elongation in both varieties. In particular, the lowest Ψ(w) (-1.5 MPa) inhibited root development by 72% and 90% for the VS-22 and AMCCG-2 varieties, respectively. The osmotic potential (Ψ(o)) was reduced substantially in both varieties to maintain root turgor; however, VS-22 had a higher root turgor (0.67 MPa) than AMCCG-2 (0.2 MPa). These results suggest that both varieties possess a capacity for osmotic adjustment. Sugar began to accumulate within the first 24 h of radicle apex growth. The sugar concentration was higher in VS-22 root apices compared to AMCCG-2, and the amount of sugar accumulation increased with a decrease in Ψ(w). Significant amounts of trehalose accumulated in VS-22 and AMCCG-2 (29.8 µmol/g fresh weight [FW] and 5.24 µmol/g FW, respectively). Starch accumulation in the root apices of these two maize varieties also differed significantly, with a lower level in VS-22. In both varieties, the proline concentration also increased as a consequence of the water deficit. At 72 h, the proline concentration in VS-22 (16.2 µmol/g FW) was almost 3 times greater than that in AMCCG-2 (5.19 µmol/g FW). Trehalose also showed a 3-fold increase in the tolerant variety. Accumulation of these solutes in the root growth zone may indicate an osmotic adjustment (OA) to maintain turgor pressure.

Physiological adjustment to salt stress in Jatropha curcas is associated with accumulation of salt ions, transport and selectivity of K+, osmotic adjustment and K+/Na+ homeostasis.

This study assessed the capacity of Jatropha curcas to physiologically adjust to salinity. Seedlings were exposed to increasing NaCl concentrations (25, 50, 75 and 100 mm) for 15 days. Treatment without NaCl was adopted as control. Shoot dry weight was strongly reduced by NaCl, reaching values of 35% to 65% with 25 to 100 mm NaCl. The shoot/root ratio was only affected with 100 mm NaCl. Relative water content (RWC) increased only with 100 mm NaCl, while electrolyte leakage (EL) was much enhanced with 50 mm NaCl. The Na(+) transport rate to the shoot was more affected with 50 and 100 mm NaCl. In parallel, Cl(-) transport rate increased with 75 and 100 mm NaCl, while K(+) transport rate fell from 50 mm to 100 mm NaCl. In roots, Na(+) and Cl(-) transport rates fell slightly only in 50 mm (to Na(+)) and 50 and 100 mm (to Cl(-)) NaCl, while K(+) transport rate fell significantly with increasing NaCl. In general, our data demonstrate that J. curcas seedlings present changes in key physiological processes that allow this species to adjust to salinity. These responses are related to accumulation of Na(+) and Cl(-) in leaves and roots, K(+)/Na(+) homeostasis, transport of K(+) and selectivity (K-Na) in roots, and accumulation of organic solutes contributing to osmotic adjustment of the species.

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

BACKGROUND AND AIMS: Osmolytes are low-molecular-weight organic solutes, a broad group that encompasses a variety of compounds such as amino acids, tertiary sulphonium and quaternary ammonium compounds, sugars and polyhydric alcohols. Osmolytes are accumulated in the cytoplasm of halophytic species in order to balance the osmotic potential of the Na(+) and Cl(-) accumulated in the vacuole. The advantages of the accumulation of osmolytes are that they keep the main physiological functions of the cell active, the induction of their biosynthesis is controlled by environmental cues, and they can be synthesized at all developmental stages. In addition to their role in osmoregulation, osmolytes have crucial functions in protecting subcellular structures and in scavenging reactive oxygen species. SCOPE: This review discusses the diversity of osmolytes among halophytes and their distribution within taxonomic groups, the intrinsic and extrinsic factors that influence their accumulation, and their role in osmoregulation and osmoprotection. Increasing the osmolyte content in plants is an interesting strategy to improve the growth and yield of crops upon exposure to salinity. Examples of transgenic plants as well as exogenous applications of some osmolytes are also discussed. Finally, the potential use of osmolytes in protein stabilization and solvation in biotechnology, including the pharmaceutical industry and medicine, are considered.

Research advances in major cereal crops for adaptation to abiotic stresses.

With devastating increase in population there is a great necessity to increase crop productivity of staple crops but the productivity is greatly affected by various abiotic stress factors such as drought, salinity. An attempt has been made a brief account on abiotic stress resistance of major cereal crops viz. In spite of good successes obtained on physiological and use molecular biology, the benefits of this high cost technology are beyond the reach of developing countries. This review discusses several morphological, anatomical, physiological, biochemical and molecular mechanisms of major cereal crops related to the adaptation of these crop to abiotic stress factors. It discusses the effect of abiotic stresses on physiological processes such as flowering, grain filling and maturation and plant metabolisms viz. photosynthesis, enzyme activity, mineral nutrition, and respiration. Though significant progress has been attained on the physiological, biochemical basis of resistance to abiotic stress factors, very little progress has been achieved to increase productivity under sustainable agriculture. Therefore, there is a great necessity of inter-disciplinary research to address this issue and to evolve efficient technology and its transfer to the farmers' fields.

Effects of potassium and sodium supply on drought-adaptive mechanisms in Eucalyptus grandis plantations.

A basic understanding of nutrition effects on the mechanisms involved in tree response to drought is essential under a future drier climate. A large-scale throughfall exclusion experiment was set up in Brazil to gain an insight into the effects of potassium (K) and sodium (Na) nutrition on tree structural and physiological adjustments to water deficit. Regardless of the water supply, K and Na supply greatly increased growth and leaf area index (LAI) of Eucalyptus grandis trees over the first 3 yr after planting. Excluding 37% of throughfall reduced above-ground biomass accumulation in the third year after planting for K- supplied trees only. E. grandis trees were scarcely sensitive to drought as a result of the utilization of water stored in deep soil layers after clear-cutting the previous plantation. Trees coped with water restriction through stomatal closure (isohydrodynamic behavior), osmotic adjustment and decrease in LAI. Additionally, droughted trees showed higher phloem sap sugar concentrations. K and Na supply increased maximum stomatal conductance, and the high water requirements of fertilized trees increased water stress during dry periods. Fertilization regimes should be revisited in a future drier climate in order to find the right balance between improving tree growth and limiting water shortage.

Aspectos fisiológicos e bioquímicos de cultivares de soja submetidos a déficit hídrico induzido por PEG 6000 / Phisiological and biochemical aspects of soybean cultivars submitted to water deficit induced by PEG 6000

Na cultura da soja, o déficit hídrico é um dos fatores limitantes à obtenção da máxima produtividade. A identificação de genótipos com capacidade de tolerância à seca é fundamental para a solução desse problema. Objetivou-se, neste trabalho, analisar a qualidade fisiológica e as respostas bioquímicas de cultivares de soja (MG/BR 46 Conquista, UFUS Carajás, UFUS Impacta, UFUS Riqueza e UFUS Xavante) submetidas ao estresse hídrico com soluções de PEG 6000 em diferentes níveis de potencial osmótico (0; -0,1; -0,2; -0,3 e -0,4 MPa). Avaliou-se a qualidade fisiológica das cultivares por meio dos testes de comprimento de plântulas e biomassa fresca e seca de plântulas. As respostas bioquímicas foram avaliadas pela detecção do ácido indol-acético, pelo conteúdo de sacarose e pelo transporte de água nas plântulas. A cultivar UFUS Riqueza apresentou os melhores desempenhos nos testes de qualidade fisiológica, conteúdo de sacarose, absorção e velocidade de absorção de água em plântulas. A cultivar UFUS Xavante mostrou a maior concentração de AIA e o maior massa de plântulas no teste de transporte de água.

In soybean culture water deficit is one of the most limiting factors to the maximum yield obtained. Genotypes identification with drought tolerance capacity is fundamental to solve this problem. The objective in this paper was analyze the physiological quality and physiological and biochemical responses of soybeans cultivars (MG/BR 46 Conquista, UFUS Carajás, UFUS Impacta, UFUS Riqueza and UFUS Xavante) submitted to water stress with PEG 6000 solutions in different levels of osmotic potentials (0; -0,1; -0,2; -0,3 and -0,4 MPa). Physiological quality of cultivars were evaluated by seedling length test and fresh and dry biomass. The biochemical responses were evaluated by detection of indol-acetic acid (IAA), by saccharose content and seedling water transportation. UFUS Riqueza presented the best performance in physiological quality tests, saccharose content, absorption and water absorption velocity in seedling. UFUS Xavante showed the highest IAA's concentration and the greater weight of seedling in water transportation test.

Curvas pressão-volume e expansão foliar em cultivares de algodoeiro submetidos à défcit hídrico

The response of two cotton cultivars to water deficit was studied using leaf expansion and pressure-volume curves method to compare their ability in relation to osmotic adjustment. The osmotic potential at full saturation and at the turgor loss point, for 'IAC 13-1', were 0.1 MPa lower than for `IAC 20' under later stress. Osmotic adjustment at full saturation was 0.15 and 0.03 MPa, and at turgor loss point was 0.18 and 0.07 MPa for 'IAC 13-1'and 'IAC 20', respectively. The low osmotic potential values observed for 'IAC 13-1' suggests that the tissues support water deficit longer, before cells reach plasmolysis. The values for bulk modulus of elasticity were higher when both cultivars were under water deficit, and at 'IAC 13-1' seems to have cell walls greater elasticity. Leaf expansion stopped at water potential, before sunrise, at -1.04 and -0.98 MPa for 'IAC 13-1' and 'IAC 20', respectively.

Foi avaliado o comportamento de dois cultivares de algodoeiro em resposta ao déficit hídrico, utilizando-se a expansão foliar como parâmetro discriminatório, bem como a metodologia das curvas pressão-volume para comparar suas habilidades com relação ao ajustamento osmótico. Nos tratamentos estressados, os valores dos FONT FACE="Symbol">Y /font>s em plena turgescência e em turgescência zero obtidos para 'IAC 13-1' foram 0,1 MPa menores do que os obtidos para 'IAC 20'. O ajustamento osmótico em plena turgescência foi de 0.15 e 0.03 MPa, e em turgescência zero foi de 0.18 e 0.07 MPa, respectivamente para os dois cultivares. Os menores valores obtidos para o cultivar 'IAC 13-1' parecem indicar que seus tecidos suportam o estresse por um tempo maior antes das células atingirem o estado de plasmólise. Os valores do módulo volumétrico de elasticidade aumentaram quando os dois cultivares foram submetidos ao estresse hídrico, sendo que o cultivar 'IAC 13-1' parece apresentar paredes celulares com maior elasticidade. Os valores de FONT FACE="Symbol">Y /font>a, antes do amanhecer, em que ocorreu a paralização do crescimento da folha foram -1,04 MPa e -0,98 MPa para os cultivares 'IAC 13-1' e 'IAC 20', respectivamente, mas não detectou-se diferenças significativas entre os dois cultivares.

Curvas pressão-volume e expansão foliar em cultivares de algodoeiro submetidos à défcit hídrico

The response of two cotton cultivars to water deficit was studied using leaf expansion and pressure-volume curves method to compare their ability in relation to osmotic adjustment. The osmotic potential at full saturation and at the turgor loss point, for 'IAC 13-1', were 0.1 MPa lower than for `IAC 20' under later stress. Osmotic adjustment at full saturation was 0.15 and 0.03 MPa, and at turgor loss point was 0.18 and 0.07 MPa for 'IAC 13-1'and 'IAC 20', respectively. The low osmotic potential values observed for 'IAC 13-1' suggests that the tissues support water deficit longer, before cells reach plasmolysis. The values for bulk modulus of elasticity were higher when both cultivars were under water deficit, and at 'IAC 13-1' seems to have cell walls greater elasticity. Leaf expansion stopped at water potential, before sunrise, at -1.04 and -0.98 MPa for 'IAC 13-1' and 'IAC 20', respectively.

Foi avaliado o comportamento de dois cultivares de algodoeiro em resposta ao déficit hídrico, utilizando-se a expansão foliar como parâmetro discriminatório, bem como a metodologia das curvas pressão-volume para comparar suas habilidades com relação ao ajustamento osmótico. Nos tratamentos estressados, os valores dos FONT FACE="Symbol">Y /font>s em plena turgescência e em turgescência zero obtidos para 'IAC 13-1' foram 0,1 MPa menores do que os obtidos para 'IAC 20'. O ajustamento osmótico em plena turgescência foi de 0.15 e 0.03 MPa, e em turgescência zero foi de 0.18 e 0.07 MPa, respectivamente para os dois cultivares. Os menores valores obtidos para o cultivar 'IAC 13-1' parecem indicar que seus tecidos suportam o estresse por um tempo maior antes das células atingirem o estado de plasmólise. Os valores do módulo volumétrico de elasticidade aumentaram quando os dois cultivares foram submetidos ao estresse hídrico, sendo que o cultivar 'IAC 13-1' parece apresentar paredes celulares com maior elasticidade. Os valores de FONT FACE="Symbol">Y /font>a, antes do amanhecer, em que ocorreu a paralização do crescimento da folha foram -1,04 MPa e -0,98 MPa para os cultivares 'IAC 13-1' e 'IAC 20', respectivamente, mas não detectou-se diferenças significativas entre os dois cultivares.

Drought acclimation among tropical forest shrubs (Psychotria, Rubiaceae).

Mechanisms of dry-season drought resistance were evaluated for five evergreen shrubs (Psychotria, Rubiaceae) which occur syntopically in tropical moist forest in central Panama. Rooting depths, leaf conductance, tissue osmotic potentials and elasticity, and the timing of leaf production were evaluated. From wet to dry season, tissue osmotic potentials declined and moduli of elasticity increased in four and five species, respectively. Irrigation only affected osmotic adjustment by P. furcata. The other seasonal changes in leaf tissue properties represented ontogenetic change. Nevertheless, they made an important contribution to dry-season turgor maintenance. Small between-year differences in dry season rainfall had large effects on plant water status. In 1986, 51 mm of rain fell between 1 January and 31 March, and pre-dawn turgor potentials averaged <0.1 MPa for all five Psychotria species in March (Wright 1991). In 1989, 111 mm of rain fell in the same period, pre-dawn turgor potentials averaged from 0.75 to 1.0 MPa for three of the species in April, and only P. chagrensis lost turgor. The relation between leaf production and drought differed among species. P. limonensis was buffered against drought by the lowest dry-season conductances and the deepest roots (averaging 244% deeper than its congeners) and was the only species to produce large numbers of leaves in the dry season. P. chagrensis was most susceptible to drought, and leaf production ceased as turgor loss developed. For the other species, water stress during severe dry seasons may select against dry-season leaf production.