Wild Hordeum species, from the four genome groups of X, H, I and Y, were assessed for physiological traits associated with tolerance to salinity and waterlogging. When grown in saline conditions, a number of wild Hordeum species had exceptional ‘exclusion’ of Na+ and Cl- from the young leaves, and also maintained tissue K+ concentrations, compared with Hordum vulgare ssp. vulgare (cv. ‘Golf’). For example, at 150 mol m-3 NaCl, the K+:Na+ in youngest, fully expanded leaf blades of wild Hordeum species averaged 5.2, compared with 0.8 in H. vulgare. H. marinum was more salt tolerant than H. vulgare, with a relative growth rate 30% higher than H. vulgare at 150 mol m-3 NaCl. At 300 mol m-3 NaCl, glycinebetaine plus proline contributed to 15% of πsap in expanding leaf blades of H. marinum, compared with 8% in H. vulgare. When grown in stagnant conditions, 16 accessions (approximately half of those evaluated) formed a barrier to radial O2 loss (ROL) in basal zones of adventitious roots. In the Triticeae, this trait had previously only been described in one species, H. marinum. The barrier to ROL occurred only in accessions from wetland or intermediate habitats, and was also related to genome type, being present in accessions with the X or the H genome (Hordeum vulgare has the I genome). In stagnant conditions, aerenchyma formed was, on average; 22% in accessions with the X genome; 19% in those with the H genome; and 15 and 16% in those with the I or the Y genomes, respectively. The combination of a barrier to ROL and aerenchyma enhances longitudinal O2 movement in adventitious roots, permitting roots to penetrate deeper into anaerobic substrates. In H. marinum, induction of the barrier to ROL was associated with a 97% reduction in apparent O2 diffusivity across the external layers of the basal zones of roots, compared with near the root tip. The barrier results from physical resistance to radial O2 movement, although when roots were cooled to suppress respiration some additional leakage of O2 was detected, indicating respiration also contributes to the low rates of ROL from the basal regions of roots. Low radial O2 permeability in the roots of stagnantly-treated H. marinum was associated with secondary thickening, putatively lignin or suberin deposits, in the hypodermis. These changes in root structure, however, did not influence root hydraulic conductivity, assessed for individual adventitious roots and whole root systems. Thus, diversity amongst Hordeum species in expression of traits for tolerance to waterlogging (an inducible barrier to ROL and aerenchyma) and salinity (Na+ and Cl- ‘exclusion’) were documented in this study. Traits for root aeration did not compromise the capacity of roots to take up water, presumably being of importance for growth in soils with fluctuating water levels (i.e. wet/dry cycles). The high degree of salinity tolerance in several Hordeum species, and especially in H. marinum, is consistent with field observations that these species occur in salt affected areas

Thesis (Ph. D. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references.

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on November 1, 2007) Includes bibliographical references.

Thesis (M.S.)--University of Delaware, 2008. / Principal faculty advisor: Kuo-Chuin Wong, College of Marine and Earth Studies. Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 74-79). Also available on the World Wide Web.

Thesis (M.A.)--Old Dominion University. / Includes bibliographical references.

Thesis (M.S.)--Joint Program in Oceanography/ Applied Ocean Science and Engineering, Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution, 2005. / Bibliography: p.57-59.

The present study was conducted to investigate the water relations of individual plant cells and the biophysical parameters controlling plant growth in the context of salt stress. Growth and water relations were studied in growing as well as in mature zones of the first emerged leaf of wheat seedlings (cv. Flanders, a British variety) in the context of NaCl stress. Various levels of NaCl (0,25,50,75,100,125 and 150 mol m) -3 were used to salinize the media. I In the case of leaf elongation rate a two phase response was found i. e. an immediate decrease and then, a recovery in the elongation rate. Leaf elongation rate decreased within 1-2 minutes of the onset of stress and, later, a recovery started 1-2 h after the salt addition. The time taken for the recovery was proportional to the levels of external salinity. After 24 h the elongation rate was almost fully recovered for all the NaCl concentrations. A similar response was observed when equi-osmolar concentrations (with NaCl) of mannitol were added to the media. In control plants turgor pressure of the expanding cells was about 0.45 MPa while tissue osmotic pressure was equal to 1.1 MPa showing that the cell had a low water potential (-0.6 MPa). The transpiration tension was equivalent to 0.1 MPa. Turgor pressure in th e growing cells did not change after the salt addition (0- 150 mol m-3 NaCl), however, the tissue osmotic pressure continuously increased with time. Turgor pressure dropped when more -3 than 150 mol m NaCl were applied to the media i. e. 200 and 250 mol m. -3 This is presented as evidence that growing leaf cells - maintained their turgor pressure In response. to . the salt stress by taking up osmotically -active solutes present in the cell wall. The salt stress had not any effect on Instron tensiometric measurements of elastic and plastic extension of the cell wall. A different turgor pressure response was found in the mature cells. Turgor pressure was about 1.0 MPa, almost twice that in the growing cells, while tissue osmotic pressure was similar to that found in the growing cells i. e. 1.1 MPa. After the application of the stress the turgor pressure dropped within 15- 20 min of the application of all the concentrations of NaCl. The osmotic pressure of osmotically active solutes present in the cell wall, nwr was almost negligible i. e. 4 0.1 MPa, in mature cells and so could not contribute to turgor maiýtenance. The extent of decrease was proportional to the external stress of 25, 50 and 75 mol m-3 NaCl only. Turgor pressure recovery, due to osmotic adjustment, started after about 10-12 h of the stress initiation. Complete turgor recovery was achieved after 24-48 h of the onset of stress depending on the applied NaCl concentration. Tissue osmotic pressure increased continuously with time. An increase in the nw was inferred during the whole experimental period and after 6d of the stress application that appeared to correspond to the magnitude of external stress. The concentrations of major ions and sugars were determined to measure their contribution towards the osmotic adjustment. Under control conditions Na +, ci-, PO 4 3- ' so 4 2- , glucose, fructose and sucrose were present in small amounts, while, K+ and No 3- were the-major osmotica. Their concentrations were about 200. mol _m-3. After the stress a large increase in the concentrations of Na + and Cl was observed, the sucrose concentration increased to a small extent. However, other osmotica remained Uniform for whole of the experimental time. A small decrease was observed in k+ concentration in response to higher salt levels. volumetric elastic modulus, -c, of mature cells was remained unchanged by the salt stress. However, the apparent resistance of the root cortex to osmotically driven water flow increased with the increase in stress level. No conclusion could be drawn about the contribution of these parameters to the control of growth and to leaf water relations in the context of salt stress. The possible use of turgor pressure recovery in the mature cells was investigated for assessing the extent of salt tolerance of various Pakistani wheat varieties. These varieties were previously rated according to their performance in absolute grain yield in response to NaCl stress. No simple correlation was found.

Made available in DSpace on 2014-06-11T19:26:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-07-30Bitstream added on 2014-06-13T20:15:40Z : No. of bitstreams: 1 silva_ao_me_botfca.pdf: 2497584 bytes, checksum: acd2b658d1dbff5be344d07027c33e34 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Universidade Estadual Paulista (UNESP) / O uso em execesso de fertilizantes em cultivo sobre ambiente protegido pode levar à salinização, e esse processo pode ser monitorado pela condutividade elétrica na solução do solo. O presente trabalho foi realizado com o objetivo de avaliar a utilização de extratores em cápsulas porosas no manejo da fertirrigação e no controle do processo de salinização em cultivo de beterraba (Beta vulgaris L.). Duas cultivares de beterraba (Early Wonder Tall Top e Itapuã) foram avaliadas em função de dois manejos de fertirrigação, sendo o primeiro o manejo tradicional utilizado pelos produtores rurais e o segundo com uso de extratores de solução do solo para controle da salinidade. O experimento foi realizado em vasos de 14 L e salinizados artificialmente a diferentes níveis de condutividade elétrica no extrato de saturação (1,0; 3,0; 6,0; 9,0; 12,0; dSm-1). Os resultados obtidos demonstram que o controle através de extratores em cápsulas porosas é eficiente no monitoramento de solos com problemas de salinização. Observou-se também que o controle da solução do solo em níveis de condutividade elétrica desejados, proporcionou um efeito benéfico no cultivo da beterraba evitando desequilíbrios iônicos e salinização do solo. O cultivo em ambiente protegido proporcionou menor consumo hídrico e coeficiente de cultivo do que os citados na literatura para cultivo convencional. Os manejos da fertirrigação utilizados proporcionaram efeitos significativos nas variáveis relacionadas ao crescimento e produtividade da... / The excessive use of fertilizers in farming on protected environment can lead to salinization, and this process can be monitored by electrical conductivity in the soil solution. The present study was carried out to evaluate the extraction of soil solution by porous cups, which were used with the purpose to manage the fertigation and control the salinization in beet crop (Beta vulgaris L.) Two beet cultivars (Early Wonder Tall Top and Itapuã) were evaluated against two fertigation managements, the first being the traditional management used by farmers and the second with the use of soil solution extractors to control salinity. The experiment was carried out in 14 L pots and artificially salinized with different levels of electrical conductivity in the saturation extract (1.0, 3.0, 6.0, 9.0, 12.0, dS m-1). The results obtained show that control through porous cup extractors is effective in monitoring soil salinization problems. It was also observed that control of soil solution at desired levels of electrical conductivity, provided a beneficial effect in the beet cultivation avoiding ionic imbalance and salinization. The protected cultivation resulted in less water consumption and crop coefficient than those reported in the literature for conventional farming. The fertigation managements used offered significant effects on variables related to the growth and yield of beet, possibly due to increased fertilizer which increased soil salinity and caused nutrient imbalances in plants. The relative yield of the trees showed a drop from the salinity threshold... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:32:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2003-08-01Bitstream added on 2014-06-13T21:04:10Z : No. of bitstreams: 1 silva_sg_dr_rcla.pdf: 4874331 bytes, checksum: f1933d353551a744a5860e62933a6663 (MD5) / No estado do Rio Grande do Norte, a exemplo de todo o semi-árido nordestino, os aqüíferos fissurais em terrenos cristalinos são caracterizados por apresentar freqüentemente elevado conteúdo de sais e baixas vazões, onde aproximadamente 40% dos poços perfurados têm fluxo abaixo de 200 l/h, independentemente do grau de salinidade da água. Do restante, somente 27,9% fornecem água doce (com teor de resíduo seco abaixo de 1000 mg/l). A deficiência na circulação das águas subterrâneas resulta em altas salinidades e concentrações de cloreto (até 36,7 g/l de resíduo seco (RS) e 15 g/l de Cl) em determinadas regiões e baixas vazões (média de 1 a 3 m3/h) de um modo geral. Foram identificados dois grupos principais de águas: um grupo predominantemente Na-Cl, com Ca e Mg em concentrações secundárias, característico das regiões centro-norte e leste e outro grupo com composição mais variável, em que por vezes, o HCO3 predomina sobre o Cl e os cátions divalentes (Ca e Mg) aumentam de importância, presente nas regiões sul e oeste. As águas das regiões leste e centro-norte apresentam salinidade média elevada (5774.37 mg/l e 5125.43 mg/l de resíduo seco, respectivamente); enquanto o sul e o oeste do estado possuem águas com menor concentração média de sais (1872.60 mg/l e 1699.32 mg/l de resíduo seco, respectivamente). O processo de salinização dos aqüíferos fissurais tem origem em duas escalas: (i) através de mecanismos que atuam em escala regional, na qual os principais elementos que interferem na qualidade de água são o clima e a morfologia do relevo, que determinam a quantidade de água a ser evaporada e a qualidade das águas superficiais (fatores de extrema importância, já que estas águas abastecem os aqüíferos) e (ii) através de fatores que atuam em escala local ou até mesmo pontual, como (a) a liberação de significativas...