In dié studie is sekere aspekte van voedingswaarde van droogtebestandegewasse, tussen twee seisoene en op drie verskillende lokaliteite nl Hatfield, Mier en Lovedale, geondersoek. Die spesies wat met mekaar vergelyk is, was: C. sturtii, A. nummularia, A. halimus A. canescens(Santa Rita), A. canescens (Veldreservaat 1), en A. canescens(Rincon). Die twee seisoene was herfs en winter. Uit dié resultate kan die volgende afleiding gemaak word:betekenisvolle(P < 0.05) laer blaar-totstamverhouding gedurende die winter as die herfs kon by die onderskeie proefpersele van, C. sturtii en A. canescens (Veld 1)(Hatfield); A. canescens(Veld 1) en A. canescens(Rincon)(Mier); A. canescens(Veld 1) en A. canescens(Santa Rita)(Lovedale), waargeneem word. In teenstelling met die bogenoemde bevindinge het A. nummularia(Lovedale) betekenisvol (P < 0.05) hoër blaar-totstamverhouding in die winter as die herfs gehad. Vir A. canescens (Santa Rita) het die Mier proefperseel betekenisvolle (P < 0.05) hoër blaar-tot-stamverhouding as die ander twee lokaliteite getoon. By al drie proefpersele, vir alle spesies, is die blaar RP % sowel as die IVDMV % van die blare betekenisvol (P < 0.05) hoër as dié van stamme. Vir al die spesies geoes by Mier, was die NBV % in die winter betekenisvol (P < 0.05) hoër as in die herfs. C. sturtii (Lovedale) het geen betekenisvolle (P > 0.05) verskille in die chemiese samestelling tussen seisoene getoon nie, terwyl die ander spesies wel betekenisvolle (P < 0.05) verskille getoon het. Slegs in die geval van A. nummularia kon betekenisvolle (P < 0.05) verskille in IVDMV % tussen lokaliteite waargeneem word. Indien die tempo van degradasie (c) gedurende die herfs by Hatfield geoes, tussen spesies vergelyk word, het A. canescens (Veld 1)betekenisvolle (P < 0.05) hoër c-waarde as dié vanaf A. nummularia en A.canescens (Santa Rita) gehad. Slegs monsters op Hatfield gedurende die herfs geoes kon betekenisvolle (P < 0.05) verskille in PD tussen A. canescens (Veld1) en A. nummularia waargeneem word. Slegs by Mier, in die herfs, het A. nummularia betekenisvol(P < 0.05) hoër ED as A. canescens (Veld 1) gehad. Vir wintermonsters kon geen betekenisvolle (P > 0.05) verskille in die c-waarde tussen spesies en lokaliteite waargeneem word nie. Wintermonsters, geneem te Mier, het A. canescens (Veld 1) betekenisvol (P < 0.05) laer PD as die ander spesies gehad, terwyl by Lovedale het A. canescens(Santa Rita) betekenisvol (P < 0.05) laer PD as die ander spesies gehad. A. nummularia het betekenisvol (P < 0.05) hoër ED as die ander spesies, by Mier en Lovedale, vir monsters wat gedurende winter geoes is, gehad. Wanneer gasproduksiewaardes tussen spesies vergelyk word, het A. canescens (Veld 1) betekenisvol (P < 0.05) minder gas as die ander spesies, vir inkubasie tye 20,30 en 44 ure, geproduseer. Betekenisvolle (P < 0.05) verskille in die a-waarde kon tussen die hoë C. sturtii en die lae A. canescens. (Santa Rita), maar nie tussen die ander spesies, waargeneem word. Betekenisvollen (P < 0.05) verskille in die b-waarde kon tussen: C. sturtii (145.1 ml/g DM), A. canescens (Veld 1)(127.9 ml/g DM)en A. canescens (Rincon)(164.9 ml/g DM) waargeneem word. Betekenisvolle verskille (P < 0.05) in die tempo van gasproduksie kon net tussen die hoë C. sturtii (0.086/h) en die lae A. canescens (Santa Rita)(0.065/h) waargeneem word. Betekenisvolle (P < 0.05) verskille in die potensiële gasproduksie (a + b) kon tussen: C. sturtii, A. canescens. (Veld 1) en A. canescens (Rincon) waargeneem word. Droogtebestande gewasse kan as medium tot lae kwaliteit voerbronne beskou word,wat op strategiese tye(droogte tye) benut kan word. ENGLISH : The nutritive value of four drought tolerant crops were investigated at three localities during two seasons. The species which have been compared, were C. sturtii, A. nummularia, A. halimus, A. canescens (Santa Rita), A. canescens (Field reserve 1), and (Rincon). The two seasons were autumn and winter. A significantly (P < 0.05) lower leaf-to-stem ratio was recorded for the species <i<C. sturtii and A. canescens (Field 1) at Hatfield, while at Mier A. canescens (Field 1) and A. canescens (Rincon) were found to have significant (P < 0.05)lower values in the winter than in the autumn. At Lovedale, the winter leaf-to-stem ratios were significantly (P < 0.05) lower than in the autumn for A. canescens (Field 1) and A. canescens (Santa Rita). In contrast to the above, A. nummularia had a significantly (P < 0.05) higher leaf-to-stem ratio in winter than in autumn at Lovedale. Overall, A. canescens (Santa Rita) harvested at Mier had a significantly (P < 0.05) higher leaf-to-stem ratio than material from the other two sites. At all the sampling sites and for all accessions the CP % and the IVDMD % of the leaves were significantly (P < 0.05) higher than those of the stems. The NDF % in most of the species harvested during winter, was significantly (P < 0.05) higher than those harvested during autumn. C. sturtii was the only species for which no significant (P > 0.05) differences in the chemical composition could be found between the two seasons. Only in the case of A. nummularia could significant (P < 0.05) differences in the IVDMD % be found between localities. A. canescens (Field 1) harvested during autumn at Hatfield, had a significantly higher rate of passage(c) than A. nummularia and A. canescens (Santa Rita). Samples harvested at Hatfield in autumn also produced significant (P < 0.05) differences in PD between A. canescens (Field 1) and A .nummularia. Mier was the only sampling site where significantly (P < 0.05) higher (A. nummualaria) and lower (A. canescens(Field1)) ED were observed for samples taken during autumn. No significant (P > 0.05) differences in the rate of passage (c) were observed between species or sampling sites for samples taken during the winter. Winter samples taken from A. canescens (Field 1) at Mier and A. canescens (Santa Rita) taken from Lovedale, showed significantly (P < 0.05) lower PD than the other species. A. nummularia had significantly (P < 0.05) higher ED than the other species harvested at Mier and Lovedale, during winter. When gas production values between species were compared it was clear that A. canescens (Field1) produced significantly (P < 0.05) less gas compared to the other species at incubation times of 20, 30 and 44 hours. Significant (P < 0.05) differences in the a-values were also observed between the high C. sturtii and the low A. canescens (Santa Rita) values. Significant (P < 0.05) differences in the b-value were observed between C. sturtii (145.1ml/g DM), A. canescens (Field 1)(127.9 ml/g DM) and A. canescens (Rincon)(164ml/g DM). C. sturtii (0.086/h) and A. canescens (Santa Rita)(0.065/h) were the only species that differed significantly (P < 0.05) in terms of the rate of passage(c). Significant (P < 0.05) differences in the potential gas production (a + b) were observed between C.sturtii, A. canescens (Field 1) and A. canescens (Rincon). Drought resistant crops can be considered as a medium to low quality source of fodder which can be used at strategic times, especially during periods of drought. Copyright / Dissertation (MScAgric)--University of Pretoria, 2010. / Animal and Wildlife Sciences / unrestricted

Coleogyne ramosissima Torr. (blackbrush) and Atriplex confertifolia [Torr. & Frem.] Wats. (shadscale) are cold desert shrubs from different families that often grow together in the Great Basin and the Colorado Plateau in the life zone between 800 and 2000 m elevation. Tissue and seeds from the two species were collected from several localities. Metabolic heat and carbon dioxide production rates were measured with calorespirometry on tissue from field-grown plants and on seedlings at temperatures from 5 to 35°C at 5°C intervals. Blackbrush adapts to higher temperatures earlier than does shadscale, and once it has adjusted to higher temperatures, anabolic rates keep rising with increasing temperature while for shadscale rates flatten out or drop off between 25 and 35°C. Both species are metabolically adapted to temperatures during the growth season determined by the historical rainfall pattern.

The herbaceous Atriplex species which occur in Utah are revised. This study is based on herbarium specimens and field observations throughout the state. My treatment largely follows that of Rall and Clements (1923). A brief discussion of the history, diagnostic characteristics and phylogeny is given. A descriptive key that includes all taxa has been prepared: type locality, synonyms, general habitat and distribution is reported for each entity. Illustrations and maps are included. One variety is described as new.

Atriplex is a genus in the Chenopodiaceae, the perennial members of which are ecologically important in western North America. Seventeen species and one subspecies of perennial Atriplex occur in Utah and the northern deserts. Three of these species and the subspecies were described by the writer in a recent publication as a result of extensive field work leading to this study. These are A. welshii, A. navajoensis, A. bonnevillensis, and A. cuneata ssp. introgressa. This study is an investigation of the systematics and phytogeography of the perennial Atriplex in Utah and the northern deserts, with emphasis on the A. gardneri and A. garrettii groups. Since the publication of the Phylogenetic Method in Taxonomy (Hall and Clements, 1923) little systematic work has been done on North American Atriplex. The results of this study indicate that considerable reorganization of taxa occurring within the northern deserts is necessary. The five species formerly classified within A. "nuttallii" Wats. are considered specifically distinct because they are not only discrete morphologically, but soil analysis indicate they have differing edaphic requirements and do not interbreed when sympatric. Nine hybrids are fully discussed. Of these, only one was previously recognized as a hybrid. In addition, one species (A. bonnevillensis) and the subspecies (A. cuneata ssp. introgressa) were found to be of hybrid origin. Scatter diagram analyses are included for six of these hybrids and their parents and the two taxa of hybrid origin. Each taxon is thoroughly described and collection sites are given. Almost all the northern desert species and their hybrids are figured with photographs, and the newly described species and members of the A. "nyttallii" group are figured with line drawings. As the fruiting bract appears to have the most useful diagnostic value, these are illustrated for all northern desert species and hybrids. An attempt has been made to put the nomenclature in order and all synonyms are given. The epithet A. "nuttallii" Wets. is invalid because it is antedated by A. gardneri (Moq.) Dietr .

Uma das caracterÃsticas fisiolÃgicas mais importantes das halÃfitas pertencentes ao gÃnero Atriplex à a enorme habilidade de acumular solutos orgÃnicos e inorgÃnicos com o intuito de se ajustar osmoticamente em condiÃÃes de elevada salinidade e deficiÃncia hÃdrica. Contudo estudos compreensivos sobre a contribuiÃÃo relativa desses solutos inorgÃnicos e orgÃnicos no ajustamento osmÃtico de folhas dessas halÃfitas ainda sÃo poucos explorados na literatura. Esse trabalho pretende pela primeira vez na literatura fazer um estudo detalhado, da participaÃÃo e da contribuiÃÃo relativa da maioria dos solutos orgÃnicos e inorgÃnicos no potencial osmÃtico de folhas de Atriplex nummularia, submetidas a concentraÃÃes crescentes de NaCl, ciclos sucessivos de seca e ao polietileno glicol (PEG). Para responder as questÃes acima mencionadas foram conduzidos trÃs grandes experimentos seqÃenciais. No primeiro experimento, mudas de Atriplex nummularia com quatro meses de idade, foram cultivadas em vasos de argila contendo como substrato areia, sendo irrigadas a cada dois dias com soluÃÃo contendo concentraÃÃes crescentes de NaCl (0, 100, 200, 300 e 400 mmol L-1) durante 120 dias. O experimento foi realizado em condiÃÃes de casa de vegetaÃÃo. No segundo experimento, mudas de A. nummularia, com idade de 18 meses foram transplantadas para recipientes de polietileno contendo 5.0 kg de vermiculita, em condiÃÃes de casa de vegetaÃÃo, onde foram submetidas aos seguintes tratamentos (Controle; seca; NaCl + seca; NaCl) por trÃs ciclos sucessivos de seca-reidrataÃÃo (3 semanas) seguido de uma recuperaÃÃo no final do Ãltimo ciclo (apÃs 48 h). No terceiro experimento, plÃntulas de A.nummularia, com idade de dois meses foram transplantadas para cultivo hidropÃnico em vasos plÃsticos com capacidade para 0,8 em sala de crescimento sob condiÃÃes controladas onde sofrerÃo um prÃ-condicionamento com ou sem NaCl por duas semanas. ApÃs foram submetidas aos seguintes tratamentos (controle; PEG; NaCl; NaCl + PEG). Em conclusÃo, os resultados da presente investigaÃÃo demonstram que as plantas de Atriplex nummularia foram capazes de manter o seu crescimento mesmo em condiÃÃes de alta salinidade, principalmente pela capacidade de manutenÃÃo de seu status hÃdrico. Os resultados tambÃm sugerem que a GB à o maior soluto orgÃnico envolvido com o ajustamento osmÃtico (AO) do citoplasma e que sua acumulaÃÃo parece ser uma resposta adaptativa ao estresse provocado pelo NaCl. Em adiÃÃo, o Ãons salinos Na+ e Cl- contribuÃram para a maioria do AO das folhas submetidas ao NaCl. O impacto relativo do K+ sobre o AO das folhas foi reduzido consideravelmente com o aumento da dose externa de NaCl. Os resultados evidenciam tambÃm que o prÃ-condicionamento com NaCl influenciou positivamente no crescimento de Atriplex nummularia, em condiÃÃes de seca, evidenciado pelo maior acÃmulo de massa seca e melhor status hÃdrico das folhas. Dentre os solutos inorgÃnicos analisados, o Na+ e o Cl- foram os que mais contribuÃram para a osmorregulaÃÃo das folhas em condiÃÃes de deficiÃncia hÃdrica. Enquanto, GB foi o soluto orgÃnico mostrou o maior percentual de contribuiÃÃo para o potencial osmÃtico. Entretanto os resultados mostraram que o prÃ-condicionamento das plÃntulas de Atriplex nummularia com NaCl nÃo foram capazes de atenuar os efeitos induzidos pelo PEG.

Made available in DSpace on 2016-08-31T13:24:14Z (GMT). No. of bitstreams: 1 EdymaraSRM_DISSERT.pdf: 1076092 bytes, checksum: 0144c1453af5878d0247ae1b472b4e9c (MD5) Previous issue date: 2013-03-06 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Rural communities located in the Brazilian Northeast, especially in semiarid region, live with water shortages resulting from erratic rainfall in this region, resulting in problems with the drinking water supply. The use of groundwater enables of the water supply in many of these communities, but due to the high levels of salts such waters often need to be treat ed in treatment plants by the process of desalination by reverse osmosis, generating apart from potable water, water of high salinity called saline waste of high capacity polluting of the soil and water sources requiring the study of viable alternatives to its deposition in the environment. In this context, this work proposes the cultivation of the halophyte known as herb salt (Atriplex nummularia), on Project of settlement Rural of Good Faith, in Mossoró, RN as an alternative to deposition of saline waste for forage production. The statistical design was a split-plot, being four treatments at the plots, related to levels of soil moisture and having based on the moisture in the Field Capacity (FC) (T1 -100% of FC; T2 85% of FC; T3 70% of FC and T4 50% of FC) and in subplots, two levels of organic manure (Fo: not fertilized and F1: fertilized), with four replications. Were analyzed Variables of growth, yield and quality of forage crop at harvest of material, after three months of cultivation. It was observed that herb salt has good production capacity of fresh matter and drought of herb salt under a level of 85% soil moisture in relation to its field capacity, presenting minimal loss of yield, 5,74% and 3,54%, respectily, and proved to be productive even with the dry soil. The total productivity was 5689,62 kg ha-1 showing its viability for forage production. The quantities of salts extracted were high, mainly for Cl-and Na+, demonstrating the phytoextraction ability of the herb salt, compatibilizing up with the problematic of disposal of waste from desalination, also presented good quality of forage produced / As comunidades rurais situadas no Nordeste brasileiro, em especial na região semiárida, convivem com a escassez de água resultante da irregulari dade das chuvas, acarretando em problemas com o abastecimento de água potável. A utilização de águas subterrâneas permite o abastecimento hídrico em diversas comunidades nordestinas, mas, devido aos elevados níveis de sais, estas águas necessitam muitas vezes ser tratadas em estações de tratamento pelo processo de dessalinização por osmose reversa, gerando além da água potável, uma água de elevada salinidade chamada rejeito salino , de alto poder poluente do solo e de mananciais, sendo necessário o estudo de alternativas viáveis para sua deposição no ambiente. Neste contexto, o presente trabalho propôs cultivar a halófita conhecida como erva sal (Atriplex nummularia), no Projeto de assentamento Rural Boa Fé, em Mossoró-RN, como alternativa à deposição do rejeito salino para a produção de forragem. O delineamento estatístico utilizado foi o de parcelas subdivididas, sendo quatro tratamentos nas parcelas, referentes a níveis de umidade do solo tendo como base a umidade na Capacidade de Campo (CC) (T1 -100% da CC; T2 85% da CC; T3 70% da CC e T4 50% da CC) e nas subparcelas, dois níveis de adubação orgânica (não adubado A0 e adubado A1), com quatro repetições. Foram analisadas variáveis de crescimento, produção, composição mineral do tecido vegetal e a qualidade da forragem, após a colheita do material aos três meses de cultivo. Observou-se que a erva sal possui boa capacidade de produção de matéria fresca e seca total sob um nível de 85% de umidade do solo em relação à sua capacidade de campo, apresentando mínimas perdas de rendimento, de 5,74% e 3,54%, respectivamente , mastambém se mostrou produtiva mesmo com o solo mais seco. A produtividade total de matéria fresca para o tratamento testemunha foi de 5689,62 kg ha-1 mostrando sua viabilidade para a produção de forragem. As quantidades de sais extraídos pela erva sal do solo foram elevadas, principalmente, para o Cl-e o Na+, evidenciando a capacidade fito -extratora da erva sal, compatibilizando-se com a problemática da deposição do rejeito da dessalinização, além de ter apresentado boa qualidade da forragem produzida

The saltbush is an C4 species extremely tolerant to soils and saline waters and has good capacity to accumulate quantities of salts in their tissues, also serving as forage potential. Therefore, it is an excellent material for the identification of physiological and biochemical mechanisms involved in the resistance to salinity. The objective of this study was to evaluate the ecophysiological and biochemical responses of saltbush under increasing levels of NaCl. Plants were grown in pots kept in a greenhouse and irrigated every 2 days at concentrations of 0, 150, 300, 450 and 600 mM NaCl over time. Were determined biometric (height and stem diameter), gas exchange (photosynthetic assimilation of CO2 (A), stomatal conductance (gS), the internal concentration of carbon (Ci), transpiration (E) and vapor pressure deficit between leaf and air (DPVair-leaf)), the content of chlorophyll (Chl a, Chl b, Chl total and Chl a / b) and content of proline in leaves. The experimental design was completely randomized in a 5x4 factorial scheme, with five levels of salinity and for evaluation periods (0, 15, 30 and 45 days) with 5 replications. At 60 days evaluated the effect of levels 0, 150 and 300 mM NaCl on growth, fresh and dry biomass of shoot (stem+leaves) and root, gas exchange, content of chlorophyll, content of Na+, K+ and Na+/K+ in shoot and roots, and content of proline in leaves. The experimental design was DIC, with three levels of salinity and five replications. Until 45 days saltbush presented a stimulating growth at all levels of NaCl, and 0, 150 and 300 mM NaCl showed the highest values of height and stem diameter. As for the gas exchange saltbush presented an adaptive period of 15 days, followed by increase in photosynthetic assimilation. The saltbush accumulated more Na+ than K+, with greater accumulation in the shoot than in the root, to the 300 mM NaCl level, this is the salinity level that the highest yield of fresh biomass (46,38 g) and dried (19,69 g). Increased salinity promoted accumulation of proline, whose highest concentration (3,11 micromol g-1 FM) was observed in 600 mM NaCl treatment. At 60 days the salt stress induced no significant differences in plant growth, but promoted reduction of photosynthetic assimilation and increased internal carbon concentration. After 60 days, saltbush accumulated Na+ in shoot with growth and biomass production was enhanced up to 300 mM NaCl level. Increased levels of salinity reduces the photosynthetic assimilation of the saltbush, but did not significantly affect the production of chlorophylls. In response to salinity saltbush has increased the concentration of proline in their leaves. With increasing salinity, the saltbush develops physiological and biochemical mechanisms to ensure its growth, with the 300 mM NaCl level which favors its maximum production. / A erva-sal e uma especie C4 extremamente tolerante aos solos e as aguas salinas e possui boa capacidade de acumular quantidades de sais em seus tecidos, servindo tambem como potencial forrageiro. Portanto, e um excelente material para a identificacao de mecanismos fisiologicos e bioquimicos envolvidos na resistencia a salinidade. O objetivo deste trabalho foi avaliar as respostas ecofisiologicas e bioquimicas da erva-sal sob niveis crescentes de NaCl. As plantas foram cultivadas em vasos mantidos em casa de vegetacao e irrigadas a cada 2 dias nas concentracoes 0, 150, 300, 450 e 600 mM de NaCl ao longo do tempo. Foram determinados a biometria (altura e diametro do caule), trocas gasosas (assimilacao fotossintetica de CO2 (A), condutancia estomatica (gS), concentracao interna de carbono (Ci), transpiracao (E) e deficit de pressao de vapor entre o ar e a folha (DPVfolha-ar)), teor relativo de clorofilas (Chl a, Chl b, Chl total e relacao Chl a/b) e teor de prolina nas folhas. O delineamento experimental foi inteiramente casualizado, em esquema fatorial 5x4, sendo cinco niveis de salinidade e quatro periodos de avaliacao (0, 15, 30 e 45 dias), com 5 repeticoes. Aos 60 dias avaliou-se o efeito dos niveis 0, 150 e 300 mM de NaCl no crescimento, biomassa fresca e seca da parte aerea (caule+folhas) e raiz, trocas gasosas, teor relativo de clorofilas, teor de Na+, K+ e relacao Na+/K+ na parte aerea e raiz, e teor de prolina nas folhas. O delineamento experimental foi DIC, sendo tres niveis de salinidade e cinco repeticoes. Ate os 45 dias a erva-sal apresentou um estimulo do crescimento em todos os niveis de NaCl, sendo 0, 150 e 300 mM de NaCl os que apresentaram maiores valores de altura e diametro do caule. Quanto as trocas gasosas a erva-sal apresentou um periodo adaptativo de 15 dias, seguido de incremento da assimilacao fotossintetica. A erva-sal acumulou mais Na+ que K+, com maior acumulo na parte aerea que na raiz, ate o nivel 300 mM de NaCl, sendo este o nivel de salinidade que proporcionou maior producao de biomassa fresca (46,38 g) e seca (19,69 g) . O aumento da salinidade promoveu acumulo de prolina, cuja maior concentracao (3,11 Êmol g-1 MF) foi verificado no tratamento 600 mM de NaCl. Aos 60 dias o estresse salino nao induziu diferencas significativas no crescimento das plantas, mas promoveu reducao da assimilacao fotossintetica e aumento da concentracao interna de carbono. Apos 60 dias, a erva-sal acumulou Na+ em sua parte aerea, com crescimento e producao de biomassa favorecidas ate o nivel 300 mM de NaCl. O aumento nos niveis de salinidade reduz a assimilacao fotossintetica da erva-sal, mas nao afetou significativamente a producao de clorofilas. Em resposta a salinidade a erva-sal apresenta aumento na concentracao de prolina em suas folhas. Sob salinidade crescente, a erva-sal desenvolve mecanismos fisiologicos e bioquimicos capazes de assegurar seu crescimento, sendo o nivel 300 mM de NaCl o que favorece seu maximo de producao.

Throughout the arid and semi-arid regions, researchers have been looking at different ways to deal with the salinity problem of the soil and water as well as feed for the livestock. Study 1 focused on a pilot project conducted in an irrigation district in Marana, AZ, USA, looking at using Reverse Osmosis (RO) concentrate on Atriplex lentiformis (quailbush) and then harvesting the plant to be tested for its possible use as a supplement in feed for livestock. Three irrigation treatments were tested based on the potential evapotranspiration rate (ET(o)): (1) plots irrigated at ET(o) adjusted daily via an on-site micrometeorology station; (2) plots irrigated at 1.5 ET(o) adjusted daily; (3) plots irrigated at a constant rate throughout the year based on the mean of annual ET(o). The plants produced 15-24 tons ha⁻¹ year⁻¹ of biomass and could be irrigated at the rate of ET(o), ca. 2 m yr⁻¹ at this location. It was concluded that irrigation of halophyte forage crops provide a viable strategy for extending water supplies and disposing of saline water in arid-zone irrigation districts. Study 2 focused on a field data from Study 1 and two greenhouse experiments. The greenhouse experiments were conducted in 2007 and 2010. The 2010 greenhouse trials, under well-watered conditions, showed that the apparent zero-point-salinity for yield was 47.3 g L⁻¹ TDS. An additional greenhouse experiment was conducted in which plants in sealed pots were grown to the wilting point on a single application of water. The experiment was conducted at different salinities to see if salinity and water stress were additive factors in reducing yield and Water Use Efficiency (WUE). To the contrary, yield and WUE actually increased as a function of salinity, perhaps due to conversion from C3 to C4 photosynthesis over the salinity range (noted in other studies with A. lentiformis). We conclude that xerohalophytes such as A. lentiformis could greatly extend the useful range of salinities under which forage crops can be grown in arid-zone irrigation districts.

This study evaluated the early establishment phase of various monocultures and mixed species plantings of Agropyron desertorum (AGDE), Medicago sativa (MESA), and Atriplex canescens (ATCA). The study was conducted under both greenhouse and field conditions. In the green-house, the experimental design was a split-plot, randomized-block design in time, using transplanted seedlings. The treatments were exposed to three water levels to determine species response to varying moisture availability. Plastic pots of 15.4 cm (diameter) by 17.9 cm (depth) were filled with 2,800 g of sandy-loam soil and brought to field capacity. The pots were weighted twice weekly and the water lost to evapotranspiration was replaced. The plants were measured for plant height on six occasions at two week intervals. On the last measurement date, plants were harvested for above-and-below ground biomass. The field used the species treatment as in the greenhouse study and these were hand sown in 1 m2 plots. Using a line-source sprinkler system, species responses at four water levels were examined. Soil water content in the various field plots was determined at various depths via access tubes and a neutron soil moisture probe. The experimental design was a split-plot design in time. Seedling emergence was recorded daily for the first 35 days after seeding. Plant height was measured six times during the growing season. All the species were clipped, oven-dried, and weighed at the end of the experimental period in 1982. In the greenhouse, AGDE was the dominant species, yet produced more in the MESA combination. MESA exhibited a marked decrease in production when grown with AGDE. ATCA showed a remarkable ability to survive under high water stress. Variable soil water content created in the field resulted in significant differences in germination, emergence, and establishment among planting treatments. MESA germinated and emerged faster than AGDE and ATCA, allowing it to utilize water and nutrient resources earlier than the competing species. The greatest shoot production occurred when MESA grew alone. In the AGDE-MESA combination, shading apparently reduced AGDE growth and shoot production at the two most favorable water levels. ATCA exhibited poor germination and emergence in treatments with low soil water availability.

Root respiratory response of mature Atriplex confertifolia plants growing in established communities was measured during two growing seasons using freshly excised root segments and gas chromatography techniques. Respiratory response at fixed test temperatures changed significantly during the growing season, and this pattern of respiratory adjustment varied for root segments located at different depths in the soil profile. Respiration measured at a constant test temperature was highest during early sumner, and declined to minimum values in late summer and fall. Root segments taken from the top 30 cm of the soil profile displayed peak activity several weeks before root segments from greater depths reached maximum activity. The significance of these patterns of respiration is discussed in relation to the carbon balance of Atriplex plants and the uses of respiratory energy within the root system.