Bibliography: p. 191-200. / 200 p. : ill. (chiefly col.), map (fold.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Persistence mechanisms of Erodiophyllum elderi are investigated in terms of life history strategies and patchy population theory. / Thesis (Ph.D.)--University of Adelaide, Dept. of Botany, 1999

Festuca novae-zelandiae (Hack.) Cockayne is an endemic New Zealand perennial tussock forming grass of the family Poaceae. Morphologically F. novae-zelandiae exhibits a number of leaf adaptations associated with dehydration postponement as reflected in the climatic distribution of this species and its occurrence as a physiognomic dominant grass in semi arid short-tussock grasslands. Biochemical studies into the drought tolerance of this species have indicated the occurrence of tissue specific responses with respect to abscisic acid (ABA) and proline accumulation and protein turnover suggestive of a preferential protection of the tiller base and associated meristematic zones at the expense of lamina tissues. Further tissue specific biochemical responses to water-deficit stress in F. novae-zelandiae have been investigated. Changes in water-soluble carbohydrates (WSC) were monitoured over a 49-day dry-down period (decline in soil water content from 30% to 4%) in consecutive leaf segments comprising the leaf base (meristem region), elongation zone, the enclosed and exposed lamina, as well as basal sheath segments from the two next oldest leaves. In fully hydrated leaf tissues polymers of fructose (fructans) were the main WSC present and were mainly low molecular weight fructans of the inulin and neokestose series with the average degree of polymerization (DP) of fructan pools from 6 to 9. The highest fructan concentrations were present towards the leaf base. Fructan concentrations decreased over the course of the dry-down, although remained significantly higher in the meristem region of the tiller base with respect to any other tissue, until tissue water content fell below 45%. By day 49 of the dry-down period, the average DP of the fructan pool in tissues was from 3 to 5. Sucrose content increased in each tissue during the course of the dry-down, and was highest at the leaf base, where a concentration of 200 µmol g-1 dry weight was measured after 49 days of dry-down. The negative correlation between fructan and sucrose content, which indicates an inter-conversion dependent on tissue water content, suggests that, in this specises, fructans serve as a carbohydrate storage pool, while sucrose stabilises the meristem during extreme water deficit.

Bibliography: leaves 201-228. / xvii, 228 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Widespread deficiencies of mineral nutrients in soils along with limited moisture supply are considered major environmental stresses leading to yield losses in chickpea. This study was conducted to determine the zinc requirement of chickpea and the effect on plant water relations. Critical zinc concentration was estimated. It was found that high and low moisture regimes had no effect on critical zinc concentration and that the value remained almost the same in all chickpea genotypes. Sensitivity of 28 chickpea genotypes were evaluated at two zinc levels. Field studies on zinc fertilization in both Australia and Pakistan showed that the application of zinc increased grain yield in all chickpea genotypes. It was found that plants grown under zinc deficiency could not exploit available soil moisture and water use and water use efficiency was reduced, and concluded that high zinc availability may enhance the ability of plants to endure periods of drought by promoting osmotic adjustment. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1999

Bibliography: p. 191-200. Persistence mechanisms of Erodiophyllum elderi are investigated in terms of life history strategies and patchy population theory.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In the rainfed areas of the South African sugar industry the unpredictability of rainfall is of major concern for producers. Currently, research into the drought tolerance of South African sugarcane varieties is very limited. Knowledge of varietal drought tolerance potential would allow for more informed decision making when it comes to planting a crop that stays in the ground for between five and fifteen years. The aim of this study was to ascertain the drought tolerance potential of commercial sugarcane varieties using historical field trial data by employing statistical modelling. The first step was to establish a reliable methodology of quantifying the level of drought stress, defined through a drought stress index (DSI), employing the sugarcane growth modelling software Canesim. The second step was to use the selected DSI to evaluate and rate the drought tolerance potential of commercial varieties. Of the six DSI’s calculated, the index comprising a ratio of Canesim simulated rainfed yield (representative of a water stressed environment) to Canesim simulated irrigated yield (representative of a water unstressed environment) was the best at quantifyingthe level of trial drought stress. Using three varieties with previously identified drought potential, two intermediate susceptible (IS) and one intermediate (I) variety, this was the only DSI that was able to quantify all the differences between the varieties. Using the selected DSI, two different methodologies were used to evaluate varietal drought tolerance potential: General linear regression and Residual maximum likelihood meta-analysis. The regression method proved to be a better method of varietal rating when using historical field data. The two rainfed regions, coastal and midlands were analyzed separately due to the difference in climatic conditions. Using the regression analysis, with N12 as the observed intermediate reference variety, coastal varieties were rated as being susceptible (N16, N19, N39 and NCO376) or intermediate (N27, N29, N33, N36, N41, N45, N47). Rating of the midlands varieties, with both statistical methods, were unsuccessful. / AFRIKAANSE OPSOMMING: Binne die droëland produksiegebied van die Suid-Afrikaanse suikerindustrie is die wisselvalligheid van reënval ʼn groot bron van kommer vir produsente. Navorsingsresultate aangaande die droogtetoleransie van Suid-Afrikaanse suikerrietvariëteite is baie beperk. Aangesien suikerriet aanplantings vir vyf tot vyftien jaar in produksie mag bly, is kennis aangaande droogtetoleransie noodsaaklik vir ingeligte besluite rondom variëteit keuse. Die doel van hierdie studie was om die droogtetoleransie van kommersiële variëteite met behulp van historiese veldproef resultate en statistiese modellering te bepaal. Die eerste stap was die ontwikkeling van betroubare metodiek wat die graad van droogtestremming kwantifiseer deur middel van droogtestremmingsindekse (DSI’s) wat met die suikerriet produksiemodel, Canesim, bereken is. Die tweede stap was om die DSI’s te gebruik om geselekteerde kommersiële variëteite vir droogtetoleransie te evalueer en volgens toleransie te rangskik. Van die ses DSI’s wat geëvalueer is, was die indeks wat die verhouding tussen Canesim gesimuleerde droëland opbrengs (verteenwoordigend van ʼn omgewing met droogte) en Canesim gesimuleerde besproeide opbrengs (verteenwoordigend van ʼn omgewing sonder droogte) omskryf het, die mees effektiefste om die graad van droogtestremming te kwantifiseer. Hierdie DSI was vervolgens die enigste wat verskille in droogtetoleransie tussen drie variëteite van bekende droogte toleransie kon kwantifiseer. Deur gebruik van hierdie DSI is twee verskillende metodes aangewend om die droogtetoleransie van variëteite te evalueer naamlik: Algemene Lineêre Regressie en Residuele Maksimum Aanneemlikheid. Die regressiemetode was die mees effektiefste om variëteite volgens droogtetoleransie, op grond van historiese veldproef resultate, te rangskik. Die twee droëland produksiegebiede, naamlik die kusstrook en Natalse Middellande is afsonderlik geanaliseer as gevolg van klimaatsverskille. Met behulp van die regressiemetode is die kus-variëteite as droogtesensitief of -intermediêr geklassifiseer, met N27, N29, N33, N36, N41, N45 en N47 as droogte-intermediêr en N16, N19, N39 en NCO376 as droogtesensitief. Soortgelyke klassifisering van die variëteite wat in die Natalse Middellande verbou word was nie met enige van die statistiese metodes suksesvol gewees nie.

Plants of the genus Saccharum (sugarcane), focus of this study, are the most versatile plant species domesticated by man, Is the great possibilities of using these or its adaptability, after its domestication and evolution of genetical enhancement. The present study was to evaluate morphophysiological responsesof of sugar cane and energy cane genotypes Submitted to water restriction in the initial phase of growth. The experiment was conducted in a greenhouse of Plant Physiology department of the Academic Unit of Agricultural Sciences Center, Campus Delza Gitai, the Federal University of Alagoas, located in Rio Largo city (09 ° 28 'S, 35 ° 49' W and 127 m altitude), State Alagoas. The experimental design consisted of randomized blocks (DBC), composed of five replicates in a factorial arrangement of 6 x 2, totaling 60 installments, consisting of six genotypes of sugarcane (RB29579, RB867515, RB11999, RB330, IN8484, IN8272) subjected to two levels of water stress: no stress (soil with 100% of field capacity (FC)) and water stress (50% DC), tax at 78 days after planting (DAP). We evaluated the growth of plants, leaf water potential (Ψw) and spad index. At the end of the experiment (112 DAP) plants were collected to determine the dry mass, growth rates, Physiological indices and biochemical analyzes. There was genotypic variation in the morphophysiological responses of sugarcane to the water deficit. The genotypes of sugarcane and energy cane presented Different behavior in response to water restriction for plant height and accumulation of dry mass in the aerial part. The variety RB867515 presented greater tolerance to the oxidative stress induced by the water deficit in relation to the others. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / As plantas do gênero Saccharum (cana-de-açúcar), foco deste estudo, são as espécies vegetais mais versáteis dentre aquelas domesticadas pelo homem, seja pela grande gama de possibilidades de utilização destas e/ou pela sua capacidade de adaptação, após a sua domesticação e/ou evolução do melhoramento genético. O presente trabalho foi desenvolvido como objetivo de avaliar respostas morfofisiológicas de genótipos de cana-de-açúcar e cana energia submetidas à restrição hídrica na fase inicial de crescimento. O experimento foi conduzido na casa-de-vegetação do setor de Fisiologia Vegetal da Unidade Acadêmica Centro de Ciências Agrárias, Campus Delza Gitaí, da Universidade Federal de Alagoas, localizada no município de Rio Largo (09° 28’ S, 35° 49’ W e 127 m de altitude), Estado de Alagoas. Foi utilizado o delineamento em blocos casualizado (DBC), composto por cinco repetições em arranjo fatorial 6 x 2, totalizando 60 parcelas, constituído de seis genótipos de cana, (RB29579, RB867515, RB11999, RB330, IN8484 e IN8272) submetido a dois níveis de estresse hídrico: sem estresse (solo com 100% da capacidade de campo (CC) e com estresse hídrico (50% da CC), imposto aos 78 dias após o plantio ( DAP). Foram avaliados o crescimento de plantas, potencial hídrico foliar (Ψw) e índice spad. Ao final do experimento (112 DAP) as plantas foram coletadas para determinação da massa seca, taxas de crescimento, índices fisiolóagicos e análises bioquímicas. Houve variação genotípica nas respostas morfofisiológicas da cana ao déficit hídrico. Os genótipos de cana-de-açúcar e cana energia apresentaram comportamento diferente em resposta à restrição hídrica para altura de plantas e acumulo de massa seca na parte aérea. A variedade RB867515 apresentou maior tolerância ao estresse oxidativo induzido pelo déficit hídrico em relação as demais.

Two aspects of drought resistance were investigated on wet and dry ecotypes of three conifer species: 1) the relative importance of drought avoidance and drought tolerance mechanisms in resisting drought stress was assessed on Douglas-fir (Pseudotsuga menzieseii) and lodgepole pine (Pinus contorta) seedlings, and 2) the effects of drought on root hydraulic conductance and low temperature, on root water flow rates Were assessed on first-year seedlings of Douglas-fir, lodgepole pine and white spruce (Picea glauca). To study drought avoidance, Douglas-fir and lodgepole pine seedlings were grown in sealed containers in wet (522% water content) or dry (318% water content) peat/vermiculite soil in a factorial treatment design. Dry weights, water use, and root length were determined for seedlings at each of five harvests and stomatal conductance and shoot water potentials were measured during the last 12 weeks of the experiment. Lodgepole pine seedlings had greater dry matter production, water use, stomatal conductance and new root length than Douglas-fir seedlings. New root weight of lodgepole pine seedlings exceeded that of Douglas-fir seedlings during the last five weeks of the experiment, and specific root length of new roots was higher for lodgepole pine seedlings throughout the experiment. Douglas-fir seedlings showed higher water use efficiency (WUE) than lodgepole pine seedlings, although water uptake rates per unit of root dry weight showed little difference between species. Soil water treatment influenced specific root length of new roots, water uptake per unit of new root length, and WUE in Douglas-fir seedlings more than in lodgepole pine seedlings. To study drought tolerance, Douglas-fir and lodgepole pine seedlings were grown under drought and well-watered conditions. At each of three harvests a pressure-volume curve was produced for each seedling. Douglas-fir maintained a lower osmotic potential at full saturation [special characters omitted] and lower turgor loss point [special characters omitted] than lodgepole pine under both watering regimes,. Both species had lower [special characters omitted] when drought-stressed. Douglas-fir appears to be a more conservative species, maintaining low stomatal conductance and tolerating drought conditions, whereas lodgepole pine avoids drought by producing large amounts of roots to exploit the soil resource. To study root hydraulic conductance (Lproot) and water flow rates through roots (WFRR), water flow was measured through de-topped roots of Douglas-fir, lodgepole pine, and white spruce seedlings in a pressure chamber. In a drought experiment, seedlings were grown in sandy soil in a greenhouse under drought and well-watered conditions during their first growing season and, in a low temperature experiment, seedlings were grown in sandy soil in growth chambers at 25/20°C (day/night) and 15/10°C, In the drought experiment, water flow through roots was measured at three pressures. No differences in Lproot were found for Douglas-fir and white spruce seedlings grown under the two watering regimes, however, lodgepole pine seedlings had reduced Lproot when grown under drought conditions. Welk watered seedlings of lodgepole pine and white spruce had higher Lpr00t in 1989 than in 1990 whereas Douglas-fir seedlings had the same Lproot in both years. In the low temperature experiment, WFRR was measured at 1.0 MPa and temperatures of 20°C for 24 hours or 20°, 12°, and 4°C for 18, 15, and 15 hours respectively. At 20°C, white spruce seedlings had higher WFRR than the other two species. Lodgepole pine and white spruce seedlings grown in the 1S°/10°C growth chamber had higher WFRR than seedlings grown in the 25°/20°C growth chamber. Water flow rate decreased with temperature in all three species. After correcting for viscosity, all seedlings had lower WFRR with reduced temperature, except for Douglas-fir and white spruce seedlings grown at 15°/10°C which had the same WFRR at 20°C and 12°C. Therefore, Douglas-fir and white spruce seedlings were found to become less sensitive to low temperature (chilling) stress when pre-conditioned at low temperatures. In the drought and low temperature studies, dry weight biomass of white spruce was lowest but white spruce had a greater specific root length than lodgepole pine and Douglas-fir. In the drought study, biomass production in seedlings from wet ecotypes of each species was more reduced when drought-stressed than seedlings from dry ecotypes. / Graduate

Made available in DSpace on 2015-03-26T13:53:33Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1136366 bytes, checksum: 78962870de2c0891b84e47ea7889faea (MD5) Previous issue date: 2013-07-31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In Brazil, eucalyptus have been planted under different climatic and edaphic conditions. As regard to climate, the plantations have been located in a wide range of conditions, from regions with no restrictions to regions with strong water deficit. Similarly, soils are quite variable in terms of fertility and physical characteristics. The combination of soil and water restrictions can be overcome by the selection of genetic material adapted to such conditions. Soil low fertility can easily be resolved by mineral fertilization, whereas climatic and soil physical restrictions are of more difficult solution. Selecting genotypes adapted to such restrictions has been one of the alternatives adopted in the Brazilian silviculture. Early selection attributes, as biomarkers of such adaptations, including morphological, anatomical and physiological characteristics, are of great practical interest. The objective of this study was to evaluate characteristics and morpho-anatomic adaptations of eucalypt clones, differing in tolerance to water deficit and relate these adaptations to isotopic carbon discrimination (13CO2 ()). The study was carried out in commercial eucalypt stands located in two different climate conditions (mean of 900 mm and 1,500 mm per year) on an soil Yellow Ultisol, in the Northeast of Bahia State, Brazil. In both sites, three clones (1277, a hybrid of Eucalyptus urophylla x E. camaldulensis, 1404, E. urophylla, and 1407, a hybrid of E. urophylla x E. grandis) respectively considered of high, medium and low tolerance to water deficit, were planted at 3 x 3 m spacing and the stands were approximately 5 year old at the assessment time. In each site were selected and felled four trees of average size (diameter and height) per clone. At the stem base, a disc of 5 cm width was removed for 13 CO2 () determination. Wood samples were collected from each disc in radial sections, dried in the laboratory and submitted to a mass spectrometer. Ten completely expanded and active leaves of the third or fourth worl of branches located at the top, half and base of the crown were also collected from each sampled tree for morphometric analyses and dimension determination (area, width, length and perimeter). An additional leaf was also collected for micrimorphometric analyses (cuticle, epidermis and mesophyll width and intercellular space). In the region of lower precipitation, clone 1277 presented higher Δ13C, lower leaf area at the top of the crown, lower water diffusion time of leaves at the half and bottom of the crown and less mesophyll intercellular space than the other two clones. All these characteristics are indicators of adaptation to xeromorphic conditions. Therefore, quantitative and qualitative characteristics were associated with the tolerance to water restrictions. Xeric characteristics were more evident on clone 1277, which showed higher tolerance and adaptation to conditions where water restrictions predominate. / O cultivo do eucalipto no Brasil tem ocorrido em diferentes condições edafoclimáticas. Quanto ao clima, os plantios têm sido feitos desde regiões onde não ocorrem déficits até regiões com fortes restrições hídricas. De modo semelhante, há plantios em solos com restrições variáveis quanto à fertilidade e, ou, características físicas. A combinação de tais restrições requer a seleção de material genético que possa suplantá-las. Enquanto a baixa fertilidade do solo pode ser contornada pela técnica de fertilização, a restrição física e climática é de mais difícil solução. A escolha de genótipos tolerantes ao déficit hídrico tem sido a principal opção para plantio em tais condições. Por isso, a definição de biomarcadores dessa tolerância, como alterações morfológicas, anatômicas e fisiológicas, é de alto interesse prático. O objetivo deste estudo foi avaliar características e adaptações morfoanatômicas em clones de eucalipto com tolerância diferencial ao déficit hídrico e sua relação com a discriminação isotópica do 13CO2 (). O estudo foi conduzido em plantios comerciais de eucaliptos situados em duas condições edafoclimáticas no norte do estado da Bahia. As árvores tinham, aproximadamente, cinco anos de idade, no espaçamento inicial de 9 m2 por planta, e os plantios se situam em áreas com precipitação média anual de 900 mm e 1500 mm. Em cada área, os clones 1277 (híbrido de E. urophylla x E. camaldulensis), 1404 (E. urophylla) e 1407 (híbrido de E. urophylla x E. grandis), considerados com alta, média e baixa tolerância à seca, respectivamente, foram selecionados em talhões situados em Argissolos Amarelo para avaliações biométricas e fisiológicas. Foram selecionadas e abatidas quatro árvores médias por clone e área e, na base de cada uma, foi retirado um disco do tronco com, aproximadamente, 5 cm de espessura, do qual foram obtidas amostras das seções radiais do lenho para determinação dos isótopos do C. De cada árvore foram, ainda, selecionadas folhas completamente expandidas do terceiro ou quarto nó do ápice para a base do ramo, em três posições distintas da copa: basal, mediana e apical. Foram coletadas dez folhas para cada uma dessas posições as quais foram utilizadas nas análises morfométricas para obtenção da área, largura, comprimento e perímetro. Adicionalmente, uma folha sadia e completamente expandida foi também coletada de cada árvore para as seguintes análises micromorfométricas, em secção transversal: (espessura total, da cutícula, da epiderme e do mesofilo, bem como porcentagem de espaços intercelulares). As características avaliadas foram comparadas pelo teste t a 5% de probabilidade. O clone 1277, mais tolerante à seca, na área com precipitação média anual de 900 mm, mostrou maior Δ13C em comparação com os demais clones, possivelmente, devido à manutenção da condutância estomática. O clone tolerante (1277), na área com precipitação média anual de 900 mm, apresentou menor área foliar nas folhas do ápice da copa, menor tempo de difusão do vapor de água nas posições basal e mediana, e menores porcentagens de espaço intercelular no mesofilo em todas as posições da copa, características indicadoras de xeromorfismo. Portanto, foram verificadas características qualitativas e quantitativas associadas à tolerância dos clones ao déficit hídrico. As características xeromórficas mais evidentes do clone 1277 lhe conferem maior tolerância e condições de se adaptar e desenvolver sob restrição hídrica.

Orientador: Paulo Mazzafera / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-14T08:03:59Z (GMT). No. of bitstreams: 1 Santos_AdrianaBrombinidos_M.pdf: 1079927 bytes, checksum: 028eeeefe5616e233dd57be085df965f (MD5) Previous issue date: 2009 / Resumo: Plantas das cultivares Catuaí Vermelho e Mundo Novo de Coffea arabica L. e da cultivar Apoatã de C. canephora Pierre ex Froehner, e plantas de Mundo Novo enxertadas sobre Apoatã foram avaliadas quanto a possíveis estratégias utilizadas para suportar a baixa disponibilidade de água no solo. Em paralelo, foi conduzido um ensaio com suspensões celulares de Catuaí Vermelho sob estresse osmótico induzido por PEG. Assim, este estudo teve por objetivo examinar alguns mecanismos de tolerância à seca em café através da avaliação de aspectos morfológicos (sistema radicular), fisiológicos (ajuste osmótico) e moleculares (expressão de deidrinas e aquaporinas) em plantas jovens e cultura de células. A análise de expressão do gene CaDh1 (deidrina) em suspensão celular de café tratada com PEG (15% m/v), por 8, 24 e 72 h, mostrou aumento na atividade sob estresse osmótico, o que poderia estar associado a um possível mecanismo de proteção de membranas e macromoléculas contra a dessecação. Não foi verificada alteração na resposta dos genes PIP1, PIP2 e TIP1(aquaporinas) sob condição de estresse nas células de café. Plantas de café cultivadas em vasos (4,0 L) foram submetidas a estresse hídrico moderado por suspensão da irrigação, sob condições de casa de vegetação, até que o potencial hídrico da folha no "predawn" atingisse cerca de -2,0 MPa. Verificou-se que as taxas de crescimento nos genótipos de café arábica, avaliada pelo acúmulo de biomassa total (folhas e raízes), foram intensamente afetadas pela seca, com redução em torno de 26,5% em Catuaí e 29,0% em Mundo Novo. Por outro lado, as plantas enxertadas não apresentaram redução significativa de crescimento em relação às plantas irrigadas, sugerindo uma contribuição positiva da enxertia para melhorar a eficiência na captação de água pelo porta-enxerto Apoatã, sob condição de baixa disponibilidade de água no solo. O conteúdo de açúcares solúveis totais nas folhas das plantas irrigadas foi maior que o observado para as plantas sob déficit hídrico. A maior redução foi constatada entre os genótipos de café arábica (23,0% em Catuaí e 43,8% em Mundo Novo), enquanto as reduções em Apoatã e MN/Apoatã não foram significativas. Verificou-se maior acúmulo de aminoácidos totais nas folhas e raízes de plantas de Catuaí sob estresse hídrico comparado a Mundo Novo. Apoatã e MN/Apoatã não mostraram aumentos significativos em relação às respectivas plantas irrigadas. Em todos os genótipos analisados, os teores de prolina (Pro) nas folhas e raízes de plantas sob estresse foram aumentados e, nas raízes, esse acúmulo foi bastante acentuado, sendo 6 vezes maior nos genótipos de café arábica, 4 vezes em Apoatã e 16 vezes na enxertia MN/Apoatã em relação às plantas irrigadas. Entretanto, tais aumentos não parecem estar diretamente associados a maiores graus de tolerância à seca em café. Os conteúdos dos aminoácidos asparagina (Asn), ácido ?- aminobutírico (Gaba), glutamato (Glu) e alanina (Ala) também foram alterados, observandose, de modo geral, aumento nos teores de Asn e Gaba e redução de Glu e Ala nas folhas e raízes das plantas sob estresse. Em conclusão observou-se que os genótipos com sistema radicular mais vigoroso como Apoatã e Catuaí foram menos afetados pela seca, provavelmente porque foram mais hábeis em explorar o perfil do solo para a captação de água. / Abstract: Seedlings of the cultivars Catuaí Vermelho and Mundo Novo of Coffea arabica L., of the cultivar Apoatã of C. canephora Pierre ex Froehner, and plants of Mundo Novo grafted on Apoatã were evaluated for possible strategies to withstand low water availability in the soil. In parallel, an assay with cellular suspension culture (Catuaí Vermelho) was carried out under osmotic stress induced by PEG. Thus, this study aimed to examine morphological (root systems), physiological (osmotic adjustment) and molecular (expression of dehydrins and aquaporins) traits in coffee plants and coffee cell suspension cultures as possible mechanisms of drought tolerance. The expression analysis of CaDh1 (dehydrin) in coffee cell suspensions grown with PEG (15% w/v) for 8, 24 and 72 h, showed an increase in activity under osmotic stress indicating a possible protection mechanism against desiccation. No changes were observed in the response of PIP1, PIP2 and TIP1 genes (aquaporins) under stress condition in coffee cells. Under greenhouse conditions, coffee seedlings were cultivated in 4.0 L pots submitted to moderate drought stress by suspending irrigation until leaf water potential at predawn reach about -2.0 MPa. Among the genotypes of arabica coffee subjected to water stress there was reduction in total dry weight, around 26.5% in Catuaí and 29.0% in Mundo Novo when compared with irrigated control plants. On the other hand, the grafted plants were not affected, suggesting a positive contribution of the grafting due to bigger efficiency in the water acquisition by the rootstock Apoatã under low water availability in the soil. The content of total soluble sugars was greater in leaves of irrigated plants than plants under water stress. The greatest reduction was verified among the genotypes of arabica coffee (23.0% in Catuaí and 43.8% in Mundo Novo) while the reduction in Apoatã and MN/Apoatã was not statistically significant. The accumulation of total amino acids was higher in leaves and roots of water stressed Catuaí than Novo Mundo. Apoatã and MN/Apoatã did not show significant increase in the content of amino acids in relation to irrigated control plants. In all genotypes, water stress induced an increase in the levels of proline (Pro) in leaves and roots. In the roots this increased was about 6 times in the genotypes of arabica coffee, 4 times in Apoatã and 16 times in the grafting MN/Apoatã in relation to irrigated control plants. However this increase in the levels of Pro does not seem to be directly associated to higher degrees of drought tolerance in coffee. The content of amino acids asparagine (Asn), ?-aminobutiric acid (Gaba), glutamate (Glu) and alanine (Ala) was also changed in the leaves and roots of stressed plants. In general, there was increase in levels of Asn and Gaba while was observed reduction in content of Glu and Ala. In conclusion it was found that the genotypes with more vigorous root system as Apoatã and Catuaí were less affected by drought, probably because they were more efficient in exploring the soil profile for the water absorption. / Mestrado / Biologia Vegetal / Mestre em Biologia Vegetal

The success of C₄ plants lies in their ability to concentrate CO₂ at the site of Rubisco thereby conferring greater efficiencies of light, water and nitrogen. Such characteristics should advantage C₄ plants in arid, hot environments. However, not all C₄ subtypes are drought tolerant. The relative abundance of NADP-ME species declines with increasing aridity. Furthermore, selected species have been demonstrated as being susceptible to severe drought showing metabolic limitations of photosynthesis. However there is a lack of phylogenetic control with many of these studies. The aims of this study were to determine whether the NADP-ME subtype was inherently susceptible to drought by comparing six closely related C₃ and C₄ (NADP-ME) Panicoid grasses. Gas exchange measurements were made during a natural rainless period and a controlled drought / rewatering event. Prior to water stress, the C₄ species had higher assimilation rates (A), and water use efficiencies (WUE[subscript leaf]) than the C₃ species, while transpiration rates (E) and stomatal conductances (g[subscript s]) were similar. At low soil water content, the C₃ species reduced gs by a greater extent than the C₄ species, which maintained higher E during the driest periods. The C₄ species showed proportionally greater reductions in A than the C₃ species and hence lost their WUE[subscript leaf] and photosynthetic advantage. CO₂ response curves showed that metabolic limitation was responsible for a greater decrease in A in the C₄ type than the C₃ type during progressive drought. Upon re-watering, photosynthetic recovery was quicker in the C species than the C₄ species. Results from whole plant measurements showed that the C₄ type had a significant whole plant water use efficiency advantage over the C₃ type under well-watered conditions that was lost during severe drought due to a greater loss of leaf area through leaf mortality rather than reductions in plant level transpiration rates. The C₃ type had xylem characteristics that enhanced water-conducting efficiency, but made them vulnerable to drought. This is in contrast to the safer xylem qualities of the C₄ type, which permitted the endurance of more negative leaf water potentials than the C₃ type during low soil water content. Thus, the vulnerability of photosynthesis to severe drought in NADP-ME species potentially explains why NADP-ME species abundance around the world decreases with decreasing rainfall.