Estudio de los efectos en el vi��edo de la modificaci��n del d��ficit h��drico continuo en los periodos anterior y posterior al envero (cv. Cabernet Sauvignon; Vitis vinifera L.)

En regiones semi��ridas, con veranos c��lidos, evapotranspiraciones elevadas, humedades relativas bajas, adem��s de precipitaciones intermitentes y escasas (400 mm al a��o) que reducen la recarga del perfil en invierno, se puede ver afectada la productividad y sostenibilidad de los vi��edos. Por eso en estas zonas puede ser necesario utilizar el riego suplementario para mantener la calidad y aumentar la productividad. En este marco de circunstancias es en el que se desarrolla la mayor��a de la viticultura espa��ola, y en concreto en la zona centro donde se realiz�� el estudio. Con este trabajo se pretende estudiar la influencia del agua del riego, con distintas dosis y aplicada en diferentes fases de crecimiento y maduraci��n de la baya, en la producci��n y calidad de la uva. Se estudi�� la influencia del d��ficit moderado continuo aplicado antes y despu��s de envero, en el aprovechamiento de los recursos ambientales y en la respuesta del cv. Cabernet Sauvignon. El ensayo se desarroll�� en 2010 y 2011 en la finca ���La Alcoholera���, perteneciente a bodegas LICINIA S.L., ubicada en la localidad de Chinch��n, Comunidad de Madrid, Espa��a. Durante 2010 y 2011 se realizaron estudios en cepas del cv. Cabernet Sauvignon (clon 15), injertadas sobre 41B y plantadas en 2005. Con poda corta en Cord��n Royat unilateral de 80 cm de altura, y cuya vegetaci��n alcanz�� una altura de 97 cm. Las cepas del ensayo fueron conducidas verticalmente en espaldera (VSP), con 10 yemas por metro lineal. Las plantas dentro de la fila fueron separadas 1 m y la distancia de la calle fue de 3 m. La orientaci��n de las filas norte ��� sur. Se plantearon cuatro tratamientos experimentales con diferentes dosis y momento de aplicaci��n del riego. - T: Testigo. D��ficit ligero, con un aporte continuado de agua desde floraci��n (420 mm). - DMc: D��ficit moderado continuo. Manejo del riego convencional, empezando en pre-envero (154 mm) - DM1: D��ficit moderado a partir de pre-envero. Aporte de riego continuado desde floraci��n reduci��ndose la dosis de riego en pre-envero (312 mm). - DM2: D��ficit moderado hasta pre-envero. Se empez�� a regar a partir de preenvero (230 mm). Se observ�� que bajo condiciones de estr��s h��drico leve, el crecimiento se reduce disminuyendo la migraci��n de fotoasimilados hacia los ��rganos vegetativos. Generando menor ��rea foliar en las plantas sometidas a d��ficit h��drico moderado entre floraci��n y cuajado. Disminuyendo su consumo. En maduraci��n la humedad del suelo dependi�� principalmente del riego aplicado y del consumo de la planta; dicho consumo dependi�� a la vez del desarrollo foliar del canopy y de la necesidad h��drica de la vid. El aumento del d��ficit h��drico disminuy�� el contenido de agua en el suelo, lo que provoc�� diferencias en el estado h��drico y en el intercambio gaseoso de las hojas. En condiciones de d��ficit moderado, la fotos��ntesis se encontr�� altamente correlacionada con el potencial h��drico foliar medido a mediod��a solar. Adem��s en condiciones de d��ficit moderado continuo la disponibilidad h��drica, la demanda atmosf��rica y el nivel de hidrataci��n de las hojas, interaccionaron de forma compleja en la regulaci��n estom��tica de las hojas, condicionando el intercambio gaseoso y la eficiencia en el uso del agua. Al aumentar el volumen de agua aplicado el peso de madera de poda por metro de fila fue superior. Las diferencias encontradas en el rendimiento fueron debidas a las diferencias en el peso de baya. El cual estuvo condicionado por la estrategia de riego, ya que, el d��ficit h��drico moderado antes de envero fue m��s cr��tico para el rendimiento que el d��ficit impuesto durante la madurez. Por otro lado, la biomasa dependi�� de la actividad fisiol��gica de la planta, la cual fue altamente dependiente de la disponibilidad h��drica. D��ficit h��drico moderado aplicado de cuajado a envero, gener�� bayas m��s peque��as y aument�� la relaci��n hollejo:pulpa. El d��ficit moderado aplicado despu��s de envero favoreci�� la acumulaci��n de IPT y antocianos extra��bles, mejorando la calidad de la uva, pero disminuy�� la acidez de la baya. El riego aplicado de envero a vendimia desaceler�� la concentraci��n de az��cares en bayas que fueron sometidas a d��ficit antes de pre-envero. ABSTRACT Mediterranean climate is characterized by hot summers, high evapotranspiration rates, and scarce precipitations (400 mm per year) during grapevine cycle. These extremely dry conditions affect vineyard productivity and sustainability. Supplementary irrigation is needed practice in order to maintain yield and quality. Almost all Spanish grape growing regions are characterized by these conditions, especially in the center region, where this trial was performed. The main objective of this work is to study the influence of water irrigation on yield and quality. For this aim, different levels of irrigation (mm of water applied) were applied during different stages of growth and berry maturity of Caberent Sauvignon grapevines. The work was conducted from 2010 to 2011 and located in Licinia (40�� 12�� N, 3�� 28�� W), Madrid, Spain. The cultivar utilized was Cabernet Sauvignon, clone 15 grafted onto rootstock 41B, planted in 2005. The vineyard was oriented north-south, with spacing on 3 meters between rows and 1 meter between plants. Vines were spurpruned to 10 buds per meter and trained in unilateral cordon with a height of 80 cm. Shoots were positioned vertically (VSP). Considering the amount of water and the moment of the application, four experimental treatments were applied: - T: Control sample. Slight deficit (420 mm) applied from bloom to maturity. - DMc: Continuous moderate deficit. Traditional irrigation: application of 154 mm of water from pre-veraison to maturity. - DM1: Deficit moderate from pre-veraison. Irrigation of 312 mm of water from bloom to pre-veraison. - DM2: Deficit moderate to pre-veraison. Irrigation of 230 mm of water from preveraison to maturity Under moderated water stress conditions it was seen than leaf growth decreases due to the reduction of migration of photo-assimilates to vegetative organs. Vines with moderate water deficit between flowering and ripening develop less leaf area and decrease its water consumption. During maturation of berries, soil moisture depends on irrigation and plant consumption. This consumption further depends on vegetation development and on the vine needs for water. By increasing water deficit, the water content in the soil decreases. This causes differences in leaf water status and in the gases exchange. Under moderate deficit conditions, photosynthesis was found highly correlated with midday leaf water potential. Further, atmospheric demand and the level of leaves hydration interact in complex ways in the stomatal regulation, which affects leaf gas exchange and the efficiency of water use. The amount of water applied is directly proportional to pruning weight. Changes in berry weight cause differences in yield ratios. The differences in berry weights are conditioned by the irrigation strategy, the moderate water deficit before veraison influences more than the deficit applied from veraison. Biomass generated for the plant depends on its physiological activity, which is highly related to the water availability. Moderate water deficit applied from fruit set to ripening generates smaller berries, increasing the pulp/skin ratio. Moderate deficit applied after veraison promotes the accumulation of extractables anthocyans and TPI. Despite this treatment improves color parameters of the grapes, it decreases its total acidity. Irrigation applied from veraison to harvest slows down sugar accumulation in berries compared to those under deficit before veraison conditions.

Respuesta fisiol��gica, productiva y cualitativa del cultivar Syrah (Vitis vinifera L) con diferentes frecuencias de riego y densidad de goteros en suelos arcillosos

La disponibilidad h��drica es uno de los principales factores que determinan el rendimiento del vi��edo en muchas regiones vit��colas, por lo que sus consecuencias han sido ampliamente estudiadas. Sin embargo, para una cantidad de agua de riego determinada, otros aspectos como la frecuencia de aplicaci��n, o la combinaci��n entre el caudal de los goteros y la distancia entre los mismos (es decir, el patr��n de distribuci��n de agua en el suelo), pueden jugar un papel relevante, pero estos factores han sido poco estudiados. El objetivo de este trabajo ha sido evaluar las implicaciones agron��micas y fisiol��gicas de dos frecuencias de riego (IrrF, cada 2 y 4 d��as) y dos patrones de distribuci��n de agua (DisP, goteros de 2 L h-1 separados 0,6 m vs. goteros de 4 L h-1 separados 1,2 m). El experimento se llev�� a cabo durante cuatro temporadas consecutivas en un vi��edo cv. Syrah con un suelo arcilloso en el centro de Espa��a, y los dos factores fueron evaluados bajo dos condiciones de disponibilidad h��drica (Baja: 20% de ETo y Media: 40% de ETo). El efecto de la frecuencia de riego y el patr��n de distribuci��n de agua en la respuesta agron��mica del cv. Syrah se ha estudiado en el cap��tulo 1. La frecuencia de riego y el patr��n de distribuci��n de agua en el suelo afectaron a algunos aspectos de los componentes de rendimiento y desarrollo vegetativo en las dos condiciones de disponibilidad h��drica, aunque los efectos observados no fueron los mismos todos los a��os. Los efectos fueron m��s evidentes para IrrF en condiciones de baja disponibilidad h��drica y para DisP en condiciones de disponibilidad h��drica media. Dos de los cuatro a��os del experimento, el pasar de frecuencia de riego de 2 d��as a 4 d��as caus�� un incremento medio de rendimiento del 20% para la situaci��n de baja disponibilidad h��drica. La textura del suelo, sin duda ha condicionado los resultados obtenidos en los tratamientos regados con el 20% de la ETo, ya que regar cada dos d��as implicaba la aplicaci��n de peque��as cantidades de agua y se formaban bulbos de riego superficiales, probablemente favoreciendo las p��rdidas por evaporaci��n. En el cap��tulo 2, se ha analizado el efecto de la frecuencia de riego y del patr��n de distribuci��n de agua en el estado h��drico de la planta y el intercambio gaseoso a nivel de hoja con el fin de explicar las diferencias observadas en la respuesta agron��mica. En lo que respecta a la frecuencia de riego, en condiciones de baja disponibilidad h��drica, las plantas regadas cada 4 d��as (plantas 4d), mostraron mayores tasas de asimilaci��n neta y conductancia estom��tica que las plantas regadas cada 2 d��as (plantas 2d), lo que es consistente con la hip��tesis de que con la frecuencia de riego de 2 d��as se produjo una p��rdida de eficiencia del uso del agua, probablemente debido a una mayor evaporaci��n como consecuencia del hecho de que el volumen de suelo mojado creado era peque��o y cerca de la superficie. En condiciones de disponibilidad h��drica media, las diferencias en el intercambio gaseoso a nivel de hoja fueron mucho m��s peque��as. Al comienzo del verano cada frecuencia de riego se comport�� mejor uno de los d��as de medida, compensando al final del ciclo de riego de 4 d��as. Sin embargo, a medida que avanz�� el verano y el d��ficit de agua se hizo m��s alto, las diferencias significativas aparecieron s��lo en el 'd��a 4' del ciclo de riego, cuando las plantas 2d se comportaron mejor que las plantas regadas 4d que llevaban tres d��as sin regarse. Estas diferencias fisiol��gicas fueron menores que en condiciones de baja disponibilidad h��drica y al parecer no suficientes para afectar el comportamiento agron��mico. En cuanto al patr��n de distribuci��n de agua, el efecto fue poco significativo, pero la mayor densidad de goteros tendi�� a presentar un mayor intercambio gaseoso a nivel de hoja, especialmente a media ma��ana. El efecto fue m��s importante para las condiciones de disponibilidad h��drica media. En el cap��tulo 3, se han comparado las relaciones entre el intercambio gaseoso a nivel de hoja, el estado h��drico y la demanda atmosf��rica, con el fin de explicar los cambios en la intensidad de la respuesta fisiol��gica observados en el Cap��tulo 2. No se han encontrado diferencias en dichas relaciones para el patr��n de distribuci��n de agua, por lo que s��lo se ha analizado el efecto de la frecuencia de riego. El estudio se ha centrado fundamentalmente en si las plantas mostraron una respuesta fisiol��gica diferente a los cambios en el estado h��drico y en la demanda atmosf��rica seg��n el tiempo transcurrido desde el ��ltimo riego. Las diferencias observadas explican los resultados obtenidos en los cap��tulos anteriores, y sugieren la existencia de procesos de aclimataci��n vinculados a la frecuencia de riego y a la disponibilidad h��drica. Las plantas bajo condiciones de baja disponibilidad h��drica se mostraron m��s aclimatadas al estr��s h��drico que aquellas en condiciones de disponibilidad h��drica media. La frecuencia de riego afect�� claramente la relaci��n entre los par��metros de intercambio gaseoso a nivel de hoja, el estado h��drico de la planta y las condiciones atmosf��ricas, y junto con la cantidad de agua aplicada tuvo implicaciones en el desarrollo de mecanismos de aclimataci��n que afectaron a la respuesta fisiol��gica de la planta, afectando a la eficiencia del riego. ABSTRACT Water availability is one of the major factors that determine vineyard performance in many grape growing regions, so its implications have been widely studied before. However, for a given irrigation water amount, other aspects such as application frequency, or emitter spacing and flow rate (i.e., distribution pattern), may play a relevant role, but these factors have been scarcely studied. The aim of this work was to evaluate the agronomic and physiological implications of two irrigation frequencies (IrrF, every 2 and 4 days) and two water distribution patterns (DisP, 2 L h���1 emitters every 0.6 m vs. 4 L h���1 emitters every 1.2 m). The experiment was carried out during four consecutive seasons in a cv. Syrah vineyard with a clay soil in central Spain, and the two factors were evaluated under two water availability conditions (LOW WA: 20% of ETo and MEDIUM WA: 40% of ETo). The effect of irrigation frequency and water distribution pattern on the agronomical response of cv. Syrah was studied in Chapter 1. IrrF and DisP affected some aspects of vegetative development and yield components under both water availability conditions, although the effects observed were not the same every year. The effects were more evident for IrrF under low water availability and for DisP under medium water availability. Two out of the four years of the experiment, the change of irrigation frequency from 2 days to 4 days promoted an average yield increase of 20% for the LOW WA situation. Soil texture certainly conditioned the results obtained under LOW WA conditions, since high frequency irrigation implied applying small amounts of water that resulted in limited superficial water bulbs, which probably favored water evaporation. In Chapter 2, the effect of irrigation frequency and water distribution pattern on plant water status and leaf gas exchange was analyzed to explain the differences observed in the agronomical response. Concerning irrigation frequency, under LOW WA conditions, applying irrigation every 4 days, resulted in higher net assimilation rates and stomatal conductance than doing it every 2 days, supporting the hypothesis that the latter frequency resulted in a water use efficiency loss, probably due to higher evaporation as a consequence of the fact the wetted soil volume created was small and close to the surface. Under MEDIUM WA conditions, differences in leaf gas exchange were much smaller. At the beginning of the summer each irrigation frequency behaved better one of the measurements days, compensating at the end of the 4-day irrigation cycle. However, as the summer progressed and water deficit became higher, significant differences appeared only on ���day 4��� of the irrigation cycle, when 2d plants behaved better than 4d plants. These physiological differences were smaller than under LOW WA conditions and apparently not sufficient to affect agronomical performance. Regarding water distribution pattern, the effect was less significant but the closest emitter spacing resulted in general terms in a higher leaf gas exchange, especially at midmorning. The effect was more noticeable for MEDIUM WA conditions. In Chapter 3, the relationships between leaf gas exchange and leaf water status and atmospheric demand were compared to explain the changes in the intensity of the physiological response observed in Chapter 2. No differences were found in the relationships for water distribution pattern, so only the effect of irrigation frequency was analyzed focusing on whether the plants have a different physiological response to changes in water status and atmospheric demand according to the time elapsed since the last irrigation. Differences observed in the relationships explained the results obtained in the previous chapters, and point at the occurrence of acclimation processes linked to irrigation frequency and to water availability. Plants under LOW WATER AVAILABILITY conditions seemed to be more acclimated to water stress than those under MEDIUM WATER AVAILABILITY conditions. Irrigation frequency clearly affected the relationship between leaf gas exchange parameters, plant water status and atmospheric conditions, and together with the amount of water applied had implications in the development of acclimation mechanisms that affected plant physiological response, thus affecting irrigation efficiency.

Stomatal plugs of Drimys winteri (Winteraceae) protect leaves from mist but not drought

Two outstanding features of the flowering plant family Winteraceae are the occlusion of their stomatal pores by cutin plugs and the absence of water-conducting xylem vessels. An adaptive relationship between these two unusual features has been suggested whereby stomatal plugs restrict gas exchange to compensate for the presumed poor conductivity of their vesselless wood. This hypothesized connection fueled evolutionary arguments that the vesselless condition is ancestral in angiosperms. Here we show that in Drimys winteri, a tree common to wet forests, these stomatal occlusions pose only a small fixed resistance to water loss. In addition, they modify the humidity response of guard cells such that under high evaporative demand, leaves with plugs lose water at a faster rate than leaves from which the plugs have been experimentally removed. Instead of being adaptations for drought, we present evidence that these cuticular structures function to maintain photosynthetic activity under conditions of excess water on the leaf surface. Stomatal plugs decrease leaf wettability by preventing the formation of a continuous water film that would impede diffusion of CO2 into the leaf. Misting of leaves had no effect on photosynthetic rate of leaves with plugs, but resulted in a marked decrease (���40%) in leaves from which the plugs had been removed. These findings do not support a functional association between stomatal plugs and hydraulic competence and provide a new perspective on debates surrounding the evolution of vessels in angiosperms.

Rubisco activase constrains the photosynthetic potential of leaves at high temperature and CO2

Net photosynthesis (Pn) is inhibited by moderate heat stress. To elucidate the mechanism of inhibition, we examined the effects of temperature on gas exchange and ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) activation in cotton and tobacco leaves and compared the responses to those of the isolated enzymes. Depending on the CO2 concentration, Pn decreased when temperatures exceeded 35���40��C. This response was inconsistent with the response predicted from the properties of fully activated Rubisco. Rubisco deactivated in leaves when temperature was increased and also in response to high CO2 or low O2. The decrease in Rubisco activation occurred when leaf temperatures exceeded 35��C, whereas the activities of isolated activase and Rubisco were highest at 42��C and >50��C, respectively. In the absence of activase, isolated Rubisco deactivated under catalytic conditions and the rate of deactivation increased with temperature but not with CO2. The ability of activase to maintain or promote Rubisco activation in vitro also decreased with temperature but was not affected by CO2. Increasing the activase/Rubisco ratio reduced Rubisco deactivation at higher temperatures. The results indicate that, as temperature increases, the rate of Rubisco deactivation exceeds the capacity of activase to promote activation. The decrease in Rubisco activation that occurred in leaves at high CO2 was not caused by a faster rate of deactivation, but by reduced activase activity possibly in response to unfavorable ATP/ADP ratios. When adjustments were made for changes in activation state, the kinetic properties of Rubisco predicted the response of Pn at high temperature and CO2.

Evidence for the existence of a sulfonylurea-receptor-like protein in plants: Modulation of stomatal movements and guard cell potassium channels by sulfonylureas and potassium���channel���openers

Limitation of water loss and control of gas exchange is accomplished in plant leaves via stomatal guard cells. Stomata open in response to light when an increase in guard cell turgor is triggered by ions and water influx across the plasma membrane. Recent evidence demonstrating the existence of ATP-binding cassette proteins in plants led us to analyze the effect of compounds known for their ability to modulate ATP-sensitive potassium channels (K-ATP) in animal cells. By using epidermal strip bioassays and whole-cell patch-clamp experiments with Vicia faba guard cell protoplasts, we describe a pharmacological profile that is specific for the outward K+ channel and very similar to the one described for ATP-sensitive potassium channels in mammalian cells. Tolbutamide and glibenclamide induced stomatal opening in bioassays and in patch-clamp experiments, a specific inhibition of the outward K+ channel by these compounds was observed. Conversely, application of potassium channel openers such as cromakalim or RP49356 triggered stomatal closure. An apparent competition between sulfonylureas and potassium channel openers occurred in bioassays, and outward potassium currents, previously inhibited by glibenclamide, were partially recovered after application of cromakalim. By using an expressed sequence tag clone from an Arabidopsis thaliana homologue of the sulfonylurea receptor, a 7-kb transcript was detected by Northern blot analysis in guard cells and other tissues. Beside the molecular evidence recently obtained for the expression of ATP-binding cassette protein transcripts in plants, these results give pharmacological support to the presence of a sulfonylurea-receptor-like protein in the guard-cell plasma membrane tightly involved in the outward potassium channel regulation during stomatal movements.

Restrictions to Carbon Dioxide Conductance and Photosynthesis in Spinach Leaves Recovering from Salt Stress

Salt accumulation in spinach (Spinacia oleracea L.) leaves first inhibits photosynthesis by decreasing stomatal and mesophyll conductances to CO2 diffusion and then impairs ribulose-1,5-bisphosphate carboxylase/oxygenase (S. Delfine, A. Alvino, M. Zacchini, F. Loreto [1998] Aust J Plant Physiol 25: 395���402). We measured gas exchange and fluorescence in spinach recovering from salt accumulation. When a 21-d salt accumulation was reversed by 2 weeks of salt-free irrigation (rewatering), stomatal and mesophyll conductances and photosynthesis partially recovered. For the first time, to our knowledge, it is shown that a reduction of mesophyll conductance can be reversed and that this may influence photosynthesis. Photosynthesis and conductances did not recover when salt drainage was restricted and Na content in the leaves was greater than 3% of the dry matter. Incomplete recovery of photosynthesis in rewatered and control leaves may be attributed to an age-related reduction of conductances. Biochemical properties were not affected by the 21-d salt accumulation. However, ribulose-1,5-bisphosphate carboxylase/oxygenase activity and content were reduced by a 36- to 50-d salt accumulation. Photochemical efficiency was reduced only in 50-d salt-stressed leaves because of a decrease in the fraction of open photosystem II centers. A reduction in chlorophyll content and an increase in the chlorophyll a/b ratio were observed in 43- and 50-d salt-stressed leaves. Low chlorophyll affects light absorptance but is unlikely to change light partitioning between photosystems.

Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Content, Assimilatory Charge, and Mesophyll Conductance in Leaves1

The content of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) (Et; EC 4.1.1.39) measured in different-aged leaves of sunflower (Helianthus annuus) and other plants grown under different light intensities, varied from 2 to 75 ��mol active sites m���2. Mesophyll conductance (��) was measured under 1.5% O2, as well as postillumination CO2 uptake (assimilatory charge, a gas-exchange measure of the ribulose-1,5-bisphosphate pool). The dependence of �� on Et saturated at Et = 30 ��mol active sites m���2 and �� = 11 mm s���1 in high-light-grown leaves. In low-light-grown leaves the dependence tended toward saturation at similar Et but reached a �� of only 6 to 8 mm s���1. �� was proportional to the assimilatory charge, with the proportionality constant (specific carboxylation efficiency) between 0.04 and 0.075 ��m���1 s���1. Our data show that the saturation of the relationship between Et and �� is caused by three limiting components: (a) the physical diffusion resistance (a minor limitation), (b) less than full activation of Rubisco (related to Rubisco activase and the slower diffusibility of Rubisco at high protein concentrations in the stroma), and (c) chloroplast metabolites, especially 3-phosphoglyceric acid and free inorganic phosphate, which control the reaction kinetics of ribulose-1,5-bisphosphate carboxylation by competitive binding to active sites.

Ozone Sensitivity in Hybrid Poplar Is Correlated with a Lack of Defense-Gene Activation1

Ozone is a major gaseous pollutant thought to contribute to forest decline. Although the physiological and morphological responses of forest trees to ozone have been well characterized, little is known about the molecular basis for these responses. Our studies compared the response to ozone of ozone-sensitive and ozone-tolerant clones of hybrid poplar (Populus maximowizii �� Populus trichocarpa) at the physiological and molecular levels. Gas-exchange analyses demonstrated clear differences between the ozone-sensitive clone 388 and the ozone-tolerant clone 245. Although ozone induced a decrease in photosynthetic rate and stomatal conductance in both clones, the magnitude of the decrease in stomatal conductance was significantly greater in the ozone-tolerant clone. RNA-blot analysis established that ozone-induced mRNA levels for phenylalanine ammonia-lyase, O-methyltransferase, a pathogenesis-related protein, and a wound-inducible gene were significantly higher in the ozone-tolerant than in the ozone-sensitive plants. Wound- and pathogen-induced levels of these mRNAs were also higher in the ozone-tolerant compared with the ozone-sensitive plants. The different physiological and molecular responses to ozone exposure exhibited by clones 245 and 388 suggest that ozone tolerance involves the activation of salicylic-acid- and jasmonic-acid-mediated signaling pathways, which may be important in triggering defense responses against oxidative stress.

Regulation of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase by Carbamylation and 2-Carboxyarabinitol 1-Phosphate in Tobacco: Insights from Studies of Antisense Plants Containing Reduced Amounts of Rubisco Activase1

The regulation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity by 2-carboxyarabinitol 1-phosphate (CA1P) was investigated using gas-exchange analysis of antisense tobacco (Nicotiana tabacum) plants containing reduced levels of Rubisco activase. When an increase in light flux from darkness to 1200 ��mol quanta m���2 s���1 was followed, the slow increase in CO2 assimilation by antisense leaves contained two phases: one represented the activation of the noncarbamylated form of Rubisco, which was described previously, and the other represented the activation of the CA1P-inhibited form of Rubisco. We present evidence supporting this conclusion, including the observation that this second phase, like CA1P, is only present following darkness or very low light flux. In addition, the second phase of CO2 assimilation was correlated with leaf CA1P content. When this novel phase was resolved from the CO2 assimilation trace, most of it was found to have kinetics similar to the activation of the noncarbamylated form of Rubisco. Additionally, kinetics of the novel phase indicated that the activation of the CA1P-inhibited form of Rubisco proceeds faster than the degradation of CA1P by CA1P phosphatase. These results may be significant with respect to current models of the regulation of Rubisco activity by Rubisco activase.

Does Leaf Position within a Canopy Affect Acclimation of Photosynthesis to Elevated CO2?1 : Analysis of a Wheat Crop under Free-Air CO2 Enrichment

Previous studies of photosynthetic acclimation to elevated CO2 have focused on the most recently expanded, sunlit leaves in the canopy. We examined acclimation in a vertical profile of leaves through a canopy of wheat (Triticum aestivum L.). The crop was grown at an elevated CO2 partial pressure of 55 Pa within a replicated field experiment using free-air CO2 enrichment. Gas exchange was used to estimate in vivo carboxylation capacity and the maximum rate of ribulose-1,5-bisphosphate-limited photosynthesis. Net photosynthetic CO2 uptake was measured for leaves in situ within the canopy. Leaf contents of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), light-harvesting-complex (LHC) proteins, and total N were determined. Elevated CO2 did not affect carboxylation capacity in the most recently expanded leaves but led to a decrease in lower, shaded leaves during grain development. Despite this acclimation, in situ photosynthetic CO2 uptake remained higher under elevated CO2. Acclimation at elevated CO2 was accompanied by decreases in both Rubisco and total leaf N contents and an increase in LHC content. Elevated CO2 led to a larger increase in LHC/Rubisco in lower canopy leaves than in the uppermost leaf. Acclimation of leaf photosynthesis to elevated CO2 therefore depended on both vertical position within the canopy and the developmental stage.

Ultraviolet-B Radiation Effects on Water Relations, Leaf Development, and Photosynthesis in Droughted Pea Plants1

The effects of ultraviolet-B (UV-B) radiation on water relations, leaf development, and gas-exchange characteristics in pea (Pisum sativum L. cv Meteor) plants subjected to drought were investigated. Plants grown throughout their development under a high irradiance of UV-B radiation (0.63 W m���2) were compared with those grown without UV-B radiation, and after 12 d one-half of the plants were subjected to 24 d of drought that resulted in mild water stress. UV-B radiation resulted in a decrease of adaxial stomatal conductance by approximately 65%, increasing stomatal limitation of CO2 uptake by 10 to 15%. However, there was no loss of mesophyll light-saturated photosynthetic activity. Growth in UV-B radiation resulted in large reductions of leaf area and plant biomass, which were associated with a decline in leaf cell numbers and cell division. UV-B radiation also inhibited epidermal cell expansion of the exposed surface of leaves. There was an interaction between UV-B radiation and drought treatments: UV-B radiation both delayed and reduced the severity of drought stress through reductions in plant water-loss rates, stomatal conductance, and leaf area.

A GIS-based methodology to quantitatively define an Adjacent Protected Area in a shallow karst cavity: The case of Altamira cave

Different types of land use are usually present in the areas adjacent to many shallow karst cavities. Over time, the increasing amount of potentially harmful matter and energy, of mainly anthropic origin or influence, that reaches the interior of a shallow karst cavity can modify the hypogeal ecosystem and increase the risk of damage to the Palaeolithic rock art often preserved within the cavity. This study proposes a new Protected Area status based on the geological processes that control these matter and energy fluxes into the Altamira cave karst system. Analysis of the geological characteristics of the shallow karst system shows that direct and lateral infiltration, internal water circulation, ventilation, gas exchange and transmission of vibrations are the processes that control these matter and energy fluxes into the cave. This study applies a comprehensive methodological approach based on Geographic Information Systems (GIS) to establish the area of influence of each transfer process. The stratigraphic and structural characteristics of the interior of the cave were determined using 3D Laser Scanning topography combined with classical field work, data gathering, cartography and a porosity���permeability analysis of host rock samples. As a result, it was possible to determine the hydrogeological behavior of the cave. In addition, by mapping and modeling the surface parameters it was possible to identify the main features restricting hydrological behavior and hence direct and lateral infiltration into the cave. These surface parameters included the shape of the drainage network and a geomorphological and structural characterization via digital terrain models. Geological and geomorphological maps and models integrated into the GIS environment defined the areas involved in gas exchange and ventilation processes. Likewise, areas that could potentially transmit vibrations directly into the cave were identified. This study shows that it is possible to define a Protected Area by quantifying the area of influence related to each transfer process. The combined maximum area of influence of all the processes will result in the new Protected Area. This area will thus encompass all the processes that account for most of the matter and energy carried into the cave and will fulfill the criteria used to define the Protected Area. This methodology is based on the spatial quantification of processes and entities of geological origin and can therefore be applied to any shallow karst system that requires protection.

Stable isotope ratios, carbon content and primary production of three sediment cores from the subantarctic eastern Atlantic

We present three new benthic foraminiferal delta13C, delta18O, and total organic carbon time series from the eastern Atlantic sector of the Southern Ocean between 41��S and 47��S. The measured glacial delta13C values belong to the lowest hitherto reported. We demonstrate a coincidence between depleted late Holocene (LH) delta13C values and positions of sites relative to ocean surface productivity. A correction of +0.3 to +0.4 [per mil VPDB] for a productivity-induced depletion of Last Glacial Maximum (LGM) benthic delta13C values of these cores is suggested. The new data are compiled with published data from 13 sediment cores from the eastern Atlantic Ocean between 19��S and 47��S, and the regional deep and bottom water circulation is reconstructed for LH (4-0 ka) and LGM (22-16 ka) times. This extends earlier eastern Atlantic-wide synoptic reconstructions which suffered from the lack of data south of 20��S. A conceptual model of LGM deep-water circulation is discussed that, after correction of southernmost cores below the Antarctic Circumpolar Current (ACC) for a productivity-induced artifact, suggests a reduced formation of both North Atlantic Deep Water in the northern Atlantic and bottom water in the southwestern Weddell Sea. This reduction was compensated for by the formation of deep water in the zone of extended winter sea-ice coverage at the northern rim of the Weddell Sea, where air-sea gas exchange was reduced. This shift from LGM deep-water formation in the region south of the ACC to Holocene bottom water formation in the southwestern Weddell Sea, can explain lower preformed d13CDIC values of glacial circumantarctic deep water of approximately 0.3 per mil to 0.4 per mil. Our reconstruction brings Atlantic and Southern Ocean d13C and Cd/Ca data into better agreement, but is in conflict, however, with a scenario of an essentially unchanged thermohaline deep circulation on a global scale. Benthic delta18O-derived LGM bottom water temperatures, by 1.9��C and 0.3��C lower than during the LH at deepest southern and shallowest northern sites, respectively, agree with the here proposed reconstruction of deep-water circulation in the eastern South Atlantic Ocean.

Selection of species and provenances for low-rainfall areas: physiological responses of Eucalyptus cloeziana and Eucalyptus argophloia to seasonal conditions in subtropical Queensland

Responses of stomatal conductance (g(s)) and net photosynthesis (A) to changes in soil water availability, photosynthetic photon flux density (Q), air temperature (1) and leaf-to-air vapour pressure deficit (D) were investigated in 4-year-old trees of a dry inland provenance of Eucalyptus argophloia Blakely, and two dry inland provenances (Coominglah and Hungry Hills) and a humid coastal provenance (Wolvi) of Eucalyptus cloeziana F. Muell. between April 2001 and April 2002 in southeast Queensland, Australia. There were minimal differences in A, g, and water relations variables among the coastal and inland provenances of E. cloeziana but large differences between E. argophloia and E. cloeziana. E. argophloia and to a lesser extent the Hungry Hills (inland) provenance of E. cloeziana maintained relatively higher pre-dawn water potential (psi(pd)) during the dry season suggesting possible access to water at depth. Simple phenomenological models of stomatal conductance as a function of Q, T and D explained 60% of variation in gs in E. cloeziana and more than 75% in E. argophloia, when seasonal effect was incorporated in the model. A Ball-Berry model for net photosynthesis explained between 70 and 80% of observed variation in A in both species. These results have implications in matching the dry and humid provenances of E. cloeziana and E. argophloia to suitable sites in subtropical environments. (C) 2004 Elsevier B.V. All rights reserved.