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Both sea-level rise and the attendant changes in wave overwash events can greatly modify or destroy coastal terrestrial ecosystems; thus, it is essential to have a priori identification of particularly sensitive forests (and other ecosystems). This article reports an application of airborne LIDAR (light detection and ranging) to study vulnerable coastal forests- the important case of natural mid-Atlantic maritime pine forests. We investigate the Experimental Advanced Airborne Research LIDAR (EAARL) for its accuracy in making detailed forest structural measurements, producing inferential statistics for remote monitoring, and detecting changes in barrier island forest ecohydrology. Results show that EAARL can be deployed with high confidence in loblolly pine (Pinus taeda L) ecosystems for baseline biophysical descriptions. EAARL measurements predict plot-level volume, height indices, and basal area with coefficients of determination ranging from 0.72 to 0.95. EAARL data also provide one-dimensional vertical metrics: maximum canopy height, height of peak canopy density, and bare earth elevation at standard errors of 1.8, 1.3, and 0.3 m, respectively. LIDAR-determined structural data are significantly correlated with environmental gradients on Assateague Island, thus providing an important reference state for continued ecological study. EAARL data model the plant area index (PAD at an r2 of 0.73 over the study area. Soil-water availability is estimated using the depth to water table, and a soil texture index is correlated with PAI at rs = 0.54, p = 0.004. This basic ecohydrological relationship is monitored in a conceptual model predicting the structural changes expected with rising water over landscapes. The model predicts forest structural decline for most of the study area with incrementally higher sea surfaces. It is expected that the methods and theories developed here can be adapted to the LIDAR-based monitoring of similar habitats. [ABSTRACT FROM AUTHOR]

Fluctuation in proline content is a widespread phenomenon among plants in response to heavy metal stress. To distinguish between the participation of water deficit and copper on changes in proline metabolism, potted plants and floating leaf discs of tobacco were subjected to CuSO treatments. The application of copper increased the proline content in the leaves concomitantly with decreased leaf relative water content and increased abscisic acid (ABA) content in the potted plant. Excess copper increased the expression of two proline synthesis genes, pyrroline-5-carboxylate synthetase (P5CS) and ornithine aminotransferase (OAT) and suppressed proline catabolism gene, proline dehydrogenase (PDH). However, in the experiment with tobacco leaf discs floating on CuSO solutions, the excess copper decreased proline content and suppressed the expression of the P5CS, OAT and PDH genes. Therefore, proline accumulation in the potted tobacco plants treated with excess Cu treatment might not be the consequence of the increased copper content in tobacco leaves but rather by the accompanied decrease in water content and/or increased ABA content. [ABSTRACT FROM AUTHOR]

Our aim was to examine the effect of water stress on plant growth and development of two native plant species ( Tetraclinis articulata and Crithmum maritimum) and on microbial community composition and activity in the rhizosphere soil, following the addition of an organic amendment, namely sugar beet residue (SBR), and/or the inoculation with an arbuscular mycorrhizal (AM) fungus, namely Glomus mosseae, in a non-sterile heavy metal-polluted soil. The AM inoculation did not have any significant effect on plant growth of both species. In T. articulata, SBR increased shoot growth, foliar P, total phospholipid fatty acids (PLFA), fungi-related PLFA, AM fungi-related neutral lipid fatty acid, bacterial gram-positive/gram-negative PLFA ratio and the β-glucosidase and dehydrogenase activities. SBR and AM inoculation increased phosphatase activity in T. articulata plants grown under drought conditions. In both plants, there was a synergistic effect between AM inoculation and SBR on mycorrhizal colonisation under drought conditions. In C. maritimum, the increase produced by the SBR on total amounts of PLFA, bacterial gram-positive-related PLFA and bacterial gram-negative-related PLFA was considerably higher under drought conditions. Our results suggest that the effectiveness of the amendment with regard to stimulating microbial communities and plant growth was largely limited by drought, particularly for plant species with a low degree of mycorrhizal colonisation. [ABSTRACT FROM AUTHOR]

Photosynthetic acclimation to highly variable local irradiance within the tree crown plays a primary role in determining tree carbon uptake. This study explores the plasticity of leaf structural and physiological traits in response to the interactive effects of ontogeny, water stress and irradiance in adult almond trees that have been subjected to three water regimes (full irrigation, deficit irrigation and rain-fed) for a 3-year period (2006–08) in a semiarid climate. Leaf structural (dry mass per unit area, N and chlorophyll content) and photosynthetic (maximum net CO2 assimilation, Amax, maximum stomatal conductance, gs,max, and mesophyll conductance, gm) traits and stem-to-leaf hydraulic conductance (Ks-l) were determined throughout the 2008 growing season in leaves of outer south-facing (S-leaves) and inner northwest-facing (NW-leaves) shoots. Leaf plasticity was quantified by means of an exposure adjustment coefficient (ɛ = 1-XNW/XS) for each trait (X) of S- and NW-leaves. Photosynthetic traits and Ks-l exhibited higher irradiance-elicited plasticity (higher ɛ) than structural traits in all treatments, with the highest and lowest plasticity being observed in the fully irrigated and rain-fed trees, respectively. Our results suggest that water stress modulates the irradiance-elicited plasticity of almond leaves through changes in crown architecture. Such changes lead to a more even distribution of within-crown irradiance, and hence of the photosynthetic capacity, as water stress intensifies. Ontogeny drove seasonal changes only in the ɛ of area- and mass-based N content and mass-based chlorophyll content, while no leaf age-dependent effect was observed on ɛ as regards the physiological traits. Our results also indicate that the irradiance-elicited plasticity of Amax is mainly driven by changes in leaf dry mass per unit area, in gm and, most likely, in the partitioning of the leaf N content. [ABSTRACT FROM PUBLISHER]

Abstract: A number of evidences have shown that triticale produces more above-ground dry matter (AGDM) than other winter cereals in dry environments. As AGDM accumulated by crop before anthesis has been pointed out as an important attribute under rainfed environments, the comparison of its physiological attributes (i.e. accumulated intercepted radiation – IPAR and radiation use efficiency – RUE), comparing among different cultivars and respect to other cereals, could be valuable to identify prospective traits to be used in breeding programs. Three experiments were carried out during the 2004 and 2005 growing seasons to (i) determine the effect of water stress on the yield and the eco-physiological components of biomass (i.e. accumulated intercepted radiation and RUE throughout the crop cycle) in a wide range of triticale cultivars to evaluate the genotypic variability (in interaction with water regime) for those traits and (ii) to analyze the causes for the commonly found differences in yield and AGDM between triticale and wheat under different water and nitrogen conditions. The triticale cultivars showed an important variability in yield and yield components sensitivity to drought. Water restrictions reduced AGDM, more than its partitioning to the reproductive organs, due to reductions in crop growth rate mainly through reduced RUE when different triticale cultivars were analyzed. Triticale outyielded wheat due to an increased biomass at anthesis and at maturity associated with higher RUE, probably due to a better light distribution into the canopy, more than by differences in IPAR. Triticale advantages were especially noticeable in the Mediterranean-type environment where yield and biomass were almost twice than that of wheat, associated with differences of similar magnitude in RUE. [Copyright &y& Elsevier]

Abstract: This study is focused on enzymatically upgrading the functional properties of flax fibres. Green flax fibres were treated with a polygalacturonase and a pectate lyase (PaL) and their properties were compared with dew-retted fibres. Morphological observations, vapour-sorption analyses and mechanical measurements showed that PaL-treatment was able not only to mime retting in terms of bundle division, but also to improve the mechanical properties of technical fibres. Conversely, these properties were shifted down after the polygalacturonase treatment, mainly due to the presence of contaminating glycanases. At the level of the elementary fibres, nanoindentation data indicated the highest stiffness of the secondary wall for PaL-treated fibres. The tensile properties exhibited equal, but moderate values of the Young''s modulus (∼37±14GPa) and breaking strength (∼650±300MPa) for retted and PaL-treated fibres; we hypothesize an impact of the growth conditions on the fibre chemical structure with an excess of matrix pectins compared to the amount of glucomannan coating the cellulose microfibrils. [Copyright &y& Elsevier]

Water stress impaired cowpea plant growth and decreased ion percentage and chlorophyll and carbohydrate concentration in the shoot as well as yield and its quality. Foliar-applied chitosan, in particular 250 mg/l, increased plant growth, yield and its quality as well as physiological constituents in plant shoot under stressed or nonstressed conditions as compared to untreated plants. Anatomically, water stress decreased thickness of leaf blade at midrib region, thickness of mesophyll tissue, thickness of midrib vascular bundle. Treatment with chitosan, in particular, 250 mg/l and their interactions with stress conditions increased all the above mentioned parameters in either non-stressed or stressed plants. It is suggested that the severity of cowpea plants damaged from water stress was reduced by 250 mg/l chitosan application. [ABSTRACT FROM AUTHOR]

Abstract: Although much is known about drivers of productivity in Douglas-fir and red alder stands, less is known about how productivity may relate to stand transpiration and water use efficiency. We took advantage of a 15-year-old experiment involving Douglas-fir (Pseudotsuga menziesii) and red alder (Alnus rubra) in the western Cascade Range of western Oregon to test the following hypotheses: (a) more productive stands transpire more water, (b) the relationship between productivity and transpiration differs between species, and (c) the relationship between productivity and transpiration differs between sites varying in soil moisture and fertility. Furthermore, the experimental design included alder, a facultative nitrogen-fixing species, which could also affect fertility. Fixed area plots (20×20m) were planted as monocultures of each species or in mixtures at a common density (1100treesha−1) in a randomized-block design. Transpiration of Douglas-fir and red alder was measured using heat dissipation sensors installed in eight trees per plot and scaled to the plot level based on sapwood basal area for each species. Although up to 53% of the variability in tree transpiration was explained by basal area, irrespective of species or site conditions, the two stands with the highest biomass and sapwood basal area did not transpire the most. Instead of more productive stands transpiring more water, the greatest variability in both productivity and transpiration was determined by site conditions and to a lesser degree, species composition. For example, 70% of the variation in tree biomass increment (TBI) was determined by leaf area index, which was much higher at the site with higher fertility and soil moisture (p <0.05). Despite marked phenological and physiological differences, Douglas-fir and red alder performed similarly. Only 19% of annual water use of Douglas-fir occurred between October and March when alder was leafless. Also, there was no evidence of a fertilization effect of the nitrogen-fixing red alder on the Douglas-fir: the nitrogen concentration and N-isotopic ratio of Douglas-fir needles did not differ whether trees were grown in monoculture or in mixtures with red alder. We conclude that lower soil fertility and contrasting microclimate at one site relative to the other suppressed NPP while maintaining higher transpiration, thus reducing water use efficiency. [Copyright &y& Elsevier]

A precise and accurate knowledge of the effects of plant water stress is crucial to framing strategies for improving agricultural productivity in regions of agricultural water (water required for agricultural and allied operations such as field preparation, seeding, irrigation, drainage, livestock production, and dairying) shortage. Success would depend upon the reliability, precision, and accuracy of the techniques used for creating water stress. This paper reports a simple, inexpensive, reproducible, and eco-friendly laboratory technique that essentially consists of a specially designed potometer for creating plant water stress. In this technique, the mode of step-by-step root-zone water stress development resembles in situ field water deficit, exhibiting parallel physiological responses to stress and, at the same time, it takes care of the anomalies, deficiencies, and difficulties generally inherent in other techniques of creating water stress at the whole-plant level. This new technique is superior to the other available ones being used by researchers working for enhancing crop productivity under deficit irrigation and dryland agriculture. [ABSTRACT FROM PUBLISHER]

To elucidate the effect of selenium (Se) on the ascorbate-glutathione (ASC-GSH) cycle under drought stress, the activities of antioxidant enzymes and the levels of molecules involved in ASC-GSH metabolism were studied in Trifolium repens seedlings subjected to polyethylene glycol (PEG)-induced water deficit alone or combined with 5 μM NaSeO. Compared to the control, HO, thiobarbituric acid reactive substances (TBARS), ascorbate (ASC), dehydroascorbate (DHA), and glutathione disulfide (GSSG) contents increased, whereas a constant content of glutathione (GSH) and decreases in ASC/DHA and GSH/GSSG ratios were observed in the presence of PEG. The activities of ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) were upregulated, except for monodehydroascorbate reductase (MDHAR) activity during PEG-induced water deficit. Se application decreased the contents of HO, TBARS, DHA, and GSSG, increased the levels of GSH and ASC, and inhibited the decreases of ASC/DHA and GSH/GSSG ratios. Although it did not affect APX activity significantly, Se addition improved the activities of MDHAR, DHAR, and GR. Furthermore, GR activity showed the highest increase followed by that of DHAR and MDHAR in decreasing order. These data indicated that fluctuations in ASC-GSH metabolism resulting from Se may have a positive effect on drought stress mitigation, and the regulation in the ASC-GSH cycle can be attributed mainly to GR and DHAR in PEG + Se-treated T. repens seedlings. [ABSTRACT FROM AUTHOR]

The composition of high-molecular-weight glutenin subunit (HMW-GS) and low-molecular weight glutenin subunit (LMW-GS) in wheat (Triticum aestivum L) kernel affects the size of ~lutenin macropolymer (GMP), which is consid&ed the important flour quality traits in wheat. Three wheat cultivarswith differentend-use quali1ty were used to study the effects of water-nitrogen (W x N) management on relative HMW-GS and GMP contents. Under irrigation, increased levels promoted the accumulation of HMWand LMW-GS, GMP content, and the proportion of the larger particle of GMP, with higher yield and better end-use quality. Under rainfed conditions, increased N fertilizer also increased protein content in the three cultivars. As opposed to Gaochengo9Ol', 'Shannongl39l' and 'Taishan23' got higher HMWand LMW-GS contents and larger GMP particles, but reduced yields of both. Irrigation increased the yield markedly, the N application significantly affected the glutenin, but the W x N interaction was not significant. On one hand, increased N levels improved the dough development time by increasing the numbers of larger GMP particles and enhane of volume and surface area percentages on the other. It was suggested that the interaction as a complicated network and some individual effect might be important. When managing for wheat yield and quality, growers should first consider the water factor, then the N fertilizer factor to improve the end-use quality of wheat. [ABSTRACT FROM AUTHOR]

This study aims at estimating trends in spring phenology from vegetation index and air temperature at 2 m height. To this end, we have developed a methodology to infer spring phenological dates from Global Inventory Modeling and Mapping Studies (GIMMS) Normalized Difference Vegetation Index (NDVI) time-series, which are then extrapolated to the period 1948-2006 with the help of Reanalysis data, using its 2 m height air temperature parameter. First, yearly NDVI is fitted to a double-logistic function for the whole extent of the GIMMS database (1981-2003). This fitting procedure allows us to describe, on a yearly basis, the NDVI evolution for each pixel through the estimation of six parameters which include the spring date. Retrieved spring date time-series are then upscaled to Reanalysis database resolution and compared to degree-day amounts. Those degree-day amounts are estimated for various thresholds in order to determine the best thresholds for their calculations on a pixel-by-pixel basis. Once the correct thresholds are identified by correlation with corresponding GIMMS spring date time-series, spring dates are estimated for the whole extent of the Reanalysis database (1948-2006). Finally, Mann-Kendall trend tests are conducted on degree-day-retrieved spring date time-series and trends are estimated only for those pixels that show statistically significant trends. These trends in spring occurrence have an average value of -0.03 days per year, but range between -0.9 and +0.9 days per year, depending on the considered areas. Since the approach is based only on air temperature, retrieved spring dates for vegetation whose growth is limited by water are unreliable, as correlation analysis confirms. The obtained spring date trends show good coherence with previous studies and could be used for climate change impact studies, especially in polar and temperate areas, where the model is more reliable. [ABSTRACT FROM AUTHOR]

The photosynthetic characterization of the oriental lily ( Lilium) cv. Sorbonne and its response to increasing water stress were analyzed based on the net photosynthetic rate ( P), stomatal conductance ( g), intercellular CO concentration (C), transpiration rate ( E), water use efficiency (WUE), and stomatal limitation (Ls) in the Horqin Sandy Land of western China. A photosynthesis-PAR response curve was constructed to obtain light-compensation and light-saturation points (LCP and LSP), the maximum photosynthetic rates ( P) and dark respiration rates ( R). The growth of lilies in the pots was analyzed after anthesis. Various intensities of water stress (5, 10, and 20 days without water, and an unstressed control) were applied. The results indicated that drought stress not only significantly decreased P, E, g, photosynthetic pigment content (Chl a, Chl b, and Chl ( a + b)) and increased intrinsic water use efficiency (WUE), but also altered the diurnal pattern of gas exchange. Drought stress also affected the photosynthesis ( P)-PAR response curve. Drought stress increased LCP and R and decreased LSP and P. There were both stomatal and nonstomatal limitations to photosynthesis. Stomatal limitation dominated in the morning, whereas nonstomatal limitation dominated in the afternoon. Thus, drought stress decreased potential photosynthetic capacity and affected the diurnal pattern of gas exchange and P-PAR response curves, thereby reducing plant quality (lower plant height, flower length, flower diameter, and leaf area). Water stress is likely the main limitation to primary photosynthetic process in the lily. Appropriate watering is recommended to improve photosynthetic efficiency and alleviate photodamage, which will increase the commercial value of the lily in the Horqin Sandy Land. [ABSTRACT FROM AUTHOR]

Abstract: Withholding irrigation during last stages of onion crops is a common practice to minimize losses in storage due to rots. However, it is unclear whether extended periods of water deprivation may affect bulb postharvest behaviour. In this study we analyze the effects of water deficit during the crop cycle on bulb weight loss and sprouting during storage. Two experiments were conducted: one in a glasshouse with two onion cultivars subjected to three treatments of water availability (100%, 80% and 60% of field capacity); the other in the field, with one of these cultivars, subjected to two water availability treatments (dryland and irrigated twice during bulb filling). In both experiments five destructive samplings were done along crop development to assess plant height, number of green leaves, bulb and neck diameter, and whole-plant dry weight. Bulbs were harvested when 50% or more of the tops fell over. Harvested bulbs were classified by weight and then kept in a ventilated chamber at a mean temperature of 15°C and weighted every two weeks, up to six months. Water deficit led to a significant reduction of bulb size, an acceleration of sprouting and an increased rate of weight loss during storage in both cultivars and under both experimental conditions. Hence, restricted irrigation during extended periods may have negative effects on the conservation of stored onion bulbs which suggests the need to finely adjust water management in this crop. [Copyright &y& Elsevier]

Abstract: Salinity and water level fluctuations are important factors that influence mangrove species distribution, zonation patterns and succession. Increases in salinity and prolonged inundation are predicted along the south eastern African coast associated with sea level rise due to climate change. This study investigated the response of red mangrove seedlings (Rhizophora mucronata Lam.) to these factors in controlled laboratory experiments. Seedlings were exposed to five salinity treatments (0, 8, 18, 35 and 45PSU) and a semi-diurnal tidal cycle in an experimental tank set-up. In a separate experiment the effects of different inundation treatments: no inundation, 3, 6, 9h tidal cycles and continuous inundation (24h) were investigated. Both morphological and physiological responses of R. mucronata seedlings were measured. There was a decrease in growth (plant height, biomass and leaf production) with increasing salinity. Seedlings in the seawater, hypersaline and no inundation treatments showed symptoms of stress such as increased leaf necrosis (‘burn marks’). The highest seedling growth occurred in the low salinity (8PSU) treatment, but the highest photosynthetic performance and stomatal conductance occurred in the freshwater treatment (0PSU). The typical response of stem elongation with increasing inundation was observed in the 24h inundation treatment. Seedlings in the no inundation treatment had significantly lower seedling height compared to the other treatments. [Copyright &y& Elsevier]

The interaction of salt and water stress to infect the roots by Macrophomina phaseolina, and affect the ion composition and growth of sorghum (Sorghum bicolor) was studied in a greenhouse experiment (19-35°C). Treatments consisted of 4 levels of salinity (0, 1400, 2100 and 2800 mg of NaCl kg-1 soil) and three water stress levels (3, 7 and 10 irrigation intervals). Infested soil containing 100 viable microsclerotia g-1 of a melon isolate of M. phaseolina and non-infested soil were used for all treatments. The experiment was arranged in a completely randomized design with four replications. Six-week-old sorghum seedlings after their transferring to infested and non-infested soil were exposed to salt stress, after which, water stress was started. Shoot dry weights were reduced by increasing salinity levels. This reduction was more pronounced in infested soil than in non-infested. Increasing irrigation intervals reduced salt injuries. Shoot and root colonization by M. phaseolina significantly increased by increasing salinity levels up to 1400 mg of NaCl kg-1 soil. Moreover, salinity and M. phaseolina interaction increased the concentrations of Na+ and Cl- compared to salt stress per se, but negatively correlated with increasing irrigation intervals. Concentration of K+ was in contrast with Na+ and Cl-. Also, disease symptoms appeared only in the highest irrigation intervals (7 and 10 days). Consequently, more infected crown and root were observed by increasing irrigation intervals and NaCl levels up to 1400 mg kg-1 soil. [ABSTRACT FROM AUTHOR]

Abstract: Sunagoke moss Rachomitrium japonicum is a good potential for greening material. One of the primary determinants of Sunagoke moss growth is water availability. Too much or too little water can cause water stress in plants. Water stress in plants can be detected by imaging. This study is part of on-going research aimed at developing machine vision-based precision irrigation system in a closed bio-production system for cultured Sunagoke moss. The objective of this study is to propose nature-inspired feature selection techniques to find the most significant set of Textural Features (TFs) suitable for predicting water content of cultured Sunagoke moss. The proposed Feature Selection (FS) methods include Neural-Intelligent Water Drops (N-IWD), Neural-Simulated Annealing (N-SA), Neural-Genetic Algorithms (N-GAs) and Neural-Discrete Particle Swarm Optimization (N-DPSO). TFs consist of 120 features extracted from grey, RGB, HSV, HSL and L∗a∗b∗ colour spaces using ten Haralick’s textural equations. Back-Propagation Neural Network (BPNN) model performance was tested successfully to describe the relationship between water content of Sunagoke moss and TFs. Red Colour Co-occurrence Matrix (CCM) TFs, L∗ CCM TFs, grey CCM TFs, value(HSV) CCM TFs, green CCM TFs and lightness(HSL) CCM TFs are recommended as individual feature-subset to be used for predicting water content of Sunagoke moss using Artificial Neural Networks. However, FS methods improve the prediction performance. The results show a significant difference between model using FS and models using individual feature-subsets or without FS. Comparative analysis shows the superiority of Neural-Intelligent Water Drops (N-IWD) compared to the other FS methods, since it achieve better prediction performance. The best N-IWD’s fitness function converged with the lowest validation-set Root Mean Square Error (RMSE) of 1.07×10−2 when using 36 TFs. [Copyright &y& Elsevier]

Abstract: Plant stress significantly reduces plant productivity. Automated on-the-go mapping of plant stress would allow for a timely intervention and mitigation of the problem before critical thresholds were exceeded, thereby maximizing productivity. The spectral signature of plant leaves was analyzed by a hyperspectral camera to identify the onset and intensity of plant water stress. Five different levels of water treatment were created in young apple trees (cv. ‘Buckeye Gala’) in a greenhouse. The trees were periodically monitored with a hyperspectral camera along with an active-illuminated spectral vegetation sensor and a digital color camera. Individual spectral images over a 385–1000nm wavelength range were extracted at a specific wavelength to estimate reflectance and generate spectral profiles for the five different water treatment levels. Various spectral indices were calculated and correlated to stress levels. The highest correlation was found with Red Edge NDVI at 705 and 750nm in narrowband indices and NDVI at 680 and 800nm in broadband indices. The experimental results indicated that intelligent optical sensors could deliver decision support for plant stress detection and management. [Copyright &y& Elsevier]

Due to the rapid depletion of water resources, water must be used more efficiently in agriculture to maintain current levels of yield in irrigated areas. The efficiency of irrigation systems can be increased by adjusting the amount of water applied to specific conditions of soil and crop, which may vary in a field. Taking into account spatial and temporal variability, it is evident that an equipment capable of providing different irrigation levels is necessary to meet the water requirement of the soil. This work aims to develop and evaluate a flow rate sprinkler to be used in center pivots or linear moving irrigation systems, with potential for utilization in irrigation scheduling. A prototype was developed by duplicating its calibrations, and discharge coefficient adjustment was carried out in the laboratory. To predict the flow rate, a successful model that represented the operation of the flow rate sprinkler was established. The calibration of the flow rate sprinkler prototype showed satisfactory statistical and technical results. Automation of the prototype was achieved by driving a step motor using communication from the parallel port of a microcomputer, which was controlled by a software developed for this purpose. The results were satisfactory and technically feasible. [ABSTRACT FROM AUTHOR]

Abstract: Ubiquitin (Ub)-conjugating enzymes (UBCs) are key enzymes involved in ubiquitination. Although UBCs have been shown to play important roles in regulating various aspects of plant growth and development, the role of plant UBCs in abiotic stress response needs to be examined further. Here we report the characterization of a ubiquitin-conjugating enzyme gene AhUBC2 from dehydrated peanut plants. The expression of AhUBC2 gene in peanut plants is responsive to physiological water-stress induced by polyethylene glycol (PEG6000), high salinity, abscisic acid (ABA) or low temperature. The constitutive expression of AhUBC2 gene in wild-type Arabidopsis confers improved tolerance to water-stress induced by sorbitol or soil drought in 35S::AhUBC2 transgenic plants. Constitutive expression of AhUBC2 results in significantly increased expressions of three stress-responsive genes P5CS1, RD29A and KIN1 in 35S::AhUBC2 Arabidopsis grown under normal conditions, whereas the expressions of other four stress-responsive genes NCED3, ABF3, RD29B and RD22 are not affected. The proline level in 35S::AhUBC2 Arabidopsis is significantly higher than that in wild-type Arabidopsis under both soil-drought stressed and control conditions. In contrast, there is no significant difference in the levels of NCED3 transcript and endogenous ABA between wild-type and 35S::AhUBC2 Arabidopsis. These results suggest that constitutive expression of AhUBC2 in Arabidopsis confers improved water-stress tolerance likely through activating an ABA-independent signaling pathway, including regulating the expression of ABA-independent stress-responsive genes and promoting the synthesis of osmolyte proline to protect plants from water deficit. [Copyright &y& Elsevier]

A standard-free method for living plants in in-air PIXE has been developed in order to clarify the mechanism of elemental transportation and movement in farm products. The components of the continuous X-rays originated from air and a backing film can be exactly subtracted using a blank spectrum after normalization by the yields of Ar Kα X-rays. It is found by observing the yield of continuous X-rays with passage of time that water content is continuously decreasing during irradiation with a proton beam in a case of pinched leaves. In contrary, it is kept almost constant during irradiation for the living plants to which water is continuously provided through the roots. Stability of the yield of continuous X-rays is a required condition for a standard-free method, which makes use of the yield of continuous X-rays mainly emitted from water content. It is confirmed that potassium concentration shows no large position dependence on a leaf, and it keeps almost constant during irradiation, which also indicates that regular metabolism is going on. As potassium is always contained in all kinds of plants in large amount, it is designated as an index element. As a result, it is found that the potassium concentration obtained by the present standard-free method shows quite consistent values with those obtained by the internal-standard method. The present method is confirmed to be quite useful for investigating movement of not only toxic elements but also essential elements reflecting metabolism in plants. [ABSTRACT FROM AUTHOR]

Perennial ryegrass is a globally cultivated obligate outbreeding diploid species (2 n = 2 x = 14) which is subjected to periods of waterlogging stress due to flood irrigation during winter and the lead-up to summer. Reduction of oxygen supply to root systems due to waterlogging produces consequent deleterious effects on plant performance. Framework genetic maps for a large-scale genetic mapping family [ F(NA × AU)] were constructed containing 91 simple sequence repeat and 24 single nucleotide polymorphism genetic markers. Genetic trait dissection using both control and waterlogging treatments was performed in the glasshouse, a total of 143 maximally recombinant genotypes being selected from the overall sib-ship and replicated threefold in the trial. Analysis was performed for nine quantitative morphological traits measured 8 weeks after stress treatments were applied. A total of 37 quantitative trait loci (QTLs) were identified; 19 on the NA parental genetic map, and 18 on the AU parental genetic map. Regions of particular interest were identified on linkage groups (LGs) 4 and 3 of the respective maps, which have been targeted for further analysis by selection of critical recombinants. This first study of genetic control of waterlogging tolerance in ryegrasses has important implications for breeding improvement of abiotic stress adaptation. [ABSTRACT FROM AUTHOR]

Gross primary productivity (GPP) is a critical response variable for many environmental problems, including terrestrial carbon accounting and the calculation of catchment water balances. Various approaches for modelling GPP have been developed and applied at continental and landscapes scales, but little attention has been given to the sensitivity of GPP to the spatial scale of its driving variables. A key driving variable is surface radiation (R s ) which is influenced by both meso-scale factors (latitude, time of year, cloudiness) and the topographic variables of slope, aspect and horizon shading. We compared the sensitivity of modelled GPP to two different sources of surface radiation (R s ): (1) the ANUCLIM method which only captures the meso-scaled factors; and (2) the SRAD method which incorporates the topographic effects GPP was calculated using the radiation use efficiency (RUE) model () to discern general patterns of vegetation productivity at a sub-catchment (i.e. sub-water shed) scale. The radiation use efficiency approach uses the normalized difference vegetation index (NDVI) derived from satellite data (MODIS TERRA), along with estimates of solar radiation at the top of the atmosphere (R o ) and canopy (R s ). In this approach, R o and R s capture the influence of diffuse irradiance in canopy photosynthesis and vegetation productivity respectively. This research showed that R s calculated using the SRAD program provides important discrimination of GPP regimes at a sub-catchment scale, as the result of minimum and maximum daily radiation varying between shaded and exposed surfaces. However, mean daily radiation at a whole-of-catchment scale did not differ between the two sources as the differences in the minimum and maximum daily values tend to cancel each other out. Applications of GPP models therefore need to consider whether topographic factors are important and select the appropriate source of R s values. GPP models should also reflect understanding of radiation use efficiency. However, further research is required especially with respect to the influence of water stress on plant response. [Copyright &y& Elsevier]

The effect of various combinations of temperature and relative humidity on dormancy alleviation of sunflower seeds during dry after-ripening was investigated. The rate of dormancy alleviation depended on both temperature and embryo moisture content (MC). Below an embryo MC of 0.1 g H2O g−1 dw, dormancy release was faster at 15 °C than at higher temperatures. This suggests that dormancy release at low MC was associated with negative activation energy, supported by Arrhenius plots, and low Q10 values. At higher MC, the rate of dormancy alleviation increased with temperature, correlating well with the temperature dependence of biochemical processes. These findings suggests the involvement of two distinct cellular mechanisms in dormancy release; non-enzymatic below 0.1 g H2O g−1 dw and associated with active metabolism above this value. The effects of temperature on seed dormancy release above the threshold MC were analysed using a population-based thermal time approach and a model predicting the rate of dormancy alleviation is provided. Sunflower embryo dormancy release was effective at temperatures above 8 °C (the base temperature for after-ripening, TbAR, was 8.17 °C), and the higher the after-ripening temperature above this threshold value, the higher was the rate of dormancy loss. Thermodynamic analyses of water sorption isotherms revealed that dormancy release was associated with less bound water and increased molecular mobility within the embryonic axes but not the cotyledons. It is proposed that the changes in water binding properties result from oxidative processes and can, in turn, allow metabolic activities. [ABSTRACT FROM PUBLISHER]

Analysis of the growth of pot chrysanthemum, Puritan cultivar, irrigated under different substrate water tensions in greenhouse. Irrigation is an important practice in chrysanthemum growing, but water management has been neglected, resulting in quality losses and yield reduction. The experiment was conducted at the Steltenpool farm, in the Holambra II District of the city of Paranapanema (23°4'S and 49°00'W). The aim of this research was to identify the best substrate water tension that could assure quality and high yield for the chrysanthemum, Puritan cultivar. Treatments were composed of six levels of substrate water tension: -2, -3, -4, -6, -10 and -30 kPa. Results showed that -2, -6 and -10 kPa substrate water tension resulted in the highest number of pots with A1 quality, considered the highest level in the grower's scale. Postharvest was also evaluated and plants irrigated when substrate water tension reached -30 kPa presented longer durability. [ABSTRACT FROM AUTHOR]

The understanding developed through intensive monitoring over 18 years of Eighteen Mile Swamp on North Stradbroke Island, south-eastern Queensland, Australia, is discussed in this paper. This wetland is the largest coastal peat swamp in eastern Australia and is typified by its sandy, poor nutrient substrate and peat base. On-ground and remote monitoring was commissioned to detect any changes resulting from water extraction from the Swamp, which commenced in 1992. During the monitoring period (1988 until 2006) the Swamp was subject to fires and drought. The vegetation has displayed great resilience to many environmental perturbations, but changes in water level can, and have, altered the biota profoundly. Through analysis of structural and floristic data collected against the backdrop of natural and artificial change, the limitations to monitoring, when the basic function of the ecosystem is unknown, are highlighted. The monitoring goal is confounded by a high degree of natural variation, the long cycles of natural change, and the effect of extreme events. In order to determine the effect of human activity on such areas it is imperative to have a network of reference sites in similar areas and to sustain monitoring for long periods—at least 50 years—accompanied by information on relevant environmental effectors. [ABSTRACT FROM AUTHOR]

The emergent sedge Lepironia articulata (Retz.) Domin is a prominent aquatic plant growing in coastal dune lakes on North Stradbroke Island (south east Queensland, Australia) where it is an important source of three-dimensional habitat structure for lake biota. Despite the obvious importance of the species to wetland ecosystems, it has been little studied either in Australia or elsewhere. In order to understand more about the habitat attributes that support this important species, we surveyed the bathymetry of two dune lakes, Blue Lake and Swallow Lagoon, and identified that stands of Lepironia articulata occur growing from the wetland margin and in water up to 5.5 m deep in Blue Lake and 4.4 m deep in Swallow Lagoon. The different optical properties and stratification regimes of the two wetlands may have influenced the distributions of L. articulata. Alterations to wetland water depth may have important ramifications for the ecology of these lakes as many other species are dependent upon either habitat provided by L. articulata or upon free water that is not populated by this sedge. [ABSTRACT FROM AUTHOR]

Cottonwoods, riparian poplars, are dioecious and prior studies have indicated that female poplars and willows can be more abundant than males in low-elevation zones, which are occasionally flooded. We investigated the response to flooding of clonal saplings of 12 male and 9 female narrowleaf cottonwoods (Populus angustifolia) grown for 15 weeks in a greenhouse, along with three females of a co-occurring native hybrid (Populus × jackii = Populus deltoides × Populus balsamifera). Three water-level treatments were provided, with substrate inundation as the flood treatment. In the non-flooded condition, the hybrids produced about four-fold more dry weight (DW) than the narrowleaf cottonwoods (P < 0.01). In both cottonwood taxa, flooding reduced stem height and DW, root and leaf area and weight, leaf chlorophyll and stomatal conductance (all P < 0.01). Inundation increased the foliar carbon-to-nitrogen ratio (+11%; P < 0.05) but did not significantly alter leaf water potential (mean −1.5 MPa), or foliar δ13C, which was lower in P. angustifolia (−32.8‰) than P. × jackii (−31.5‰; P < 0.05). Water level influenced the root distribution as roots were sparse in the saturated substrate and abundant in the capillary fringe above. The male and female P. angustifolia genotypes grew similarly with the favorable water levels, but the males tended to be more inhibited by flooding. Sapling DW of males was reduced by 56% compared with a 44% reduction for females (P = 0.1), and there were similar lower reductions for leaf, stem and root DW in females. These results demonstrate the inundation response of floodplain trees and suggest relative flood tolerance as: P. angustifolia female > P. angustifolia male > P. × jackii female. This indicates that narrowleaf cottonwoods are relatively flood tolerant and suggests that females are more flood tolerant than males. We propose the concept of ‘strategic positioning’, whereby the seed-producing females could be better adapted to naturally flooded, low-elevation streamside zones where seedling recruitment generally occurs. [ABSTRACT FROM AUTHOR]

Seasonally dry tropical forests (SDTF) are characterized by pronounced seasonality in rainfall, and as a result trees in these forests must endure seasonal variation in soil water availability. Furthermore, SDTF on the northern Yucatan Peninsula, Mexico, have a legacy of disturbances, thereby creating a patchy mosaic of different seral stages undergoing secondary succession. We examined the water status of six canopy tree species, representing contrasting leaf phenology (evergreen vs. drought-deciduous) at three seral stages along a fire chronosequence in order to better understand strategies that trees use to overcome seasonal water limitations. The early-seral forest was characterized by high soil water evaporation and low soil moisture, and consequently early-seral trees exhibited lower midday bulk leaf water potentials (Ψ) relative to late-seral trees (−1.01 ± 0.14 and −0.54 ± 0.07 MPa, respectively). Although Ψ did not differ between evergreen and drought-deciduous trees, results from stable isotope analyses indicated different strategies to overcome seasonal water limitations. Differences were especially pronounced in the early-seral stage where evergreen trees had significantly lower xylem water δO values relative to drought-deciduous trees (−2.6 ± 0.5 and 0.3 ± 0.6‰, respectively), indicating evergreen species used deeper sources of water. In contrast, drought-deciduous trees showed greater enrichment of foliar O (∆O) and C, suggesting lower stomatal conductance and greater water-use efficiency. Thus, the rapid development of deep roots appears to be an important strategy enabling evergreen species to overcome seasonal water limitation, whereas, in addition to losing a portion of their leaves, drought-deciduous trees minimize water loss from remaining leaves during the dry season. [ABSTRACT FROM AUTHOR]

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In many arid zones around the word, the vegetation spontaneously forms regular patterns to optimize the use of the scarce water resources. The patterns act as early warning signal that fragile ecosystems may suddenly undergo irreversible shifts, thus, interpreting the structural shape of vegetation patterns is crucial to deciphering the ecosystem history and its expected further development. The sudden and irreversible shift of delicate ecosystems as a consequence of minor variation of the climatic forcing has been studied extensively in the past. The attitude of the ecosystem to recover after a catastrophic event, such as fire, did not receive as much attention so far. Here we modelled fire, as a sudden shift of the ecosystem state variables and functionality and evaluated post-fire scenarios under the hypothesis that two major feedbacks shaped the vegetation patterns: a positive feedback between preferential infiltration and plant growth, and a second feedback between infiltration and vegetation burning. A simple model solving a set of partial differential equations for soil moisture, plant biomass, surface water and dead biomass balance predicted significantly diverse post-fire vegetation patterns depending on the fire severity and on the degree of soil water repellency induced by the vegetation burning. [Copyright &y& Elsevier]

Fresh seeds of lentil cultivars 'Pul 11', 'Sultan 1' and Meyveci 2001' were subjected to hydropriming with an objective to improve germination and seedling vigor underwater stress induced by PEG-6000 at the water potentials of 0.0 (distilled water), -0.3 and-0.6 MPa. Results revealed that germination delayed in increasing water stress with variable germination among cultivars. Root, shoot length and germination were higher but mean germination time were lower in the primed seeds. Seeds were able to germinate at all concentrations of PEG but higher germination and improved seedling growth was observed in primed seeds. Cultivars showed variable response to water stress and cv. 'Pul 11' with the lightest seed weight gave better performance. Whereas, cv. 'Sultan 1' enhanced germination percentage with hydropriming under increased water stress. It was concluded that inhibition of germination due to water stress should be overcome by using primed lentil seeds. [ABSTRACT FROM AUTHOR]

The depth of plant roots depends on a variety of conditions, including soil properties, vegetation type, nutrient availability, and climate. A water-optimal root depth is determined by equating the marginal carbon cost of deeper roots with the benefit of those roots to continued transpiration. This work compares the effect of two bounding strategies of plant uptake, conservative and intensive, on the water-optimal root depth and the response of that depth to changes in precipitation. While there are some differences between the models, both indicate similar responses of root depth to climate. The deepest roots are found in climates for which precipitation and potential transpiration are approximately equal, and root depths are more sensitive to changes in precipitation depth than frequency under dry conditions and more sensitive to rainfall frequency when the climate is wet. For all climate conditions, the water-optimal root depth is deeper and mean transpiration is lower when plant uptake is represented by the conservative model. These results highlight the explanatory power of water with respect to root depth and identify potential effects of a changing climate. [ABSTRACT FROM AUTHOR]

A fruit thinning strategy is introduced for 'Conference' pear to mitigate water stress and to maximise yield. Three irrigation and four thinning treatments were applied. The three irrigation treatments were: full irrigation (FI); deficit irrigation, receiving 50% of the water in FI (DI-50); and deficit irrigation receiving 20% of the water in FI (DI-20). The four fruit thinning treatments were: no thinning (NT); light thinning (LT), leaving more than 80% of the crop load; medium thinning (MT) leaving 50% of the crop load; and heavy thinning (HT) leaving 20% of the crop load. All thinning treatments were combined with DI-20, but only NT and MT were combined with FI and DI-50. Fruit thinning improved fruit size in FI and DI-50, but is not recommended because of the high labour cost and reduction in total fresh-market yield. For DI-20, thinning increased the midday stem water potential (Ψstem), improved yield (with LT), and increased fruit size (with HT). A three-dimensional regression model was developed to optimise fresh-market yield by fruit thinning, and showed the impact of Ψstem. Using the model, it was also possible to choose, for each value of Ψstem, a suitable crop load to maximise the fresh-market yield. [ABSTRACT FROM AUTHOR]

We describe the development of a water-use strategy for horticulture in England and Wales. Data were gathered from a literature review as well as from industry and grower surveys, and combined with information from interviews with key informants, in order to assess current practices and underlying trends in water-use within seven horticultural sectors. The spatial distribution of horticultural holdings relative to water availability and stress were mapped for both direct abstraction and mains water supplies. From this, a strategy was developed to define the key priorities at grower and industry levels, and the actions required, including research, communication, and knowledge transfer, to improve water-use efficiency and to reduce environmental water impacts. The key priorities identified included: improving our knowledge of the impacts of irrigation on diffuse pollution, including leaching of nitrate, phosphate, and pesticides; the need to improve grower understanding of water regulation; and quantifying the links between poor uniformity of irrigation, crop production, and profitability. [ABSTRACT FROM AUTHOR]

Water vapor flux and carbon dioxide (CO2) exchange in croplands are crucial to water and carbon cycle research as well as to global warming evaluation. In this study, a standard three-layer feed-forward back propagation neural network technique associated with the Bayesian technique of automatic relevance determination (ARD) was employed to investigate water vapor and CO2 exchange between the canopy of summer maize and atmosphere in responses to variations of environmental and physiological factors. These factors, namely the photosynthetically active radiation (PAR), air temperature (T), vapor pressure deficient (VPD), leaf-area index (LAI), soil water content in root zone (W), and friction velocity (U*), were used as inputs in neural network analysis. Results showed that PAR, VPD, T and LAI were the primary factors regulating both water vapor and CO2 fluxes with VPD and W more critical to water vapor flux and PAR and T more crucial to CO2 exchange. Furthermore, two time variables “day of the year (DOY)” and “time of the day (TOD)” could also improve the simulation results of neural network analysis. The important factors identified by the neural network technique used in this study were in the order of PAR> T >VPD>LAI> U*>TOD for water vapor flux and in the order of VPD> W >LAI> T >PAR>DOY for CO2 exchange. This study suggests that neural network technique associated with ARD could be a useful tool for identifying important factors regulating water vapor and CO2 fluxes in terrestrial ecosystem. [Copyright &y& Elsevier]

The aim of this study was to investigate how alternative irrigation strategies affected grapevine (Vitis viniferaL.) stomatal response to atmospheric vapour pressure deficit (VPD). In two sites, application of partial rootzone drying (PRD) at 90–100% of crop evapotranspiration (ETc) increased stomatal sensitivity of Shiraz (Syrah) grapevines to high VPD compared with control vines irrigated with the same amount of water but applied on both sides of the vine. PRD significantly reduced vine water use (ESF) measured as sap flow and in dry conditions increased the depth of water uptake from the soil profile. In both experiments, PRD reduced vine water use by up to 50% at moderate VPD (~3 kPa) compared with control vines irrigated at the same level. In the same vines, the response to PRD applied at 100% ETcand deficit irrigation applied at 65% ETcwas the same, increasing stomatal sensitivity to VPD and decreasing sap flow. Hydraulic signalling apparently did not play a role in changing stomatal sensitivity as there was no difference in stem water potentials between any of the treatment (PRD and DI) and control vines. This suggests that a long distance root-based chemical signal such as ABA may be responsible for the changes in stomatal behaviour. Shiraz grapevines have previously been classified as anisohydric-like, but application of PRD and DI increased stomatal closure in response to conditions of high evaporative demand making the vines behave in a more isohydric-like manner. [ABSTRACT FROM AUTHOR]

A study of 36 wheat (Triticum aestivumL.) genotypes with different levels of stem solidness was conducted to assess the heritability and relationship among stem morphological properties, stem water-soluble carbohydrates (WSC) storage capacity and grain yield. The total amount of pith-fill in the upper stem internode (VOL) was highly correlated with the total content of WSC per stem under both water deficit (DEF) (r=0.56) and well irrigated conditions (IRR) (r=0.49). A positive correlation was also found between VOL and grain yield under DEF (r=0.49), which was explained by the positive contribution of WSC to grain yield. A closer association of grain yield and morphological traits was identified under DEF than under IRR. The closer associations found among estimations of %WSC and WSC-area and grain yield under DEF indicate that these variables may be adaptive rather than constitutive traits. High heritability values (0.77–0.84) observed for stem morphological traits reinforce their potential use in breeding for high WSC and ultimately, higher grain yield under water-limited environments. Stem length, diameter and solidness could be combined in an ideal plant ideotype to maximise WSC reserves as a strategy to improve yield under water-limited conditions. [ABSTRACT FROM AUTHOR]

• The homoploid hybrid species Pinus densata is restricted to alpine habitats that exceed the altitude range of its two parental species, Pinus tabulaeformis and Pinus yunnanensis. Alpine habitats usually generate cold-induced water stress in plants. To understand the ecological differentiation between these three species, we examined their physiological responses to drought stress. • Potted seedlings of three species were subjected to low, mild, moderate and severe water stress in an automatic-controlled glasshouse. Fifteen indicators of fitness were measured for each species in each treatment, and most of these decreased as drought increased. • Pinus densata exhibited higher fitness than both parental species in terms of total dry mass production (TDM) and long-term water use efficiency (WUEL) across all treatments; several other ecophysiological traits were also extreme but not across every treatment, and not always in the highest stress treatment. • These results indicate that extreme characters that have become well fixed in P. densata, confer a faster seedling growth rate and more efficient water use, which in turn should confer increased drought tolerance. These traits of P. densata likely promoted its ecological separation from its parental species and facilitated its successful colonization and establishment in high-altitude habitats. [ABSTRACT FROM AUTHOR]

Disturbances may add or remove resources from communities and can facilitate the spread of some invaders. Differential successes of exotic plants to spread into different communities suggest that some habitats are more invasible than others. Hesperis matronalis (dame's rocket) is widespread across the continent and has potential to become a major problem in natural communities owing to its ability to exploit excess resources and its negative effect on native species. We grew H. matronalis seedlings in a Colorado foothill community at various levels of nitrogen and water with and without neighbors. We expected H. matronalis to maximize its growth under high resource conditions especially without neighbors because ruderal species are able to take advantage of excess resources. Our results reveal that presence or absence of neighbors was the main decisive factor for H. matronalis (aboveground biomass and relative growth rate) success, though seedlings particularly suffered under low resource conditions. Early determination of the potential invasiveness of a widespread exotic species such as H. matronalis in natural communities may promote effective management. [ABSTRACT FROM AUTHOR]

Early responsive to dehydration ( ERD) genes could be rapidly induced to respond to dehydration and to various other abiotic stresses. Here, we report on an ERD gene ( ZmERD4) from maize cloned by rapid amplification of complementary DNA (cDNA) ends. The ZmERD4 cDNA had a total length of 2,536 bp with an open reading frame of 2,196 bp, 5′-untranslated region (UTR) of 48 bp, and 3′-UTR of 292 bp. The gene encoded a predicted polypeptide of 732 amino acids. The ZmERD4 protein shared a high amino acid sequence similarity with ERD4 of Oryza sativa and Arabidopsis thaliana. A reverse-transcription polymerase chain reaction analysis revealed that ZmERD4 was constitutively expressed in different tissues. RNA gel blot showed that ZmERD4 could be induced by both drought and salt stress and also responded to abscisic acid treatment, but it was not induced by low temperature (4°C). Transgenic Arabidopsis plants constitutively expressing the ZmERD4 gene under the control of the 35S cauliflower mosaic virus 35S promoter exhibited slightly smaller-sized leaves under normal growing conditions. Moreover, 35S:: ZmERD4 transgenic plants displayed enhanced tolerance to water deficit and high salinity when compared to wild-type plants. Altogether, these findings suggested that ZmERD4 played an important role in early stages of plant adaptation to stress conditions and might be useful in improving plant tolerance to abiotic stress. [ABSTRACT FROM AUTHOR]

Abstract  We examined the effects of tidal fluctuations on CO2 and CH4 fluxes from sediment or soil to the atmosphere in the littoral zone of a brackish-water lake during the growing seasons in 2004 and 2005. The dominant plants at the study site formed three sub-zones (Phragmites zone, Juncus zone and Miscanthus zone) across a topographic gradient on the shoreline. In the Phragmites and Juncus zones, we observed a positive correlation between hourly changes in CO2 and CH4 fluxes and changes in the water table. In particular, the magnitude and pattern of daily variation in CO2 and CH4 fluxes were different on days during spring tide and neap tide in the Phragmites and Juncus zones. Variations in CO2 and CH4 fluxes in the Phragmites and Juncus zones over the course of a day during spring tide were correlated with water-table level. We found that the rate of change of the water table, as distinguished from just differences in the water table, was a major environmental factor controlling the CO2 and CH4 fluxes. In the Miscanthus zone during spring tide, soil temperature was the main factor affecting daily variation in CO2 and CH4 fluxes. [ABSTRACT FROM AUTHOR]

In this study, eighteen olive varieties, originating from Spain, France, Italy, Greece and Algeria, and maintained at the olive experimental station of Boughrara (arid region of Tunisia) were evaluated for their oil yield and fatty acid composition. The analysis of variance revealed significant differences among varieties for all traits (p < 0.01). The Hierarchical Cluster Analysis (HCA) classified the varieties into three main groups. The first group included a subgroup which is composed of seven olive varieties (Cornezuelo, Verdial de Vélez-Málaga, Leccino, Coratina, Koroneiki, Lechín de Granada and Changlot Real) characterized by high oil yield with high oleic, low palmitic and linoleic acid contents. The fatty acid compositions of the oils from these varieties comply with international standards and show more beneficial characteristics than the oil obtained from Chemlali: the most abundant olive cultivar in Tunisia. Finally, the main fatty acids (palmitic (C16:0), oleic (C18:1) and linoleic (C18:2)) of nine of the studied virgin olive oils were compared to those sampled from their traditional areas. Except for Koroneiki and Oliviere oils which showed an unchanged fatty acid composition and for Cornezuelo oil in which the level of oleic acid raised and the level of linoleic acid decreased, most of oils showed a decrease in oleic acid rates and an increase in palmitic and linoleic acid percentages as compared to those from their original sites. [ABSTRACT FROM AUTHOR]

The effects of water deficit conditions on the qualitative and quantitative characteristics of sunflower seed and seed oils were assessed. Two sunflower cultivars (Gulshan-98 and Suncross) were sown in the field. The water stress treatment was applied at the vegetative or the reproductive stage. Analysis of the sunflower seed showed that the oil content decreased (a decline of 10.52% relative to the control) significantly (p ≤ 0.05) due to water stress when imposed at either of the growth stages. Both of the sunflower cultivars studied showed differential responses to water stress with respect to oil oleic and linoleic acid contents. A significant negative correlation in oil oleic and linoleic acid was observed in cv. Gulshan-98 under water deficit conditions as compared to Suncross in which no such effect of water stress on oleic and linoleic acid was observed. Water deficit conditions caused a reduction in linolenic acid in Gulshan-98, whereas it remained unaffected in Suncross. The stearic acid content increased in cv. Gulshan-98 due to drought, whereas no effect due to water stress was observed on oil palmitic acid content in either sunflower cultivar. Overall, oil unsaturated fatty acids remained unchanged in the drought stressed or normally irrigated plants of both cultivars but saturated fatty acid increased in Gulshan-98. Individual (α, γ and δ) and total tocopherol contents in the seed oil increased significantly with the application of water stress in both cultivars. An assessment of the physical and chemical characteristics of the oils of both sunflower cultivars revealed that drought stress caused a marked increase in the content of un-saponifiable matter (18.75% with respect to the control) and a decrease in iodine value (5.87% with respect to the control), but saponification value, density, specific gravity and refractive index remained unchanged. [ABSTRACT FROM AUTHOR]

Abstract: The seagrass Halophila stipulacea Forsskål, native to the Red Sea, is an invasive species in the Mediterranean that was recently observed offshore Grenada, in the Caribbean. Here, we document the presence of this seagrass in Dominica and St. Lucia, demonstrating it has spread across part of the eastern Caribbean. H. stipulacea in Dominica was present in seven locations along the west coast covering more than 22.9ha of the benthos, at depths from 2 to 18m. Populations were concentrated in or adjacent to bays frequented by recreational or commercial boats, likely vectors for the introduction. Morphological features varied from bed to bed, with depth being the predominant driving factor. H. stipulacea had a rapid mean lateral bed expansion rate of 0.5cmd−1, with a maximum rate of >6cmd−1. H. stipulacea patches often occurred exclusive of the otherwise dominant seagrasses of the Caribbean. The potential for the expansion of H. stipulacea, combined with its tolerance for a wide spectrum of environmental conditions, positions it as a potential threat to local and regional biodiversity. [Copyright &y& Elsevier]

Abstract: Experiments were conducted to evaluate the effects of light, seed burial depth, and flooding on germination, emergence and growth of Ludwigia hyssopifolia. Germination was strongly stimulated by light, suggesting that seeds of this species are positively photoblastic. Seeds sown on the soil surface gave the greatest percentage of seedling emergence in plastic trays, and no seedlings emerged from seeds buried in soil at depths of ≥1 cm. Intermittent or shallow flooding suppressed emergence and growth of L. hyssopifolia. Flooding to a depth of 2 cm for 4 days out of 7 days reduced seedling emergence by more than 71% and seedling dry matter by 97% compared to where the soil had not been flooded. Flooding up to a depth of 10 cm however, when delayed to 21 days after sowing, did not significantly suppress growth of this species. This study illustrates the role of seed burial by tillage and flooding as two important tools for the management of L. hyssopifolia. [Copyright &y& Elsevier]

Abstract: Characteristics of CO2–C exchange were studied in a temperate herbaceous wetland in 2006 and 2007, years with contrasting hydrological regimes. The wetland Mokré Louky (the “Wet Meadows” near Třeboň), Czech Republic (49°01′30″ N, 14°46′20″ E) is a sedge-grass marsh dominated by Carex acuta L. The site is situated in the inundation area of a large human-made lake (Rožmberk fishpond, 5km2). The water table is near the soil surface and is fairly stable throughout the year (±0.1m), except for flood events, when it can reach up to 2m above the soil surface. Net ecosystem production (NEP) was calculated from the CO2 fluxes measured by the eddy-covariance technique and was compared with the seasonal course of plant live aboveground biomass. The results show that: (1) the annual net uptake of CO2–C was 199 and 220gCm−1 yr−1 in 2006 and 2007, respectively. The daily net CO2–C uptake reached 12–20gCm−2 day−1 in sunny summer days. These values are among the highest values reported for wetlands of the northern hemisphere. (2) Although the observed wetland is adapted to floods, the summer flood substantially reduced its net CO2–C uptake. The daily courses of net CO2–C uptake point to reduced rates of CO2–C fixation by the vegetation cover. (3) A recovery growth of plant biomass was associated with a second peak of NEP in September 2006. (4) Lack of knowledge on the dynamics of methane emissions presently limits deeper understanding of the effect of floods on carbon balance in wetlands. [Copyright &y& Elsevier]

Abstract: Flooding regimes in arid and semi-arid regions are heavily influenced by climate change and water shortage, water regulations, and increased water demands. Wetlands managed as part of regulated water systems in agricultural landscapes often require external water supplies to sustain or support desired properties or services. Therefore, water resource managers must weigh water requirements necessary to support wetland functions alongside other water demands. This paper presents a simple method of using a modified climate diagram to display net water requirements for a managed wetland in Xi’an, China. The net water requirements were estimated using the DRAINMOD simulation model by assuming that evaporation is the only path for water loss. For this case study, the ratio of water supply to air temperature was adjusted to 1:1. Three water supply estimates were generated to support a desired water table depth of 30cm for 5%, 12.5%, and 25% of the growing season in Xi’an. When water supply reaches or exceeds a curve, it creates a wetter condition than that represented by the curve. The results also indicate that timing of recharge is very important in preserving wetland hydrology in dry regions. This modified climate diagram prompts an intuitive understanding of the relationship between recharge and consequent wetness of a wetland. It may be used as a standard tool for determining adequate water demand in arid regional water resources management that considers wetland protection or restoration. [Copyright &y& Elsevier]

Abstract: The Chiyoda basin is located in the Saga Prefecture of the Kyushu Island, Japan, and lies next to the tidal compartment of the Chikugo River, into which excess water in the basin is drained away. This basin has a total area of approximately 1100ha and is a typical flat and low-lying agricultural area. The estimation of the water levels at the gates and along the main drainage canal is a crucial issue that has recently been the subject of much research. At these locations farmers and managers need to control the operation of the irrigation and drainage systems during periods of cultivation. An attempt has been made to apply a feed-forward artificial neural network (FFANN) to model and estimate the water levels in the main drainage canal. The study indicated that the artificial neural network (ANN) could successfully model the complex relationship between rainfall and water levels in this flat and low-lying agricultural area. Input variables and the model structure were selected and optimized by trial and error, and the accuracy of the model was then evaluated by comparing the simulated water levels with the observed ones during an irrigation period in July 2007. The water levels at two locations, located upstream and downstream of a main drainage canal, were investigated by using a time series at intervals of 20, 30, and 60min. At these intervals, rainfall and tide water levels in the Chikugo River were measured, and the backward time-step numbers of the input variables of rainfall and tide water level were searched. For the upstream location, the optimal combination yielding good agreement between the observed and estimated water levels was obtained when the interval of the time series was 60min. The number of backward time-steps of the input variables of rainfall and tide water level were 5 and 4, respectively. In contrast to the downstream location, the optimal combination was obtained for the interval time series of 20min with 4 backward time-steps for both the input variables of rainfall and tide water level. The present study could provide farmers and managers with a useful tool for controlling water distribution in the drainage basin, and reduce the cost of installing water level observation points at many locations in the main drainage canal. [Copyright &y& Elsevier]

• The stomata of angiosperms respond to changes in ambient atmospheric concentrations of CO2 ( Ca) in ways that appear to optimize water-use efficiency. It is unknown where in the history of land plants this important stomatal control mechanism evolved. Here, we test the hypothesis that major clades of plants have distinct stomatal sensitivities to Ca reflecting a relatively recent evolution of water-use optimization in derived angiosperms. • Responses of stomatal conductance ( gs) to step changes between elevated, ambient and low Ca (600, 380 and 100 µmol mol−1, respectively) were compared in a phylogenetically and ecologically diverse range of higher angiosperms, conifers, ferns and lycopods. • All species responded to low Ca by increasing gs but only angiosperm stomata demonstrated a significant closing response when Ca was elevated to 600 µmol mol−1. As a result, angiosperms showed significantly greater increases in water-use efficiency under elevated Ca than the other lineages. • The data suggest that the angiosperms have mechanisms for detecting and responding to increases in Ca that are absent from earlier diverging lineages, and these mechanisms impart a greater capacity to optimize water-use efficiency. [ABSTRACT FROM AUTHOR]