Absence Of Water Deficit Research Articles

Metabolismo de nitrogênio em plantas de milho submetidas à deficiencia hidrica, brassinosteróides e azospirillum

Abstract The water deficit in particular, reduces the productivity of vegetable crops. To minimize these harmful effects on agriculture, several agronomic and physiological practices are being studied, such as the use of bacteria and water stress attenuators, such as brassinosteroids. Considering the socioeconomic relevance of corn culture and its sensitivity when exposed to water deficit, the objective of the present study was to evaluate the action of brassinosteroids and azospirillum on nitrogen metabolism in corn plants subjected to water stress conditions. The experiment was carried out in a greenhouse, in a period of 47 days, with corn plants, using the hybrid K9606 VIP3. The design was completely randomized, in a 2x2x3 factorial scheme, with six replications. The first factor corresponds to two water regimes (presence and absence of water deficit). The second corresponds to inoculation via seed of Azospirillum brasiliense and absence of inoculation. And the third corresponds to the application of three concentrations of brassinosteroids (0, 0.3 and 0.6 μM). Were determined Nitrate; nitrate reductase; free ammonium; total soluble aminoacids; soluble proteins; proline; glycine betaine and glutamine synthetase. The lack of water in plants provided a reduction in the protein and nitrate reductase contents, in leaves and roots. For ammonium, plants with water deficit inoculated at a concentration of 0.3 μM, obtained an increase of 7.16 (70.26%) and 13.89 (77.04%) mmol NH4 + .Kg-1. DM (Dry mass) on the leaf and root respectively. The water deficit in the soil provided significant increases in the concentrations of glycine betaine, nitrate, proline and aminoacids, both in the leaves and in the roots of the corn plants. On the other hand, the contents of glutamine synthetase had a reduction in both leaves and roots.

Growth and physiology of maize plants subjected to water deficit and to different brassinosteroid and azospirillum concentrations

Work that demonstrates the use of brassinosteroid and azospirillum bacteria to attenuate the harmful effect of lack of water in corn is incipient. Therefore, the search for an answer that helps to understand the attenuating effect of the use of brassinosteroid and azospirillum bacteria on the physiological characteristics and growth of corn is relevant, since the water demand of the crop is high and the search for alternatives is necessary viable ways to reduce the harmful effects of water deficit. The objective of this study was to evaluate the influence of brassinosteroid and Azospirillum brasilence on the growth and physiology of corn plants submitted to water stress conditions. The experiment was carried out in a vegetable house with a hybrid K9606 VIP3 corn. The experiment was carried out in a vegetable house, using corn plants, the hybrid K9606 VIP3. The experimental design used was completely randomized, in a 2x2x3 factorial scheme, with six replications, totaling 72 experimental units. The first factor corresponds to two water regimes (presence and absence of water deficit). The second factor corresponds to inoculation via seed (at the time of sowing) of Azospirillum brasilense and absence of inoculation. And the third factor corresponds to the application of three concentrations of brassinosteroids (0, 0.3 and 0.6 μM Br). Plant height, stem diameter, number of leaves, root dry weight, leaf and stem, relative water content, chlorophyll a, b, carotenoids, sucrose, starch and total soluble carbohydrates in the leaves and roots were determined. Chlorophyll a levels were highest in water-deficient, inoculated plants with 0.3 μM brassinosteroids. In water-deficient, inoculated plants, the carbohydrate levels were higher in plants with 0.3 and 0.6 μM brassinosteroids. Among plants that were water-deficient and inoculated, plants treated with 0.6 μM brassinosteroids had the highest relative water content. Thus, it is recommended the inoculation of seeds and application of 0.6 μM of brassinosteroids together with Azospirillum brasilense in water-deficient maize plants.

Germination performance of grain sorghum hybrid seeds treated with bioregulator under water deficit

Water stress can reduce seed germination speed and percentage, harming the development of seedlings. Thus, it is necessary to find alternatives that can mitigate these effects. Bioregulators have been intensively used in agricultural production and can provide increase in plant growth and development. Therefore, the aim of this work was to evaluate the germination performance of seeds of two grain sorghum hybrids under simulated water deficit treated with bioregulator. The experimental design was completely randomized in a 2 x 4 factorial scheme, with the following factors: two seed treatments (with and without bioregulator) and four osmotic potentials (0; -0.4; -0.8 and -1.2 MPa), with four replicates, separately for the following grain sorghum hybrids: 1G100 and 1G233. Germination, first germination count, shoot and root length and shoot and root dry matter were evaluated. Data obtained were submitted to analysis of variance and means were compared by the Tukey test at 5% probability and regression analysis. The reduction of the osmotic potential to the level of -1.2 MPa reduced the physiological quality of seeds; however, bioregulator application did not result in better seed quality under water stress. Bioregulator Stimulate® increased root length and shoot dry matter of seedlings of grain sorghum cultivar 1G233 in the absence of water deficit.

Low absorption of silicon via foliar in comparison to root application has an immediate antioxidant effect in mitigating water deficit damage in sugarcane

AbstractHigh root absorption of silicon (Si) in sugarcane plants that accumulate the element attenuates water deficit‐induced damage. However, there is a lack of research to identify whether the low relative absorption of Si via leaf spraying compared to root application has an immediate antioxidant effect on plants under water restriction. For this purpose, the objective of this research was to evaluate the effect of Si applied via leaf spraying and via nutritive solution (root) in mitigating the damage caused by short‐term water deficit induced by PEG‐6000 in pre‐sprouted sugarcane seedlings. The treatments were arranged in a 3 × 2 factorial scheme, consisting of the forms of Si supply: via nutrient solution (SiR) (2.0 mmol/L), via foliar spraying (SiL) (3.4 mmol/L) plus the absence of Si (−Si), combined with the presence (−0.6 MPa) and absence of water deficit, arranged in randomized blocks with 6 repetitions. The experiment was developed in a hydroponic system, in which Si was initially supplied during the seedling production phase; subsequently, water deficit was induced with PEG‐6000 for a period of 72 hr. Plants under water deficit increased the accumulation of Si with the supply of the element via root application and via foliar spraying by 2118% and 98%, respectively, in comparison to the absence of Si. However, although Si foliar absorption was relatively low in comparison to the root, the physiological effects in relieving water deficit‐induced stress were equal to or even higher than those of root application. In conclusion, the amount of Si absorbed by the plant is not a major factor to induce an antioxidant defence response to mitigate the immediate effects of water deficit, since the two forms of application of Si were similar. Si foliar spraying promotes physiological and biochemical effects that alleviate damage done water deficit short term, even on plants with an active absorption mechanism such as sugarcane.

On-vine grape drying combined with irrigation allows to produce red wines with enhanced phenolic and rotundone concentrations

Rotundone, the compound responsible for peppery aroma in red wines is positively correlated with the absence of water deficit during ripening which can make it problematic to produce red wines combining both superior concentrations in rotundone and phenolic compounds. To reach this double objective, on-vine drying with cutting of the fruit bearing cane or “Passerillage Éclaircissage sur Souche” (PES), a technique that consists in cutting the cane 2–3 weeks prior to harvest on a Guyot-trained vineyard was investigated combined or not with irrigation. We showed that PES had a limited impact on rotundone in wine. As the PES technique leads to an interruption of the sap flow, our results suggest that rotundone is synthesized in the berries and not translocated. A viticultural system combining irrigation and then PES induced significant gains in rotundone, in sugar concentration, in anthocyanins and in Total Phenolic Index in wine, and in skin to juice ratio. Measurements of bunch surface temperature indicate that the enhancement of rotundone production induced by irrigation is likely to be due to a direct rather than to an indirect effect through an increase in leaf area leading to a cooler bunch microclimate.

Components of production and quality of soybean sowing according to different velocities of the tractor + seeder assembly

In order to assess application on yield and yield components of soybean in the absence or presence of water stressconditionswas carried out an experiment in Guarapuava, PR. The work was conducted in a randomized block with four replications in a factorial 2 x 2, two crop cultivation systems (with and without irrigation) and two complementary N managements (with or without complementary nitrogen fertilization). The variables analyzed were: yield, thousand grain weight, number of branches per plant, number of pods per plant and number of grains per plant. The results showed that the application of complementary nitrogen contributed to increased yield in soybean under water stress conditions, the answers became more important in the absence of water deficit.

Assessing crop coefficients for Zea mays in the semi-arid Hailiutu River catchment, northwest China

To improve irrigation water-use efficiency, plant transpiration and soil evaporation in a maize (Zea mays L.) field in the Bulang sub-catchment of the Hailiutu River catchment in Northwest China were determined using in situ measurements. Crop transpiration (Tp) rates from Jul 15 to Oct 1, 2011 were measured with sap flow sensors, and soil evaporation (Ep) rates were measured with micro-lysimeters under an absence of water deficit. The two rates together gave the total evapotranspiration (ETc) of the maize field. Cumulative Tp and Ep were 245 and 85mm, accounting for 74 and 26% of total ETc (330mm), respectively. To calculate the total ETc rate of the maize field for the entire growing season, the Penman–Monteith equation combined with a single crop coefficient method (FAO-56) was used. The estimated crop coefficient (Kc) was calibrated using actual sap flow and soil evaporation data to provide accurate estimates of actual evapotranspiration. The total crop ETc of the maize field for the 2011 and 2012 growing seasons was 583 and 500mm, respectively, with a mean daily value of ∼4mmd−1. Groundwater contributed 33% of the maize ETc in 2011 (average groundwater table of 1.12m with full irrigation) and 27% in 2012 (average groundwater table of 0.89m with full irrigation). These results will improve precise planning and efficient management of irrigation for maize in this region.

Genótipos de feijoeiro comum sob deficiência hídrica

Objetivou-se com este trabalho estudar a adaptação de genótipos de fejoeiro comum à deficiência hídrica. Avaliaram-se 49 genótipos no delineamento de blocos ao acaso, com três repetições, em experimentos com e sem deficiência hídrica, na Estação Experimental da SEAGRO, em Porangatu, GO, em 2006 e 2007. Aplicou-se a análise multivariada através do método de Ward e se classificaram os genótipos em quatro grupos, considerando-se os valores médios das produtividades observadas em cada ambiente hídrico, nos dois anos de condução dos experimentos. Verificou-se que as produtividades médias dos grupos diferiram significativamente entre si tanto no ambiente com como naquele sem deficiência hídrica. Os genótipos BRA 130583 CIAT G 6490 e FT 84 - 292 foram classificados como mais produtivos tanto na ausência como na presença de deficiência hídrica enquanto os genótipos BRA 283983 CIAT G 6492, BRA 129721 CIAT G 6896 e G 983 foram classificados como produtivos na ausência de deficiência hídrica porém foram mais sensíveis a esse estresse. Verificou-se, dentre os componentes primários da produção do feijoeiro comum, que o número de vagens por planta foi o componente agronômico mais sensível à deficiência hídrica.

Water deficits uncouple growth from photosynthesis, increase C content, and modify the relationships between C and growth in sink organs

In plants, carbon (C) molecules provide building blocks for biomass production, fuel for energy, and exert signalling roles to shape development and metabolism. Accordingly, plant growth is well correlated with light interception and energy conversion through photosynthesis. Because water deficits close stomata and thus reduce C entry, it has been hypothesised that droughted plants are under C starvation and their growth under C limitation. In this review, these points are questioned by combining literature review with experimental and modelling illustrations in various plant organs and species. First, converging evidence is gathered from the literature that water deficit generally increases C concentration in plant organs. The hypothesis is raised that this could be due to organ expansion (as a major C sink) being affected earlier and more intensively than photosynthesis (C source) and metabolism. How such an increase is likely to interact with C signalling is not known. Hence, the literature is reviewed for possible links between C and stress signalling that could take part in this interaction. Finally, the possible impact of water deficit-induced C accumulation on growth is questioned for various sink organs of several species by combining published as well as new experimental data or data generated using a modelling approach. To this aim, robust correlations between C availability and sink organ growth are reported in the absence of water deficit. Under water deficit, relationships weaken or are modified suggesting release of the influence of C availability on sink organ growth. These results are interpreted as the signature of a transition from source to sink growth limitation under water deficit.

Seasonal gas exchange and water relations in juveniles of two evergreen Neotropical savanna tree species with contrasting regeneration strategies

Colonization dynamics of woody species into grasslands in Neotropical savannas are determined by two main factors: plant-available moisture and fire. Considering seasonality of precipitation and high fire frequency in these ecosystems, vegetative reproduction has been suggested as the main regeneration strategy in woody species. This study examined seasonal variations in water relations and photosynthesis in juveniles of two tree species with contrasting regeneration strategies: Palicourea rigida (sexual reproduction) and Casearia sylvestris (asexual reproduction). The studied species showed similar transpiration rates to deep-rooted adult evergreen tree species during the rainy period, suggesting little water availability limitations on surface soil layers. P. rigida juveniles significantly decreased their leaf water potentials from wet to dry seasons. In C. sylvestris resprouts, there were no seasonal differences in their predawn water potentials and gas exchange parameters, indicating a water deficit avoidance characteristic derived from their connections to deep-rooted adult counterparts allowing access to moist soil at depth even during the drought period. P. rigida rely on strict control of water losses and turgor maintenance through elastic cell walls during the dry season. The iso-hydric behavior of gas exchange and most water relations parameters in C. sylvestris enable turgor maintenance during the dry season which also gives the possibility to achieve foliar expansion under water-stressed conditions for shallow-rooted plants. Nevertheless, in absence of water deficits, P. rigida had the advantage to be physiologically independent individuals, showing an equal or even superior photosynthetic performance that eventually could be translated into a more favorable whole-plant carbon balance and higher growth rates in wet habitats.

Floret initiation, tissue expansion and carbon availability at the meristem of the sunflower capitulum as affected by water or light deficits

• The co-ordination between floret initiation and meristem expansion, and their relationships with carbon availability, were studied and quantified in sunflower (Helianthus annuus) plants subjected to light or water shortages. • Meristem size, number of floret primordia, primordium size, rate of plant biomass accumulation, leaf area, photosynthetic rate, and soluble sugar content in the capitulum were measured until completion of floret initiation. • Although treatments differentially affected tissue expansion and biomass acquisition, a common relationship between the final number of florets and the rate and duration of meristem expansion was conserved. In the absence of water deficit, changes in relative expansion rate in the meristem paralleled changes in soluble sugar content. Water deficit reduced tissue expansion both in leaves and in the capitulum, and induced the accumulation of soluble sugars in the meristem. Use of these sugars at re-watering was associated with increased meristem growth and higher floret numbers compared with control plants. • Floret initiation and meristem tissue expansion remained strongly co-ordinated under all studied circumstances, and both depended on local carbon availability when water supply was unlimited. Transient water deficits favoured reproductive meristem growth and floret production. Equations accounting for these results constitute a framework for phenotyping the response to drought.

Ecophysiology of tea

Tea [Camellia sinensis (L.) O. Kuntze] is one of the most important beverage crops in the world. The major tea-growing regions of the world are South-East Asia and Eastern Africa where it is grown across a wide range of altitudes up to 2200 m a.s.l.. This paper reviews the key physiological processes responsible for yield determination of tea and discusses how these processes are influenced by genotypic and environmental factors. Yield formation of tea is discussed in terms of assimilate supply through photosynthesis and formation of harvestable sinks (i.e. shoots). The photosynthetic apparatus and partial processes (i.e. light capture, electron transport and carboxylation) of tea show specific adaptations to shade. Consequently, maximum light-saturated photosynthetic rates of tea are below the average for C3 plants and photoinhibition occurs at high light intensities. These processes restrict the source capacity of tea. Tea yields are sink-limited as well because shoots are harvested before their maximum biomass is reached in order to maintain quality characters of made tea. In the absence of water deficits, rates of shoot initiation and extension are determined by air temperature and saturation vapour pressure deficit, with the former having positive and the latter having negative relationships with the above rates. During dry periods, when the soil water deficit exceeds a genotypically- and environmentally-determined threshold, rates of shoot initiation and extension are reduced with decreasing shoot water potential. Tea yields respond significantly to irrigation, a promising option to increase productivity during dry periods, which are experienced in many tea-growing regions.

Soil Organic Matter and Wheat Productivity in the Semiarid Argentine Pampas

AbstractCrop productivity under dryland conditions is largely limited by soil water availability. Soil organic matter (SOM) contents have been found to be a reliable index of crop productivity in semiarid regions because it positively affects soil water‐holding capacity. Our objectives were to explain differences in wheat (Triticum aestivum L.) yields in response to SOM levels and related properties and to quantify the contribution of a unit increment of SOM content to soil productivity during 1991, 1992, and 1994 on a total of 134 production fields in the semiarid Argentine Pampas. Wheat yields were related to both soil water retention and total organic C (TOC) contents in the top layers (0–20 cm) in years with low moisture availability (1992 [r = 0.51, P < 0.01] and 1994 [r = 0.59, P < 0.01]), and were related to both total N and available P contents in a year without water deficit stress (1991 [r = 0.58, P < 0.01]). Wheat yields over all years were linearly related to TOC (r = 0.68, P < 0.01) when these contents were <17.5 g kg−. Dependence of wheat yields on soil water retention and on TOC contents under water deficit was related to the positive effect of these soil components on plant‐available water. In the absence of water deficit (1991), nutrient availability was the limiting factor. Losses of 1 Mg SOM ha− were associated with a decrease in wheat yield of approximately 40 kg ha−. These results demonstrate the importance of using cultural practices that minimize losses of soil organic C in the semiarid Argentine Pampas.

Quantitative analysis of the combined effects of temperature, evaporative demand and light on leaf elongation rate in well-watered field and laboratory-grown maize plants

The respective effects of meristem temperature, vapour pressure deficit (VPD) and photosynthetic photon flux density [PPFD) on leaf elongation rate (LER) of maize, in the absence of water deficit in the soil have been quantified. This analysis was carried out in a series of field experiments in northern and southern France over several seasons and years, and in growth chamber experiments. LER was measured with 10 min steps, together with meristem temperature, VPD and PPFD at leaf level in three types of experiments: in growth chamber experiments with steps in PPFD or VPD at constant meristem temperature, in growth chamber experiments with several combinations of constant, but contrasting, PPFDs, VPDs and meristem temperatures, and in the field with fluctuating conditions, (i) When evaporative demand was low (night or day with low air VPD), LER was only linked to meristem temperature, regardless of other climatic conditions, (ii) Light had no effect per se on LER in the range from 0 to 1500 ftmo m~2 s~1 for time-scales longer than 2 h, provided that its indirect effects on meristem temperature and on evaporative demand were corrected (in the growth chamber) or taken into account (in the field), and provided that cumulated PPFD over a weekly time-scale was compatible with field conditions, (iii) Evaporative demand sensed by growing leaves, as estimated by meristem-to-a ir vapour pressure difference, markedly affected LER in the range from 1-4 kPa, at all time-scales under study, with a unique relationship in the growth chamber (constant conditions) and in the field (fluctuating conditions). This effect was only observed when PPFD was high enough for stomata to open. The negative effect of evaporative demand on LER was probably not due to long distance root-to-shoot signalling, since soil was wet, calculated root water potential remained close to 0 MPa and concentration of ABA in the xylem sap was very low. Therefore, it is proposed to model maize LER with a two-step process, involving the calculation of the maximum LER at a given meristem temperature and then the calculation of the reduction in LER due to evaporative demand. Joint analysis of the whole set of data by using the two equations yielded a r2 of 0.75. This twostep process would be more accurate than the provision of LER from temperature only in cases where air VPD frequently exceeds 2 kPa.

Interactions between Carbon Dioxide and Water Deficits Affecting Leaf Photosynthesis: Simulation and Testing

Atmospheric CO2 concentration is known to have contrasting effects on photosynthesis, particularly in C3 plant species. These effects may be produced mathematically through the combination of a biochemically based submodel of CO2 fixation in leaf chloroplasts with a physically based submodel of CO2 and H2O diffusion through leaf surfaces and atmospheric boundary layers. Water‐deficit effects may be represented in both submodels. The behavior of a combined model was tested against data recorded under atmospheric CO2 concentrations of 330 and 660 μmol mol−1 in the Soil—Plant—Atmosphere Research Units at the University of Florida. The model reproduced changes in the quantum requirements of CO2 fixation and in diurnal CO2 fluxes of soybean [Glycine max. (L.) Merr.] leaves at these different concentrations. Simulated CO2 fixation at midday responded more to increased CO2 concentration at high irradiance (22.9 vs. 42.0 μmol m−2 s−1 at 1050 μmol m−2 s−1) than at low (17.1 vs. 19.7 μmol m−2 s−1 at 330 μmol m−2 s−1), as found experimentally. Under water deficits (leaf water potential ψl = −1.55 MPa), light saturation of CO2 fixation occurred at lower irradiance, again consistent with experimental findings. Interaction between the water deficit effects in each submodel allowed the combined model to simulate a higher sensitivity of CO2 fixation at 660 μmol mol−1 (41.1 vs. 19.3 μmol m−2 s−1) than at 330 (22.9 vs. 14.2 μmol m−2 s−1) when ψl was reduced to −1.55n from −0.60 MPa, as observed experimentally. The theoretical basis for CO2 effects on photosynthesis is well established, allowing them to be reproduced with confidence in the absence of water deficits. However, the theoretical basis for water deficit effects on photosynthesis is incomplete, such that the reproduction of CO2 effects on photosynthesis in the presence of water deficits must still be regarded as speculative.

Influence of Chilling and Drought on Water Relations and Abscisic Acid Accumulation in Bean

Intact bean seedlings were subjected to either chilling (4°C) or drought stress. Leaf water relations and abscisic acid (ABA) content were monitored throughout a stress-recovery cycle. Chilling at low relative humidity (RH) and drought caused similar water deficits, as indicated by the decline in relative water content and water potentials, but they had different effects on ABA accumulation. There was a rapid increase in ABA levels in the leaves of water-deprived plants while only slight ABA accumulation was observed after 48 h of chilling (4°C). After 24 h cold treatment there were large changes in turgor but no change in ABA content. Plants chilled for 24 h accumulated ABA only when transferred to recovery conditions (20°C, 90-95% RH, in the dark) to an extent that was related to the rate of leaf rehydration. When the chilling treatment was performed in a water-saturated atmosphere, plants did not suffer any water stress and ABA levels did not increase over a period of 48 h. However, when the chilling treatment lasted for a longer period (72 h), a significant increase in ABA levels was found also in the absence of water deficit. Experiments performed with leaf discs incubated in a mannitol solution (osmotic potential - 1.6 MPa) at different temperatures indicated that low temperature markedly inhibits ABA synthesis and that water stress induces increases in ABA content only at non-limiting warm temperatures.

Early stomatal closure in waterlogged pea plants is mediated by abscisic acid in the absence of foliar water deficits

Abstract Soil waterlogging decreased leaf conductance (interpreted as stomatal closure) of vegetative pea plants (Pisuin sativum L. cv. ‘Sprite’) approximately 24 h after the start of flooding, i.e. from the beginning of the second 16 h‐long photo‐period. Both adaxial and abaxial surfaces of leaves of various ages and the stipules were affected. Stomatal closure was sustained for at least 3 d with no decrease in foliar hydration measured as water content per unit area, leaf water potential or leaf water saturation deficit. Instead, leaves became increasingly hydrated in association with slower transpiration. These changes in the waterlogged plants over 3 d were accompanied by up to 10‐fold increases in the concentration of endogenous abscisic acid (ABA). Waterlogging also increased foliar hydration and ABA concentrations in the dark.Leaves detached from non‐waterlogged plants and maintained in vials of water for up to 3 d behaved in a similar way to leaves on flooded plants, i.e. stomata closed in the absence of a water deficit but in association with increased ABA content. Applying ABA through the transpiration stream to freshly detached leaflets partially closed stomata within 15 min. The extractable concentrations of ABA associated with this closure were similar to those found in flooded plants. When an ABA‐deficient ‘wilty’ mutant of pea was waterlogged, the extent of stomatal closure was less pronounced than that in ordinary non‐mutant plants, and the associated increase in foliar ABA was correspondingly smaller. Similarly, waterlogging closed stomata of tomato plants within 24 h, but no such closure was seen in ‘flacca’, a corresponding ABA‐deficient mutant.The results provide an example of stomatal closure brought about by stress in the root environment in the absence of water deficiency. The correlative factor operating between the roots and shoots appeared to be an inhibition of ABA transport out of the shoots of flooded plants, causing the hormone to accumulate in the leaves.