Soil Water Deficit Treatment Research Articles

Design, development, and assessment of a High-Throughput Screening (HTS) system for the macroscopic root water uptake modeling

Climate change is responsible for the increasing frequency and intensity of abiotic stresses generating water scarcity conditions. There is a need to breed plants adapted to future environmental conditions and resistant to water stress. This study presents a High-Throughput Screening (HTS) system for continuously and simultaneously monitoring plant stress response to drought in a semi-controlled environment. The HTS system combines a gravimetric weighing system with soil moisture and atmospheric sensors. In operative terms, the system was tested on the Sage (Salvia officinalis L.) under two soil water deficit treatments managed according to a feedback control irrigation scheduling.The system was able to model the sage water stress function following the root water uptake macroscopic approach. The threshold of soil water status below which crop water stress occurred was also identified. The gravimetric-based daily evapotranspiration (ETa) and the time domain reflectometry (TDR)-based root water-uptake (RWU) rates showed a high correlation during the drying when the evaporation flux is minimal. Moreover, the effects of soil bulk density on the root density and the plant biomass were evaluated, indicating the importance of carrying out a homogeneous procedure of the pot-filling process.

Interspecific Differences in Physiological and Biochemical Traits Drive the Water Stress Tolerance in Young Morus alba L. and Conocarpus erectus L. Saplings.

Mitigating climate change requires the identification of tree species that can tolerate water stress with fewer negative impacts on plant productivity. Therefore, the study aimed to evaluate the water stress tolerance of young saplings of C. erectus and M. alba under three soil water deficit treatments (control, CK, 90% field capacity, FC, medium stress MS, 60% FC and high stress, HS, 30% FC) under controlled conditions. Results showed that leaf and stem dry weight decreased significantly in both species under MS and HS. However, root dry weight and root/shoot ratio increased, and total dry weight remained similar to CK under MS in C. erectus saplings. Stomatal conductance, CO2 assimilation rate decreased, and intrinsic water use efficiency increased significantly in both species under MS and HS treatments. The concentration of hydrogen peroxide, superoxide radical, malondialdehyde and electrolyte leakage increased in both the species under soil water deficit but was highest in M. alba. The concentration of antioxidative enzymes like superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase also increased in both species under MS and HS but was highest in C. erectus. Therefore, results suggest that C. erectus saplings depicted a better tolerance to MS due to an effective antioxidative enzyme system.

Adaptive plasticity in plant traits increases time to hydraulic failure under drought in a foundation tree.

The viability of forest trees, in response to climate change-associated drought, will depend on their capacity to survive through genetic adaptation and phenotypic plasticity in drought tolerance traits. Genotypes with enhanced plasticity for drought tolerance (adaptive plasticity) will have a greater ability to persist and delay the onset of hydraulic failure. By examining populations from different climate-origins grown under contrasting soil water availability, we tested for genotype (G), environment (E) and genotype-by-environment (G×E) effects on traits that determine the time it takes for saplings to desiccate from stomatal closure to 88% loss of stem hydraulic conductance (time to hydraulic failure, THF). Specifically, we hypothesized that: (i) THF is dependent on a G×E interaction, with longer THF for warm, dry climate populations in response to chronic water deficit treatment compared with cool, wet populations, and (ii) hydraulic and allometric traits explain the observed patterns in THF. Corymbia calophylla saplings from two populations originating from contrasting climates (warm-dry or cool-wet) were grown under well-watered and chronic soil water deficit treatments in large containers. Hydraulic and allometric traits were measured and then saplings were dried-down to critical levels of drought stress to estimate THF. Significant plasticity was detected in the warm-dry population in response to water-deficit, with enhanced drought tolerance compared with the cool-wet population. Projected leaf area and total plant water storage showed treatment variation, and minimum conductance showed significant population differences driving longer THF in trees from warm-dry origins grown in water-limited conditions. Our findings contribute information on intraspecific variation in key drought traits, including hydraulic and allometric determinants of THF. It highlights the need to quantify adaptive capacity in populations of forest trees in climate change-type drought to improve predictions of forest die-back.

Altered Carbohydrate Allocation Due to Soil Water Deficit Affects Summertime Flowering in Meiwa Kumquat Trees

The summertime flowers of the ever-flowering Meiwa kumquat (Fortunella crassifolia Swingle) are the most useful for fruit production in Japan; however, summertime flowers bloom in three or four successive waves at approximately 10 day intervals, resulting in fruit of different maturity occurring on the same tree. Soil water deficit (SWD) treatment has been shown to reduce the flowering frequency and improve harvest efficiency; therefore, in this study, the effects of SWD treatment on the accumulation of soluble sugars in each tree organ above-ground were examined and it was discussed how SWD affects the whole-tree water relations and sugar accumulation by osmoregulation. The number of first-flush summertime flowers was higher in SWD-treated trees than non-treated control (CONT) trees (177.0 and 58.0 flowers, respectively), whereas the second- and third-flush flowers were only observed in CONT trees. The soluble sugar content was higher in SWD treated trees than CONT trees for all organs and tended to be higher in current-year organs than previous-year organs; however, when the sugar content of the current-year spring stems exceeded approximately 100 mg g−1 dry weight, the current-year leaf water potential decreased sharply and the rate of increase in the number of first-flush flowers also tended to decrease. SWD treatment significantly increased the total sugar content of the xylem tissue of the scaffold branches to three times the value in CONT trees (p = 0.001); however, the increase was observed even in sucrose, a disaccharide, similar to that in monosaccharides such as glucose and fructose. These results suggest that the increased sugar levels in the xylem tissue resulted from not only osmoregulation but also other factors as well; therefore, these sugars may affect whole-tree water relations as well as the development of flower buds.

Leaf Production and Expansion: A Generalized Response to Drought Stresses from Cells to Whole Leaf Biomass-A Case Study in the Tomato Compound Leaf.

It is clearly established that there is not a unique response to soil water deficit but that there are as many responses as soil water deficit characteristics: Drought intensity, drought duration, and drought position during plant cycle. For a same soil water deficit, responses can also differ on plant genotype within a same species. In spite of this variability, at least for leaf production and expansion processes, robust tendencies can be extracted from the literature when similar watering regimes are compared. Here, we present response curves and multi-scale dynamics analyses established on tomato plants exposed to different soil water deficit treatments. Results reinforce the trends already observed for other species: Reduction in plant leaf biomass under water stress was due to reduction in individual leaf biomass and areas whereas leaf production and specific leaf area were not affected. The dynamics of leaf expansion was modified both at the leaf and cell scales. Cell division and expansion were reduced by drought treatments as well as the endoreduplication process. Combining response curves analyses together with dynamic analyses of tomato compound leaf growth at different scales not only corroborate results on simple leaf responses to drought but also increases our knowledge on the cellular mechanisms behind leaf growth plasticity.

Elevated atmospheric CO2 concentration improves water use efficiency and growth of a widespread Cerrado tree species even under soil water deficit

Changes in atmospheric CO2 levels are accompanied by ecological interactions involving other environmental factors, such as drought, which can severely alter the water balance of plants, thereby influencing sap flow, gas exchange, and plant growth. The objective of this study was to evaluate the water use economy, leaf gas exchange, and growth of young plants of the species Lafoensia pacari subjected to high concentrations of atmospheric CO2 ([CO2]) and soil water deficit. Increased vapor pressure deficit was observed from 1200 to 1800 hours. Plants under elevated [CO2] exhibited increased leaf photosynthesis, resulting in improved growth. Specific leaf area was lower in plants under high [CO2], mainly after soil water deficit treatment. Daily irrigated plants growing under ambient [CO2] had higher stem sap flow velocity (cm h-1) and hourly sap flow (kg h-1), mainly during the hottest hours of the day, than plants under high [CO2]. Improved water use by plants growing under high [CO2] may result in increased availability of water in the soil, partially offsetting future drought events and extending the growth period.

Xylem plays an important role in regulating the leaf water potential and fruit quality of Meiwa kumquat (Fortunella crassifolia Swingle) trees under drought conditions

Drought induce various physiological changes such as flowering advancement and carbohydrate accumulation in many plants. Soil water deficit (SWD) has been shown to significantly increase the number of first-flush summertime flowers in the ever-flowering Meiwa kumquat (Fortunella crassifolia Swingle). In this study, we examined how SWD affects transpiration and the accumulation of soluble sugars in various parts of the plant as a result of osmoregulation. Despite the rapid decrease in the transpiration of the leaves, that of the stem remained unchanged during SWD treatment at one-eighth of that from the leaves under non-stressed conditions. The SWD treatment increased the total soluble sugar content in all plant parts, except the leaves. Increase in the monosaccharides such as glucose and fructose being greater than for the disaccharide sucrose, in the stems of shoots more than 3 years of age as well as in the xylem of scaffold branches, is suggesting that these increased sugar levels were due to osmoregulation. The sucrose content decreased markedly during the 4 months after SWD treatment in the xylem of scaffold branches but was significantly higher in the fruit that were harvested from SWD-treated trees at 4 months after SWD treatment. These results suggest that the sugars that are accumulated in the xylem positively affect fruit growth after SWD treatment.

Effects of Vernalization, Temperature, and Soil Drying Periods on the Growth and Yield of Chinese Cabbage

Abstract: This study was carried out to determine the effects of vernalization, temperature, and soil water deficit (SD) on mesoph yll cells, growth, and yield of Chinese cabbage ( Brassica campestris L). The palisade parenchyma and spongy tissues of Chinese cabbage were observed under full irrigation and two weeks of SD treatment. These cells were severely collapsed by four weeks SD treatment. The SD treatment had the greatest influence on the growth of Chinese cabbage among the tested treatment factors (vernalization, temperature, and SD), growth significantly decreased by severe drought treatment (four weeks SD treatment). In addition, the relative growth rate, unit leaf rate, leaf area ratio, specific leaf area, and leaf weight ratio were si gnificantly affected by SD treatment; however, other individual factors and their combined treatments did not influence the analyzed growth parameters. The yield under vernalization after high temperature and full irrigation treatments was 3,056 kg/10 a, which was the greatest among all the tested treatments, while four-week SD treatment significantly reduced the yield. Head formation of Chinese cabbage was not altered under SD treatment, and vernalization treatments did not induce bolting. Our results indicat ed that collapsing mesophyll cells and reduced growth and yield were induced by SD treatment. Thus we suggest that optimal irrigation system should be install to avoid or overcome crippling drought conditions in the open field.Additional key words:

Response of Growth and Interspecific Competition of Pinus koraiensis and Quercus mongolica Seedlings to Drought

Broad-leaved Korean pine forest is the zonal vegetation in eastern mountains of northeast China, which accounting for a third of the China's national forest. In order to understand the response of temperate dominant tree species Korean pine and main associated tree species Mongolian oak in broad-leaved Korean pine forest under future climate change conditions( air temperature rising,decrease in precipitation),a competition pot experiment of two-year old Korean pine seedlings and one-year old Mongolian oak seedlings under different soil water contents were conducted under completely random design in April 24,2012. This experiment set up four experimental treatments,with eighteen seedling replicates for each treatment. Two levels of soil water content were respectively 75- 85 percent of the soil water-holding capacity for the high level,and 50- 60 percent of soil water-holding capacity for the low level. The competition treatments were six same seedlings in one pot for mono culture and three seedlings for each of the two species in one pot for mixed culture. We analyzed the photosynthetic and physiological parameters and changes in biomass allocation. The experimentation of a growing season showed that:( 1) Soil water deficit treatment resulted in the decreases of the maximum net photosynthetic rate in both Korean pine and Mongolian oak seedlings,the reduction rate of Mongolian oak reached a significant level,while Korean pine did not. Drought caused the decline in water use efficiency in Mongolian oak,while it increased significantly in Korean pine. Soil water deficit also led to the decreases in lateral root biomass,stem biomass,leaf biomass and whole tree leaf area in Mongolian oak seedlings,but the increases in fine root biomass and root to shoot ratio of Korean pine seedlings.( 2) Mixed culture treatment reduced the maximum net photosynthetic rate and water use efficiency of Mongolian oakseedlings,thereby reduced their stem and lateral root biomass. While for the Korean pine seedlings,mixed culture treatment also reduced their water use efficiency,but it increased the specific leaf area and whole tree leaf area of Korean pine seedlings and therefore had less impact on seedling growth. These results indicate that, Mongolian oak is more sensitive and rapid response to drought. Korean pine seedlings are more competitive than Mongolian oak seedlings in interspecific competition.

Plant water use characteristics of five dominant shrub species of the Lower Rio Grande Valley, Texas, USA: implications for shrubland restoration and conservation.

The biogeographic distribution of plant species is inherently associated with the plasticity of physiological adaptations to environmental variation. For semi-arid shrublands with a legacy of saline soils, characterization of soil water-tolerant shrub species is necessary for habitat restoration given future projection of increased drought magnitude and persistence in these ecosystems. Five dominant native shrub species commonly found in the Lower Rio Grande Valley, TX, USA, were studied, namely Acacia farnesiana, Celtis ehrenbergiana, Forestiera angustifolia, Parkinsonia aculeata and Prosopis glandulosa. To simulate drought conditions, we suspended watering of healthy, greenhouse-grown plants for 4 weeks. Effects of soil salinity were also studied by dosing plants with 10% NaCl solution with suspended watering. For soil water deficit treatment, the soil water potential of P. glandulosa was the highest (-1.20 MPa), followed by A. farnesiana (-4.69 MPa), P. aculeata (-5.39 MPa), F. angustifolia (-6.20 MPa) and C. ehrenbergiana (-10.02 MPa). For the soil salinity treatment, P. glandulosa also had the highest soil water potential value (-1.60 MPa), followed by C. ehrenbergiana (-1.70 MPa), A. farnesiana (-1.84 MPa), P. aculeata (-2.04 MPa) and F. angustifolia (-6.99 MPa). Within the species, only C. ehrenbergiana and F. angustifolia for soil water deficit treatment and A. farnesiana for the salinity treatment had significantly lower soil water potential after 4 weeks of treatment (P < 0.05). We found that soil water potential, stomatal conductance and net photosynthesis of the species significantly reduced over time for both treatments (P < 0.05). We conclude that while all species exhibited capacities to withstand current water availability, some species demonstrated limited tolerance for extreme water stress that may be important for management of future shrub diversity in Lower Rio Grande Valley.

Estimation of soil water deficit in an irrigated cotton field with infrared thermography

Plant growth and soil water deficit can vary spatially and temporally in crop fields due to variation in soil properties and/or irrigation and crop management factors. We conducted field experiments with cotton ( Gossypium hirsutum L.) over two seasons during 2007–2009 to test if infrared thermography can distinguish systematic variation in deficit irrigation applied to various parts of the field over time. Soil water content was measured with a neutron probe and thermal images of crop plants were taken with a thermal infrared camera. Leaf water potential and stomatal conductance were also measured on selected occasions. All measurements were made at fixed locations within three replicate plots of an irrigation experiment consisting of four soil-water deficit treatments. Canopy temperature related as well with soil water within the root zone of cotton as the stomatal conductance index derived from canopy temperature, but it neglected the effect of local and seasonal variation in environmental conditions. Similarities in the pattern of spatial variation in canopy temperature and soil water over the experimental field indicates that thermography can be used with stomatal conductance index to assess soil water deficit in cotton fields for scheduling of irrigation and to apply water in areas within the field where it is most needed to reduce water deficit stress to the crop. Further confidence with application of infrared thermography can be gained by testing our measurement approach and analysis with irrigation scheduling of other crops.

Fog interception by Sequoia sempervirens (D. Don) crowns decouples physiology from soil water deficit

Although crown wetting events can increase plant water status, leaf wetting is thought to negatively affect plant carbon balance by depressing photosynthesis and growth. We investigated the influence of crown fog interception on the water and carbon relations of juvenile and mature Sequoia sempervirens trees. Field observations of mature trees indicated that fog interception increased leaf water potential above that of leaves sheltered from fog. Furthermore, observed increases in leaf water potential exceeded the maximum water potential predicted if soil water was the only available water source. Because field observations were limited to two mature trees, we conducted a greenhouse experiment to investigate how fog interception influences plant water status and photosynthesis. Pre-dawn and midday branchlet water potential, leaf gas exchange and chlorophyll fluorescence were measured on S. sempervirens saplings exposed to increasing soil water deficit, with and without overnight canopy fog interception. Sapling fog interception increased leaf water potential and photosynthesis above the control and soil water deficit treatments despite similar dark-acclimated leaf chlorophyll fluorescence. The field observations and greenhouse experiment show that fog interception represents an overlooked flux into the soil-plant-atmosphere continuum that temporarily, but significantly, decouples leaf-level water and carbon relations from soil water availability.

Plasticity to soil water deficit in Arabidopsis thaliana: dissection of leaf development into underlying growth dynamic and cellular variables reveals invisible phenotypes

Genetic variability in the plasticity of leaf area expansion in response to water deficit has been reported in Arabidopsis thaliana. Here, the objective was to identify the underlying dynamic and cellular processes involved in this variability. Twenty-five accessions were subjected to identical soil water deficit treatments. In all accessions, the plasticity of leaf production was low compared with that of individual leaf expansion. A subset of accessions was selected for further dissection of individual leaf expansion into its underlying variables: the rate and duration of leaf expansion and epidermal cell number and area. In all accessions, water deficit had opposite effects on the rate and duration of leaf expansion. The accumulation of these effects was reflected in changes in final leaf area. At the cellular level, moderate water deficits had opposite effects on cell number and cell size, but more severe ones reduced both variables. The importance of these opposing effects is highlighted by the behaviour of the accession An-1, for which the compensation between the decrease in leaf expansion rate and the increase in the duration of expansion is total. This dynamic plasticity in response to water deficit is not detectable when only final measurements are done.

Yield performance of spring wheat improved by regulated deficit irrigation in an arid area

A field experiment was conducted in 2003 and 2004 growing seasons to evaluate the effects of regulated deficit irrigation on yield performance in spring wheat ( Triticum aestivum) in an arid area. Three regulated deficit irrigation treatments designed to subject the crops to various degrees of soil water deficit at different stages of crop development and a no-soil-water-deficit control was established. Soil moisture was measured gravimetrically in the increment of 0–20 cm every five to seven days in the given growth periods, while that in 20 increments to 40, 40–60, 60–80, and 80–100 cm depth measured by neutron probe. Compared to the no-soil-water-deficit treatment, grain yield, biomass, harvest index, water use efficiency (WUE), and water supply use efficiency (WsUE) in spring wheat were all greatly improved by 16.6–25.0, 12.4–19.2, 23.5–27.3, 32.7–39.9, and 44.6–58.8% under regulated deficit irrigation, and better yield components such as thousand-grain weight, grain weight per spike, number of grain, length of spike, and fertile spikelet number were also obtained, but irrigation water was substantially decreased by 14.0–22.9%. The patterns of soil moisture were similar in the regulated deficit treatments, and the soil moisture contents were greatly decreased by regulated deficit irrigation during wheat growing seasons. Significant differences were found between the no-soil-water-deficit treatment and the regulated soil water deficit treatments in grain yield, yield components, biomass, harvest index, WUE, and WsUE, but no significant differences occurred within the regulated soil water deficit treatments. Yield performance proved that regulated deficit irrigation treatment subjected to medium soil water deficit both during the middle vegetative stage (jointing) and the late reproductive stages (filling and maturity or filling) while subjected to no-soil-water-deficit both during the late vegetative stage (booting) and the early reproductive stage (heading) (MNNM) had the highest yield increase of 25.0 and 14.0% of significant water-saving, therefore, the optimum controlled soil water deficit levels in this study should range 50–60% of field water capacity (FWC) at the middle vegetative growth period (jointing), and 65–70% of FWC at both of the late vegetative period (booting) and early reproductive period (heading) followed by 50–60% of FWC at the late reproductive periods (the end of filling or filling and maturity) in treatment MNNM, with the corresponding optimum total irrigation water of 338 mm. In addition, the relationships among grain yield, biomass, and harvest index, the relationship between grain yield and WUE, WsUE, and the relationship between harvest index and WUE, WsUE under regulated deficit irrigation were also estimated through linear or non-linear regression models, which indicate that the highest grain yield was associated with the maximum biomass, harvest index, and water supply use efficiency, but not with the highest water use efficiency, which was reached by appropriate controlling soil moisture content and water consumption. The relations also indicate that the harvest index was associated with the maximum biomass and water supply use efficiency, but not with the highest water use efficiency.

Bt and Non‐Bt Maize Growth and Development as Affected by Temperature and Drought Stress

Seed companies have commercialized new transgenic maize (Zea mays L.) hybrids that are resistant to European corn borer [Ostrinia nubilalis (Hübner)]. Drought stress may affect the expression of Bt proteins in maize tissues, and its resistance to European corn borer (ECB). This study was conducted at the Iowa State University Hinds Irrigation Farm, Ames, IA, to characterize the effect of drought stress on Bt maize. Growth and development measurements were taken in 1997 and 1998 from Bt and non‐Bt maize plants subjected to various soil water deficit treatments during peak ECB egg laying periods (late June, first generation; late July, second generation) on maize plants grown in buried, 1 m deep, 123‐L containers filled with Nicollet loam soil (fine‐loamy, mixed, superactive, mesic Aquic Hapludolls). Water deficit delayed leaf appearance up to 6 d, depending on leaf number and tasseling up to 3 d. It also reduced leaf area as much as 33% and plant height by 15%, depending on leaf number and timing of water deficit. For these characteristics, there was no significant difference between Bt and non‐Bt maize plants. There were significant differences among Bt and non‐Bt plants for second generation corn borer damage with Bt plants affected the least. This resulted in significant yield differences between Bt and non‐Bt plants. Compared with non‐Bt plants, Bt plants exhibited significantly greater total plant weight in 1997 (9.7%) and grain yield in 1998 (9.4%). These differences depended on variety and seemed related to 100‐seed weights.

土壌水分制限が赤・桃および黄色型ミニトマトの着色とカロチン形成に与える影響

The effect of soil water content on fruit coloring and carotene formation of fruit was examined using four cherry tomatoes 'Mini Carol' (fruit color : red type), 'Cherry Pink' (pink type), 'Yellow Carol' (yellow type), and 'Orange Carol' (yellowish tangerine type). The soil water deficit treatment hastened the fruit coloring in the spring and fall croppings of 'Mini Carol' and in the fall cropping of 'Cherry Pink'. In most cultivars, pigmentation was advanced by soil water deficit because the color hue angle of the tomato was lower, and/or, their chroma was higher than that of control treatment. Soil water deficit on the fruit coloring was more effective in the fall cropping than it was in the spring, except for 'Orange Carol' which was unaffected by the treatment in spring or fall cropping. On the red and pink type tomatoes, total carotene per fresh weight of fully ripe fruit was increased by soil water deficit ; moreover, the ratio of lycopene per colored carotene content was higher than that of the control treatment. Soil water deficit increased the amount of β-carotene per fresh weight of 'Yellow Carol' but it had no effect on β-carotene content in 'Orange Carol' in the spring or fall cropping.

Effects of water deficit on photosynthesis in wheat plants. II. The physiological basis for the difference in photosynthetic sensitivity to water stress among plant parts.

In the previous paper, it was pointed out that the extent of depression in photosynthesis by soil water deficit treatment was different from part to part of the wheat plant. The objective of the present study was to find out the physiological basis for this phenomenon from the viewpoint of water potential and CO2 diffusion resistances, i.e. leaf resistance (r1) and mesophyll resistance (rm) using the same materials as those for the previous paper. The results are summarized as follows : 1. Water potential of each plant part was decreased by water deficit treatment. The extent of decrease in water potential was the same in every plant part. It was concluded form this finding that the difference in photosynthetic sensitivity among plant parts is not be attributable to the difference in the extent of decrease in water potential of plant parts (Figs. 1, 2). 2. Both r1 and rm were increased by the water deficit treatment. The extent of increase in r1 and rm was largest just after the start of the water deficit treatment. However, when the water deficit condition was prolonged, r1 and rm tended to decrease and come close to those of unstressed plants (Figs. 6-9). 3. Both r1 and rm increased to a larger extent in lower leaves than in upper ones by the water deficit treatment (Figs. 3-4). The extent of increase in r1 and rm resulted from water deficit was always larger in lower leaves than in upper ones (Figs. 5-9). Since there was no difference in the extent of decreasse in water potential by the water deficit treatment between lower and upper leaves, both stomata and the photosynthetic mechanism of lower leaves seemed to have greater sensitivity to decrease of water potential than those of upper leaves.