根区交替控制灌溉条件下玉米根系吸水规律

为了阐明根区交替控制灌溉(CRDAI)条件下玉米根系吸水规律,通过田间试验,在沟灌垄植模式下采用根区交替控制灌溉研究玉米根区不同点位(沟位、坡位和垄位)的根长密度(RLD)及根系吸水动态。研究表明,根区土壤水分的干湿交替引起玉米RLD的空间动态变化,在垄位两侧不对称分布,并存在层间差异;土壤水分和RLD是根区交替控制灌溉下根系吸水速率的主要限制因素。在同一土层,根系吸水贡献率以垄位最大,沟位最低;玉米营养生长阶段,10—30 cm土层的根系吸水速率最大;玉米生殖生长阶段,20—70 cm为根系吸水速率最大的土层,根系吸水贡献率为43.21%—55.48%。研究阐明了交替控制灌溉下根系吸水与土壤水分、RLD间相互作用的动态规律,对控制灌溉下水分调控机理研究具有理论意义。     

Root distribution and water uptake patterns of corn under surface and subsurface drip irrigation

Information on root distribution and uptake patterns is useful to better understand crop responses to irrigation and fertigation, especially with the limited wetted soil volumes which develop under drip irrigation. Plant water uptake patterns play an important role in the success of drip irrigation system design and management. Here the root systems of corn were characterized by their length density (RLD) and root water uptake (RWU). Comparisons were made between the spatial patterns of corn RWU and RLD under surface and subsurface drip irrigation in a silt loam soil, considering a drip line on a crop row and between crop rows. Water uptake distribution was measured with an array of TDR probes at high spatial and temporal resolution. Root length density was measured by sampling soil cores on a grid centered on crop row. Roots were separated and an estimation of root geometrical attributes was made using two different image analysis programs. Comparisons of these programs yielded nearly identical estimates of RLD. The spatial patterns of RWU and RLD distributions, respectively normalized to the total uptake and root length, were generally similar only for drip line on a crop row, but with some local variations between the two measures. Both RLD and RWU were adequately fitted with parametric models based on semi-lognormal and normal Gaussian bivariate density functions (Coelho and Or, 1996; Soil Sci. Soc. Am. J. 60, 1039–1049).     

Root length density and water uptake distributions of winter wheat under sub-irrigation

As the critical information to study flow transport in soil–plant systems, root distributions and root-water-uptake (RWU) patterns have been studied extensively. However, most root distribution data in the past were collected under surface irrigation. Less research has been conducted to characterize root distributions under sub-irrigation. The objectives of this study were to (1) test if the generalized function of normalized root length density (NRLD) in the literature was applicable to root distributions of winter wheat under natural sub-irrigation, which provides water from subsurface by capillary rise from the water table, and (2) estimate RWU distributions of winter wheat under natural sub-irrigation. Column experiments were conducted to study the distributions of root length density (RLD) and RWU of winter wheat (Triticum aestivum L. cv. Nongda 189) during a growing period of 57 days from planting to tillering stages under surface irrigation and natural sub-irrigation. Data of root distributions and soil water content were collected in the experiments with different treatments of irrigation levels. Results showed that the RLD distributions of winter wheat under both surface irrigation and natural sub-irrigation were of similar patterns. The NRLD distributions under sub-irrigation were adequately characterized by the generalized function. An inverse method was employed to estimate the average RWU rate distributions of winter wheat. In addition, based on the potential RWU coefficient and the NRLD function, a simple approach was developed to predict RWU rates at different depths. The predicted RWU rates had a good agreement with the estimated RWU rate distributions using the inverse method.Section editor: R. E. Munns     

Root growth and water uptake in winter wheat under deficit irrigation

Root growth is critical for crops to use soil water under water-limited conditions. A field study was conducted to investigate the effect of available soil water on root and shoot growth, and root water uptake in winter wheat (Triticum aestivum L.) under deficit irrigation in a semi-arid environment. Treatments consisted of rainfed, deficit irrigation at different developmental stages, and adequate irrigation. The rainfed plots had the lowest shoot dry weight because available soil water decreased rapidly from booting to late grain filling. For the deficit-irrigation treatments, crops that received irrigation at jointing and booting had higher shoot dry weight than those that received irrigation at anthesis and middle grain filling. Rapid root growth occurred in both rainfed and irrigated crops from floral initiation to anthesis, and maximum rooting depth occurred by booting. Root length density and dry weight decreased after anthesis. From floral initiation to booting, root length density and growth rate were higher in rainfed than in irrigated crops. However, root length density and growth rate were lower in rainfed than in irrigated crops from booting to anthesis. As a result, the difference in root length density between rainfed and irrigated treatments was small during grain filling. The root growth and water use below 1.4 m were limited by a caliche (45% CaCO₃) layer at about 1.4 m profile. The mean water uptake rate decreased as available soil water decreased. During grain filling, root water uptake was higher from the irrigated crops than from the rainfed. Irrigation from jointing to anthesis increased seasonal evapotranspiration, grain yield, harvest index and water-use efficiency based on yield (WUE), but did not affect water-use efficiency based on aboveground biomass. There was no significant difference in WUE among irrigation treatments except one-irrigation at middle grain filling. Due to a relatively deep root system in rainfed crops, the higher grain yield and WUE in irrigated crops compared to rainfed crops was not a result of rooting depth or root length density, but increased harvest index, and higher water uptake rate during grain filling.     

A comparison of minirhizotron,core and monolith methods for quantifying barley (Hordeum vulgare L.) and fababean (Vicia faba L.) root distribution

Root research has been hampered by a lack of good methods and by the amount of time involved in making measurements. The use of the minirhizotron as a quantitative tool requires comparison with conventional destructive methods. This study was conducted in the greenhouse to compare the minirhizotron technique with core and monolith methods in quantifying barley (Hordeum vulgare L.) and fababean (Vicia faba L.) root distribution. Plants were grown in boxes (80 cm long × 80 cm wide × 75 cm deep) in a hexagonal arrangement to minimize the effects of rooting anistrophy. Minirhizotron observations and destructive sampling to a depth of 70 cm using core and monolith methods were performed at the ripening growth stage. Total root length for the entire depth interval was generally higher in barley (159–309 m) than fababean (110–226 m). Significant correlation coefficients between monolith and core methods for root length density (RLD, cm cm^–3) was observed in both crops (p 0.01). A method and depth interaction showed no significant differences in fababean RLD distribution measured by core and monolith methods. However, the RLD was different for the uppermost 40 cm depth in barley. The relationship for RLD between minirhizotron and core methods was significant only in barley (r=0.77^*). For both crops, estimates of RLD in the top 10-cm layer by the minirhizotron technique were lower than those by core and monolith techniques. In contrast, estimates of RLD were higher in fababean at a depth >30 cm. Destructive sampling still remains the method to quantify root growth in the 0–10 cm soil layer. ei]B E Clothier     

Physiological Responses of Spring Durum Wheat Cultivars to Early-season Drought in a Mediterranean Environment

The Mediterranean climate of North Africa is characterized byuncertain rainfall immediately after seedling emergence, leadingto drought early in the growing season which depresses durumwheat production. However, there is limited understanding ofthe physiological basis of resistance of spring durum wheatto drought in rainfed Mediterranean regions. The objectivesof this study were to examine differences in some physiologicalcharacters among spring durum wheat cultivars in response toduration of early-season drought, and to determine the relationshipof these characters to drought resistance. In two field experiments(1995 and 1996 growing seasons) and a glasshouse experiment(1996), six spring sown durum wheat cultivars were evaluatedunder four water regimes: well irrigated and three differentwater deficits from emergence until the onset of tillering,mid-tillering or at the end of tillering. Cultivars differedin their response. Decreases in photosynthesis soon after droughtstress was imposed resulted mainly from reduced stomatal conductance.Continued water deficits also reduced mesophyll photosyntheticactivity. Possible factors determining the drought-resistanceof a cultivar are lower sensitivity of CO₂exchange rate, netCO₂uptake to water loss ratio, stomatal resistance, relativewater content and greater osmotic adjustment under stress. Furthermore,there is sufficient intraspecific variation in these physiologicalattributes to suggest their use as selection tools.Copyright1998 Annals of Botany Company Wheat;Triticum durumDesf.; early-season drought; physiological responses.     

Genetic dissection of seminal root architecture in elite durum wheat germplasm

Although root architecture has been shown to play an important role in crop performance, particularly under drought conditions, no information is available on the genetic control of root traits in durum wheat, a crop largely grown in rainfed areas with low rainfall. In our study, a panel of 57 elite durum wheat accessions were evaluated under controlled conditions for root and shoot traits at the seedling stage. Significant genetic variability was detected for all the root and shoot traits that were investigated. Correlation analysis suggested that root and shoot features were only partially controlled by common sets of genes. The high linkage disequilibrium (up to 5 cM) present in the germplasm collection herein considered allowed us to use simple sequence repeat‐based association mapping to identify chromosome regions with significant effects on the investigated traits. In total, 15 chromosome regions showed significant effects on one or more root architectural features. A number of these regions also influenced shoot traits and, in some cases, plant height measured in field conditions. Major effects were detected on chromosome arms 2AL (at Xgwm294), 7AL (at Xcfa2257 and Xgwm332) and 7BL (at Xgwm577 and Xcfa2040). The accessions with the most remarkable differences in root features will provide a valuable opportunity to assemble durum wheat mapping populations well suited for ascertaining the effects of root architecture on water use efficiency and grain yield.     

盐旱复合胁迫对小麦幼苗生长和水分吸收的影响

为明确盐害、干旱及盐旱复合胁迫对小麦幼苗生长和水分吸收的影响,从而为盐害和干旱胁迫下栽培调控提供理论依据。以2个抗旱性不同的小麦品种(扬麦16和耐旱型洛旱7号)为材料,采用水培试验,以NaCl和PEG模拟盐旱复合胁迫,研究了盐旱复合胁迫下小麦幼苗生长、根系形态、光合特性及水分吸收特性的变化。结果表明,盐、旱及复合胁迫下小麦幼苗的生物量、叶面积、总根长与根系表面积、叶绿素荧光和净光合速率均显著下降,但是复合胁迫处理的降幅却显著低于单一胁迫。盐旱复合胁迫下根系水导速率和根系伤流液强度显著大于单一胁迫,从而提高了小麦幼苗叶片水势和相对含水量。盐胁迫下小麦幼苗Na~+/K~+显著大于复合胁迫,但复合胁迫下ABA含量却显著小于单一的盐害和干旱胁迫。因此,盐旱复合胁迫可以通过增强根系水分吸收及降低根叶中ABA含量以维持较高光合能力,这是盐旱复合胁迫提高小麦适应性的重要原因。洛旱7号和扬麦16对盐及盐旱复合胁迫的响应基本一致,但在干旱胁迫下洛旱7号表现出明显的耐性。     

不同水分条件对冬小麦根系时空分布、土壤水利用和产量的影响

为了明确华北严重缺水区晚播冬小麦灌水对根系时空分布和土壤水分利用规律的影响,以冬小麦石麦15为材料,利用田间定位试验研究了不同灌水处理(春季不灌水W0;春季灌拔节水75mm,W1;春季灌起身水、孕穗水和灌浆水共225mm,W3)对根系干重密度(DRWD)、根长密度(RLD)、体积密度、分枝数等在0—200cm土层的垂直分布、动态变化及其对耗水和产量的影响,结果表明:随着春季灌水量的减少,开花后0—80cm土层的根干重密度、根长度密度、体积密度和分枝数密度均显著减少,80cm—200m土层的根干重密度、根长度密度、体积密度和分枝数密度却显著增加,并且显著增加冬小麦在灌浆期间对100cm以下深层土层水分的利用,总耗水量W1和W0分别比W3减少70.9mm、115.1mm,土壤耗水量分别比W3增加79.1mm、108.9mm,子粒产量W1和W0分别比W3减少653.3kg/hm2、1470kg/hm2,水分利用效率(WUE)则分别比W3提高0.09kg/m3、0.06kg/m3。晚播冬小麦春季灌1水(拔节水)可以促进根系深扎,增加深土层的根系分布量,提高对深层土壤贮水的吸收利用量,有利于实现节水与高产的统一。     

断根对冬小麦竞争能力与产量的影响

 采用简化的deWit替代系列法研究了盆栽冬小麦‘长武135’（Triticum aestivum cv. Changwu 135）在拔节初期断根对冬小麦根冠关系、竞争能力及其与产量性状的关系。无论干旱或湿润，单栽条件下断根降低了小麦的根冠比，在混栽条件下，断根小麦的相对穗重和相对地上部生物量均显著低于未断根小麦，说明断根降低了小麦的竞争能力。根冠比越大竞争能力越强，即作物的竞争能力与根冠比存在正相关关系。单栽湿润条件,断根降低了小麦的穗重和籽粒产量，而在中等干旱条件下，断根小麦穗重和籽粒产量高于未断根小麦 。说明在水资源充分的条件下，较高的作物个体竞争能力则具有较高的生产能力，而在水资源有限的情况下，降低作物个体竞争能力反而提高了群体籽粒产量。     

Root distribution and interactions between intercropped species

Even though ecologists and agronomists have considered the spatial root distribution of plants to be important for interspecific interactions in natural and agricultural ecosystems, few experimental studies have quantified patterns of root distribution dynamics and their impacts on interspecific interactions. A field experiment was conducted to investigate the relationship between root distribution and interspecific interactions between intercropped plants. Roots were sampled twice by auger and twice by the monolith method in wheat (Triticum aestivum L.)/maize (Zea mays L.) and faba bean (Vicia faba L.)/maize intercropping and in sole wheat, maize, and faba bean up to 100 cm depth in the soil profile. The results showed that the roots of intercropped wheat spread under maize plants, and had much greater root length density (RLD) at all soil depths than sole wheat. The roots of maize intercropped with wheat were limited laterally, but had a greater RLD than sole-cropped maize. The RLD of maize intercropped with faba bean at different soil depths was influenced by intercropping to a smaller extent compared to maize intercropped with wheat. Faba bean had a relatively shallow root distribution, and the roots of intercropped maize spread underneath them. The results support the hypotheses that the overyielding of species showing benefit in the asymmetric interspecific facilitation results from greater lateral deployment of roots and increased RLD, and that compatibility of the spatial root distribution of intercropped species contributes to symmetric interspecific facilitation in the faba bean/maize intercropping. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Genotype and Planting Density Effects on Rooting Traits and Yield in Cotton （Gossypium hirsutum L,）

Root density distribution of plants is a major Indicator of competition between plants and determines resource capture from the solh This experiment was conducted in 2005 at Anyang, located in the Yellow River region, Henan Province, China. Three cotton （Gossyplum hlrsutum L.） cultivars were chosen： hybrid Btcultlvar CRI46, conventional Btcultlvars CRI44 and CRI45. Six planting densities were designed, ranging from 1.5 to 12.0 plants/m^2. Root parameters such as surface area, diameter and length were analyzed by using the DT-SCAN Image analysis method. The root length density （RLD）, root average diameter and root area Index （RAI）, root surface area per unit land area, were studied. The results showed that RLD and RAI differed between genotypes; hybrid CRI46 had significantly higher （P 〈0.05） RLD and RAI values than conventlonal cultlvars, especially under low planting densities, less than 3.0 plants/m^2. The root area index （RAI） of hybrid CRI46 was 61% higher than of CRI44 and CRI45 at the flowering stage. The RLD and RAI were also significantly different （P = 0.000） between planting densities. The depth distribution of RAI showed that at Increasing planting densities RAI was Increasingly distributed in the soil layers below 50 cm. The RAI of hybrid CRI46 was for all planting densities, obviously higher than other cultivars during the flowering and boll stages. It was concluded that the hybrid had a strong advantage in root maintenance preventing premature senescence of roots. The root diameter of hybrid CRI46 had a genetically higher root diameter at planting densities lower than 6.0 plants/m^2. Good associations were found between yield and RAI In different stages. The optimum planting density ranged from 4.50 plants/m^2 to 6.75 plants/m^2 for conventional cultlvars and around 4.0-5.0 plants/m^2 for hybrids.     

Marker-free transgenic durum wheat cv. Karim expressing the AlSAP gene exhibits a high level of tolerance to salinity and dehydration stresses

We have recently isolated the AlSAP (stress-associated protein) gene from the halophyte grass Aeluropus littoralis and demonstrated that AlSAP expression improves tolerance to continuous salt and drought stresses in transgenic tobacco. To extend these findings to an important crop, we generated marker-free transgenic durum wheat plants of the commercial cv. Karim expressing the AlSAP gene. The integration and expression of AlSAP in T3 homozygous plants were ascertained by Southern, Northern and Western blotting respectively. AlSAP wheat lines exhibited improved germination rates and biomass production under severe salinity and osmotic stress conditions. Following a long-term salt or drought stress greenhouse trial, AlSAP lines produced normally filled grains whereas wild-type (WT) plants either died at the vegetative stage under salt stress or showed markedly reduced grain filling under drought stress. Measurements of the RWC (relative water content) and endogenous Na⁺ and K⁺ levels in leaves of AlSAP plants, showed a lower water loss rate and a higher Na⁺ accumulation in senescent-basal leaves, respectively, compared to those of WT plants. Taken together, these results extend to cereals the high potential of the AlSAP gene for engineering effective drought and salt tolerance.     

Commercially available plant growth regulators and promoters modify bulk tissue abscisic acid concentrations in spring barley, but not root growth and yield response to drought

Field and lysimeter experiments were conducted in 2002 to investigate the effects of an antigibberellin growth regulator (Moddus, active ingredient trinexapac‐ethyl, Syngenta Crop Protection UK Ltd, Whittlesford, Cambridge, UK) and an auxin‐stimulating (Route, active ingredient zinc ammonium acetate, De Sangosse Ltd, Swaffham Bulbeck, Cambridge, UK) growth promoter on root growth, soil water extraction and the drought response of spring barley. The effects on root growth and distribution were investigated in the field. The effects on the drought response were studied in 1.2‐m‐deep lysimeters packed with a loamy sand subsoil and sandy loam topsoil. Lysimeters were located under a fixed rain shelter, and drought was imposed by withholding irrigation. In both field and lysimeter experiments, growth regulator/promoters were applied to cv. Optic at early tillering according to the manufacturers’ recommendations. After withholding irrigation from lysimeters at Zadoks growth stage (GS) 21 (37 days after sowing), 50% of the profile available water had been depleted by flag leaf emergence (GS 37/39; 62 days after sowing). Drought significantly reduced stem biomass at ear emergence (GS 59; 78 days after sowing) but not leaf or ear dry weight; this was before there was any significant reduction in leaf water potential or stomatal conductance to water vapour. The reduction in stem biomass may reflect a change in partitioning between shoot and root in response to soil drying. When averaged over growth regulator/promoter treatments, drought reduced grain yield by approximately 1 t ha^?1. This was associated with a reduction in both ears per m² and grains per ear. The mean grain weight was not reduced by drought, in spite of significant reductions in stomatal conductance and canopy lifespan post‐anthesis. Route, and to a lesser extent Moddus, significantly increased abscisic acid accumulation in the stem base of droughted plants, and there was some indication of a possible delay in stomatal closure in Route‐treated plants as the soil moisture deficit developed. However, there was no significant effect on the amount of soil water extracted or grain yield under drought. Similarly, in field experiments, neither Route nor Moddus significantly altered total root length, biomass or distribution. There is little evidence from these experiments or in the literature to support the use of antigibberellin or auxin‐simulating growth regulator/promoters to modify root growth and drought avoidance of spring barley.     

毛白杨人工林吸收根判定阈值对其空间分布特征的影响

通过林木根系研究中不同吸收根的判定标准下根系空间分布特征的差异对比,阐明根系分级标准对吸收根空间分布格局的影响,提升根系研究精度,明确林木根系有效“觅食”区域。在7年生毛白杨林分中于5株样树周围挖取780个土柱,选取根系形态指标：根系平均直径(RD)、根系表面积密度(RAD)、根长密度(RLD)和根系体积密度(RVD)研究其垂向与径向的分布动态,并分析不同吸收根判定标准对毛白杨细根空间分布以及各形态指标的影响。结果表明：选取2 mm作为吸收根判定标准确实会导致运输根被误判为吸收根,但其空间分布特征仍能反映吸收根的真实空间分布格局。而且在该判定标准下,判定标准对于实际的细根形态和空间分布情况是否会产生的影响由于监测指标的不同以及研究位置的变化而不同。其中RAD、RLD和RVD的空间分布特征基本相同,但RVD的差值比例远高于其他指标,且深土层的差值比例普遍高于浅土层。因此,以2 mm为吸收根判定标准时,选取RLD和RAD更能准确反映吸收根的真实空间分布格局,且该标准更适用于在进行相对较浅的土层中开展研究,采用2 mm为阈值划分吸收根研究细根垂直分布特征时建议以各形态指标在各个土层所占比例来...     

Root aquaporins contribute to whole plant water fluxes under drought stress in rice (Oryza sativa L.)

Aquaporin activity and root anatomy may affect root hydraulic properties under drought stress. To better understand the function of aquaporins in rice root water fluxes under drought, we studied the root hydraulic conductivity (Lpr) and root sap exudation rate (Sr) in the presence or absence of an aquaporin inhibitor (azide) under well‐watered conditions and following drought stress in six diverse rice varieties. Varieties varied in Lpr and Sr under both conditions. The contribution of aquaporins to Lpr was generally high (up to 79% under well‐watered conditions and 85% under drought stress) and differentially regulated under drought. Aquaporin contribution to Sr increased in most varieties after drought, suggesting a crucial role for aquaporins in osmotic water fluxes during drought and recovery. Furthermore, root plasma membrane aquaporin (PIP) expression and root anatomical properties were correlated with hydraulic traits. Three chromosome regions highly correlated with hydraulic traits of the OryzaSNP panel were identified, but did not co‐locate with known aquaporins. These results therefore highlight the importance of aquaporins in the rice root radial water pathway, but emphasize the complex range of additional mechanisms related to root water fluxes and drought response.     

Root Respiration,Photosynthesis and Grain Yield of Two Spring Wheat in Response to Soil Drying

The effects of soil water regime and wheat cultivar, differing in drought tolerance with respect to root respiration and grain yield, were investigated in a greenhouse experiment. Two spring wheat (Triticum aestivum) cultivars, a drought sensitive (Longchun 8139-2) and drought tolerant (Dingxi 24) were grown in PVC tubes (120 cm in length and 10 cm in diameter) under an automatic rain-shelter. Plants were subjected to three soil moisture regimes: (1) well-watered control (85% field water capacity, FWC); (2) moderate drought stress (50% FWC) and (3) severe drought stress (30% FWC). The aim was to study the influence of root respiration on grain yield under soil drying conditions. In the experiment, severe drought stress significantly (p < 0.05) reduced shoot and root biomass, photosynthesis and root respiration rate for both cultivars, but the extent of the decreases was greater for Dingxi 24 compared to that for Longchun 8139-2. Compared with Dingxi 24, 0.04 and 0.07 mg glucose m⁻² s⁻¹ of additional energy, equivalent to 0.78 and 1.43 J m⁻² s⁻¹, was used for water absorption by Longchun 8139-2 under moderate and severe drought stress, respectively. Although the grain yield of both cultivars decreased with declining soil moisture, loss was greater in Longchun 8139-2 than in Dingxi 24, especially under severe drought stress. The drought tolerance cultivar (Dingxi 24), had a higher biomass and metabolic activity under severe drought stress compared to the sensitive cultivar (Longchun 8139-2), which resulted in further limitation of grain yield. Results show that root respiration, carbohydrates allocation (root:shoot ratio) and grain yield were closely related to soil water status and wheat cultivar. Reductions in root respiration and root biomass under severe soil drying can improve drought tolerant wheat growth and physiological activity during soil drying and improve grain yield, and hence should be advantageous over a drought sensitive cultivar in arid regions.     

The cooperative relation between non-hydraulic root signals and osmotic adjustment under water stress improves grain formation for spring wheat varieties

Non-hydraulic root signals (nHRS) and osmotic adjustment (OA) are two important adaptive responses of plants to water stress. There is little understanding of their relationships during water stress. The threshold range of soil water potential to occurrence of nHRS, the capacity for OA, grain yield and water use efficiency (WUE) were examined in three spring wheat ( Triticum aestivum L.) varieties (two bred after 1975 and one bred before 1900) under water stress conditions. The threshold range of nHRS was significantly correlated with the maintenance rate of grain yield (MRGY) ( r  = 0.99, P  < 0.05) under moderate drought (−0.49 to −0.55 MPa) but not under severe drought (−0.70 to −0.76 MPa). There were similar correlations between OA and the MRGY. However, regulation of nHRS precedes OA during gradual water stress. The threshold range of nHRS and OA was positively correlated ( r  = 0.93, P  < 0.05), suggesting a mechanism for adapting to drought. WUE was higher for modern than for old varieties and was correlated with the root efficiency (full biomass weight including root per root weight, r  = 0.78, P  < 0.05) and the root water uptake efficiency (water consumption per root weight, r  = 0.72, P  < 0.05). However, there was a significant negative correlation between WUE and root weight ( r  = –0.84, P  < 0.01). The cooperative relationship between the threshold range of nHRS and OA under water stress was beneficial for improving grain formation for spring wheat varieties.