玉米作物水分胁迫指数(CWSI)基线差异原因初探

为了探讨相同作物水分胁迫指数(CWSI)基线,在不同试验条件下存在差异的原因,于2010年及2011年连续2年在南方红壤区进行了不同施肥处理的玉米小区试验。结果表明,不同的氮素处理,玉米形态学指标及叶龄存在差异,其中不施氮的处理与施氮的处理差异显著(P<0.05),施氮多和施氮少的处理差异较小。在玉米不同的生育期,CWSI下基线不完全相同。施肥能够影响玉米冠气温差的降低程度,施用氮肥越多,冠气温差降幅越大,从而可使不同施肥处理的CWSI下基线产生差异。此外,在作物发生干旱时,施用不同类型的肥料还能够影响作物冠气温差的增加程度,其中施用化肥处理玉米冠气温差要比施用有机肥和不施肥的处理高,施用有机肥处理的玉米冠气温差也较不施肥的处理高。研究结果认为,相同作物CWSI基线的差异与作物本身品种,以及不同生长条件下作物生长状况之间的差异密切相关,而气候条件是造成这种差异的辅助因素。     

Thermal imaging for assessment of maize water stress and yield prediction under drought conditions

Maize production in Thailand is increasingly suffering from drought periods along the cropping season. This creates the need for rapid and accurate methods to detect crop water stress to prevent yield loss. The study was, therefore, conducted to improve the efficacy of thermal imaging for assessing maize water stress and yield prediction. The experiment was carried out under controlled and field conditions in Phitsanulok, Thailand. Five treatments were applied, including (T1) fully irrigated treatment with 100% of crop water requirement (CWR) as control; (T2) early stress with 50% of CWR from 20 days after sowing (DAS) until anthesis and subsequent rewatering; (T3) sustained deficit at 50% of CWR from 20 DAS until harvest; (T4) late stress with 100% of CWR until anthesis and 50% of CWR after anthesis until harvest; (T5) late stress with 100% of CWR until anthesis and no irrigation after anthesis. Canopy temperature (FLIR), crop growth and soil moisture were measured at 5-day-intervals. Under controlled conditions, early water stress significantly reduced maize growth and yield. Water deficit after anthesis had no significant effect. A new combination of wet/dry sponge type reference surfaces was used for the determination of the Crop Water Stress Index (CWSI). There was a strong relationship between CWSI and stomatal conductance (R² = 0.90), with a CWSI of 0.35 being correlated to a 64%-yield loss. Assessing CWSI at 55 DAS, that is, at tasseling, under greenhouse conditions corresponded best to the final maize yield. This linear regression model validated well in both maize lowland (R² = 0.94) and maize upland fields (R² = 0.97) under the prevailing variety, soil and climate conditions. The results demonstrate that, using improved standardized references and data acquisition protocols, thermal imaging CWSI monitoring according to critical phenological stages enables yield prediction under drought stress.     

Nutrient Management Effects on Light Interception, Photosynthesis, Growth, Dry-matter Production and Yield of Indian Mustard (Brassica juncea)

A field experiment was conducted on sandy loam acidic soil to study the effect of nutrient managements on light interception, photosynthesis, growth, biomass production and yield of Indian mustard [Brassica juncea (L.) Czern & Coss.]. Plant height, number of branches per plant, number of siliqua per plant, number of seeds per siliquae, 1000‐seed weight, seed and oil yield of Indian mustard improved at 100 % recommended rates of NPK (N‐P‐K at 80‐17.2‐33.2 kg ha^?1) + 10 t ha^?1 farmyard manure (FYM) (T₃) compared with 100 % NPK rate (T₂). It was also at par with 100 % NPK + 10 kg ha^?1 borax + 20 kg ha^?1 ZnSO₄ (T₆) and 50 % NPK + 10 t ha^?1 FYM +10 kg ha^?1 borax + 20 kg ha^?1 ZnSO₄ (T₁₀). The rate of photosynthesis increased due to appropriate nutrient management treatments (T₃, T₆ or T₁₀) with concomitant increase in photosynthetically active radiation, internal CO₂ concentration and rate of transpiration and decrease in stomatal resistance. Consequent upon the higher rate of photosynthesis, dry‐matter accumulation increased. The crop receiving nutrient treatment T₃ or T₆ maintained higher light interception ratio (LIR), leaf area index (LAI), biomass production, crop growth rate (CGR) and net assimilation rate (NAR) that resulted in greater rate of photosynthesis, harvest index and seed yield. Similarly, T₁₀ was equally efficient in registering greater LIR, LAI, CGR, NAR and seed yield of mustard. The average seed yields were 1692, 1683 and 1668 kg ha^?1 in T₃, T₆ and T₁₀, respectively, and these three treatments were significantly superior to T₂ (1332 kg ha^?1), control (723 kg ha^?1) and other treatments. Significantly greater seed oil contents of 41.30, 40.60 and 41.07 % were recorded in T₃, T₆ and T₁₀, respectively. Thus, significant improvement due to appropriate combination of NPK, FYM, borax and ZnSO₄ was observed for uptake of nutrients.     

Deficit Irrigation of Soya Bean [Glycine max (L.) Merr.] in a Sub-humid Climate

An experiment was conducted to investigate the influence of different levels of water deficit on yield and crop water requirement of soya beans in a sub‐humid environment (Southern Marmara region, Bursa, Turkey) in 2005 and 2006. One full‐irrigated treatment (T₁), one non‐irrigated treatment (T₅) and three different deficit irrigation (T₂ = 25 % water deficit, T₃ = 50 % water deficit, T₄ = 75 % water deficit) treatments were applied to ‘Nova’ soya bean planted on a clay soil. Non‐irrigated and all deficit irrigation treatments significantly reduced biomass and seed yield and yield components. The full‐irrigated (T₁) treatment had the highest yield (3760 kg ha^?1), while the non‐irrigated (T₅) treatment had the lowest yield (2069 kg ha^?1), a 45.0 % seed yield reduction. T₂, T₃ and T₄ deficit irrigation treatments produced 11.7–27.4 % less seed yield than the T₁ treatment. Harvest index showed less and irregular variation among irrigation treatments. Both leaf area per plant and leaf area index were significantly reduced at all growth stages as amount of irrigation water was decreased. Evapotranspiration increased with increased amounts of irrigation water supplied. Our results indicate that higher amounts of irrigation resulted in higher seed yield, whereas water use efficiency and irrigation water use efficiency values decreased when irrigation amount increased.     

Rainfall Harvesting and Mulches Combination for Corn Production in the Subhumid Areas Prone to Drought of China

A field study was conducted to determine the effect of a combination of the plastic‐covered ridge and furrow rainwater harvesting (PRFRH) with different mulching materials, namely, 0.08‐mm‐thick plastic film (T₁), 10‐cm‐thick corn straw (T₂), 8 % biodegradable film (T₃), liquid film (T₄), bare furrow (T₅) and conventional flat (CF), on corn production, soil water storage and water use efficiency (WUE) in the subhumid areas prone to drought of China (SAPDC). The T₁–T₅ plots at 0–100 cm depth had higher (P < 0.05) soil water storage than CF, while at 100–200 cm soil layer there was no difference (P > 0.05) among treatments. The T₁–T₄ plots produced 209–1 107 kg ha^?1 more grain yields than the T₅ plots. Meanwhile, almost all treatments had WUE over 2 kg m^?3. The order of WUE increase among different mulch treatments was as follows: T₃ > T₁ > T₂ > T₄. In the case of environmental and economic feasibility, a combination of the PRFRH system with biodegradable film and straw mulches would be an option with high potential to increase crop sustainability in dry land farming systems and can be adopted in many areas without irrigation capability.     

Response of Mung Bean (Vigna radiata (L.) R. Wilczek) to an Increasing Natural Temperature Gradient under Different Crop Management Systems

Increasing temperatures pose a significant threat to crop production in the tropics. A field experiment was conducted with mung bean at three locations in Sri Lanka representing an increasing temperature gradient (24.4–30.1 °C) during two consecutive seasons to (i) determine the response of mung bean to increasing temperature and (ii) test a selected set of crop management practices aimed at decreasing essential inputs such as water, synthetic pesticides and inorganic nitrogen fertilizer. The control treatment (T₁) consisted of standard crop management including irrigation, chemical crop protection and inorganic fertilizer application. Adaptation system 1 (T₂) included mulching with rice straw at 8 t ha^?1 with 30 % less irrigation and crop protection and nutrient management as in T₁. Adaptation system 2 (T₃) included crop protection using a pretested integrated pest management package with water and nutrient management as in T₂. In adaptation system 3 (T₄), 25 % of the crop's nitrogen requirement was given as organic manure (compost) at 0.8 t ha^?1 while 75 % was given as inorganic fertilizer with water management and crop protection as in T₃. Durations of both pre‐ and post‐flowering phases were reduced with increasing temperature. In the warmer (25.4–30.1 °C) yala season, seed yield (Y) of T₁ decreased with increasing temperature at 366 kg ha^?1 °C^?1. However, in maha season, Y did not show a significant relationship across the narrower temperature gradient from 24.4 to 25.8 °C. Pooling the data from both seasons showed a second‐order polynomial response with an optimum temperature of 26.5 °C. In addition to shortened durations, reduced crop growth rates and reduced pod numbers per plant were responsible for yield reductions at higher temperatures. In yala, yields of all adaptation systems at all locations were on par with yields of the respective controls. Furthermore, yala yields of T₂ and T₃ were less sensitive than T₁ to increasing temperatures (265 and 288 kg ha^?1 °C^?1). In maha, T₃ and T₄ had greater yields than the control at the relatively cooler site while having lower yields than the control at the warmer site. Maha yields of T₂ were on par with the control at both temperature regimes. While demonstrating the significant temperature sensitivity of mung bean yields, results of the present work showed that components of the tested adaptation systems could be promoted among smallholder farmers in Asia, especially in view of their long‐term environmental benefits and contributions to sustainable agriculture in a warmer and drier future climate.     

Infrared Thermal Imaging as a Rapid Tool for Identifying Water‐Stress Tolerant Maize Genotypes of Different Phenology

The main task of this research was to evaluate canopy temperature and Crop Water Stress Index (CWSI) by assessing genotype variability of maize performance for different water regimes. To that end, three hundred tropical and subtropical maize hybrids with different phenology in terms of date of anthesis were evaluated. The influence of phenology on the change in canopy temperatures and CWSI was not equal during the three dates of measurement. At the end of vegetative growth (82 days after sowing, DAS) and at the blister stage (DAS 97), a high significant difference in temperatures and CWSI (P < 0.001) were obtained between the early‐ and late‐maturity genotypes. During anthesis (DAS 89), phenology had a significant effect (P < 0.01) only for the well‐watered genotypes, while under water‐stress conditions, no differences were found between early and late genotypes in terms of canopy temperature and CWSI. High significant differences (P < 0.001) in stomatal conductance (g_s) between early and late genotypes for different treatments were observed. A relationship (R² = 0.62) between g_s and canopy temperature was obtained. Under a water‐stress canopy, temperature was measured at anthesis, which was negatively correlated with grain yield of the early (r = ?0.55)‐ and late (r = ?0.46)‐maturity genotypes in the water‐stressed condition.     

1H-NMR Method Enables Early Identification of Degeneration in the Quality of Sweet Potato Tubers

In sweet potato tuber, which is a tropical plant, long‐term storage leads to loss of water and carbohydrate, thus water mobility was investigated using ¹H‐NMR spectroscopy. Electrolyte leakage indicated that tubers stored at 15 °C for 1 year were partly injured and that frozen‐thawed tissues were dead. Nuclear magnetic resonance (NMR) spin–lattice relaxation time (T₁) and spin–spin relaxation time (T₂) clearly increased with the duration of storage, whereas these values decreased in the dead tissues. Furthermore, Arrhenius plots for T₁ and T₂ were determined at temperatures ranging from 20 to 0 °C in 2.5 °C steps. In the fresh tubers, a strong converse temperature dependency was shown in the T₂ measurement. On the contrary, there was no temperature dependency in the T₂ of the dead tissues. Thus, the existence of inverse temperature dependency reflected tissue viability. Additionally, any change in the T₂ of the fresh tubers occurred at about 14 °C, which virtually coincided with the storage temperature of 15 °C. The slope change in T₂ might have responded to a physiological change as a primary event. In conclusion, monitoring water status by NMR could provide early identification of changes in the quality of post‐harvest crops; this method shows great promise for use in environmental‐stressed crop yield research.     

不同水分条件下棉花光谱数据对冠层叶片温度的响应特征

利用Fluke热像仪和ASD地物非成像高光谱仪,分别记录棉花新陆早33号、13号2个品种、4个水分处理、5个关键生育时期的冠层红外热图像和反射光谱数据;在红外热图像上提取棉花冠层受光叶片的温度,同时处理高光谱数据获得归一化植被指数(NDVI)、比值植被指数(RVI)、红光620 nm和近红外850 nm波段的反射率(ρ620,ρ850)。分析表明,棉花2个品种4个水分处理的冠层叶片温度(TL)在盛花期、盛花结铃期较高,在盛铃期达到最大值,在开花期和吐絮初期较低;棉花受到水分胁迫,冠层近红外波段光谱的反射率降低,红光波段的反射率升高,NDVI和RVI变小,TL升高;在充分灌溉条件下棉花近红外、红光波段的光谱反射率、NDVI和RVI及TL则与水分胁迫处理的表现相反。和620 nm和850 nm波段反射率与TL的线性相关比较,棉花NDVI和RVI与TL的线性相关性更强。研究表明,将红外热图像和高光谱遥感技术相结合,具有实时、非破坏性地监测棉花水分状况的潜力。     

Molecular mapping of a locus controlling resistance to Albugo candida in Indian mustard

Brassica juncea (L.) Czern & Coss is widely grown as an oilseed crop in the Indian subcontinent. White rust disease caused by Albugo candida (Pers.) Kuntze is a serious disease of this crop causing considerable yield loss every year. The present study was undertaken to identify molecular markers for the locus controlling white rust resistance in a mustard accession, BEC‐144, using a set of 94 recombinant inbred lines (RILs). The screening of individual RILs using an isolate highly virulent on the popular Indian cultivar ‘Varuna’ revealed the presence of a major locus for rust resistance in BEC‐144. Based on screening of 186 decamer primers employing bulked segregant analysis (BSA), 11 random amplified polymorphic DNA markers were identified, which distinguished the parental lines and the bulks. Five of these markers showed linkage with the rust resistance locus. Two markers, OPN0_l000 and OPB06₁₀₀₀, were linked in coupling and repulsion phases at 9.9 cM and 5.5 cM, respectively, on either side of the locus. The presence of only two double recombinants in a population of 94 RILs suggested that the simultaneous use of both markers would ensure efficient transfer of the target gene in mustard breeding programmes.     

Moisture Stress Effects on the Yield and Water Use of Sorghum Hybrids and their Parents*

Little is known of the relationship between hybrids and parental material with respect to water use and drought resistance. Responses of sorghum (Sorghum bicolor [L.] Moench) F₁ hybrids to moisture deficits are partially determined by parental material. The yield and water use of six sorghum hybrids and their respective male and female parents were evaluated under stressed and well irrigated conditions during 1980 and 1981 at Tucson, Arizona. The soil was Comoro loamy sand (coarse-loamy, mixed, calcareous, thermic typic Torrifluvent) with an average available soil moisture of 16 % at field capacity. Changes in soil moisture were monitored semi-weekly by neutron modulation. Meteorological data were collected daily. The 1980 season had higher maximum temperatures and pan evaporation than the 1981 season. Differences in cumulative water use among entries were apparent within the same water treatments during 1981. Mean cumulative evapotranspiration (ET) for the stressed treatment was 248 and 281 mm for 1980 and 1981, respectively, and ET under well irrigated conditions was 419 and 528 mm for 1980 and 1981, respectively. Hybrids produced greater grain yield than their parents under both water treatments. This was due to greater seed number for hybrids. Seed numbers were more stable for hybrids over both treatments than for parents. Hybrids four and seven had the greatest grain yield in 1980 and 1981, respectively, under stressed conditions. Water use efficiency (WUE) was significantly different within water treatments but was not so between the irrigated and stressed treatments. Hybrids WUE was generally greater than that of parents except for hybrid five under irrigated conditions in 1981. Hybrids with WUE and stable yields were not necessarily reflective of parental material under stressed and non-stressed environments.     

Modelling soil tillage and mulching effects on soil water dynamics in raised-bed vegetable rotations

Reduced tillage and mulching may bring about new production systems that combine better soil structure with greater water use efficiency for vegetable crops grown in raised bed systems. These are especially relevant under conditions of high rainfall variability, limited access to irrigation and high soil erosion risk. Here we evaluate a novel combination of empirical models on water interception and infiltration, with a soil-water balance model to evaluate water dynamics in raised bed systems on fine Uruguayan soils to analyze the effect of reduced tillage, cover crops and organic matter addition on soil physical properties and water balance. In the experiment mulching increased water capture by 9.5% and reduced runoff by 37%, on average, leading to less erosion risk and greater plant available water over four years of trial. Using these data we calibrated and evaluated different models that predicted interception + infiltration efficiently (EF = 0.93 to 0.95), with a root mean squared error (RMSE) from 0.32 to 0.40 mm, for an average observed interception + infiltration of 28.8 mm per day per rainfall event. Combining the best model with a soil water balance resulted in predictions of total soil water content to 1 m depth (SWC_T) with RMSE ranging from 4.5 to 10.3 mm for observed SWC_T ranging from 180.4 to 380.6 mm. Running the model for a four-year crop sequence under 10 years of Uruguayan historical weather revealed that reduced tillage required on average 141 mm yr⁻¹ less irrigation water than conventional tillage combined with organic matter application, thus enabling a potential increase in irrigated area of vegetable crops and crop yields. Results also showed the importance of inter-annual rainfall variability, which caused up to 3-fold differences in irrigation requirements. The model is easily adaptable to other soil and weather conditions.     

Leaf Area Index,Leaf Transpiration and Stomatal Conductance as Affected by Soil Water Deficit and VPD in Processing Tomato in Semi Arid Mediterranean Climate

In order to assess the effects of soil water availability and climatic conditions on leaf growth, leaf transpiration (E) and stomatal conductance (g_s) of processing tomato, under deficit irrigation regimes in the Mediterranean climate, open‐field experiments were carried out in two sites differing from soil and climatic characteristics, in Sicily, South Italy. A wide range of soil water availability from dry, deficit irrigation to full irrigation was examined. Leaf area greatly changed with soil water availability but not with the experimental site. The effect of soil drying on physiological indices was small over a certain range of soil water deficit (from 0 % to approximately 40 %). Within this range, vapour pressure deficit (VPD) strongly affected g_s. To this regard, the adoption of two experimental sites differing in climatic conditions (i.e. air temperature, RH, VPD) has been useful for a better understanding of the mechanisms, which regulate stomatal opening. Therefore, in Mediterranean environment, the combined effect of soil water availability (mostly upon leaf growth) and climatic conditions (mostly upon plant physiology) must be considered in models for biomass production in tomato crop.     

Assessment of irrigation scenarios to improve performances of Lingot bean (Phaseolus vulgaris) in southwest France

In the context of climate change, producing the same amount of food with less water has become a challenge all over the world. This is also true for the Lingot bean production in the area of Castelnaudary of southwest France where market competition with imported bean has made it crucial to achieve high yields to maintain production in the area. The use of an appropriate and robust crop model can help to identify crop management solutions to face such issues. We used SSM-legumes, a crop model generic to legume species, as well as field observations recorded over five years on eight farms of the Castelnaudary area to assess the effect of different irrigation scenarios on bean yield and water consumption. First, it was demonstrated that the SSM-legumes model is robust in simulating the development and growth of Lingot bean in non-stressed or moderately stressed conditions of this region regarding water and nutrient availability. Then, the use of the model to compare irrigation scenarios provided guidance on how to improve irrigation management for Lingot bean production. These results showed that farmers could achieve slightly higher yields with less water by basing irrigation decisions on the water content of the soil.     

Influence of the root endophyte Piriformospora indica on the plant water relations,gas exchange and growth of Chenopodium quinoa at limited water availability

This study aimed to evaluate the ability of Piriformospora indica to colonize the root of Chenopodium quinoa and to verify whether this endosymbiont can improve the growth, performance and drought resistance of this species. The study delivered, for the first time, evidence for successful colonization of P. indica in quinoa. Hence, pot experiment was conducted in the greenhouse, where inoculated and non‐inoculated plants were subjected to ample (40%–50% WHC) and deficit (15%–20%WHC) irrigation treatments. Drought adversely influenced the plant growth, leading to decline the total plant biomass by 74%. This was linked to an impaired photosynthetic activity (caused by lower g_s and C_i/C_a ratio; stomatal limitation of photosynthesis) and a higher risk of ROS production (enhanced ETR/A_gross ratio). P. indica colonization improved quinoa plant growth, with total biomass increased by 8% (controls) and 76% (drought‐stressed plants), confirming the growth‐promoting activity of P. indica. Fungal colonization seems to diminish drought‐induced growth hindrance, likely, through an improved water balance, reflected by the higher leaf ψ_w and g_s. Additionally, stomatal limitation of photosynthesis was alleviated (indicated by enhanced C_i/C_a ratio and A_net), so that the threat of oxidative stress was minimized (decreased ETR/A_gross). These results infer that symbiosis with P. indica could negate some of the detrimental effects of drought on quinoa growth, a highly desired feature, in particular at low water availability.     

Effects of corn deficit irrigation and soil properties on water use efficiency. A 25-year analysis of a Mediterranean environment using the STICS model

This study analyses the role of variability induced by climate and soil properties (texture and total available soil water in the root zone, TAW) on the “corn deficit irrigation–water use efficiency” relation over a 25-year period, between 1981 and 2005, in three different sites located in the South of Italy. The analysis of water use efficiency was carried out by means of three indexes: crops water use efficiency (WUE_ET and WUE_T) and irrigation water use efficiency (IWUE). These indexes can be obtained by calculating the ratio between the yield and the seasonal values of evapotranspiration (ET), transpiration (T) and irrigation volume (I). After its validation, the STICS model was retained to simulate the variables required to determine these indexes.Climatic variability affected the three indexes in different ways during the 25-year period studied. The dispersion around the mean values of the water use efficiency is 17% on average for the WUE (ET or T) indexes, whereas it could reach 54% for the IWUE index. This last index is only poorly reliable due to the high variability of rainfall during the corn growing season in the Mediterranean region.For the same level of soil water deficit, TAW led to an improvement (the case of the site with a high TAW and loam–clay soil texture), a stabilisation (the case of the site with a high TAW and clay soil texture) or a decrease (the case of the site with a poor TAW and clay soil texture) in WUE_ET and WUE_T values. For the same conditions of soil water deficit and TAW, crops water use efficiency was higher in loam textured soil than in clay soil.The results derived by analyzing three indexes (WUE_ET, WUE_T and IWUE) converge to the same conclusions on the “corn deficit irrigation–water use efficiency” relation observed at the three different sites.The hypotheses which may explain the differences observed in the different sites studied in terms of water use efficiency are discussed, with the presentation of some suggestions devised for corn irrigation practices.     

Leaf,canopy and agronomic water‐use efficiency of field‐grown sugar beet in response to potassium fertilization

Potassium (K) fertilization is important to maintain adequate concentrations of plant available K in agricultural soils to achieve best yields and improve crop stress tolerance and water‐use efficiency (WUE). Water‐use efficiency (WUE) can be expressed on various spatiotemporal scales, and it is known that responses of WUE to external stress are not uniform across scales. Multiscale evaluations of the impact of varying K fertilization on the WUE of C₃ crops under field conditions are missing so far. In the present field study, we evaluated effects of K fertilization on WUE of sugar beet (Beta vulgaris L.) on short‐termed leaf‐ (WUE_Leaf) and canopy‐scales (WUE_Canopy) and as the agronomic ratio of white sugar yield (WSY) to in‐season water use (i.e. WUE_WSY). In K‐fertilized plots, WUE_WSY was enhanced by 15.9%. This effect is attributed to increased beet yield and WSY, as no differences in total in‐season water use between fertilized and unfertilized plots were observed. Potassium (K) fertilization significantly enhanced the leaf area index, resulting in a more efficient depletion of soil moisture by roots in K‐fertilized plots. As a consequence, WUE_Leaf was increased due to stomatal adjustment. Potassium (K) improved WUE_Canopy only by tendency. It is concluded that K fertilization improves the WUE of field‐grown sugar beet across scales, but processes that regulate WUE are highly scale dependent.     

Relationship between Carbon Isotope Discrimination,Mineral Content and Gas Exchange Parameters in Vegetative Organs of Wheat Grown under Three Different Water Regimes

Carbon isotope discrimination (Δ) has been proposed as an indirect selection criterion for transpiration efficiency and grain yield in wheat. However, because of high cost for Δ analysis, attempts have been made to identify alternative screening criteria. Ash content (m_a) has been proposed as an alternative criterion for Δ in wheat and barley. A pot experiment was conducted to analyse the relationship between Δ, mineral content and gas exchange parameters in seedlings and leaves of bread wheat (Triticum aestivum L.). Plants of 10 genotypes were cultivated under three different water regimes corresponding to moderate (T₃), intermediate (T₂) and severe drought (T₁) stress obtained by maintaining soil humidity at 75 %, 55 % and 45 % of the humidity at field capacity respectively. Δ and m_a in seedlings and leaves showed significant differences among the three water treatments. Significant positive correlations were found between Δ and m_a in seedlings and leaves at elongation and anthesis stages in severe drought stress (T₁). Δ was negatively associated with potassium (K) content in intermediate drought stress (T₂) and positively with magnesium (Mg) content in T₂ and T₃ (moderate drought stress) in flag leaf at anthesis. There were negative correlations between Δ and single‐leaf intrinsic water‐use efficiency (W_T) in T₂ and T₃ at anthesis stage. Stronger positive associations were noted between Δ and stomatal conductance (g_s) in T₁ and T₂ than in T₃ at anthesis. These results suggested that Δ is a good trait as an indirect selection criterion for genotypic improvement in transpiration efficiency, while m_a is a possible alternative criterion of Δ in wheat vegetative organs, especially in stressed environments. Significant association was found between Δ and K, Mg and Ca contents that would merit being better investigated.     

基于红外热图像的棉花冠层水分胁迫指数与光合特性的关系

 利用Fluke红外热像仪获取两个棉花品种4水平水分处理5个关键生育时期冠层的红外热图像;并在红外热图像测试的样本区内,分别测试棉花叶片净光合速率（P_n）、气孔导度（G_s）和叶面积指数（LAI）。应用图像处理技术,提取棉花冠层受光叶片温度,并将人工参考湿表面（WARS）的温度运用到Jones定义的作物水分胁迫指数CWSI的经验公式中,计算CWSI;分析棉花冠层CWSI和光合参数的生育期变化,表明棉花冠层CWSI升高,P_n、G_s和LAI相应降低;不同水分处理条件下,生育期CWSI平均值分别与Pn、Gs和LAI平均值呈极显著的负相关关系（r_CWSI-Pn=-0.9182^**,r_CWSI-Gs=-0.8819^**,r_CWSI-LAI=-0.8661^**,n=16）,CWSI与Pn、Gs和LAI可同步反映棉花冠层水分胁迫的状况。研究结果表明,先进的红外热图像技术,提供了一种获得作物冠层表面温度的高分辨率空间信息的手段,能够消除背景干扰因素的影响,更精确的计算棉花冠层CWSI,可快速、有效、准确地监测棉花冠层的水分状况。     

Limited contribution of water availability in genotype-by-environment interaction in sugarcane yield and yield components

Water deficit is an important abiotic stress factor limiting sugarcane production. Understanding the effect of water deficit on cane yield, yield components and genotype × environment (G × E) interaction can aid in selecting genotypes that are adapted to water deficit conditions. In this study, response of cane yield and yield components of 10 sugarcane genotypes grown under 3 irrigation treatments—fully irrigated, semi-irrigated and rainfed—was examined across 3 locations and 3 crop-years within each location. Cane yield reduced by 32% and 9% in the rainfed and semi-irrigated treatments, respectively, compared to the fully irrigated treatment. Genotypic variation was highly significant for cane yield and yield components in all three irrigation regimes. Cane yield in the rainfed treatment showed significant genetic correlation with stalk diameter (r_g = 0.68), leaf number (r_g = 0.64), node number (r_g = 0.67) and stalk number (r_g = 0.68). Genotype × irrigation variance was negligible compared to genotype, genotype × location and genotype × crop-year variances. Commercial genotypes had higher yield in most environments except in low-yield potential environments, which caused a significant genotype × location × irrigation effect, suggesting opportunities for improving sugarcane productivity in these environments.