Carbon isotope discrimination and water use efficiency relationships of alfalfa genotypes under irrigated and rain-fed organic farming

Carbon isotope discrimination (Δ) has been proposed as a method for evaluating water use efficiency (WUE) in C₃ plants and as a precise technique for screening plants with higer tolerance under water deficit conditions. In this research, 18 alfalfa genotypes from different geographical origins were evaluated under irrigated and rain-fed conditions in organically managed fields in Austria. Significant differences were found amongst harvests for Δ-shoot under both conditions while genotype by harvest interaction was only significant under irrigated condition. Drought stress under rain-fed condition reduced the overall mean of water use efficiency and carbon isotope discrimination responses(up to 34%), but the ratios of reduction differed for characters and genotypes. Narrow ranges were found for all traits especially for WUE-TBY (total biomass yield) (0.78 kg m⁻³) and Δ-shoot (0.53‰) based on genotype means over locations and years, although variation and ranges were higher under irrigated condition. Regarding the variable and low correlations, simultaneous assessment of genotypes for Δ-shoot and biomass production can ensure the selection of superior genotypes and minimize potential biomass reductions that may result from using Δ-shoot as the only selection criterion to improve WUE. Sitel was the most water use efficient genotype(2.79 and 4.48 kg m⁻³ based on shoot dry matter and total biomass,respectively) across two condition (widely adapted genotype) followed by Mohajeran, Fix232 and Verko under irrigated condition (as specific adapted genotypes) and Vlasta, Sanditi, Ghara-aghaj under rain-fed condition.     

大气CO_2倍增条件下冬小麦气体交换对高温干旱及复水过程的响应

探究大气CO_2浓度倍增条件下冬小麦气体交换参数对高温干旱及复水过程的生理响应机制,有助于提高生态过程模型的模拟精度,更加准确地预测全球气候变化对农田生态系统初级生产力及其生态服务功能的影响。利用4个可精准控制CO_2浓度和温度的大型人工气候室,研究了CO_2浓度倍增条件下高温干旱及复水过程对冬小麦气孔特征和气体交换参数的影响。结果表明, CO_2浓度倍增(E)导致冬小麦远轴面气孔密度增加、气孔宽度减小、气孔空间分布规则程度降低,但提高叶片的净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和水分利用效率(WUE)。高温干旱(HD)使叶片气孔长度、密度、周长和面积减小,导致叶片气体交换参数均显著下降。然而,高CO_2浓度及高温干旱(EHD)导致气体交换参数下降幅度相对较小,表明高CO_2浓度对高温干旱具有一定的缓解作用。此外,干旱复水后,不同处理条件下冬小麦叶片气体交换参数均有所升高,但高温干旱下叶片的气体交换参数仍未能恢复到对照水平,暗示光合器官可能在高温干旱时遭到损伤和破坏。     

Thresholds for leaf expansion and transpiration response to soil water deficit in a range of sunflower genotypes

The sunflower (Helianthus annuus L.) crop in southern Europe suffers from intense and frequent periods of water deficit. Minimisation of water loss in response to water deficit is a major aspect of drought tolerance and can be achieved through the lowering of either leaf area expansion rate or transpiration per unit leaf area (stomatal conductance). During three greenhouse pot experiments, leaf expansion (LE) and transpiration (TR) rates were monitored as the soil dried progressively for about 15 days. This study aimed to quantify the response of these two physiological processes to water deficit, expressed as the fraction of transpirable soil water (FTSW): response thresholds (onset of decline) were estimated on 25 sunflower genotypes from different generations of selection history. From these relationships, the thresholds below which LE and TR started to decrease from the control were calculated: little change was observed until FTSW was close to 0.6 for leaf expansion and 0.4 for daily transpiration. Variability in the response of all genotypes for expansion and transpiration control was better described using specific thresholds for each genotype rather than generic thresholds for sunflower. The ranking of genotypes was found to be unaffected for transpiration rate control, but this was not the case for leaf expansion. Identified response thresholds were not mutually correlated, suggesting that sunflower controls leaf expansion and transpiration rate independently. Neither was correlated with the release date of the genotype, suggesting that these traits were not subject to selection within evaluation environments.     

Sorghum bicolor prioritizes the recovery of its photosynthetic activity when re-watered after severe drought stress,while manages to preserve it under elevated CO2 and drought

Understanding plant response and resilience to drought under a high CO₂ environment will be crucial to ensure crop production in the future. Sorghum bicolor is a C₄ plant that resists drought better than other crops, which could make it a good alternative to be grown under future climatic conditions. Here, we analyse the physiological response of sorghum under 350 ppm CO₂ (aCO₂) or 700 ppm CO₂ (eCO₂) with drought (D) or without drought (WW) for 9, 13 and 16 days; as well as its resilience under long (R1: 9D + 7R) or short (R2: 13D + 3R) recovery treatments. Sorghum showed elevated rates of gs under aCO₂ and WW, which resulted in a significant decrease in Ψ_w, gs, E, Φ_PSII, F_v’/F_m′ when exposed to drought. Consequently, A was greatly decreased. When re-watered, both re-watering treatments prioritized A recovery by restoring photosynthetic machinery under aCO₂, whereas under eCO₂ plants required little recovery since plant were hardly affected by drought. However, sorghum growth rate for aboveground organs did not reach control values, indicating a slower long-term recovery. Overall, these results provide information about the resilience of sorghum and its utility as a suitable candidate for the drought episodes of the future.     

两种水分条件下冬小麦籽粒部分微营养含量及其基因型差异研究

为了解小麦籽粒微量元素含量的基因型差异及其对水分条件的反应,本试验在春浇2水和春不浇水2种条件下对33个小麦基因型材料籽粒部分微量元素进行了测定分析.结果表明,籽粒铁、锌、锰、铜、碘含量存在显著的基因型差异,水分处理对这些微营养成分的影响效应也因基因型而异.籽粒铁、锌、铜含量之间存在明显正相关性,而微量元素含量与粒重和产量的关系则因元素类型和水分条件而异.通过对不同基因型铁、锌含量的比较分析,筛选出几个高铁高锌基因型材料(如刘春1号).     

Pod photosynthesis and drought adaptation of field grown rape (Brassica napus L.)

In rape (Brassica napus L., cv. Global) seed growth mainly depends on husk CO₂ assimilation. In irrigated plants, the net photosynthetic rate (A_max) was 10–13 μmol CO₂ m⁻² s⁻¹ in non-maturing pods and correlated with nitrogen content. The stomatal conductance of water vapour (g_H2O) was 0.3 mol m⁻² s⁻¹ in non-maturing pods. The photosynthetic nitrogen use efficiency (NUE) was 8.3 μmol CO₂g⁻¹ N s⁻¹, about one-third of that in leaves. The photosynthetic water use efficiency (WUE; A_maxg_H2O⁻¹) was similar in pods and leaves. In severely droughted plants, the photosynthetic rate was reduced to 38%. The seed growth rate, however, was not influenced by intermittent periods of water stress, indicating translocation of assimilates to the seeds. The drought resistant character of the pods was due to low specific area, succulence, low stomatal conductance causing a small decrease of ΔΨ day⁻¹ during soil drying and maintenance of high relative water content during severe drought. A mathematical formulation of the pod water release curve was undertaken. © (1997) Elsevier Science B.V.     

The variation of relative water content,SPAD chlorophyll meter reading,stomatal conductance,leaf area,and specific leaf area of Jerusalem artichoke genotypes under different durations of terminal drought in tropical region

This work assessed the responses of Jerusalem artichoke (JA) genotypes experienced to different durations of terminal drought for relative water content (RWC), SPAD chlorophyll meter reading (SCMR), stomatal conductance (SC), leaf area (LA) and specific leaf area (SLA), investigated the significant contributor of physiological traits to yield and yield reduction and diversity of physiological traits in terminal drought tolerance genotypes. Field research was conducted during the late-rainy season for 2 years using a split-plot design with four replications. The three irrigation treatments involved no-drought (SD0), short (SD1) and long (SD2) durations of terminal drought were arranged as main plots, and sub-plots were six genotypes of JA. The current study revealed that RWC, SC, LA, and SLA, were drastically reduced whilst SCMR values slightly increased under SD1 and SD2 compared to SD0. According to multiple linear regression indicated that SLA (SD0), and RWC (SD1 and SD2) had high contributions to tuber fresh weight (TFW), whereas SC had a high contribution to TFW reduction under terminal drought. Principal component analysis also confirmed that the diversity of LA, RWC, and SLA had maximized contributing traits, followed by HI, SCMR and SC in these breeding materials of JA under three irrigation treatments. Our finding emphasized that JA125 (low SLA), HEL256 and JA37 (high SLA) lead to the high performance of TFW under SD0, and they exhibited high TFW under SD1 by performing medium RWC. Likewise, JA4 and JA37 had high TFW under SD2 caused by medium RWC. HEL253 and JA60 were identified as terminal drought-tolerant genotypes because of performed medium SC, which contributed to a low reduction in TFW. Our promising results are the basis for further studies, SLA, RWC and SC are an important keys for screening drought tolerance (low economic yield reduction) and these genotypes studied could be used for parental lines to improved drought tolerance progenies through breeding programs under different durations of terminal drought-prone areas.     

Water relations, gas exchange and growth of cool-season grain legumes in a Mediterranean-type environment

The aim of this study was to identify the physiological characteristics which may affect the yield of six cool-season grain legume species grown in a water-limited Mediterranean-type climate in Western Australia. The rate of net photosynthesis, stomatal conductance and water relations were measured from flowering to complete leaf senescence in white lupin, chickpea, faba bean, field pea, grass pea and lentil. In irrigated plants, the midday leaf water potential was about −0.6 MPa in all species, while the maximum rate of leaf photosynthesis was 30 μmol m⁻² s⁻¹ for chickpea and white lupin, and below 20 μmol m⁻² s⁻¹ for the other species. With the development of water deficits, the leaf water potential in rain-fed plants decreased to about −3 MPa in chickpea and lentil and −2 MPa in the other species. Photosynthesis and stomatal conductance decreased markedly as the leaf water potential decreased below −0.9 MPa in all six species, including chickpea and lentil, which showed a high degree of osmotic adjustment. Despite the similarity in water use, restricted to the top 40 cm of soil, and water relations characteristics, yields varied markedly among species. Yields were strongly correlated with early biomass production and early pod development.     

Leaf and green area development of durum wheat genotypes grown under Mediterranean conditions

Future increases in the potential yield of wheat will require an improvement in the photosynthetic area in early growth stages. Our aim was to investigate the genotypic and environmental effects on the pattern of leaf and green area development of durum wheat (Triticum turgidum L. cv. durum). Twenty-five genotypes were grown during 2 years under irrigated and rainfed conditions in Lleida (northeastern Spain). Leaf area index (LAI) and green area index (GAI) were determined on eight occasions from seedling to maturity and data were fitted to an asymmetric logistic peak curve. Multivariate analysis of variance was used to assess the curve characteristics responsible for differences between years, sites and genotypes. Genotypic differences in the pattern of changes in LAI and GAI from sowing to maturity were not statistically significant, indicating a lack of genetic diversity for these traits in the germplasm used in this study. A decrease in the peak of the curves of 27% for LAI and 35% for GAI was observed under rainfed conditions compared to the irrigated site. Drought caused a lengthening of crop development until anthesis of about 2% (3–4 days). Contrarily, the time from sowing to the maximum LAI and GAI values were reduced by drought in around 10%, causing an acceleration of the onset of plant senescence. Once started, the senescence of the green organs of the plant was more rapid at the irrigated than at the rainfed site. It is concluded that LAI and GAI patterns were more influenced by the environment (mainly water availability) than by the genotype. The results suggest a certain degree of independent regulation for phenological development and the swiftness of green area accumulation in the plant.     

系统调控下棉花比叶重的变化机制

[目的]比叶重是叶片经济谱功能性状关系网络中的核心指标,受到各种环境因素的影响.但是,植物不同部位叶片间存在的系统调控如何影响比叶重的变化尚不清楚.[方法]本研究通过田间密度试验和室内遮荫试验,测定棉花不同部位叶片的比叶重及其组织结构性状,分析比叶重和组织结构性状之间的关系以及影响比叶重的因素.[结果]改变棉花下部叶片...     

QTL mapping for heading date,leaf area and chlorophyll content under cold and drought stress in two related recombinant inbred line populations (Japonica rice) and meta‐analysis

Rice is highly susceptible to drought and cold. The goal of this study was to identify the QTLs affecting the rice heading date (HD), leaf area (LA) and chlorophyll content (CC) under cold and drought stress. A total of twenty‐nine and thirty‐eight additive QTLs were detected from two crosses of ‘Dongnong422’/‘Kongyu131’ and ‘Xiaobaijingzi’/‘Kongyu131’, respectively. qHD1‐7‐1, qHD1‐7‐2, qHD1‐2‐1, qLA1‐7‐1, qLA1‐6‐3 and qCC1‐7‐1 show adaptive effects under cold treatment, while qHD2‐2‐3, qHD2‐2‐2, qLA2‐7‐3 and qCC2‐5‐1 were important for explaining the genetic mechanism during drought tolerance. Additionally, nine and five additive × environment interaction QTLs were detected for two RILs, respectively. RIL26 and RIL73 were two lines that are associated with cold and drought for HD. 339 QTLs related to HD, CC and LA of rice from database and our research were projected onto the genetic map. Nine cloned genes and nineteen homologous candidate genes related to HD, CC, cold tolerance and drought tolerance were mapped by meta‐analysis. These results lay the foundation for the fine mapping of QTLs related to HD, LA and CC for marker‐assisted selection.     

Phenological development, leaf emergence, tillering and leaf area index, and duration of spring wheat across Europe in response to CO2 and ozone

Phenological development, leaf emergence, tillering and leaf area index (LAI), and duration (LAD) of spring wheat cv. Minaret, grown in open-top chambers at different sites throughout Europe for up to 3 years at each site, were investigated in response to elevated CO₂ (ambient CO₂×2) and ozone (ambient ozone ×1.5) concentrations.

Phenological development varied among experiments and was partly explained by differences in temperature among sites and years. There was a weak positive relationship between the thermal rate of development and the mean daylength for the period from emergence to anthesis. Main stems produced on average 7.7 leaves with little variation among experiments. Variation was higher for the thermal rate of leaf emergence, which was partly explained by differences in the rate of change of daylength at plant emergence among seasons. Phenological development, rate of leaf emergence and final leaf number were not affected by CO₂ and ozone exposure. Responses of tillering and LAI to CO₂ and ozone exposure were significant only in some experiments. However, the direction of responses was consistent for most experiments. The number of tillers and ears per plant, respectively, was increased as a result of CO₂ enrichment by about 13% at the beginning of stem elongation (DC31), at anthesis and at maturity. Exposure to ozone had no effect on tillering. LAI was increased as a result of CO₂ elevation by about 11% at DC31 and by about 14% at anthesis. Ozone exposure reduced LAI at anthesis by about 9%. No such effect was observed at DC31. There were very few interactive effects of CO₂ and ozone on tillering and LAI. Variations in tillering and LAI, and their responses to CO₂ and ozone exposure, were partly explained by single linear relationships considering differences in plant density, tiller density and the duration of developmental phases among experiments. Consideration of temperature and incident photosynthetically active radiation in this analysis did not reduce the unexplained variation. There was a negative effect of ozone exposure on leaf area duration at most sites. Direct effects of elevated CO₂ concentration on leaf senescence, both positive and negative, were observed in some experiments. There was evidence in several experiments that elevated CO₂ concentration ameliorated the negative effect of ozone on leaf area duration. It was concluded from these results that an analysis of the interactive effects of climate, CO₂ and ozone on canopy development requires reference to the physiological processes involved.     

不同栽培条件下大豆主要叶部性状与产量关系的研究

为探讨不同栽培条件下大豆主要叶部性状与产量的关系,以垦农4号大豆为试验材料,设置5个不同的处理,分别测定了在5个不同生育时期的叶片干重、叶面积指数和叶绿素含量3项主要叶部性状指标。试验结果表明：单位土地面积上的3种主要叶部性状均与产量呈正相关。各处理不同生育时期群体的中部、中上部节位的叶干重与产量的相关性达到显著或极显著水平;R1期与R5期的叶面积指数与产量达显著正相关,R6期叶面积指数和全生育期的平均叶面积指数与产量达极显著正相关;在R5期,单位土地面积上的叶绿素a、叶绿素b和叶绿素(a+b)的含量与产量达到了显著正相关。     

A RVI/LAI-reference curve to detect N stress and guide N fertigation using combined information from spectral reflectance and leaf area measurements in potato

More user-friendly methods are needed to detect crop N status/stress and guide the timing of in-season N application. In the current study, a reference curve method of detecting N stress was proposed to remedy practical problems of methods that require leaf sampling or maintaining a N sufficient strip in the field. The reference curve method was derived from the integrated information of ratio vegetation index (RVI) and leaf area index (LAI), which were obtained from field experimental potato crops. Different N treatments received 42 kg N ha⁻¹ at planting and, subsequently, the rest of N was applied during the season. The total N ranged from 0 to180 kg N ha⁻¹. RVI and LAI from the economically optimum 180 kg N ha⁻¹ treatments were used to derive the reference curve. RVI and LAI from 180 kg N ha⁻¹ treatment had a high (R² = 0.97) correlation and were best fitted with a 2nd order polynomial function, which was independent of season. The treatments where N fertigation was stopped before reaching 180 kg N ha⁻¹ started to deviate from the 95% confidence interval of the reference curve about 10 days after N-fertigation was stopped. This corresponded to 10–20 kg ha⁻¹ difference in total plant N uptake between reference and the N deprived treatments, implying that a deviation from the reference curve occurred for small N deficits. Besides, running crop simulation model to alert for impendent N stress closely corresponded to the reference curve and was recommended as a second management tool. Therefore two tools are hereby made available to guide supplementary N-fertilization. These will be helpful in regional potato production for diagnosis of N status, and allow discrimination between situations of sub-optimal and optimal N supply.     

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.     

Relationships between leaf morpho‐anatomy,water status and cell membrane stability in leaves of wheat seedlings subjected to severe soil drought

The impact of the genotype‐specific leaf morphological and anatomical characteristics on the ability of wheat plants to preserve leaf water balance and cell membranes stability under drought stress was investigated. Seedlings of six modern semi‐dwarf (carriers of Rht, Reduced height genes) and six old tall bread wheat varieties were subjected to soil drought by withholding watering for 6 days. Morpho‐anatomical traits (leaf area, perimeter, thickness, stomata and trichome density) of daily watered (control) plants were characterized by light microscopy, scanning and image analyses. The leaf water status in both control and stressed plants was determined by measuring the relative water content (RWC). The leaf cell membranes stability in stressed plants was estimated by conductometric determination of the membranes injury index. On average, the modern semi‐dwarf varieties had less leaf area and leaf perimeter, and less dissection index, a parameter characterizing the leaf shape. Under drought stress, the modern genotypes maintained better water balance evidenced by significantly higher leaf RWC and better‐preserved the cell membranes stability supported by significantly lower Injury index. The correlations between morpho‐anatomical traits in control plants and drought tolerance‐related traits showed that the higher the leaf dissection index (i.e. more oblong leaves), the greater the water loss and the leaf membrane damages after desiccation were. The effect of shape of the evaporating surface on the water loss was modelled using wet filter paper. Similar to plant leaves, the evaporation and, respectively, water loss from paper pieces of more oblong shape (i.e. higher dissection index) was more intensive. The elucidation of the impact of the leaf shape on transpiration might contribute to better understanding of the mechanisms used by plants to maintain water reserves during drought stress and could be a basis for developing of simple and fast screening methods aiding the selection of drought tolerant genotypes.     

水分和CO2浓度对冬小麦气孔特征、气体交换参数和生物量的影响

利用可精准控制CO₂浓度([CO₂])的大型人工气候室, 研究了水分亏缺和[CO₂]升高对冬小麦气孔特征、气体交换参数及生物量的影响。结果表明, 水分亏缺导致冬小麦气孔开度减小和气孔空间分布的规则程度降低, 提高[CO₂]能够减缓水分亏缺时气孔开度和气孔分布规则程度的下降幅度。与充分灌溉相比, 不同水分亏缺条件下冬小麦的净光合速率、气孔导度和蒸腾速率均显著降低(P<0.05), [CO₂]仅可缓解轻度亏水对气体交换过程的影响, 该缓解能力随水分亏缺程度的加剧而降低。水分亏缺降低冬小麦生物量, 但[CO₂]升高对水分亏缺时生物量产生的影响不显著(P>0.05)。水分亏缺条件下, 冬小麦通过调整气孔开度和气孔空间分布格局改变叶片的气体交换效率, [CO₂]升高对冬小麦产生的“施肥效应”受土壤水分条件的限制。     

Nitrogen deficiency effects on plant growth, leaf photosynthesis, and hyperspectral reflectance properties of sorghum

An experiment was conducted under outdoor pot-culture conditions to determine effects of nitrogen (N) deficiency on sorghum growth, physiology, and leaf hyperspectral reflectance properties. Sorghum (cv. DK 44C) was seeded in 360 twelve-litre pots filled with fine sand. All pots were irrigated with half-strength Hoagland's nutrient solution from emergence to 25 days after sowing (DAS). Thereafter, pots were separated into three identical groups and the following treatments were initiated: (1) the control (100% N) continued receiving the half-strength nutrient solution; (2) reduced N to 20% of the control (20% N); and (3) withheld N from the solution (0% N). Photosynthetic rate (Pn), chlorophyll (Chl) and N concentrations, and hyperspectral reflectance of the uppermost, fully expanded leaves were determined at 3- to 4-day-interval from 21 to 58 DAS during the N treatments. Plants were harvested 58 DAS to determine effects of N deficiency on leaf area (LA), biomass accumulation, and partitioning. Nitrogen deficiency significantly reduced LA, leaf Chl content and Pn, resulting in lower biomass production. Decreased leaf Pn due to N deficiency was mainly associated with lower stomatal conductance rather than carboxylation capacity of leaf chemistry. Among plant components of dry weights, leaf dry weight had the greatest and root dry weight had the smallest decrease under N deficiency. Nitrogen-deficit stress mainly increased leaf reflectance at 555 (R₅₅₅) and 715 nm (R₇₁₅) and caused a red-edge shift to shorter wavelength. Leaf N and Chl concentrations were linearly correlated with not only the reflectance ratios of R₄₀₅/R₇₁₅ (r² = 0.68^***) and R₁₀₇₅/R₇₃₅ (r² = 0.64^***), respectively, but also the first derivatives of the reflectance (dR/dλ) in red edge centered 730 or 740 nm (r² = 0.73–0.82^***). These specific reflectance ratios or dR/dλ may be used for rapid and non-destructive estimation of sorghum leaf Chl and plant N status.     

Inheritance of net photosynthesis and transpiration efficiency in spring wheat, Triticum aestivum L., under drought

The inheritance of net photosynthesis and transpiration effciency in spring wheat under drought were studied in two years in order to determine their heritability. The parents, F₁ and segregating generationsf (F₁, BC₁, BC₁) of four crosses between each of two drought-resistant and two drought-susceptible genotypes were evaluated under drought in pots under glasshouse conditions. Measurements of gas exchange were made using a portable gas-analysis system. Generation means and variance component analyses of the data suggested that these traits are simply inherited and controlled mainly by additive genetic variation. Narrow-sense heritability estimates varied between crosses from 61% to 84% for net photosynthesis and from 88% to 89% for transpiration effciency.     

基于APSIM模型模拟水氮调控对旱地春小麦(Triticum aestivum)叶面积的影响

本研究针对水氮调控对旱地春小麦(‘定西42号’)叶面积的影响,采用大田试验数据与农业生产系统模型(agricultural production system simulator, APSIM)的结合,分别设定不同降水和施氮梯度对叶面积的变化趋势进行研究,试验获取2015-2017年定西田间试验不同水氮肥施入的试验数据,并对模型予以检验。APSIM模型对叶面积模拟精度较高,决定系数(R2=0.96)、归一化均方根误差(NRMSE=27.37%)、模型一致性指标(D=0.91)。结果表明:(1)随施氮量的增加,叶面积指数呈现先增后减的趋势;(2)随降水量的增加,叶面积整体呈现单一增长趋势;(3)水氮耦合作用中,降水量在自然降水基础上增加20%,施氮量为157.5 kg/hm2时,叶面积指数最高达2.766。本研究为田间试验水氮肥的施入量提供科学依据,为旱地春小麦增产提供了理论参考。