早稻全生育期气温、水温、泥温特征及避灾应用

采用农田小气候与实景观测系统,辅以人工观测,以获取早稻各发育期气温、水温、泥温特点,探讨水分干预避灾措施的效果。试验表明：全生育期以水温积温最高,气温积温最低。营养生长期日平均气温落后于水温、泥温,生殖生长期气温、水温、泥温日均值均比营养生长期提高4℃左右并非常接近。叶面积指数较小或衰减时,受太阳辐射影响,午间水温常常超过气温值。水温维持较高的时间约9~ 10 h,是理想的调温目标介质。高温逼熟时采用活水灌溉3天,可拉低水稻冠层上方最高气温2.5℃、日均气温低1.0℃。且稻米粗脂肪含量、直链淀粉含量较高,垩白度较低;结实率提高,千粒重比高温逼熟对照要高6.65%。结果认为：叶面积指数与水温呈反相关特点,高温逼熟时、叶面积衰减时对应高水温、泥温。水分干预调温对产量和品质要素有确定改善,并以活水灌溉2~3天以上的控温效果较佳。     

紫外线(UV-B)照射对水稻产量及稻米蛋白质含量的影响

以抗紫外线UV-B的日本粳稻品种Sasanishiki为材料,1999年和2000年在大田条件下,探讨了不同生育时期的UV-B处理对水稻产量、糙米的大小及蛋白质含量的影响.结果表明,营养生长期(移栽至幼穗分化)、生殖生长期(幼穗分化至抽穗)及抽穗成熟期的UV-B处理对Sasanishiki的产量及其构成因素的影响不显著;生殖生长期(幼穗分化至抽穗)与     

Effect of Planting Date and Thermal Energy Intensity on Rate of Phosphorus and Potassium Accumulation by Maize (Zea mays L.)1

The effect of planting date and thermal energy intensity (TEI) on the rate of phosphorus (P) and potassium (K) accumulation by maize from a Hamerly clay loam soil (Aerie Calciaquoll) was examined with and without supplemental irrigation. Soil- and air-TEI expressed as growing degree days per day (GDD d^?1) were determined from hourly temperature measurements taken within each plot. Net K accumulation occurred during the vegetative growth stage, reached maximal rates of about 62.2 to 91.4 mg plant^?1 day^?1, and attained maximal accumulations ranging from about 1.15 to 2.3 g plant^?1. Accumulation of P occurred during vegetative and reproductive growth stages, reached maximal rates of about 4.6 to 10.3 mg and 6.5 to 12.1 mg plant^?1 day^?1, respectively and maximal accumulations of 0.175 to 0.27 g and 0.11 to 0.26 g plant^?1, respectively. During vegetative growth, K and nitrogen (N) accumulation characteristics were closely correlated with about 2 moles of N accumulated per mole of K. Maximal accumulation of K (and N) consistently preceded that of P by about 5.2 to 8.3 days and that of the plant dry weight by about 15.9 to 20.5 days during the vegetative growth stage. Time required to reach maximal accumulation during the reproductive growth stage, t_r followed the order N < P < dry weight for early plantings and followed the order N < P < dry weight for delayed plantings. Time coefficients for K and P accumulation were correlated closely with soil-TEI, but models of each coefficient relied on unique combinations of TEI. Time coefficients for dry matter accumulation were apparently unrelated to soil- or air-TEI.     

Shading,Defoliation and Light Enrichment Effects on Chickpea in Northern Latitudes

Chickpea (Cicer arietinum L.) has an indeterminate growth nature, and the plant canopy with an improved light environment during critical growth stages may increase biomass (BM) production and improve crop yield. This study examined (i) the effects of shading, light enrichment and defoliation applied at various growth stages on BM and seed yield of chickpea in northern latitudes; and (ii) the difference between cultivars with fern‐ vs. unfoliate‐leaf type in responding to the altered canopy light environments. Field studies were conducted at Saskatoon and Swift Current, Saskatchewan in 2004 and 2005. Different light environments were created by 50 % defoliation at vegetative growth and at first flower, 50 % shading from vegetative growth to first flower, and two light enrichment treatments initiated at the first flower and pod formation stages. The 50 % shade treatment prior to flowering significantly decreased harvest index (HI) and seed yield. Light enrichments increased seed yield only one of three location‐years (the fourth site excluded because of disease damage). Defoliation at vegetative growth or first flower had a marginal effect on seed yield, largely as a result of the regrowth of vegetative tissues compensating for the lost plant tissues. The cultivar CDC Yuma (fern‐leaf type) exhibited consistently greater maximum light interception (LI), cumulative intercepted radiation, HI and seed yield than the cultivar Sanford (unifoliate‐leaf type) across all location‐years. Selective use of chickpea cultivars with improved morphological traits such as fern‐leaf type will likely improve LI and increase crop yield for chickpea in northern latitudes. Moreover, optimized crop management practices should be adopted to ensure that chickpea be grown under conditions with minimum shading before flowering and optimum light environment within the canopy especially during reproductive growth period.     

The Interaction of Sowing Date and Water Availability in Determining Plant Architecture, Fruiting Pattern and Yield Components of Soybean (Glycine max L. Merr.)

A 2-year trial has been carried out in northern Italy on soybean (cv. Hodgson) grown in lysimeters, comparing three soil water regimes (well-watered conditions and water stress during vegetative and reproductive stages) at two sowing dates. Plant evapotranspiration and water uptake depth were calculated from volumes of water independently supplied to eight lysimeter layers; at harvest, plant architecture, yield components and fruit distribution along the main stem and lateral branches were evaluated.
Although water stress intensity was not severe, crop evapotranspiration and water uptake depth were severely restricted by water shortage. Both low water-availability and late sowing significantly modified the architecture of plants, decreasing total height, number and length of internodes and lateral branches. Seed allocation along the stem was shifted downwards both by delaying the sowing date and by reducing the water supply; the component most responsible for yield decrease was the number of pods per plant, while unit seed weight was only slightly affected by water stress. Grain yield reduction was higher when water availability was inadequate during the reproductive phase in the early-sown crop and during the vegetative stage in the late-sown crop. This suggests that the intensity of the water shortage, plant phenological stage of stress application, as well as the date of stress application within the growing season determine the yield response of soybean.     

Modulation of photosynthate supply by CO2 elevation affects the post‐head‐emergence frost‐induced grain yield loss in wheat

Post‐head‐emergence frost (PHEF) has a detrimental impact on grain yield of wheat, and an enhanced photosynthate supply could alleviate the negative impact. However, modulation of photosynthate availability at different growth stages may exert different effects on the plant physiology and grain yield. The objective of this study was to investigate the roles of the enhanced photosynthate supply by growing the plants at elevated [CO₂] (800 ppm) during different growth stages on yield performance of wheat exposed to PHEF. The results showed that the PHEF caused a high grain yield loss in wheat, and an increase in photosynthate supply during the reproductive growth stage mitigated the negative impact, whereas that at vegetative growth stage exacerbated the negative impact of PHEF. The opposite effects exerted by the enhanced photosynthate supply at vegetative stage versus at reproductive stage on yield performance could be associated with its distinguished roles in influencing plant physiology at the two growth stages. The positive effect of the increased photosynthate supply at reproductive stage was due to an improved grain filling and regeneration of effective tillers upon recovery from frost, whereas the negative effects of the enhanced photosynthate supply at vegetative growth stage were primarily due to an accelerated early vegetative growth that increased the sensibility of the plants to PHEF.     

The Relationship Between Sugar-Nitrogen Ratio and Reproductive Organs Abscission in Faba Bean (Vicia Faba L.)

The changes of soluble sugar and total nitrogen content of vegetative organs in faba bean, sugar-nitrogen ratio, abscission of reproductive organs and the relationship between sugar-nitrogen ratio and abscission probability were studied using the faba bean cultivar Xichang Dabai . Plants were field grown in 1986, 1988 and 1990. The lands were separated into high yield land, middling yield land and low yield land according to grain yield at maturing stage. The soluble sugar content in vegetative organs (leaf + stem) was greatest from branching to floral initiation stages and pod-set to filling grain stages, and distinctly decreased at the onset of bloom and maturing stages. The total N content was greatest at branching stage, and gradually decreased with growth. In general, the sugar and total N contents in high yield lands were greatest, followed by that in middling yield and low yield lands. The sugar-nitrogen ratio varied depending on the soluble sugar content.
Average yield on high yield lands, middling yield land and low yield land across 3 years were 5048.77 kg/ha, 3744.01 kg/ha and 2378.22 kg/ha, respectively. The total reproductive organs abscission exceeded 90 % of total flower buds. Abscission probability averaged across 3 yield lands and 3 years were 21.6 %, 84.0 % and 32.8 % in flower buds, flowers, and pods, respectively. Node 7–12 of canopy produced more flowers, and fewer flowers and pods were produced in the upper and lower regions. Photosynthate supply has been implicated in control of abscission. Faba bean reproductive organs abscission probability increased with the sugar-nitrogen ratio of vegetative organs decreasing. It seemed that the soluble sugar content influenced significantly the shedding rate during flowering and pod-growing stages.     

Aerial canopy temperature differences between fast‐ and slow‐wilting soya bean genotypes

Drought stress limits crop growth and yield in soya bean (Glycine max [L.] Merr.), but there are relatively few tools available to assess the ability of different genotypes to tolerate drought. Aerial infrared image analysis was evaluated as a potential tool for identifying drought tolerance in soya bean. Drought effects were evaluated from late vegetative to mid‐reproductive stages of soya bean development in an experiment with ten genotypes including five slow‐ and five fast‐wilting genotypes that were from a population derived from Benning×PI416937. There were two deficit irrigation levels for 2 years and one deficit irrigation level for the third year along with a fully irrigated control level. When the canopy was completely closed, relative canopy temperature was determined using an infrared camera taken from an aerial platform 50–75 m above the experiment. As water availability decreased, the relative canopy temperature generally increased. Moreover, slow‐wilting soya bean genotypes generally had lower canopy temperature compared to fast‐wilting genotypes, and grain yield was generally positively associated with cool canopy temperatures. The results indicate that the determination of canopy temperature is a promising tool for rapid characterization of drought‐related traits in soya bean.     

Using Digital Image Analysis to Describe Canopies of Winter Oilseed Rape (Brassica napus L.) during Vegetative Developmental Stages

In our experiment digital image processing is used to predict characteristics in a winter oilseed rape canopy. A large series of images was taken in 2002–2003 in close intervals from a measuring area of 1 m². These images were automatically evaluated by a self‐written computer program analysing the red/green/blue colour channels of each pixel. The number of determined green pixels was then related to the total pixel count of the image. Image evaluation helped to determine canopy structure by digital image analysis subjected to several applications, i.e. soil coverage, leaf area index (LAI), dynamics of plant number during vegetative developmental stages including entire winter season. Furthermore, number of plants per m² and position of each plant were determined by image analysis. Results show that all parameters are dynamic during the vegetative developmental stages (germination–beginning of flowering) mainly depending on temperature. During the vegetative developmental stages number of plants varied. Emergence lasted 30 days resulting in large differences in growth and development of individual plants. During winter number of plants decreased due to longer phases of frost. Plant growth indicated by dynamics of LAI alternated with phases of cessation due to low temperatures above zero or frost. Reductions in soil coverage and LAI clearly started at daily mean temperatures below 5 °C. After the analysis, differences in LAI as well as changes in number of plants during the early phase crop development can serve (i) as input parameters to growth models, (ii) to improve canopy reflectance measurements by separating spectral signatures of soil and canopy and (iii) to determine and explain heterogeneities within the canopy.     

Drip Irrigation Frequency: The Effects and Their Interaction with Nitrogen Fertilization on Maize Growth and Nitrogen Use Efficiency under Arid Conditions

Differences in soil moisture and wetting pattern under different irrigation frequencies mean that vegetative growth and nitrogen use efficiency in maize can differ even when the same total amount of irrigated water is applied under different frequency regimes. The goal of this study was to evaluate the effects of drip irrigation frequency and its interaction with nitrogen fertilization on vegetative growth and nitrogen use efficiency of a maize crop at different growth stages and on grain quality at maturity stage in a sandy soil. The experiment was conducted for 2 years (2005 and 2006) using a randomized complete block split–split plot design with four irrigation frequencies (once every 2, 3, 4 and 5 days), two nitrogen levels (190 and 380 kg N ha^?1) and two maize hybrids (three‐way cross 310 and single cross 10) as the main‐plot, split‐plot and split–split plot variables, respectively. Irrigation water, totalling 524 mm ha^?1, applied for each irrigation frequency was divided into 28, 21, 17 and 14 doses for the F2, F3, F4 and F5 treatments, respectively. Results indicated that vegetative growth, crop growth and nitrogen efficiency parameters at the 10‐leaf and tasseling growth stages increased with increasing drip irrigation frequency, whereas grain protein content decreased. Although the values of the vegetative growth and crop growth parameters increased with increasing nitrogen levels, significant decreases in nitrogen efficiency parameters were also observed indicating the need for further optimization with a reduced nitrogen application rate. Significant interaction effects between irrigation frequency and nitrogen levels were detected for all parameters measured. In most cases, the parameters were not significantly different between the two nitrogen levels at an irrigation frequency of once every 5 days, but did differ significantly at irrigation frequencies of once every 2, 3 or 4 days. The relationship between the nitrogen use efficiency parameters and retained available soil water content at the 10‐leaf and tasseling growth stages was best represented by a second order polynomial equation with an R² ranging from 0.73 to 0.98. Based on our findings, an irrigation frequency of once every 2 and 3 days is recommended to enhance growth and nitrogen use efficiency of drip‐irrigated maize in sandy soil in Egypt.     

Lint Yield Compensatory Response to Main Stem Node Removal in Upland Cotton (Gossypium hirsutum)

Hail storm damage to the cotton (Gossypium hirsutum L.) plants can destroy vegetative and reproductive structures, modify canopy architecture and impact lint yield. Field studies were conducted at University of Arizona Maricopa Agricultural Center in 2011, 2012 and 2013 to examine cotton plant architecture changes and compensatory growth in response to removal treatments of uppermost nodes on main stem (terminal bud removal, 2 node removal and 4 node removal) as simulation of hail damage at the node 2, 4, 8, 12, 16 and 24 growth stages. Main stem node removal caused significant decrease in leaf area and biomass, especially at early growth stages. However, significant lint yield reduction only occurred by removing 2 nodes at the node 4 stage and removing 4 nodes at the node 8 stage in 2011, removing terminal bud at the node 12 stage in 2012 and removing terminal bud, 2 nodes and 4 nodes at the node 8 stage in 2013. The lint yield reduction did not exceed 13 % in all three growing seasons. Yield loss due to main stem node removal was mainly compensated by increased boll number on the vegetative branches at early growth stages and on fruiting branches at late growth stages. Yield compensation from vegetative branches increased with number of main stem nodes removed. This study suggests that the cotton crop has a strong compensatory ability to plant structure damage due to its indeterminate growth and longer growing season in the region.     

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.     

The Effect of Nitrogen and Phosphorus Fertilization on the Nitrogen Absorption by Sunflowers

Little is known about the effect of fertilization on the N uptake of sunflowers. A 4² factorial trial with 0, 60, 120 and 180 kg N ha⁻¹ and 0, 15, 30 and 45 kg P ha⁻¹ was conducted over three years. The N content and concentration of leaves, stems and capitula were determined at three growth stages. High N levels increased the N content and concentration of all plant parts at all growth stages sharply. High P levels increased the N content of all plant components through better growth. P has an inconsistent effect on N concentration but tended to decrease it. After flowering the crop assimilated 20 to 25 % of the total N. This implies that N applied can still be applied and utilized by the crop at a late stage. This should be substantiated by further research.     

不同光温条件谷子光温互作模式研究及SiCCT基因表达分析

光周期和温度是影响作物生长发育、生态适应性和产量的2个重要环境因素,揭示光温互作对作物生长发育的效应及其分子机制对育种实践和理论研究具有重要意义。本研究设置长日照高温、长日照低温、短日照高温、短日照低温4个光温处理,调查‘黄毛谷’抽穗期、株高、叶片数和穗长。结果表明,光周期对谷子的发育起关键作用,温度的改变不影响长日照比短日照延迟谷子生殖生长的效应,温度的作用随光周期的不同而异,短日照条件下,高温缩短谷子营养生长期而低温延长营养生长期,长日照条件下则相反;对谷子生殖生长的促迚作用是短日照高温短日照低温长日照低温长日照高温。利用RT-PCR技术从‘黄毛谷’叶片兊隆了一个CCT结构域基因(SiCCT),该基因编码286个氨基酸,属于CMF亚家族成员,基于CCT域基因氨基酸序列的系统迚化分析,谷子与高粱、玉米亲缘关系较近。实时荧光定量PCR分析发现, SiCCT基因在‘黄毛谷’叶片中高表达,其次为幼穗和叶鞘;长日照、短日照处理SiCCT基因均表现24h昼夜节律性特点,短日照七叶期表达水平最高,八叶期(抽穗)及穗后表达迅速降低,长日照七叶至十叶期‘黄毛谷’处于营养生长期,SiCCT基因维持较高表达水平;无论高温低温,长日照条件下SiCCT基因在各叶期表达量整体高于短日照处理,长日照条件下低温处理SiCCT基因的相对表达量明显低于高温处理, SiCCT基因的总体表达量与‘黄毛谷’营养生长期存在正相关。总之SiCCT基因受光周期调控,同时也受温度调控,因而推测SiCCT基因参与了光周期途径和感温性途径,并通过二者互作调控谷子营养生长和生殖生长的全过程。     

Identification of Physiological Traits Underlying Cultivar Differences in Drought Tolerance in Rice and Wheat

Rice is used as a model cereal to study drought response at the molecular level, with the goal of applying results to other cereals. To assess the relevance of results from rice to other species, the kinetics of drought development and plant response of tolerant and susceptible tropical rice ( Oryza sativa L.) and subtropical wheat ( Triticum aestivum L.) cultivars were compared under vegetative and reproductive stage drought in pot experiments. Water was withheld during reproductive stage until plant available soil moisture content was 30 % of field capacity (FC) or leaf wilting was observed, and then reapplied. Rice reached 30 % FC 9 days after withholding water and wheat after 13 days. Before rewatering, both species reached leaf water potentials of −12 bars and similarly low transpiration rates. Stress reduced leaf relative water content, leaf elongation and membrane stability. When water stress was imposed during reproductive stage, pollen fertility was most affected in wheat, while panicle exsertion and anther dehiscence were severely affected in rice. When water stress was imposed during vegetative stage, wheat was less affected to vegetative stage drought than rice. The nature of differences between tolerant and susceptible cultivars was similar for the two species. However, the differential growth habitats and growth rate of plants needs to be considered in these kinds of experiments.     

棉花早、中熟品系营养器官碳氮含量变化的差异及与干物质积累的相关性

为探究不同生育期棉花品种的干物质积累及产量与其碳氮代谢相关性,采用生育期不同的2个陆地棉近等基因系早熟系4003-10和中熟系4003-6,测定生殖生长阶段蕾期至吐絮期根、茎、叶的全氮、氨基酸、非结构性碳水化合物（己糖、蔗糖和淀粉）含量及棉株各部位生物量,比较2个品系的差异,并分析营养器官含氮量与生物量的相关性。结果表明,4003-6比4003-10具有更大的铃重、衣分及皮棉产量。生殖生长阶段4003-6叶片比4003-10具有较高的全氮、氨基酸、非结构性总碳、淀粉含量及碳氮比,表明前者叶片具有较强的碳氮代谢活性和碳水化合物生产能力;4003-6的根系氨基酸水平高于4003-10,且具有更高的氮素吸收效率。在营养器官中,根系含氮量对棉花植株地上部、根系、营养器官和生殖器官的生物量积累影响最大。早熟系4003-10单株根、茎、叶的含氮量与生殖器官生物量的相关系数均高于中熟系4003-6,表明早熟品系的吸氮能力对产量影响更大。     

播期对雨养旱地春玉米生长发育及水分利用的影响

为了解决陕西渭北旱塬地区玉米播种期干旱缺水造成出苗不全、不整齐,导致产量低而不稳的问题,设置6个不同播期,研究对春玉米生长发育、干物质生产、产量形成、水分利用及环境因子的影响。结果表明,随着播期的推迟,玉米的生育期明显缩短,营养生长期、营养生长与生殖生长并进期变化范围为2~19 d,生殖生长阶段则相对稳定,变化范围仅为?3~5 d。在一定的时间范围内,不同播期处理间的单株干物质生产没有明显差异,但由于受播期调整后的土壤含水量变化影响,适宜播期的玉米花后雌穗干物质积累量、籽粒产量及水分利用效率分别较早播和晚播提高4.0%~23.6%、3.9%~24.5%和6.6%~14.5%。早播影响产量的主要因素是播种期土壤含水量低而造成的出苗差,实际收获穗数不足;晚播影响产量的主要因素是生殖生长期后移,有效积温和日照时数减少造成的花后干物质积累减少、千粒重下降。适期播种可以增加田间实际收获穗数,促进雌穗花后干物质积累,提高玉米的水分利用效率。结合该区生态因素,5月4日以前适墒播种是玉米高产的有效避旱播期。研究结果可为该区春玉米抗逆避旱高产栽培提供有效的技术参考。     

Modulation of Brassica napus source–sink physiology through film antitranspirant induced drought tolerance amelioration that is dependent on the stress magnitude

Increase in drought conditions during the oilseed rape (OSR) reproductive phase is predicted to occur more often in the temperate zone, leading to significant yield losses. Crop management solutions such as film antitranspirant (AT) applied at key drought‐sensitive growth stages on both wheat and oilseed rape have recently been shown to alleviate drought‐induced yield losses. However, there is a lack of information regarding potential AT effectiveness to reduce drought damage on OSR plants at different soil moisture regimes. Therefore, two similar experiments were performed in a computer‐controlled glasshouse/phenotyping centre to investigate the physiological responses of OSR to well‐watered (WW), moderate water stress (MWS), water stress (WS) and severe water stress (SWS) conditions. Stress treatments were imposed at the initiation of flowering and treated with an AT or water onto the leaf canopy. Stress limited the gas‐exchange and increased leaf temperature, leaf‐to‐air temperature, bud‐to‐air temperature and ABA concentrations which increased with stress intensity in all tissues analysed. Yield components were significantly reduced by WS and SWS treatments when compared to the WW plants. Application of AT counteracted the detrimental effect of WS and SWS by decreasing water use over the first few days of stress application thus improving relative water content and leaf water‐use efficiency, decreasing ABA accumulation in leaf and all the reproductive organs analysed (buds, flowers and pods) and avoiding bud‐to‐air temperature increases. AT application sustained pod formation and seed production under WS but only seed production under SWS conditions. These data suggest that leaf‐canopy application of AT at key phenological stages under particular magnitudes of soil moisture deficit may sustain OSR reproduction and reduce yield losses.     

Late‐season photosynthetic rate and senescence were associated with grain yield in winter wheat of diverse origins

There is a lack of studies that have investigated grain yield, its components and photosynthesis in late stages of wheat growth, giving us insufficient understanding of how these factors interact to contribute to yield during this period. As a result, three field experiments were carried out examining 20 winter wheat genotypes of diverse origins under irrigated, terminal drought and dryland conditions in the southern Idaho. Our objective was to evaluate the interaction between post‐anthesis physiological traits, especially leaf‐level photosynthetic capacity, senescence and yield components on grain yield in different moisture regimes. Genotype differences were found in leaf‐level photosynthesis and senescence, canopy temperature depression, grain yield and yield components in each water regime. Grain yield was closely associated with traits related to grain numbers. In all three moisture regimes, positive correlations were observed between grain yield and photosynthesis that were dependent on the timing or physiological growth stage of the photosynthetic measurement: highly significant correlations were found in the mid‐ and late grain filling stages, but no correlations at anthesis. Consistent with these findings, flag leaf senescence at the late grain filling stage was negatively correlated with grain yield and photosynthetic rate (under terminal drought and dryland conditions). These findings provided evidence that grain yield was sink‐limited until the final stages of growth, at which time sustained photosynthesis and delayed senescence were critical in filling grain. Because the trends were consistent in moisture sufficient and deficient conditions, the results suggest that late‐season photosynthesis and delayed leaf senescence are driven by the size of the reproductive carbon sink, which was largely governed by factors affecting grain numbers.     

Using Hemispherical Radiation Measurements to Predict Weight-Related Growth Traits in Oilseed Rape (Brassica napus L.) and Barley (Hordeum vulgare L.) Canopies

Methods for determining growth traits in the field are mostly work‐intensive and/or often erroneous. Further development of multi‐temporal techniques of growth analyses provided by fast and non‐destructive tools for monitoring canopy properties may result in a substantial gain for practical use. Among them, the LAI‐2000 Canopy Analyzer can be used to determine the canopy area index (CAI) resulting from radiation measurements. In plant breeding, single‐date measurements were usually made across a wide number of genoptypes. In contrast, multi‐temporal information on canopy status is needed in agronomy. In our study, data of the CAI based on hemispherical radiation measurements with the LAI‐2000 were used to estimate developmental courses of weight‐related growth traits. For this purpose, seasonal courses of shoot fresh matter, shoot dry matter, shoot N and water content and CAI of winter oilseed rape (Brassica napus L.) and spring barley (Hordeum vulgare L.) were investigated simultaneously in field experiments from 2002 to 2006 in northern Germany with and without nitrogen (N) fertilization. Courses of 2003 and 2004 were used to calculate relationships between CAI and growth traits. Results show that each of the weight‐related growth trait is related to the CAI. In this mechanistic approach relationships were found gathered across 2 years, two N‐treatments and several growth stages being unaffected by N‐fertilization, cultivar and experimental year. These relationships were verified using independent data sets of the years 2005 (winter oilseed rape and spring barley) and 2006 (winter oilseed rape). The results of the current study show that the use of LAI‐2000 and its rapid and non‐destructive determination of weight‐related growth traits over the entire growth period will substantially improve the determination of weight‐related growth traits in agriculture.