Canola genotypes differ in potassium efficiency during vegetative growth

There is no knowledge about the differential capacity of canola genotypes to take up potassium (K) and produce dry matter under conditions of low soil K availability. Hence, 84 canola genotypes were screened for K efficiency in the glasshouse. Plants were grown in sealed pots containing K-responsive, sandy soil without or with K added. Twelve genotypes were selected for advanced screening in the glasshouse in a different K-responsive soil. Genotypes with a mean K efficiency ratio (the ratio of shoot dry weight at deficient and adequate K supply) greater than one standard error above or below the median genotype value were classified as K-efficient or K-inefficient, respectively. There were significant differences between genotypes in the K efficiency ratio in both screening experiments, indicating that genotypes responded differently to K availability. In the initial screening experiment, 19 genotypes were rated as K-efficient and nine genotypes rated as K-inefficient based on the K efficiency ratio. In the advanced screening experiment with 12 genotypes, three genotypes were rated as K-efficient and two as K-inefficient. Genotypes Wesbarker and Rainbow were K-efficient and Genkai K-inefficient in both experiments. Correlation of the K efficiency ratio with (i) shoot K content in the initial and advanced screening and (ii) shoot K concentration in the advanced screening, indicates that the observed differences in K efficiency were due to genotypic differences in both the uptake and the utilization of K. K-efficient genotypes have a potential to improve canola yields on soils with low K availability.     

Disturbed Mendelian segregations at isozyme marker loci in early backcrosses of Lolium multiflorum × Festuca pratensis hybrids to L. multiflorum

Summary The segregation of interspecific recombinant Festuca pratensis (Fp) alleles, introgressed into the germolasm of Lolium multiflorum (Lm), at four loci (PGI/2, AcP/2, GOT/3 and BAP) is described. Heterozygous (Lm/Fp) plants were backcrossed to L. multiflorum (2n=2×=14) and subsequent BC2 Lm/Fp sibling genotypes intercrossed.In crosses between BC1 heterozygous plants (Lm/Fp) used as males and L. multiflorum, there was a reduced transmission of the F. pratensis (Donor Parent) derived alleles in the populations with PGI/2 and AcP/2 marker loci compared to the reciprocal cross but the reduction was not significantly different in those with GOT/3 and BAP markers.Two PGI/2 marked BC2 half-sib families in particular exhibited a more extreme deficiency of Fp/Fp progeny plants than anticipated from the BC2 segregations indicating possible linkage to zygotic lethals. Deficiencies of F. pratensis alleles were, in most cases, less marked in BC2 half-sib families indicating that a further round of recombination had reduced the size of the introgressed chromosome segment or that deleterious linkages had been broken. A tendency towards heterozygote advantage was found in one BAP marked halfsib family.The significance for forage grass breeding of reduced transmission rates of Donor Parent alleles in early back-cross generations especially through the male gametes is discussed.     

Parental influences on gas exchange rates in grain sorghum

Summary Significant genetic variation in CO₂ assimilation rate (A), stomatal conductance (g), and A: g ratio, which are indicators of intrinsic differences in productivity and water use efficiency (WUE), has been demonstrated in grain sorghum [Sorghum bicolor (L.) Moench] hybrids. The primary objective was to determine the possible parental influence on the components of the A: g relationship in sorghum hybrids across a range of water supplies. Thirty F₁ hybrids resulting from a 6 × 6 diallel crossing pattern constituted the genetic material. Field experiments were conducted using four water supply treatments established through differential irrigation. Carbon assimilation rate (A), g, and leaf water potential (_w) of individual leaves were monitored every 15 to 20 days. Genetic analyses revealed that general- and specific-combining ability effects were evident for A. However, reciprocal and maternal effects were more important in governing the A-g and A-_w relationships. Since the maternal effects were the major determinants in causing reciprocal differences, A can be improved by selecting specific female parents to exploit cytoplasmic factors or physiological characteristics of this parent. Substantial genetic variation in the A-g relationship resulting from significant genetic control of A offers the opportunity to impose selection for high A and stability of A, which might directly contribute to whole plant WUE and productivity in grain sorghum.Abbreviations A carbon assimilation rate - g stomatal conductance to water vapor - GCA General Combining Ability - SCA Specific Combining Ability - WUE Water Use Efficiency     

Effects of climate on different potato genotypes 1. Radiation interception, total and tuber dry matter production

In 11 field trials in Rwanda, Tunisia and The Netherlands, the total dry matter production and tuber dry matter production of eight potato cultivars were analysed in terms of radiation interception and radiation use efficiency. The variation in length of the growing season was the most important factor explaining the differences in both total and tuber dry matter production among cultivars and sites. Radiation interception was the most important factor because the radiation-use efficiency was negatively correlated with radiation intensity and the variation in harvest index was of minor importance. Variation in length of the growing season among sites was related to daylength and temperature, in that shorter days at emergence and higher temperatures throughout the season resulted in a shorter growth cycle. The extent of these effects differed among cultivars, and it was concluded that climatic effects on tuber dry matter production could be attributed to the effects of temperature and daylength on the length of the growth cycle.     

Nitrogen efficiency components of winter cereals

A model to describe the importance of different physiological processes to explain grain yield differences (ΔG_w) between cropping systems (Huggins and Pan, 1993) was modified to evaluate the nitrogen use efficiency of different cereals. The method uses measurements of grain yield (G_w), grain N (N_g), above-ground plant biomass (B), above-ground plant N (N_t), applied fertilizer N (N_f), and post-harvest inorganic soil N in control plots without fertilizer (N_h). The components are N supply (N_s), N uptake efficiency (N_t/N_s), assimilation efficiency (B/N_t), harvest index (G_w/B) and N harvest index (N_g/N_t). For a first verification of the model different winter cereal species, i.e., one genotype of winter wheat, one of winter rye and one of spelt wheat, were compared in a 2-year field experiments at two sites with different soil fertility and climate. The modified nitrogen efficiency component analysis provided a good understanding of yield differences at different levels of applied N and soil fertility. The method could be useful for selection of genotypes with a high N use efficiency in breeding programmes.     

不同水肥条件下旱地小麦水肥利用率研究

探讨了不同水肥条件对旱地小麦产量和水肥利用率的影响。结果表明,不同水肥条件对小麦株高、穗长、穗粒数和千粒重有明显影响;补充灌水和不灌水施肥处理分别比相应对照增产39．2％～142．6％和34．2％～152．3％,同时补充灌水比不灌水各处理增产21．0％～40．2％。不同肥料配比以N1P1处理的肥料利用效率最高,并以适当补灌效果最佳,补充灌水和不灌水每千克N分别增产小麦18．0kg和13．0kg。不同肥料配比处理灌水利用效率分别比对照提高0．17～0．72kg／m^3,并以N1P1最高,为1．16kg／m^3。     

向环境采集能量的WSN中的自适应周期机会路由算法

如何让可以采集能量的节点充分利用环境能量,从而提高整个网络持续高效工作的能力是在能量采集无线传感网中的关键问题。目前的研究主要集中在如何均衡分配可进行能量采集的节点的能量,从而在提高节点寿命的基础上,实现网络寿命延长,但是仍然存在环境能量变化的不确定性导致的风险。笔者提出了自适应周期机会路由算法,首先对节点进行地理分区,再分配优先级,最后进行优化后路由处理。仿真结果表明,该算法能实现对环境能量更加高效的利用,并能有效提升网络的吞吐量和网络效率。     

Modelling Biomass Accumulation and Partitioning in Chickpea (Cicer arietinum L.)

Quantitative information regarding biomass accumulation and partitioning in chickpea (Cicer arietinum L.) is limited or inconclusive. The objective of this study was to obtain baseline values for extinction coefficient (K_S), radiation use efficiency (RUE, g MJ^?1) and biomass partitioning coefficients of chickpea crops grown under well‐watered conditions. The stability of these parameters during the crop life cycle and under different environmental and growth conditions, caused by season and sowing date and density, were also evaluated. Two field experiments, each with three sowing dates and four plant densities, were conducted during 2002–2004. Crop leaf area index, light interception and crop biomass were measured between emergence and maturity. A K_S value of 0.5 was obtained. An average RUE of 1 g MJ^?1 was obtained. Plant density had no effect on RUE, but some effects of temperature were detected. There was no effect of solar radiation or vapour pressure deficit on RUE when RUE values were corrected for the effect of temperature. RUE was constant during the whole crop cycle. A biphasic pattern was found for biomass partitioning between leaves and stems before first‐seed stage. At lower levels of total dry matter, 54 % of biomass produced was allocated to leaves, but at higher levels of total dry matter, i.e. under favourable and prolonged conditions for vegetative growth, this portion decreased to 28 %. During the period from first‐pod to first‐seed, 60 % of biomass produced went to stems, 27 % to pods and 13 % to leaves. During the period from first‐seed to maturity, 83 % of biomass was partitioned to pods. It was concluded that using fixed partitioning coefficients after first‐seed are not as effective as they are before this stage. Environmental conditions (temperature and solar radiation) and plant density did not affect partitioning of biomass.     

小麦品种的抗旱性试验测定

在豫西邙岭旱区和豫西红土丘陵旱区，连续进行了４年小麦品种抗旱性筛选试验，选出了１０个抗旱性强、水分利用效率较高、耗水系数较低的小麦品种。并在豫西进行了大面积示范推广，取得了很好的效果     

微热管阵列平板太阳能集热器中空保温层厚度优化

为分析微热管阵列平板太阳能集热器的热性能,该文建立了集热器的CFD模型,对其进行数值模拟,将模拟结果与试验结果进行对比,验证了模型的可靠性。采用该CFD模型对集热器保温层厚度进行优化,结果表明,当实心保温层导热系数分别为0.02、0.03、0.04、0.05W/(m·K)时,优化的实心保温层厚度分别为4.5、5.0、5.5、5.5cm。合理设计的中空保温层(空气层与实心保温层相结合的保温层形式)集热器能够达到与实心保温层集热器相当的保温隔热效果,同时可使集热器保温层成本及质量降低25%~50%。最后,该文给出了保温层总厚度分别为4、5、6cm时的中空保温层厚度优化结果,为该类集热器保温层的设计提供了理论依据。