Effect of the Herbicide Paraquat on the Decomposition of Wheat Straw

The effect 1,1'-dimethyl-4,4'-bipridinium dichloride (paraquat) has on wheat residue decomposition was investigated in laboratory studies. Field dried straw containing 0.30% nitrogen and 42.9% C was incubated in laboratory bioreactors for 8 weeks. Treatment combinations per gram of straw were control (no paraquat or spreader), 0.26, 2.6, and 26 ng paraquat, 0.7 nl Valent X-77,0.26 ng paraquat plus spreader and 2.6 ng paraquat plus spreader. Decomposition was monitored by CO, production and dry weight changes. Neither paraquat nor its spreader, alone or in combination, were found to effect CO2 production or dry weight Ioss. Paraquat should not increase the rate of wheat straw decomposition at field application rates.     

Temporal Variation of Infiltration Rate in a Vertisol under Lentil–Wheat Rotation

Understanding of the effect of tillage and plant residue incorporation on infiltration rate during plant growth is vital to improve tillage–plant residue management practices, especially in vertisols. These soils may shrink and swell markedly which, in turn, affects their physical properties. From 1992 to 1994, the effect of two tillage practices and two plant residue management treatments on final infiltration rate in a vertisol (very fine, smectitic, thermic, chromic Haploxerert) on a less than 1 % slope was investigated in a lentil–wheat rotation. The experiment consisted of two tillage treatments – moldboard (T1) and chisel (T2) – and two plant residue treatments – grazing after harvest for 1 month, followed by incorporation in August by ploughing (R1), and grazing after harvest for 1 month, followed by incorporation in mid-October (R2). Results indicated that the final infiltration rate of T1 was higher than that of T2 in the lentil season, while in the wheat season it was lower under T1 than under T2. Plant residue incorporation had no significant effect on final infiltration rate. Final infiltration rate in winter was approximately 3 to 4 times higher than in summer; it was significantly lower in the lentil season than in the wheat season.     

Effect of Post-Anthesis Water Stress on Accumulation of Dry Matter, Carbon and Nitrogen and Their Partitioning in Wheat Varieties Differing in Drought Tolerance

In four wheat ( Triticum aestivum L.) cultivars of tall (C306 and Narmada) and dwarf (HD2329 and Kundan) type, post-anthesis water stress affected the dry matter accumulation in plant parts with respect to main shoot controls. HD2329 among the dwarf types and Narmada 112 among the tall types were more adversely affected by stress, with greater reductions in their biomass and grain yield. Of the tolerant types, C306 (tall) showed a marginal reduction while Kundan (dwarf) had no reduction in these parameters as a result of stress. The results also indicated a varietal response to carbon and nitrogen accumulation and their partitioning in the main shoot when subjected to post-anthesis stress. In the susceptible dwarf cultivar HD2329, and in the susceptible tall cultivar Narmada 112, carbon and nitrogen contents were reduced in the grains of stressed main shoots. Of the tolerant cultivars, the dwarf type Kundan was not affected by stress, while the tall type C306 registered an increase in carbon content and its partitioning to grain.     

Studies on Intergenotypic Competition in a Wheat Multiline Using Alternative Row Design

Differences between the isolines in a multiline may result in differences in competitive ability and lead to changes in the frequency of the components after a few cycles of multiplication. Alternative-row design of Hanson et al. (1961) was used to detect and characterize the presence of intergenotypic interactions among eight isolines of a multiline of bread-wheat‘Kalyansona’. The material was grown in 1.5 meter row plots using a unique sequence of arrangement. The observations were recorded with respect to plant height and grain yield per plan:. The results of the analysis showed the components of variance for average competitive ability and specific combination to be highly significant, indicating the existence of intergenotypic interactions. Significant genotypic differences between isolines revealed that the genotype of the recurrent parent had not been fully reconstituted. On the basis of the effect of the border genotype averaged over all the genotypes (Ck.), the genotypes were classified into four groups, viz. a) highly depressive, b) mildly depressive, c) mildly cooperative and d) highly cooperative. Categories c and d were indicated as useful for the synthesis of multilines.     

Physiological Genetics of Salt Tolerance in Wheat (Triticum aestivum L.): Performance of Wheat Varieties, Inbred Lines and Reciprocal F1 Hybrids under Saline Conditions

Four bread wheat cultivars were studied at two salinity levels. Tobari 66 had the lowest uptake of Na⁺ and Cl⁻, and the highest K⁺/Na⁺ ratio; Pato had the highest uptake of these ions and Lyallpur 73 was intermediate. Intervarietal differences were greater at higher salinity, suggesting that they were not caused by variation at the Kna1 locus. There were significant differences between inbred lines for Na⁺, particularly in Blue Silver, suggesting the possibility of selecting genotypes with enhanced tolerance from within existing cultivars. Pato, Tobari 66 and their reciprocal F₁ hybrids were further evaluated at four salinity levels. The hybrids exhibited similar relative grain yield to Tobari, with better Na⁺ and Cl⁻ exclusion and higher K⁺/Na⁺ ratios than Pato. Overall, Tobari had the highest absolute yield under salinity, and the hybrids were closer to Tobari than to Pato. Tiller and grain numbers, 100-grain weight and yield were more affected by salinity than were height, spike length and spikelet number. We conclude that intervarietal variation for salt tolerance in wheat is controlled by genes which could be transferred to sensitive genotypes to improve their tolerance, and that the K⁺/Na⁺ ratio of the youngest leaf could be used to screen for salt tolerance.     

Phosphorus Deficiency Affects the Early Development of Wheat Plants

The effect of phosphorus nutrition on the development of wheat plants, was studied. Phosphorus deficiency increased the duration of the phyllochron when the concentration in shoots was less than 0.8 %. Phosphorus concentration in shoots appeared to be a good indicator of the effect of plant phosphorus status on wheat development.     

亚精胺对小麦幼苗耐冷性的影响

文中对亚精胺(spermidine，Spd)在耐冷性不同的小麦品种中的作用进行了研究。研究发现，耐冷品种周麦16号在冷胁迫处理时，其叶片中的Spd含量明显大于不耐冷的温麦6号。用Spd合成的抑制剂MGBG处理周麦16号，则导致Spd含量下降和耐冷性降低，外源Spd又可逆转MGBG对周麦16号在冷胁迫下的伤害。外源Spd可以明显提高温麦6号的叶片内Spd含量，并相应提高其耐冷性。以上结果表明，冷胁迫下，Spd可以提高小麦幼苗的耐冷性。     

外源激素对冬小麦春化作用的影响

在２５℃的恒温条件政,将冬小麦４１８５的种子用不同浓度的ＫＴ,ＧＡ３和ＺＥＮ水溶液浸种１８h,然后用蒸馏水冲洗放于１０℃的连续光照（１５００lx）培养箱中进行不同程度的春化处理（０－２０d)。之后将幼苗分成两部分,一部分移栽于温室内的花盆,别一部分移栽于网室的微分,分别调查分蘖株率、主茎总叶数、抽穗时间和幼穗分化时间。结果表明,对于春化比较的小麦植株,ＫＴ可以进一步提高其抽穗株率,对于春化不充分的小麦植株,ＫＴ可以代替部分低温使其通过春化阶段;在某种环境条件下,ＧＡ３和ＺＥＮ了能提高春化比较育分的小麦植株的抽穗率;３种激素之间的素作受温度内外环境条件和春化时间的影响很大。     

物理性限制籽粒容积对冬小麦籽粒生长的影响

在温室和大田条件下,用6个冬小麦品种,于籽粒胚乳细胞分化高峰之后,以物理性限制籽粒容积的方法,研究了粒重的增长与籽粒含水率、淀粉合成速率之间的关系。物理性限制处理改变了籽粒的形状,加速了籽粒的脱水过程,影响了淀粉的合成能力,缩短了有效灌浆期,最终降低了粒重,这是物理性限制和生理性抑制共同作用的结果,说明籽粒容     

Effect of Tillage System on Soil Strength and Bulk Density of Vertisols

Improving the soil environment for seedling emergence and plant growth is possible using a good tillage system. From March 1993 until June 1994, the effect of tillage system and plant residue incorporation practices on the bulk density and the soil strength of the surface layer of a vertisol (very fine, smectitic, thermic, chromic Haploxerert), on a less than 1 % slope, was investigated. The two tillage methods were moldboard (T1) and chisel (T2). The two plant residue incorporation dates were in August (R1) and in October (R2). Results indicated that R1 gave significantly higher bulk density than R2, while the different tillage treatments had no significant effect. Soil strength was significantly lower under T1 and R2 than under the other treatments.     

Effect of the Russian Wheat Aphid on the Composition and Synthesis of Water Soluble Proteins in Resistant and Susceptible Wheat

The effect of Russian wheat aphid ( Diuraphis noxia) infestation on polypeptide composition and protein synthesis in the presence or absence of chloramphenicol and cycloheximide were studied in genetically comparable wheat ( Triticum aestvum) resistant (cv. PI 137739/5* Tugela) and susceptible (cv. Tugela) to the aphid. The aim is to gain information of molecular nature on the resistance phenomenon which may promote future breeding programmes. In the absence of feeding aphids polypeptide profiles of the two wheat lines were similar indicating the absence or presence at low levels of a constitutive resistance factor. Aphid infestation induced enhanced expression of certain genes in the resistant wheat only. A 100 kD nuclear encoded polypeptide is strongly induced in the resistant wheat. It is also evident that the synthesis of a 56 kD organel encoded polypeptide is suppressed by the feeding aphids in the susceptible wheat.     

Oxidative Stress and Antioxidants in Wheat Genotypes: Possible Mechanism of Water Stress Tolerance

The role of plant antioxidant systems in water stress tolerance was studied in three contrasting wheat genotypes. Water stress imposed at different stages after anthesis resulted in an increase in lipid peroxidation and a decrease in membrane stability and chlorophyll and carotenoid contents. The antioxidant enzymes ascorbate peroxidase, glutathione reductase and non-specific peroxidase also increased significantly under water stress. Genotype PBW 175, which had highest ascorbate peroxidase, glutathione reductase and peroxidase activity, had the lowest lipid peroxidation (malondialdehyde content) and highest membrane stability and contents of chlorophyll and carotenoids under water stress, while the susceptible genotype WH 542 exhibited the lowest antioxidant enzyme activity, membrane stability and contents of chlorophyll and carotenoids and the highest lipid peroxidation. Genotype HD 2402 showed intermediate behaviour. It seems that drought tolerance of PBW 175, as represented by higher membrane stability and chlorophyll and carotenoid contents and lower lipid peroxidation, is related to its higher antioxidant enzyme activity.     

Morphological Traits Associated with Lodging Resistance of Spring Wheat (Triticum aestivum L.)

Throughout the world, lodging in cereals causes great losses in yield each year. A two year field study was conducted to determine the relationship of morphological traits to lodging resistance in spring wheat ( Triticum aestivum L.) breeding lines and to find easily measurable traits related to lodging resistance. A set of 15 breeding lines, representing a wide range of combinations of plant height and lodging resistance, was evaluated.
During the first year, 29 morphological traits were measured at two growth stages and correlated with the lodging score. Higher correlations were found for traits measured at anthesis (DC 65) than for traits measured at maturity (DC 92); most of the fresh weight traits correlated better to lodging resistance than did the corresponding dry matter parameters. During the second year the six traits of plant height, stem length, stem diameter, ear weight, stem weight and stem weight per cm were measured at anthesis and correlated with the lodging score.
From the pooled data of four experiments, significant correlations between the lodging score and single morphological traits were found for stem diameter and stem weight per cm. Thicker stems and heavier stems (mg per cm) were indicative for better lodging resistance. Stem diameter and stem weight cm⁻¹ explained 48.5 % and 49.7 %, respectively, of the phenotypic variation in lodging resistance. Multiple linear regression equations indicated that 77.2 % of the variation in lodging resistance was based on stem weight cm⁻¹ and on the weight of the ear.     

Effects of Cropping System, Seed Bed Management and Fertility Interactions on Biomass of Crops Grown on a Vertisol in the Central Highlands of Ethiopia

In the Ethiopian highlands, where integrated crop and livestock production takes place, the inadequate supply, in both quantity and quality, of feeds during the year is a major constraint. Native pastures and crop residues are the major feed sources, but their quality is often poor. Integration of forage legumes in the cropping system is one alternative to improve the fodder quality. Results of field work conducted over two seasons in order to assess and evaluate the potential yields of crops, crop/forage combinations and rotation systems on a Vertisol under two seed bed preparation systems showed that intercropping wheat with clover or sequential cropping of an oat/vetch mixture followed by chickpea provided high-quality fodder; the effect was greater under fertilized conditions. In addition, where monocropping treatment was tested, legume–cereal rotation resulted in higher grain and fodder yield when compared to cereal–cereal rotation. The study also showed that two short-duration crops could be produced in sequence per year. It is therefore suggested that the Vertisols in the Ethiopian highlands could provide a good opportunity for longer period cropping using improved food and forage crops, thereby improving the availability and quality of animal feed and protecting the land against erosion.     

组织培养途径改良定型小麦品种的研究

选用ＣＡ９０７０、ＣＡＤ８６９４,京４１１三个定型品种进行组织培养,比较了三种培养方式的培养效果,调查了Ｈ２,Ｒ２株系主要农艺性状的遗传变异情况,结果表明,幼胚培养效率最高,基因型间差异小,花药培养的基因型间差异显著,花药培养后代农艺性状的变异率高于幼胚培养,且其性状值向更小的方向变异,而幼胚培育诱花的变异范围大于花药培养,获得了ＣＡＤ８６９４的花培变异株系９５Ｈ０５５,株高降低了１１．５ｃｍ,获     

Combined Effect of Zinc and Cadmium Levels on Root Antioxidative Responses in Three Different Zinc‐Efficient Wheat Genotypes

This work was undertaken to investigate the effect of zinc (Zn) nutrition on root antioxidative responses to cadmium (Cd) toxicity of three wheat genotypes differing in Zn efficiency. A hydroponic experiment was carried out in which two bread wheat genotypes (Triticum aestivum L. cvs. ‘Rushan’ and ‘Cross’) and one durum wheat genotype (Triticum durum L. cv. Durum) were exposed to three Zn²⁺ (10^?11.11, 10^?9.11 and 10^?8.81 μm ) and two Cd²⁺ (10^?11.21 and 10^?10.2 μm ) activity levels. ‘Durum’ showed the highest root sulfhydryl (‐SH) groups content and activity of catalase (CAT), ascorbate peroxidase (APX), and superoxide dismutase (SOD) and the lowest root membrane permeability among the studied wheat genotypes. In ‘Durum’, Zn nutrition increased root ‐SH groups concentration of seedlings in Cd‐free nutrient solution. In ‘Cross’, as Zn²⁺ activity increased from 10^?11.11 to 10^?9.11 μm , root ‐SH groups concentration was increased while decreased with increasing Zn²⁺ to 10^?8.81 μm . Cadmium increased root membrane permeability at both 10^?11.11 and 10^?9.11 μm Zn²⁺ levels. Activity of CAT and APX increased in roots of ‘Durum’ plants exposed to Cd at Zn²⁺ = 10^?9.11 μm and thereafter decreased with increasing Zn²⁺ activity. In contrast, CAT and APX activity in roots of ‘Cross’ and ‘Rushan’ genotypes exposed to Cd decreased by increasing Zn activity to 10^?9.11 μm and then increased at Zn²⁺ = 10^?8.81μm . The results showed an increase in activities of antioxidative enzymes in Cd‐treated plants, although this increase was dependent on the crop genotype and Zn levels in the media.     

The Effect of Gelling Agents on Wheat Anther and Immature Embryo Culture

This study was conducted to determine whether inexpensive starches and various agars could replace Ficoll, which is very expensive, and Bacto-agar, which may be inhibitory, in wheat (Triticum aestivum L.) anther and immature embryo culture. Anthers from Pavon 76’ had significantly greater embryoid-initiation frequencies (number of embryoids per anther) on PI media with corn (0.67) and wheat starch (1.50) than with Ficoll (0.47). Anthers on 85D12 media with Ficoll, corn starch and wheat starch had similar embryoid-initiation frequencies (0.51, 0.50, and 0.52, respectively). The embryoid-regeneration frequencies (number of regenerating embryoids per embryoid plated) on 85D12 media containing corn (0.32) and wheat (0.36) starch were significantly higher than on 85D12 with Bacto-agar (0.14). Embryoids on MS media with Bacto-agar, corn starch, and wheat starch had similar embryoid-regenerating frequencies (0.15, 0.20, 0.22, respectively), which were greater than with some of the other agars tested (0.05 to 0.17). When wheat starch replaced Bacto-agar in immature embryo cultures, the frequency of responding embryos was unchanged, but the frequency of green plants regenerated increased an average of fourfold for two cultivars.     

不同种及类型小麦籽粒蛋白质含量动态变化的研究

对普通小麦(Triticum aestivum L.)和硬粒小麦(Triticum durum Desf.)的冬、春性类型共16个品种的籽粒蛋白质含量变化进行研究分析。结果表明,小麦不同种及不同类型,其籽粒发育中蛋白质含量的变化趋势基本一致。即籽粒蛋白质含量、千粒蛋白质日增量与籽粒发育期的关系均可用二次抛物线方程 Y=ax~2+bx+C 来描述,千粒蛋白质积累     

Effect of Soil Moisture on Relative Leaf Water Content, Chlorophyll, Proline and Sugar Accumulation in Wheat

The responses of four wheat ( Triticum aestivum L.) varieties to soil moisture were determined by measuring plant parameters such as relative leaf water content (RLWC) and the chlorophyll, proline and sugar contents of the leaf over two seasons. Two levels of irrigation treatments were adopted: irrigated and rainfed. The rainfed plants had consistently higher amounts of proline and sugar but lower RLWC and chlorophyll content. As drought intensified, differences between the irrigated and the rainfed plants with respect to all of these characters increased. The RLWC values of the irrigated plants were significantly higher in the morning but lower values were found at noon, showing some recovery in the afternoon.     

小麦供锌状况对叶片结构及叶绿体超微结构的影响

锌缺乏或过量使小麦叶肉细胞变小,多环复式细胞显著减少。缺锌植株的叶绿体中基粒垛数少,基粒垛叠片层少,基质片层少,部分片层膨胀;叶绿体内包含较大的液泡和淀粉“泡”;叶绿体被膜模糊,甚至消失.锌过量则使小麦的叶绿体变小,基粒和基质片层明显减少,部分片层膨胀,亲锇颗粒多;在叶绿体周围线粒体出现较多.