Stability Indices for Weed Management Systems in Forage Oat (Avena sativa L.)

A set of integrated weed management systems was assessed in forage oat ( Avena sativa L.), cv. Kent, to compare efficiencies inter se in terms of mean forage productivity over different locations and different years, and relative agronomic effectiveness. Results for seven weed management systems were obtained for three consecutive years, i.e. 1995–96, 1996–97 and 1997–98, at five locations of the Indian subcontinent. Two systems – use of weeder-cum-mulcher at the 3- and 6-week crop stages (WCS) and use of weeder-cum-mulcher at the 4 WCS plus application of 2, 4-D at 0.37 kg a.i. ha^–1 at 6 WCS – were found to be effective and consistent over locations from year to year and over years from location to location. Pooled analysis over years and locations showed manual weeding at 4 WCS plus application of 2, 4-D at 0.37 kg a.i. ha^–1 at 6 WCS, on the one hand, and use of weeder-cum-mulcher at 3 WCS plus manual weeding at 5 WCS, on the other, to have equal efficiencies and to be more beneficial than the other treatments. Recommendation of the latter system is of particular interest as this system merely involves mechanical operations which provide the benefits of soil mulching and carry no risk of biotoxicity due to herbicides in crop plants or adverse effects on soil through uninterrupted use of chemicals.     

劣变时间和温度对不同含水量燕麦种子的活力影响

试验以10％和16％含水量燕麦种子为材料,研究不同控制劣变处理对种子发芽特性的影响,以期为深入探索种子劣变的生理变化提供参考.燕麦种子劣变温度设置为35,40,45℃和50℃;劣变时间分别为10％含水量种子8,16,24,32 d和40 d,16％含水量种子1,2,3,4,5d和6d.结果表明:随着劣变时间的延长,10％含水量燕麦种子在35℃下发芽率、发芽势和发芽指数呈现先下降后上升的趋势;在40℃下各指标缓慢下降但没有显著差异(p＞0.05);在45℃下,各活力指标均呈下降趋势且有显著性差异(p＜0.05);在50℃下各活力指标急剧下降,并且在劣变32 d时发芽势和发芽率均降至0％,发芽指数降至0.16％含水量燕麦种子在35℃和40℃劣变处理下,随着劣变时间的延长各活力指标下降缓慢但仍有显著差异(p＜0.05);在45℃和50℃下,随着劣变时间的延长各活力指标急剧下降,并且在劣变5d时发芽势和发芽率降至0％,发芽指数降至0.此外,劣变温度、时间以及二者之间的交互作用均对燕麦种子活力的下降有显著(p＜0.()5)影响,在45℃条件下劣变24 d处理可以较好评价不同含水量种子的活力水平.     

裸燕麦体细胞无性系的农艺性状变异

５６个１０－１品系（来源于１１个Ｒ０植株）和２１２个晋燕８号品系（来源于４５个Ｒ０植株）被评价。结果表明，组织培养能够获得有益的农艺性状。８２％的２０－１系谱和９３％的晋燕８号系谱在７个测定性状中至少有一个性状发生显著变异。对每个性状都有一些增加和降低的品系被发现，而且有益的农艺性状变化比不良的变化频率高。再生植物株后代扣进行证明：性状变异是可以遗传的，单株选择能够在作物改良中应用。获得的变异也证     

Response of Photosynthesis and Water Relations of Rice (Oryza sativa) to Elevated Atmospheric Carbon Dioxide in the Subhumid Zone of Sri Lanka

The objective of the present paper is to determine the response of the physiological parameters related to biomass production and plant water relations in a standard Sri Lankan rice (Oryza sativa) variety (BG‐300) to elevated CO₂ (i.e. 570 µmol/mol). During two seasons, rice crops were grown under three different experimental treatments; namely, at 570 µmol/mol (i.e. ‘elevated’) and 370 µmol/mol (‘ambient’) CO₂ within open top chambers, and at ambient CO₂ under open field conditions. Leaf net photosynthetic rate in the elevated treatment increased by 22–75 % in comparison to the ambient. However, the ratio between intercellular and ambient CO₂ concentrations remained constant across different CO₂ treatments and seasons. CO₂ enrichment decreased individual leaf stomatal conductance and transpiration rate per unit leaf area, and increased both leaf and canopy temperatures. However, the overall canopy stomatal conductance and daily total canopy transpiration rate of the elevated treatment were approximately the same as those achieved under ambient conditions. This was because of the significantly greater leaf area index and greater leaf–air vapour pressure deficit under CO₂ enrichment. The leaf chlorophyll content increased significantly under elevated CO₂; however, the efficiency (i.e. photochemical yield) of light energy capture by Photosystem II (i.e. F_v/F_m) in chlorophyll a did not show a significant and consistent variation with CO₂ enrichment.     

Continued response through seven cycles of recurrent selection for grain yield in oat (Avena sativa L.)

Long-term selection experiments provide germplasm to study the effects of selection in a closed population. Recurrent selection to enhance grain yield in oat has been ongoing at the University of Minnesota since 1968. The objectives of this study were: (i) estimate the GCA and SCA effects for three agronomic traits in the seventh cycle of selection, (ii) assess the effect of the current methods of selection on parental contribution and unselected traits, and (iii) determine the direct and indirect responses to seven cycles of recurrent selection for grain yield. Progeny of the Cycle 6 parents and parents for Cycles 0 through 7 were grown in two separate tests. Grain yield, heading date and plant height were evaluated in each test. Grain yield was increased by 21.7% after seven cycles of selection. Evaluation of Cycle 6 progeny showed that GCA effects were significant for all three traits studied, and SCA effects were significant only for grain yield. Four Cycle 6 parents did not have any progeny selected as Cycle 7 parents. Results from this study indicate that long term recurrent selection has continued to increase grain yield. Alternative selection strategies may be necessary to maintain the genetic variability in this population, particularly when improvement of secondary traits is required. This revised version was published online in August 2006 with corrections to the Cover Date.     

行距及间作对箭筈豌豆与燕麦青干草产量和品质的影响

在我国西北地区,普遍应用燕麦与箭筈豌豆间作生产饲草。为了研究不同间作模式的增产效果,2009—2010年在吉林省白城市采用两因子完全随机区组设计,研究了2种行距(A1：33 cm;A2：16.5 cm)和3种种植方式(B1：燕麦单作;B2：箭筈豌豆单作;B3：燕麦箭筈豌豆1∶1间作)对饲草产量、品质的影响。结果表明,行距减小播量增大时,作物单株重量减小,饲草总产量提高13%;行距减小播量不变,燕麦单株重量增大,饲草总产量提高29%;B3饲草产量比B1提高24%,比B2提高30%;B3粗蛋白产量比B1高1倍,比B2低20%;间作使燕麦的株高、单株重和粗蛋白质含量提高,使箭筈豌豆的株高增加,单株重、含氮量降低,节数减少,分枝减少。采用行距16.5 cm、燕麦播量87.5 kg hm^–2、箭筈豌豆播量75 kg hm^–2的燕麦与箭筈豌豆间作处理,全年两茬饲草产量为19.8 t hm^–2,粗蛋白产量为2.43 t hm^–2,可作为白城及气候相似地区饲草生产的基本模式。     

Effect of Sodium Chloride on Growth, Photosynthesis and Mineral Ions Accumulation of Different Types of Rice (Oryza sativa L.)

Growth, photosynthesis and mineral ions accumulation of aromatic small grain, local coarse grain and HYV types of rice were evaluated under saline conditions. Three cultivars from each type were subjected to 0, 50, 100, 150 and 200 mvi NaCl concentrations. After three weeks of 200 mvi NaCl application only Pokkali and Kalobail, both belonging to the local coarse grain type and IPK 37011 of the HYV type were able to survive. Plant height, green leaf area, leaf weight, shoot and root growth were seriously decreased by salinity. However, leaf area was decreased more than other growth parameters. In general aromatic small grain type showed higher salt-sensitiveness in relation to growth than other types of rice. Photosynthesis (Pn) was decreased by salinity and apparently stomatal resistance was partially responsible for the decreased Pn. Kalijira, an aromatic small grain eultivar, showed serious reduction in Pn, especially at the 150mM NaCl level. Na accumulation was increased while K accumulation was decreased by salinity in all types. Salt tolerant eultivars in all types of rice accumulated less Na and more K than susceptible ones. The K/Na ratio was also higher in tolerant eulti-vars. Ca and Mg eoncentrations were decreased by salinity although not all the eultivars showed clear accumulation patterns as observed for Na and K. As HYV and local coarse grain types of rice in general showed high salt tolerance, a comprehensive breeding programme should be of value for the improvement of salt tolerance of aromatic small grain rice which has a high demand in rice importing countries.     

低磷胁迫对不同水稻品种幼苗光合作用的影响

低磷胁迫下,水稻叶片的无机磷含量、光合速率、RuBP羧化酶活性下降.与低磷敏感品种沪占七相比，耐低磷品种大粒稻无机磷含量、RuBP羧化酶活性下降的幅度更小.在低磷胁迫初期(10 d)较低光强下，大粒稻与沪占七光合速率受低磷的影响相近，而较高光强下以及胁迫后期(20 d)大粒稻受低磷影响较小.叶绿素荧光参数测定表明，在低磷胁     

The Performance of Pea (Pisum sativum L.) and its Role in Determining Yield Advantages in Mixed Stands of Pea and Oat (Avena sativa L.)

On a brown warp soil (Fluventic Eutrochrept) near Goettingen, Germany, conventional leafed pea ( Pisum sativum L. cvs Messire and Bohatyr) and semileafless types (cvs Profi, Juno and Azur) were grown in mixed stands together with oat ( Avena sativa cvs Alf and Lutz) in substitutively designed experiments from 1995 to 1997. Oat was the dominant component. Crowding coefficients for oat averaged 7.4. No relationship could be detected between the crowding coefficient of oat and any yield advantage from the mixture. Crowding coefficients for pea varied substantially, between 0.1002 (Juno and Alf in 1996) and 0.2979 (Bohatyr and Alf in 1996). Crowding coefficients for semileafless pea cultivars were smaller than for conventional leafed types. The yield advantage of the mixture increased as the crowding coefficient of pea increased. The maximum yield increase for the mixture was achieved when the relative yield total (RYT)=1.17 or + 11 dt grain DM ha^–1 for mixtures of the long-strawed conventional leafed cultivars Bohatyr and Alf (in 1996). The crowding coefficients of pea were positively correlated with the level of symbiotically fixed N₂ in the mixed stands. When N₂ fixation with mixed cropping was about 30 kg N ha^–1, RYT was unity. Increasing symbiotic N₂ in the mixtures resulted in increasing yield advantages in the mixture. Short-strawed pea cultivars seem unsuitable for mixing with oat. Plant height of pea appeared to be more important than plant leaf type. Accordingly, mixtures containing the long-strawed semileafless pea cultivars Profi and Alf were more successful. It is concluded that increased competitiveness of the pea component in the mixture with oat entails increasing the level of symbiotic N₂ fixation including resource complementarity and thus yield advantage in the mixed stands.     

Interactive Effect of Sulphur and Nitrogen on the Oil and Protein Contents and on the Fatty Acid Profiles of Oil in the Seeds of Rapeseed (Brassica campestris L.) and Mustard (Brassica juncea L. Czern. and Coss.)

In long-term field experiments on loamy sand and sandy loam, legumes (pea and lupine) stimulated microbial activity in the rhizosphere more than cereals (winter rye, winter wheat and spring barley), maize and oil flax. In the rhizosphere of winter wheat and maize, microbial activity and the bacteria species Pseudomonas , Agrobacterium and Xanthomonas were more stimulated by organic manuring than by mineral fertilization. A positive correlation between the stimulated bacteria species and the growth of young plants was found. Various mineral nitrogen applications had no influence on the rhizosphere microflora. The leghemoglobin content of pea nodules – an indicator of nitrogen fixation activity – was reduced by high nitrogen application in crop rotation.     

Evaluation of the Heterosis on Leaf Photosynthesis of Remote-Cross F1 Rice (Oryza saliva L.)

The heterosis of leaf photosynthesis was studied on the main characters included in the range from CO₂exchange rate (CER) to enzymatic activity using a remote cross F, rice. The CER was significantly higher than those of the parental strains, showing a 111 % heterosis effect on average; at the same time strong heterosis was observed for the leaf area production and growth. Also stomatal and mesophyll conductances increased in the F₁ rice, which may contribute to the increase in CER. Chlorophyll content (Ch1), soluble protein content (SPC) and ribulose 1,5-bisphosphate (RuBP) carboxylase activity (RCA) were measured as the internal factors related to photosynthesis, and compared between the F₁, rice and the parents. For all these factors, the F₁ rice showed low values compared to the parents. Positive heterosis was not expressed here. On the other hand, the specific activity of RCA (RCA/SPC) increased in the F₁, rice, showing a 120% heterosis effect. This may be regarded as one of the main causes for the increase in CER of the F₁, rice. High CER expressed as heterosis concurrently with large leaf area production is one of the important findings in our study, and this may suggest a high possibility of further improvement in biomass production or yield of rice by gathering the advantageous elements into a hybrid plant.     

Chromosomal location of genes for resistance to powdery mildew in cultivated oat (Avena sativa L.). 1. Gene Eg-3 in the cultivar 'Mostyn'

The cultivar 'Mostyn' of hexaploid oat ( Avena sativa L.) possesses a dominant gene conferring resistance to powdery mildew caused by Erysiphe graminis avenae. The resistance gene, designated Eg -3, was derived from the wild oat Avena sterilis L. var. ludoviciana. Monosomic analysis revealed that this gene was located on chromosome 17, which corresponds to the missing chromosome in the 'Kanota' monosomic line Kl1. This chromosome is associated with the homoeologous group 1 of the Triticeae.     

Effect of Leaf Sugar and Starch Concentrations on Apparent Photosynthesis in Alfalfa

Rates of apparent photosynthesis (AP), dark respiration, photorespiration, mesophyll resistance, and concentrations of soluble starch, sugars, chlorophyll and nitrogen were measured in alfalfa leaves ( Medicago sativa L.) grown under high or low light levels in an attempt to evaluate the effect of nonstructural carbohydrate concentration on net CO₂ assimilation.
Leaf N and chlorophyll levels of high light plants exceeded those of low-light plants. Constant light increased both starch and sugar levels in low-light plants, but had little effect on high-light plants. Rates of AP declined in low-light plants upon transfer to constant light conditions, apparently due to increases in stomatal and mesophyll resistance. Leaf starch levels were negatively correlated (P > 0.05) with rates of AP and positively correlated with mesophyll resistance in both groups of plants but leaf sugar content was not correlated with either AP or mesophyll resistance.
Starch and sugar levels of high-light plants declined substantially upon transfer to constant darkness, while low-light plants were less affected. Rates of AP declined in both groups of plants due to increases in both mesophyll and stomatal resistances. Neither sugar nor starch levels were correlated with AP or mesophyll conductance in this treatment.
The data support the hypothesis of feedback inhibition of photosynthesis, mediated through an increase in mesophyll resistance, which is associated with high levels of starch in the leaves.     

Genetic studies of powdery mildew resistance in common oat (avena sativa L.) I. Cultivars and breeding lines grown in Western Europe and North America

Common oat (Avena sativa L.) cultivars and breeding lines grown in Western Europe and North America were tested against twelve Erysiphe graminis f. sp. avenae mildew isolates collected in Germany and Denmark. These isolates were selected for their ability to produce differential response patterns permitting characterization of five oat mildew resistance (OMR) groups. From a total of 259 cultivars and lines tested 173 accessions showed susceptible responses, 48 accessions were characterized by susceptible or intermediate responses and 38 accessions revealed isolate-specific resistance response patterns. Eight cultivars and lines had resistance patterns of OMR group 1, six cultivars of OMR group 2, and eleven cultivars of OMR group 3. Two cultivars, each possessed resistance patterns corresponding to OMR groups 1 + 3 and 2 + 3 in combination, respectively. Three cultivars exhibited the response pattern of OMR group 3 in association with an additional unknown resistance. Eight cultivars and lines showed a resistance response pattern not yet detected in the documented OMR groups. This revised version was published online in July 2006 with corrections to the Cover Date.     

Stomatal and Non-stomatal Effects of Salinity on Photosynthesis in Faba Beans (Vicia faba L.)

The effect of salinity (40 and 80 meq/1 NaCl) on stomatal conductance, chlorophyll content, ultrastructural damage and photosynthetic performance of six cultivars of faba beans ( Vicia faba L.) from different agroclimatic regions were investigated. Low levels of salinity (40 meq/1 NaCl) increased chlorophyll content in some cultivars but did not lead to simultaneous increase in photosynthesis (P). Increased salinity levels (80 meq/1 NaCl) decreased chlorophyll content and stomatal conductance. Ultrastructural damage was observed in sensitive cultivars even at low salinity levels. Based on the parameters investigated, there was no concrete evidence to suggest that the physiological processes of cultivars from arid and semi-arid regions are less affected under saline conditions as compared to cultivars from temperate regions. The results suggested increased salinity affects P not only due to its effect on stomatal closure but also due to other non-stomatal effects like ultrastructural damage and decrease in chlorophyll content below a threshold level.     

Effect of Sodium Chloride on Germination and Seedling Characters of Different Types of Rice (Oryza sativa L.)

The rice eultivars grown in the tropies and sub-tropics can be broadly categorized as aromatic small grain, local coarse grain and modern high yielding varieties (HYV). The first two categories are traditional rice, and are generally palatable. The aromatic rice has better market value than HYV rice, yet farmers are unwilling to expand its cultivation because of the low yield potential. One possibility to expand the cultivation of traditional rice is o t find stress tolerant cultivars for growing in marginal land. The salinity tolerance of nine rice cultivars representing three from each type of aromatic small grains, local coarse grains and HYV types, was analysed at germination and early seedling stage. Seeds were placed for germination and the seedlings were allowed to grow for nine days at NaCl concentrations of 0, 50, 100, 150 and 200 mM. NaCl decreased the germination index (GI), speed of germination, seedling height and seedling dry matter weight. Seedling characteristics were decreased more than GI. In general aromatic small grain type showed more salt sensitivity than the other two types. Among the nine cultivars Shakkorkhora (aromatic type) showed the least salt tolerance in relation to germination and seedling characters while the other two cultivars of the same group showed tolerance as high as the tolerant cultivars in other types. Generalization of group salt tolerance of rice, therefore, has little value from the agronomic point of view at least at early growth stage. As the number of cultivars employed in this study was only three from each type it is suggested that more cultivars be considered for the purpose of salt tolerant improvement programme of various types of rice.     

Influence of Exogenous Glycine Betaine on Gas Exchange and Biomass Production in Sunflower (Helianthus annuus L.) under Water Limited Conditions

This study investigated whether the exogenous application of glycine betaine (GB) could alleviate the adverse effects of water deficit on sunflower. Two sunflower lines, Gulshan-98 and Suncross, were subjected to water deficit at the vegetative or the reproductive stages of plant growth. Three levels (0, 50 and 100 mmol l⁻¹) of GB were applied as a pre-sowing seed treatment or as a foliar spray at the time of initiation of water deficit at the vegetative or reproductive stages. Foliar application of GB at the time of initiation of water deficit treatments showed a marginal increase in shoot biomass in drought-stressed plants. Exogenously supplied GB as a foliar spray also showed a positive role in reducing the effects of water deficit on net CO₂ assimilation rate, transpiration rate and sub-stomatal CO₂ concentration in both sunflower lines. Pre-sowing seed treatment with GB had no effects on the above-mentioned physiological and growth attributes in both normally irrigated and drought-stressed plants. Taken together, foliar application of GB increased net CO₂ assimilation rate which in turn showed a slight increase in growth of water-stressed plants but this increase was not related to stomatal regulation.     

高温-干旱对沙漠植物花花柴光合作用的影响

为了探索高温-干旱胁迫对荒漠植物光合作用的影响,通过测定高温-干旱胁迫时花花柴光合作用的变化,来解释花花柴耐高温-干旱的生物学特性。本实验利用LI-6400XT光合仪测定三种环境(绿地常温,绿地高温,沙漠高温)中花花柴的胞间CO2浓度(Ci)、净光合速率(Pn)、蒸腾速率(E)及气孔导度(gs)。结果表明一天之中花花柴的净光合速率和蒸腾速率,在绿地常温环境中于16点到19点时达到最高,此时的环境温度为33℃~34℃,同时间段沙漠高温环境中净光合速率相对降低了88.2%,蒸腾速率相对增高了2.15倍;胞间CO2浓度和气孔导度,在绿地常温环境中于11点到13点会达到最高,此时环境温度为25℃~28℃,同时间段沙漠高温环境中二者都呈现出显著下降趋势。表明高温使花花柴的光合指数都有不同程度的降低,但是干旱胁迫的叠加加剧了高温对花花柴光合作用的负效应,且在净光合速率、蒸腾速率、胞间CO2浓度的实验数据中表现明显,从而可以解释花花柴耐高温-干旱的生物学特性。     

Effects of soil drought during the vegetative phase of seedling growth on the uptake of 14co2 and the accumulation and translocation of 14C in cultivars of field bean (vicia faba L. Var. Minor) and field pea (pisum sativum L.) Of different drought tolerance

During the vegetative phase of growth of two field bean and two field pea cultivars of different drought tolerance, the effect of short and prolonged soil drought on gas exchange (CO₂ i H₂O), leaf water potential (ψ), stomatal diffusive resistance (r_S), uptake of CO₂, and the distribution and accumulation of ¹⁴C was studied. Differences in the response to drought conditions between resistant and susceptible cultivars were marked. After 5 days of soil drought, the decrease in net photosynthesis and transpiration rate and the increase of stomatal resistance were greater in the drought-resistant cultivars than in the drought-susceptible ones. In contrast, after 10 days of drought the decrease of leaf P_N (CO₂ assimilation rate), E (rate of transpiration) and ψ (water potential) was greater in the susceptible cultivars than in the resistant ones. Significant differences between the resistant and the susceptible cultivars were also observed in the assimilation and translocation of ¹⁴C by the green parts of the plant. The amount of carbon accumulation in roots in drought-susceptible cultivars increased less than in the drought-resistant cultivars. For treatments in which optimal soil watering was resumed after 5 or 10 days of drought there was no evidence of effects of drought on the majority of measurements, but the drought-resistant cultivars showed a general tendency for a more rapid recovery. Our results confirm the existence of genetic variability in drought tolerance among the cultivars of field bean and field pea. The recorded differences in the response to drought of experimental cultivars may indicate that, under water deficit in the soil and in plant tissues, they may use different strategies to avoid the damaging effects of temporary limitation of water supply; for example, the drought-resistant cultivars may more effectively conserve tissue hydration through effective stomatal closure. Also, the observed changes in carbon assimilation and accumulation might be the reason for their different responses to drought. The change in radioactivity losses in the control and stressed plants may result from the differences in demand for energy to maintain cell structure and function. Similarly, the less intense carbon accumulation in the roots of the sensitive cultivars could be caused by more harmful effects of drought on root growth.     

农田施用水葫芦对水稻钾素吸收利用的影响

以粳稻品种‘运2645’为供试材料,设计农田施用水葫芦（将晒干水葫芦按4500 kg/hm2农田施用）、不施用水葫芦处理和施N量为120 kg/hm2（LN）、240 kg/hm2（NN）处理,研究其对水稻不同生育时期K素含量、K素吸收、K素分配和K素利用效率的影响。结果表明：（1）农田施用水葫芦使水稻不同生育时期植株含K率显著提高,增加幅度从够苗期逐渐下降,到抽穗后又逐渐增加;使各生育时期吸K量显著提高;（2）农田施用水葫芦对水稻不同生育时期K素在茎鞘、叶片中分配比例多无显著影响,使成熟期K素在穗中分配比例显著降低;（3）农田施用水葫芦使水稻不同生育时期K素干物质生产效率均显著或极显著降低,使K素籽粒效率和K素收获指数均显著降低;（4）增施N肥,使水稻不同生育时期的植株K素含量和吸K量均得到极显著的增加,使K素干物质生产效率和K素籽粒生产效率均显著或极显著下降;（5）水葫芦 × N对稻株K素吸收利用多无显著互作效应。农田施用水葫芦使水稻植株含K率、K素吸收量显著提高,使K素干物质生产效率和K素籽粒生产效率显著降低。