Factors affecting pollen shedding capacity in wheat

Summary Twenty-two promising wheat varieties were studied for their plant height, length of filament, size of anther, number of pollen grains/anther and the extent of pollen shed outside the florets. Plant height and length of filament ranged from 54 cm to 136 cm and 4.5 mm to 11.9 mm, respectively. Taller plants showed a tendency to longer filaments. The number of pollen grains/anther varied from 581 to 2153. This character was particularly correlated with plant height. Tall varieties with more pollen grain/anther shed greater quantities of pollen outside the florets. This was due to longer filaments of most of the tall varieties. The size of anther was also positively correlated with pollen grain/anther.     

Factors affecting seed yield in white clover

Summary Eighteen clones of white clover chosen at random were examined for their seed setting possibilities. Large differences in the size of the inflorescence and the rate of fertilization were found among the clones, so that breeding strains of white clover with better seed-setting seems possible. The number of ovules per floret seemed not very variable.     

Factors affecting the production of filled seeds in sunflower

Summary The capitulum and stem diameter have been found to be negatively correlated with the percentage of the filled seed. The correlation is significant. The partial correlation between the above is also negative but the values are not significant which shows that it is the joint interaction of stem and capitulum diameter which markedly influences seed set. It has been concluded that increased stem thickness adversely affects seed set because of greater increase in leaf area which in turn restricts nutrient supply to the developing seeds. Both stem and capitulum diameter are important from yield point of view as they lead to increased seed producing area. It is essential for a good variety to have large capitula with well filled seeds. It has been pointed out that in a breeding program it should be possible to get desired combinations of above characters without much difficulty.     

农村居民政治参与积极性的影响因素分析

农村基层民主建设是影响农村经济发展的一个重要因素。从微观农户的角度来研究影响理性农户政治参与积极性的因素,对于加快基层民主建设,进而促进农村经济发展具有重要的意义。本文利用第一手的农户调查数据,采用有序Probit模型,从农户特征、村集体特征、候选人特征和社会资本四个方面来分析影响农村居民政治参与积极性的因素的方向和强度。分析结果表明：①农户自身特征中的政治面貌、职务经历、家人是否在村办企业工作这三个变量对农户政治参与积极性在统计上有显著的正向影响,而年龄、文化程度、是否有非农就业这三个变量在统计上不显著;②对上届村干部的满意程度、是否发身过过往纠纷这二个村集体特征中的变量表现出对农户政治参与积极性有统计上的显著影响,有无投票误工补贴、公共服务水平这二个变量对农村居民政治参与积极性的影响不显著;③竞选激烈程度、候选人特征、乡镇政府介入与否这三个变量表现出对农户政治参与积极性有统计上的显著影响,竞选规范程度、自家人有无参加候选人提名、有无拉票行为这三个变量对农村居民政治参与积极性的影响不显著;④是否参与经济组织、家里是否有人当干部这二个社会资本变量对农村居民政治参与积极性的影响均不显著。     

Factors affecting minimal growth conservation of potato microplants in vitro

Combined effects of sucrose, mannitol and photoperiod on microplant conservation were studied in four potato genotypes belonging to two different groups viz., Tuberosum and Andigena. Minimal growth medium was based on Murashige and Skoog (MS) supplemented with 6 different concentrations of sucrose (30, 40, 50, 60, 70 and 80 gl^-1) with 4 different concentrations of mannitol (0, 20, 40 and 60 gl^-1). The cultures were conserved under two photoperiod conditions i.e. continuous illumination and 16-h photoperiod at 6 ± 1 °C. There were significant interactions between photoperiod and sucrose, and between photoperiod and mannitol. Maximum microplant survival and desirable microplant growth were observed under 16-h photoperiod. Sucrose alone did not improve culture viability over 30 months of storage. Inclusion of mannitol in the conservation medium increased microplant survival. Sucrose x mannitol interaction showed that sucrose was effective in enhancing microplant survival in combination with 20 or 40 gl^-1 mannitol, but not with 60 gl^-1 mannitol. Combined effect of sucrose, mannitol and photoperiod showed that optimum microplant growth and maximum culture viability were obtained when the cultures were grown in MS medium containing 40 gl^-1 sucrose and 20 gl^-1 mannitol under 16-h photoperiod. Potato microplants can be conserved in this medium and cultural conditions up to 30 months without subculturing. This revised version was published online in July 2006 with corrections to the Cover Date.     

地铁用间接蒸发冷却器换热性能影响因素

为解决地铁站冷却塔设置难题,提出了一种采用低速电机驱动旋转布水装置的间接蒸发冷却器,在两种布置方式下,对其换热性能进行了单因素实验,并运用正交实验法对较优布置方式下影响换热器换热的因素进行了分析。结果表明：两种布置方式下,喷嘴与蒸发冷却器的间距、两组换热管束间距均存在最佳值,喷嘴双侧旋转布水优于单侧旋转布水;换热器平行气流布置且喷嘴双侧旋转布水为较优布置方式,此时,换热器换热量随喷水量、转速、空气速度、冷却水进口温度的增加以及喷水温度、空气温度的降低而增大,其中,冷却水进口温度对换热器换热影响最为显著,其他因素对其换热的影响从主到次顺序为：喷水量、空气温度、空气速度、喷水温度、转速、冷却水流量。     

Factors affecting genotypic and environmental variance for crude protein content in cereals

Summary The effects of N fertilizer, irrigation and location on genotypic and environmental variances of barley and wheat varieties were studied in a series of trials. Genotypic variance for crude protein content, as well as for grain yield, tended to be higher under high N fertilizer rate (80 kg N/ha). The effect of N fertilizer rate on environmental variance varied with variety and location. Increase in crude protein content resulted in decrease in environmental variance for only a few of the varieties tested. The effect of quantity of irrigation water on genotypic and environmental variance for crude protein content was small.This work has been carried out under Research Contract No. 1037/GS with the International Atomic Energy Agency.     

Factors affecting the degree of self-incompatibility in inbred lines of Brussels sprouts

Summary Experiments were made in which four different lines of Brussels sprout, each homozygous for S-allele 2, were tested for self-incompatibility at various stages of plant and flower development under different environmental conditions. The tests were made by counting the number of pollen tubes present in the style 24 hours after pollination, by means of the Ultra-violet Fluorescence technique.The results showed that the degree of self-compatibility varied widely, being greatest during the middle to late stages of the flowering period, at the highest temperature treatment applied. No mean differences could be detected between the effects of self- or sib-pollination; or between pollination of flowers of different ages.One of the inbred lines showed a greater response than all the others to the highest temperature at a late stage of flowering. Under these conditions this inbred line showed more than a tenfold increase in the number of tubes growing after self-pollination, as compared with the overall mean of the experiment. This result is interpreted as indicating a modifying effect of the genetic background on the expression of the major S-allele. On the basis of the results obtained, methods are suggested for more efficient selection of inbred lines of Brussels sprouts with strong and stable self-incompatibility behaviour.     

Factors affecting variation in farm yields of irrigated lowland rice in southern-central Benin

For increasing rice production in West Africa, both expansion of rice harvested area and raising rice yield are required. Development of small-scale irrigation schemes is given high priority in national rice development plans. For realizing potential of the newly developed schemes, it is essential to understand yield level, farmers’ crop management practices and production constraints. A series of field surveys were conducted in six small-scale irrigation schemes in Zou department, Benin during the dry season in 2010–2011 to assess variation in rice yields and identify factors affecting the variation. The schemes were established between 1969 and 2009. Rice yields ranged from 1.3 to 7.8 t ha⁻¹ with an average yield of 4.8 t ha⁻¹. The average yield was only 2.9 t ha⁻¹ for newer irrigation schemes developed in 2002 and 2009. Multiple regression analysis using farmers’ crop management practices as well as abiotic and biotic stresses as independent variables revealed that 75% of the variation in yields could be explained by five agronomic factors (fallow residue management, ploughing method, water stress, rat damage and N application rate) and two edaphic factors (sloped surfaces and sand content in the soil). Removing fallow residue from the fields for land preparation reduced yields. Yields were lower in plots ploughed by hand than by machine. Sloped surface, water stress and rat damage reduced yields. Yield increase due to N application ranged from 0.8 to 1.6 t ha⁻¹. Higher sand content was associated with lowered yields. The low yields in new irrigation schemes caused by sub-optimal crop management practices suggest that farmer-to-farmer learning and extension of good agricultural principles and practices can increase yields. Organizational capacity is also important to ensure the use of common resources such as irrigation water and tractors for land preparation.     

Factors affecting oat haploid production following oat × maize hybridization

Doubled haploids (DHs) are becoming increasingly important in crop breeding programmes but methods for producing oat DHs remain inefficient. In this study haploid and DH oat plants were produced using the oat × maize hybridization method. Factors influencing the rate of caryopsis and haploid embryo production including genotype, post‐pollination plant growth regulator application and temperature were investigated. The four growth regulators tested showed significant differences in their capacity to induce caryopsis formation with dicamba producing the highest numbers of caryopses, followed by picloram, 2,4‐dichlorophenoxyacetic acid (2,4‐D) and gibberellic acid (GA₃). No significant differences were observed between these growth regulators for their effect on embryo production. The concentration of dicamba was also important and was found to influence caryopsis but not embryo production, with 50 and 100 mg/l dicamba producing significantly more caryopses than 25 or 5 mg/l. Temperature had a significant impact on both caryopsis and embryo production with the magnitude and direction of response depending on genotype. Rates of haploid embryo production observed were between 0.8% and 6.7% of the pollinated florets. The proportion of haploids, which survived and were successfully doubled with colchicine following transfer to soil was between 72% and 81%.     

Factors affecting the genotype × environment interaction in spring triticale grown in a Mediterranean environment

The identification of the genotypic and environmental factors responsible for the genotype by environment interaction is essential in any breeding program. A Multi Environmental Trial (MET) including 3 years, 3 locations and 14 lines of spring triticale (× TriticosecaleWittmack) was carried out in a Mediterranean environment (Sardinia, Italy). Water available to the crops was calculated through a model run with the environmental variables and the phenological data recorded in each environment. Yield, yield components and heading date were used to perform an Additive Main effects and Multiplicative Interaction (AMMI) analysis. Interaction for yield was relevant only in 2 environments out of 8, one characterised by a late sowing, the other by the warmest pre-anthesis period. Correlations between Interaction Principal Component Axis (IPCA) scores and environmental and genotypic variables showed that genotype by environment interaction for yield and kernels per m² is related to interaction for phenology but not to the yield level. Yield level was significantly correlated with the water availability. Genotype by environment interaction for yield is mainly determined by thermal conditions in the pre-anthesis period, genotypic photoperiodic sensitivity and sowing time. This revised version was published online in August 2006 with corrections to the Cover Date.     

Factors affecting in vitro flowering and fruiting of green pea (Pisum sativum L.)

Multiple shoots were efficiently regenerated from cotyledonary node and shoot tip explants of Pisum sativum within 15 days on MS medium containing B₅ vitamins and supplelmented with 2.0 mgl^-1 6-benzylaminopurine. The elongated shoots produced on the same medium were excised and transferred to MS medium containing half strength ammonium nitrate (8.25 gml^-1) and supplemented with auxins (indole-3-butyric acid or naphthalene acetic acid) either alone or in combinations with gibberellic acid. Rooting and flowering were observed on the 7th and 15th day after their transfer to rooting medium. The flowers self-fertilised in vitro and produced mature pods within 25 days of rooting. These seeds were germinable both in vitro and in vivo. In vitro seeds sown in pots under field conditions developed into flowering plants, and subsequently produced pods with viable seeds. This revised version was published online in July 2006 with corrections to the Cover Date.     

农户重复购种行为的影响因素分析——对湖北荆州油菜种植农户的调查研究

利用相关分析、因子分析、Logistic回归分析等方法，对湖北荆州油菜种植农户购种行为调查所得数据进行实证分析。研究结果表明。品牌、种子质量、种子价格以及年龄、文化程度5个因子对农户重复购种行为有显著影响；其中，品牌对农户重复购种行为的影响最大。其次是种子质量，再次是种子价格，年龄和文化程度也有一定影响。并对相关种子企业提出了建议。     

Factors affecting seed set in cross-pollinations of green-sprouting broccoli (Brassica oleracea var. Italica)

Factors influencing the success of hand cross-pollination of broccoli were investigated. A number of experimental variables were shown to have no effect, whereas age of flower and storage of pollen had minor effects. The bulk of the variability was found to be associated with specific parental combinations. The significance of this variability is discussed in terms of the nature of the incompatibility and the influence of such behavior on the breeding program.Formerly Assistant Horticulturist, Vegetable Crops Research, Department of Horticulture, Western Washington Experiment Station, Puyallup Washington Agricultural Experiment Stations, Scientific Paper no. 2144 Work was conducted under Project 1288     

Factors affecting the postharvest soluble solids and sugar content of tomato (Solanum lycopersicum L.) fruit

Although a large component of tomato fruit taste is sugars, the choice of tomato cultivar and the postharvest practices implemented by industry are designed to reduce crop loss and lengthen shelf-life and do not prioritize sweetness. However, because there is a growing recognition that taste and flavor are key components of tomato marketability, greater emphasis is now being placed on improving traits like sugar content. In this review the factors, both pre-, post and at harvest that influence sugar content in fruits sold at market are broadly outlined. Lines of investigation that may maximise the outcome of current practices and lead, long-term, to enhanced postharvest fruit sugar contents are suggested.     

Factors affecting haploid production in wheat using the Hordeum bulbosum system. 3. Post-fertilization effects on embryo survival

Summary An investigation was made of factors affecting the frequency of development of fertilized ovules following wheat x Hordeum bulbosum hybridizations. Seed survival, a term used here to represent the relationship between seed set and fertilization, was shown to vary between the wheat genotypes tested, but was unrelated to the crossability genes present within the wheat genotype. A high seed survival was obtained in crosses involving the variety TH3929 and the single chromosome substitution line, Chinese Spring (Hope 5B). Chinese Spring showed a poor seed survival. Some influence of the H. bulbosum genotype on seed survival was detected. The two environmental factors studied, namely the post-pollination application of gibberellic acid and the ambient temperature, were both shown to affect seed survival. The application of gibberellic acid immediately after pollination or 1 and 2 days after pollination improved seed survival, although the extent of the response was dependent upon the number and timing of the application(s). A genotype-dependent response to the ambient temperature was observed, TH3929 showing a slight but insignificant reduction and Chinese Spring a significant improvement in seed survival with an increase in temperature from 20°C to 26°C. The physiological processes which may be influenced by GA and the ambient temperature and may thereby affect seed survival are discussed.     

Factors affecting the incidence of internal deviations in Brussels sprouts (Brassica oleracea L. var. Gemmifera DC.)

Summary A study was made on the incidence of internal deviations in buttons of Brussels sprouts. Sprouts picked in the autumn showed an only slight degree of internal necrosis, in contrast to those picked in the winter. Large sprouts were more sensitive than smaller ones. No clear direct effect of nitrogen and planting distance could be established. Low temperatures in the winter are considered to be the main causal factor of this type of necrosis. Very distinct differences in sensitivity between varieties and strains were found. probably resistant varieties may be bred by selection.

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Samenvating Onderzoek werd uitgevoerd over het voorkomen van inwendige afwijkingen in spruitkool. In spruiten geplukt in de herfst kwam weinig inwendige necrose voor, in tegenstelling tot de in de winter geplukte spruiten. Grote spruiten waren gevoeliger dan kleine. Er kon geen direct van stikstof en plantafstand worden vastgesteld. Lage temperaturen in de winter zijn waarschijnlijk de belangrijkste oorzaak van het optreden van de gevonden necrose. Tussen rassen en selecties werden zeer duidelijke verschillen in gevoeligheid gevonden. Misschien kunnen door selectie resistente rassen worden gekweekt.

     

Factors affecting haploid production in wheat using the Hordeum bulbosum system. 2. The effect of the timing of pollination

Summary The effect of manipulating the timing of pollination on the fertilization frequency in wheat × tetraploid Hordeum bulbosum hybridizations was investigated as a possible means of overcoming varietal incompatibility in this cross. Pre- and post-anthesis pollinations were made on previously identified highly crossable and poorly crossable wheat genotypes and the stage of development of the individual florets at pollination was expressed in days from anthesis units.In both crossable and non-crossable wheat genotypes, a significant negative linear relationship was observed between floret age and fertilization frequency. The magnitude of the response of early pollination was dependent on the number of alleles for non-crossability present at the Kr loci. The non-crossable cultivar Highbury, possessing more than one allele for incompatibility, showed a slight response. The greatest response was shown by the highly crossable cultivar Chinese Spring, possessing alleles for crossability at all Kr loci. The single chromosome substitution line, Chinese Spring (Hope 5B), possessing the most potent allele for non-crossability, Kr ₁, showed an intermediate response. The H. bulbosum genotype had no effect on the magnitude of this response, influencing only the mean fertilization frequency.     

Factors affecting root and seed yield in ahipa (Pachyrhizus ahipa (Wedd.) Parodi), a multipurpose legume crop

Ahipa (Pachyrhizus ahipa) is a legume crop, which produces carbohydrate-rich tuberous roots and seeds rich in protein and oil. In the present work, we studied the effect of different agronomic practices and climatic conditions on root and seed yield in order to make a preliminary assessment of the yield potential under different managements for the ahipa crop in south-western Europe. Sowing date affected productivity when delayed, because of growth season shortening. Reproductive pruning greatly increased root yield. Increasing planting density affected root and fruit growth per plant but increased yield to a certain extent. Seed inoculation with effective rhizobia greatly increased root and seed production. Low temperature is a main factor to be considered as it reduced productivity in areas of cool nights. Ahipa has a low environmental impact and low input requirement (fertilizer, pesticides), providing an attractive alternative to traditional sources of carbohydrates for conserving non-renewable resources and maintaining farmer profitability. Competitive yields for the simultaneous production of starch, feed protein and industrial oil may be obtained with low investment using available landraces.     

Evidence on occupational migration

"This paper tests whether persons in highly skilled and higher-income occupations (who include professionals, managers, salespersons, clerical workers, and craftsworkers) are more likely to migrate when they perceive economic opportunities than persons in the lesser skilled and lower-income ones (who include operatives, transport workers, laborers, and service workers). "A simultaneous equations model of migration and employment change is specified for the nine major occupations defined in the U.S. census, and this model is estimated using occupation-specific data....This study is limited to an investigation of the impact of migration on a variable that was deemed to have been a significant determinant of the direction and magnitude of migration; this variable is occupation-related employment change by industry.... In order to analyze the migration response of persons in different occupations to varying economic conditions, this paper [includes] sections on theory and model specification, empirical results, and conclusions." Data are from the 1970 census.