小麦温敏不育系BNS366育性研究

为了揭示小麦温敏不育系BNS366的育性转换规律,为不育系的转育及杂种优势利用提供依据,于2011-2013年度连续2年采用大田分期播种试验分析了BNS366、BNS、矮抗58和扬麦13的育性特点。结果表明,随着播种期的推迟,BNS366表现出规律性育性转换特征。9月23日至10月17日播种,花粉败育率为99.77%~100%,自交不育度为99.21%~99.81%,每穗自交实粒数为0.10~0.51。10月25日播种,花粉败育率为91.78%~98.89%,自交不育度为92.86%~94.96%,每穗自交结实粒数为3.20~4.37,12月4日播种可育。BNS366具有两个育性转换的临界期,10月25日播期为不育变为高度不育的育性转换临界期,12月4日播期为半不育转换为可育的育性转换临界期,不育期花粉以典型败育为主。BNS366可以作为小麦杂种优势利用新的不育系。     

小麦BNS雄性不育系晚霜冻抗性和低温不育特性观察

BNS是一个低温敏感型小麦雄性不育系，穗分化期间8 ℃以下低温可诱导其花粉败育。为了持续观察BNS的不育特性，于2017年秋季分期播种了BNS及其保持系郑麦366。2018年4月5日至6日该地区发生晚霜冻，草面温度-1.7 ℃，许多小麦品种受到冻害。抽穗后，观察BNS和郑麦366两个材料的冻害特征、穗分化进程和自交结实率，结果发现，10月9日正季播种的郑麦366冻害严重，受冻株率超过75%，11月18日播种的郑麦366未受冻；10月1日和11月17日播种的BNS未受冻，期间的5个播期均出现轻度冻害，受冻株率3.7%～5.4%；郑麦366和BNS两个品种冻害发生的温度敏感期均为药隔期至减数分裂期，并且冻害组织单位是整小穗，而非小花；10月1日和9日播种的BNS自交结实率分别为5.08%和10.41%，高于过去年份的结实率水平，分析发现是霜冻发生前12 d 连续15 ℃以上高温所诱导；BNS对低温敏感始于雌雄蕊分化始期，1周左右即可完成不育诱导，此后高温仅转换少部分小花为可育，后来的霜冻强低温也未能恢复BNS为完全不育。     

高温不育小麦育性转换特性研究

为研究高温雄性不育小麦周13S -1的育性转换特性,2004～2005年在广东湛江进行了分期播种试验.结果表明,周13S -1育性变化趋势为"部分不育-高度不育-部分不育",不育的时间长,不育期败育程度高.温度是引起周13S -1雄性育性发生转换的主要原因,日长对其雄性育性没有显著影响.抽穗前26～18 d平均日均温与自交结实率的相关达极显著水平.当抽穗前25～21 d平均日均温在20.32℃以上时周13S -1表现完全不育;低于19℃表现部分不育,能够自交结实,且育性随着温度的降低而升高.说明周13S -1的育性临界温度在20℃左右.在湛江10月15日至11月15日播种表现高度不育,自交结实率在1.5%以下,可以用于生产杂交种;10月15日以前和11月15日以后播种均表现部分不育,可以自交繁殖.育性转换对温度的敏感时期为抽穗前26～18 d,此时生育时期为倒二叶露尖前后,穗分化时期为药隔期.相关分析表明花粉育性和自交结实率无显著相关.     

小麦温度敏感不育系A3314温敏特性研究

为了建立技术简便、成本低廉的二系杂交小麦种子生产体系 ,选育适应范围广泛的温敏不育系 ,采用多点分期播种和分期剪穗再生分蘖等方法 ,调查分析了小麦温度敏感不育系 A3314的育性转换条件 ,结果表明 :A3314在中国黄淮冬麦区、云贵冬麦区、西北春麦区、东北春麦区各点 ,按当地小麦生产正季播种均表现稳定雄性不育 ,雄性不育的安全播种期达 6 0 d左右 ;而在黄淮和云贵冬麦区春播、夏播则自交结实 ,适宜条件下自交结实率可达 6 0 %以上。杨陵 10期分期播种和 8期分期剪穗再生分蘖的育性与各期孕穗至开花期间的日平均气温、空气相对湿度、日长的关系分析表明 :A3314的育性具有温度敏感特性 ;孕穗期前后 8d,即减数分裂至单核期 ,是其育性转换的敏感时期 ,此期处于 >18.3℃温度条件下 ,A3314则由雄性不育转换为可育 ;育性转换与日长无显著相关 ;在敏感期>18℃的可育环境下 ,自交结实率与 4 0 %～ 80 %范围内的空气相对湿度呈显著正相关。根据 A 3314的温敏特性 ,推测它在中国大部分小麦产区均可安全用于杂交小麦制种。     

高温对甘蓝型油菜隐性上位互作核不育稳定性的影响

为深入了解生产中出现的微粉现象,研究了人工高温和分期播种情况下甘蓝型油菜隐性上位互作核不育纯合型不育系9012A和杂合型不育系12-204A的不育稳定性。结果表明,两种类型不育系在一定高温胁迫下,均出现育性转换现象,但对高温的敏感性有明显差异。对于9012A系,育性转换临界温度介于30~35℃之间;40℃持续处理16~32h,或者间歇处理3h/d×6d、6h/d×5d、9h/d×4d、12h/d×3d、15h/d×2-4d(累计40℃处理18~60h),或35℃间歇处理15h/d×2-4d(即35℃累计30~60h)均发生育性转换,其中35℃时15h/d×3d(即35℃累计45h)处理育性转换最为明显,说明高温对9012A育性转换具有累加效应。自然条件下6个播期(从2014年10月16日到2015年2月9日,即秋冬播种,避开30℃以上持续高温)的不育性彻底稳定。对于12-204A系,育性转换临界温度为29℃,不低于29℃时育性发生转换,其中35℃15h连续处理育性转换效果最为明显;自然条件下6个播期均发生育性转换。当高温胁迫下育性发生转换时,9012A和12-204A均可自交结实,但是结实性差。     

两系小麦BNS花粉育性与气象因子的关系

为探讨小麦温光敏不育系BNS花粉育性转化规律,2009年9月至2010年5月采用分期播种试验,测定了不同播期的小麦花粉育性,同时对其花粉育性与气象因子的关系进行了分析.结果表明:BNS花粉育性随播期的推迟而变化,出现了从完全不育到可育的育性转换过程,11月10日前播种花粉败育率为95％以上,表现为高度不育,11月10日、11月18日和11月26日播种,育性处在转换期,随播期推迟花粉败育率逐渐降低;BNS的花粉败育率与抽穗前10～15d的平均温度和抽穗前7～15d的平均最低温度呈极显著负相关;低温是影响BNS育性转换的主要因素,表现低温不育,高温可育,当温度低于8.9℃时表现彻底不育,此后随着温度的升高花粉败育率逐步降低;BNS的花粉败育率与抽穗前10～15d的日照时数呈极显著负相关.BNS花粉育性与温度和日照时数有极显著相关性,且其温度的影响大于日照时数的影响.     

籼型三系不育系育性与温、光的关系初探

通过分期播种试验,对生产上应用的水稻三系不育系天丰A、龙特浦A、Ⅱ-32A、金32A的花粉败育类型与始穗前15 d温、光条件的关系进行了探讨.结果表明,供试三系不育系的花粉败育程度在不同的温度下表现不同,天丰A的花粉可染率和自交结实率及Ⅱ-32A的花粉可染率均与始穗前15 d的日平均气温呈显著正相关,龙特浦A的花粉可染率和自交结实率均与始穗前15 d的日平均气温呈显著负相关,不育系育性与光长相关不显著.据初步观察,温度对不育系育性的影响时期为幼穗雌雄蕊分化期至减数分裂期.     

BNS小麦雄性不育性表现及其恢复性的研究

为研究来自河南的小麦温光敏雄性不育材料BNS在陕西关中地区用于杂交小麦育种的可能性,在陕西杨凌进行了BNS连续四年的分期播种试验和杂种F₁育性恢复测验。结果表明,BNS在10月17日以前播种的自交结实率平均值为1.41%,变幅为0.07%~4.96%,呈全不育至高不育,可进行BNS杂交种制种;11月18日以后播种的自交结实率平均值为68.23%,变幅为42.91%~98.96%,育性得到恢复,可进行BNS繁种;10月25日至11月10日之间播种BNS的自交结实率为17.48%~46.77%,表现为半不育特性。BNS的育性随播期的上述变化趋势年度间较稳定。测恢试验的78个杂种F₁组合中,3个组合的育性得到恢复,分别为BNS/9833、BNS/SN055525和BNS/CL0442,其自交结实率分别为118.54%、104.564%和102.021%,说明9833等三个材料携带对BNS的育性恢复基因。综上,BNS在陕西关中地区可同时实现繁种和制种,在普通小麦中亦能找到恢复源,因此在该地区具备应用于杂交小麦育种的潜力。     

重庆温光敏核不育小麦C49S的育性稳定性分析

为了研究重庆温光敏核不育小麦C49S在杂种优势利用中的价值,根据7年田间分期播种试验结果分析了C49S年度间的育性稳定性及其可育与不育的临界播种期.结果表明,在气温正常年份,C49S随着播期的变化表现出"完全不育-半不育-高度可育"的育性转换特性,且在不同年份间育性转换特性稳定;在重庆,10月31日是C49S的不育临界播种期,在此之前播种表现完全不育或高度不育,自交结实率在5%以下;12月10日是其正常可育的临界播种期,在此之后播种表现正常可育,自交结实率在50%以上;11月10日至11月30日之间播种,处于半不育状态,自交结实率为5%～50%.可以通过调整其播期来进行制种或繁殖.     

YM型小麦雄性不育系KTM3314A的温敏特性

为了明确YM型小麦温敏不育系KTM3314A的育性转换特性,以1B/1R类型K型小麦雄性不育系K3314A和YM型小麦雄性不育系KTM3314A为试验材料,进行分期播种(秋播、春播)和剪穂再生试验,以K3314A为对照,比较不同播期及再生分蘖穗的自交结实率,并与同期的温度、湿度等气象数据对照,以确定KTM3314A的温度敏感期和临界温度。结果表明,K3314A秋播、春播及再生分蘖穗皆完全雄性不育,KTM3314A秋播完全雄性不育,春播及再生分蘖穗育性部分恢复,育性转换的温度敏感期在孕穗前后5 d,临界温度为18.14℃,表明KTM3314A具有温度敏感特性。     

小白菜对土壤中5种重金属的富集特征及土壤安全临界值的研究

通过采集珠三角地区蔬菜产地各重金属浓度土壤(非人工添加重金属)进行盆栽试验,研究5种重金属(Cd、Pb、As、Hg、Cr)在种植小白菜(Brassica chinensis L.)土壤中的活性、小白菜可食部分对土壤中重金属全量和有效态含量的富集特征,并探讨了产地环境土壤中5种重金属的安全临界值以及影响小白菜吸收重金属的因素。结果表明:种植小白菜的土壤中重金属的活性高低顺序为Cd>Pb>As>Cr>Hg,小白菜对重金属的富集能力顺序为Cd>(Cr、As、Hg)>Pb。依据食品卫生标准的限量值进行方程拟合,得出适合小白菜种植土壤的重金属全量限量值分别是Cd:1.74mg/kg,Pb:494.78mg/kg,As:113.58mg/kg,有效态重金属限量值分别是Cd:0.83 mg/kg,Pb:146.87 mg/kg,As:21.94 mg/kg。小白菜对Hg表现为低积累。土壤中有机质、CEC与土壤全量Hg正相关,CEC与土壤全量Cr负相关,土壤pH能增强土壤中Cr活性。     

Row spacing and weed control timing affect yield of aerobic rice

Field experiments were conducted during the wet season of 2009 and dry season of 2010 to determine the effects of row spacing and timing of weed control on weed growth and yield of aerobic rice. Ten weed management treatments were used to identify critical periods of weed competition with aerobic rice grown in three different row spacings (15-cm, 30-cm, and as paired rows 10-20-10-cm). Dominant weed species during both growing seasons were Rottboellia cochinchinensis, Digitaria ciliaris, Echinochloa colona, and Eleusine indica. Rice grown in 30-cm rows had greater weed biomass and less grain yield than in 15-cm and 10-20-10-cm rows; weed growth and grain yields were similar between 15-cm and 10-20-10-cm rows. Rice yields in the wet season ranged from 170 kg ha⁻¹ where weeds were not controlled throughout the crop duration to 2940 kg ha⁻¹ in weed-free treatment, indicating a 94% yield loss with uncontrolled weed growth. Similarly in the dry season, plots with no weed control (140 kg ha⁻¹) compared to weed-free plots (3640 kg ha⁻¹) indicate a 96% yield loss with no weed control. Gompertz and logistic equations were fitted to yield data resulting from increasing durations of weed control and weed interference, respectively. Critical periods for weed control in the wet season, to obtain 95% of a weed-free yield, were estimated as between 18 and 52 days after sowing (DAS) for crops in rows at 15-cm, 20-51 DAS at 10-20-10-cm, and 15-58 DAS at 30-cm. These intervals in the dry season were 17-56 DAS for crops in rows at 15-cm and 17-60 DAS at 10-20-10-cm and 15-64 DAS at 30-cm. Durations of the critical periods in the wet season were 31 days at 10-20-10-cm, 34 days at 15-cm and 43 days at 30-cm, while in the dry season, these were 43 days at 10-20-10-cm, 39 days at 15-cm and 49 days at 30-cm. In both seasons, crops in the wider spacing (30-cm) were vulnerable to weed competition for the longest period. The information gained from this study suggests that the aerobic rice yields better in 15-cm rows and 10-20-10-cm arrangements than in 30-cm rows and there is very little benefit of weed control beyond 8 weeks after sowing.     

杂交籼稻气候适应性及播种期的研究

通过播种期试验结果分析,杂交籼稻的播种期对其生育进程、植株性状、产量及其构成因子均有较为显著的影响,结合气象资料分析,杂交籼稻在中纬度地段（苏北地区）,保证安全齐穗和安全成熟的临界播种期均为5月15日。     

A joint influence of the distributions of fiber length and fineness on the strength efficiency of the fibers in yarn

The length and fineness of fibers are critical to the strength of yarns. Much research has been conducted on the issue in the past decades. Zeidman and Sawhney introduced a new parameter called strength efficiency (SE) of fibers in a yarn using an elaborate probabilistic method. Their final formula, a non-dimensional measure, describes the influence of the fiber length distribution on the strength of yarn. The result, however, is based on the assumption that the fibers are identical in all respects including their cross-sectional area. The influence of fiber fineness can not be seen in their formula. In fact the joint influence of fiber length and fineness is rarely studied. We derive a new strength efficiency of the joint influence of fiber length and fineness on the basis of Zeidman’s result. The conclusion is helpful to the understanding of the comprehensive influence of fiber length and fineness on the strength of yarn. Furthermore, we give a plausible method to estimate the critical length defined by Zeidman. The result can be applied to the research of the properties between fibers and yarns.     

The critical period for weed control in three corn (Zea mays L.) types

Knowledge of the crop-weed competition period is vital for designing effective weed management strategies in crop production systems. Field studies were conducted at the Agricultural Research Institute, Kahramanmaras, Turkey in 2013 and 2014 to determine the critical period for weed control (CPWC) in three corn (Zea mays L.) types (field corn, popcorn, and sweet corn). A four parameter log-logistic model described the relationship between relative crop yield to both increasing duration of weed interference and length of weed-free periods. The relative yield of corn was influenced by duration of weed-infested or weed-free period, regardless of corn types. Increasing periods of weed interference significantly reduced corn yields in both years. In field corn, the CPWC ranged from 175 to 788 growing degree days (GDD) in 2013 which corresponded to V2–V12 growth stages, and 165–655 GDD (V1–V10 growth stages) in 2014 based on the 5% acceptable yield loss (AYL) level. In popcorn, the CPWC ranged from 92 to 615 GDD (VE–V10 growth stages) in 2013 and 110–678 GDD (V1–V10 growth stages) in 2014. In sweet corn, the CPWC ranged from 203 to 611 GDD in 2013 (V2–V10 growth stages) and 182–632 GDD (V2–V10 growth stages) in 2014. The practical implication of this study is that weed management should be initiated around V1 stage and maintained weed-free up to V12 stage in all corn types to prevent yield losses greater than 5%. These findings could help corn producers improve the cost effectiveness and efficacy of their weed management programs.     

Buckling of fibers under distributed axial load

The analysis of buckling of fibers with continuously varying cross section under distributed axial load has been investigated by using numerical method. The eigenvalues and critical length of the vertical fiber column which the moment of inertia and the intensity of distributed axial load vary according to a power of the distance are given in a tabulated form.     

硼素对甜菜产质量效应及施用技术的研究

试验结果表明,不同土壤类型,硼素施用效果不同.黑土区在NP基础上施硼平均增产块根11％,含糖提高0.3～0.9度,产糖量平均提高15％.在碳酸盐黑钙土区,施硼效果不明显.硼与氮、磷、钾的最佳配比为:N:P_2O_5:KaO:B=1:1.6:1:0.07.要素总用量为11.2kg/亩.土壤中有效硼的临界值为0.5ppm。试验还看出,施硼有明显提高叶绿素含量和促进生长发育作用,     

The influence of fiber length distribution on the accelerated points in drafting: A new perspective on drafting process

The distribution of the accelerated points of fibers in roller drafting is the key to the evenness of the drafted slivers. The fiber length distribution is believed to affect the accelerated points. This approach is trying to give a quantitative expression of the influence. A parabolic density function is introduced for the expression of density functions and a generalized method is presented. The experiment shows that the parabolic-type density function is a better explanation for the distribution of the accelerated points in the drafting zone in terms of the consequent yarn unevenness. The statistical test verifies the distribution type. The analysis helps to understand the mechanism of the roller drafting and can be used in the optimization of the parameters in roller drafting.     

Photoperiodic Regulationof Apical Growth Cessation in Northern Tree Species

Summary

Tree species adapted to the climatic conditions of the northern boreal and subarctic vegetation zones have a capacity to develop a very high level of frost hardiness, even to survive the temperature of liquid nitrogen in midwinter. Proper timing of hardening, as well as of dehardening, is crucial for winter survival of these species. In northern tree species, cessation of apical elongation growth and bud set is a prerequisite for developmental and metabolic processes leading to hardening, and this chain of events is induced by photoperiod. The northern tree species are closely adapted to the local light climate and display photoperiodic ecotypes. The critical photoperiod is under genetic control and increases with increasing latitude of origin of the eco-type. The photoperiod is probably perceived by the phytochrome system, but the role of other pigment systems, like cryptochrome, has not been studied in woody plants. Phytochrome genes have been cloned from both conifers and deciduous species, but so far we do not have any information about possible differences between photoperiodic ecotypes at the phytochrome level. Northern and southern ecotypes have different responses to red:far red ratios, which could indicate differences in composition of their phytochrome systems, for example, the proportions of phytochrome A and B. Both phytochrome A and phytochrome B can be involved in photoperiodic responses. Experiments with transgenic hybrid aspen suggest that responses to photoperiod could be affected by the amount of phytochrome A present in plants. In deciduous species, the plant hormone gibberellin A₁ (GA1) can completely substitute for a long photoperiod, and short day induced cessation of growth is preceded by a significant reduction of GA1 levels, particularly in the elongation zone. Photoperiodic control of GA metabolism is supported by several studies, but very little is known about the interaction between phytochrome and GA metabolism and/or responsiveness to GA1. Although our knowledge is still very fragmentary, available results suggest that cessation of growth and initiation of hardening in trees can be controlled both through the phytochrome and the GA mediated systems. Research with tree species is a tedious and slow process, but with the emerging new methods and approaches, we may expect exciting new results in the near future.     

The critical period for weed competition in French bean (Phaseolus vulgaris L.) in Mediterranean areas

Field experiments were carried out in 2004 and repeated in 2005 and 2006 in central Italy to determine the effect of competition from a natural weed flora on growth and yield of French bean (Phaseolus vulgaris L.). Two treatments were applied; weeds were either allowed to infest the crop or plots were kept weed free for an increasing duration of time (0, 7, 21, 28, 35, 45 days) after crop emergence. To assess the critical period of weed competition (CPWC) and the influence of weed infestation on yield, the Gompertz and logistic equations were fitted to data which represented the increasing duration of weed-free and weed-infested periods, respectively. During the three years of the experiment weeds, allowed to interfere for the whole growing season, reduced fresh pods yields up to 60%, 65% and 59% of the weed-free bean plots. Based upon an arbitrary yield loss (AYL) of 5%, the CPWC was from 50 Growing Degree Days (GDD) to 284 GDD, i.e. from 11 days after emergence (DAE) to 28 DAE. These values correspond to the lowest and highest values observed in the three experiments respectively for the weed-infested and weed-free period.