种子质量的一个重要指标——种子活力及其测定

本文简述了国内外在种子活力方面的研究,论述了种子活力作为种子质量指标的重要性,并对活力测定的使用范围、主要测定方法进行了讨论。     

柏木(Cupressus funebris Endl)材质、材性要素的宏观生态变异

在随机抽取木材样件并进行材质材性测定的基础上,通过典型正交分析,研究了柏木材质的宏观生态变异规律。结果表明林型、立地类型、栽培区和经营类型的改变显著地影响到柏木的材质材性要素。与阔叶树种混交显著增大了气干密度、管胞长度和年轮宽度,提高了木材抗压,抗弯强度;随着立地的贫瘠化,木材抗压、抗弯强度增大;栽培区和经营类型的改变主要通过调节木材数量生长影响及材质、材性。研究结果为柏木材质定向培育提供了科学的措施依据。     

Determining spatial and temporal variability in quantity and quality of vegetation for estimating the predictable sustainable stocking rate in the semi-arid savanna

This study assessed the importance of spatial and temporal variation in plant quality and quantity for determining sustainable stocking rates in game, commercial and communal ranches in semi-arid savanna of the Northern Cape Province, South Africa, in wet and dry seasons over a two-year period. We focussed on variation in plant biomass, phosphorus (P), crude protein (CP) concentrations and dry matter digestibility as parameters most likely to affect sustainable stocking rates. Habitat type had greater effects on plant quality, plant biomass and species composition than management type. The commercially-managed area had the highest tree density in the rocky habitat and lower plant quality than other management types. All of these features indicate that land degradation is occurring on commercial ranches in spite of rotational grazing and lower stocking density than on communal ranches. We recommend that commercial ranchers should introduce a greater variety of stock and/or game to reduce selective grazing of certain plant species. Quality measures (CP and P) gave more conservative predictions of stocking density than biomass. In this region of the Northern Cape, seasonally-inundated pan habitats are particularly valuable in spite of low-standing crop because they have the highest year-round quality. Contrastingly, ranchers should only lightly stock open savanna habitats, in spite of high standing biomass, because they have low vegetation quality and may be particularly susceptible to degradation and invasion by poisonous and unpalatable plants.     

有机肥对鱼腥草产量品质及养分吸收的影响

采用盆栽试验 ,研究了猪粪、牛粪的不同用量对鱼腥草产量、品质及养分吸收的影响。结果表明 :猪粪用量较少时无明显增产作用 ,用量增至 2 2 5g/盆 (相当大田用量 76 5 0 0kg/hm2 )时才获得显著增产 (P =0 0 5 ) ;在粘质土中 ,施用牛粪的增产量比猪粪平均高 34 5 %。适宜有机肥用量能提高根可溶性糖含量 ,用量过大反而使其含量降低 ;根Vc含量则随有机肥用量的增加而逐渐降低。牛粪对鱼腥草中甲基正壬酮的形成有不利影响 ,而获得最大药用价值的猪粪用量为 15 0 g/盆 (相当大田用量 5 10 0 0kg/hm2 ) ,猪粪用量过大 ,反使甲基正壬酮含量大为降低。施用有机肥能明显提高植株氮、磷、钾含量 ,是改善鱼腥草氮、磷、钾营养的有效途径     

肌纤维生长的影响因素分析

采用三因子多水平有重复试验的方法 ,对可能影响肌纤维生长的 3个因素 (品种、氟烷基因型、营养 )进行研究。结果表明 :不同的品种和组合对肌纤维的生长和杂种优势的产生有极其重要的作用 ,影响达极显著水平 (F =9 0 3,Pr =0 0 0 0 1) ,荣昌猪 (RC)的肌纤维面积显著地低于长白猪 (L)和约克猪 (Y) ;约克猪 (Y)的肌纤维面积又显著地低于长白猪 (L)。长约猪 (LY)的肌纤维面积接近两亲本均值 ,表现出较微弱的杂种优势 (5 0 0 % ) ;长荣猪(LR)的肌纤维面积远高于两亲本均值 ,表现出极高的杂种优势 (12 6 3% ) ,达显著水平 ;氟烷阳性纯合子个体 (nn)的肌纤维面积明显大于阴性纯合子个体 (NN)和杂合子个体 (Nn) ,而阴性纯合子个体 (NN)和杂合子个体 (Nn)间差异不显著 ;不同能量、蛋白质水平对肌纤维面积的影响不显著 ,但品种与营养水平的交互效应对肌纤维面积有一定程度的影响     

单胚甜橙优系—王字4号的生物学特性及经济性状研究

王字４号是四川新胜茶场选出的甜橙（ＣｉｔｒｕｓＳｉｎｅｎｓｉｓ）优良单株，具果大、质优、少核、晚熟、较耐低温等综合优良性状。特别是单胚率高而稳定，１９９０—１９９２年镜检，单胚率分别为９８．１５％、９５．６％、９７．７％。     

中国南方小麦优质高效生产的若干问题

文章分析了当前我国南方麦区小麦生产存在的问题和解决这些问题的可能方法。近二十年来 ,中国南方麦区小麦生产的发展落后于北方麦区 ,主要原因是育成的小麦新品种和北方麦区相比 ,表现为品质差、产量低和抗病性丧失快。本文批驳了南方麦区可以不种小麦的观点 ,指出在农业结构调整中 ,小麦生产仍然是重要的内容。南方小麦的品质差的主要原因不是气候因素 ,而是没有与南方生态条件相适应的优质品种。文中提出了培育南方麦区优质小麦品种的策略。本文指出 ,根据南方麦区的气候和生态特点 ,认真研究适应南方麦区的优质高产抗病小麦新品种和高效栽培的方法 ,是使南方小麦生产走出困境的途径     

桃树黄化病施铁矫正的效果

１９９２－１９９３年在有严重黄化病的桃树上进行施铁试验。用根系输入法施用ＴＬ－Ｆｅ，７－１０天即可使叶片转绿，复绿果达１００％，并使叶片含铁量增加７１．２％，叶绿素增加３．４倍，过氧化氢酶活性提高５倍，单株挂果数增加４．２倍。果重增加７０．９％，果实品质也得到明显改善。     

应用主成分分析法构建肉质指数的研究

应用主成分分析法 ,通过综合所选定的各项肉质指标的成绩 ,得到一个客观的量化指标———肉质指数(MQI)。这个肉质指数能准确地反应个体间肉质的差异 ,各猪只的肉质优劣可根据其肉质指数的高低直接进行评判。这就将主观性极强的肉质评定过程转化成了一个客观的量化指标 ,为肉质性状纳入育种计划提供了可能 ,并为选育提高群体肉质创造了条件     

Kikuyu over-sown with ryegrass and clover: dry matter production,botanical composition and nutritional value

The seasonality of growth and low nutritional value of kikuyu (Pennisetum clandestinum) pasture restrict milk production. The aim of the study was to determine the dry matter yield, botanical composition and nutritional value of irrigated kikuyu over-sown with annual ryegrass (Lolium multiflorum var. westerwoldicum), white clover (Trifolium repens) and red clover (T. pratense) or a mixture of perennial ryegrass (Lolium perenne) with white and red clovers under intensive grazing conditions with dairy cows. The incorporation of annual ryegrass, perennial clover or perennial ryegrass–clover into kikuyu pasture changed the seasonal fodder flow and increased the spring dry matter (DM) production. The over-sowing of kikuyu with annual ryegrass had no effect on the DM production of kikuyu during the summer and autumn. Kikuyu and kikuyu–ryegrass, fertilised with nitrogen fertiliser, had a higher DM production rate than kikuyu–clover pastures. Kikuyu–ryegrass pasture transformed from ryegrass-dominant in spring to kikuyu-dominant in summer and only kikuyu in autumn. This led to a decrease in metabolisable energy (ME) and increase in neutral detergent fibre (NDF) content of the pasture during spring, summer and autumn as kikuyu became more dominant. The clover content of kikuyu over-sown with clover decreased annually but was still higher than 30% at the end of two years after establishment. As the kikuyu content of the kikuyu–clover pastures increased, the seasonal growth rate changed from a low autumn growth (37.9 kg DM ha^?1 d^?1) in the first year to a higher autumn growth (48.5 kg DM ha^?1 d^?1) in the second year. The over-sowing of kikuyu with clover resulted in lower DM production and NDF values and higher crude protein (CP), ME and calcium (Ca) values. The lowest CP content in kikuyu–ryegrass pasture was during summer and autumn when kikuyu was dominant. The Ca content of the grass pastures (kikuyu and kikuyu–ryegrass) was low. The phosphorus (P) content of both the kikuyu–clover and grass pastures exceeded the requirement needed for dairy production (0.38%). The mean Ca:P ratio of the kikuyu–clover pasture meets the 1.6:1 ratio needed by dairy cows. The kikuyu and kikuyu–ryegrass pasture had a Ca:P ratio lower than 1:1 and Ca supplementation would be needed for dairy cows. The incorporation of annual ryegrass, perennial clover or perennial ryegrass–clover into kikuyu pasture improved the seasonal DM production and nutritional value of the pasture.