The behaviour of roots encountering cracks in soil

Summary It is shown that probabilities of root penetration across cracks in soil can be calculated effectively using a mathematical model involving root stress and soil distributions and penetrometer/root stress ratios. Penetration criteria are developed, and it is found that the effective penetrometer/root stress ratios take values of about 4 for crack widths smaller than about 2 mm and about 8 for wider cracks. Root swelling does not appear to contribute significantly to the probability of root penetration through any effect on root buckling stress. Suggestions are made for further work on the effects of soil structure and strength on root behaviour.     

The Influence of the Application of Mineral Fertilizers with the Biopreparation Supresivit ( Trichoderma Harzianum ) on the Health and the Yield of Different Crops

The biopreparation Supresivit based on spores from the fungus Trichoderma harzianum was applied as a dressing mixed with mineral fertilizers: NPK, LAV (ammonium nitrate with limestone) and DASA (ammonium nitrate and ammonium sulphate). Our experimental plots with spring barley, winter wheat, winter oil rape, maize and potatoes were fertilized with the mixtures of the biopreparation (1 g, 0.5 g and 0.1 g per 1 kg of fertilizer). There were two check variants, the first variant without any fertilization and without biopreparation, the second with fertilizer and without biopreparation. We observed the infestation of plants with pathogenic fungi and yield parameters. In our experiments it was indicated that Trichoderma harzianum suppresses pathogenic fungi at the concentration 0,5 g of Supresivit per 1 kg of the fertilizer and higher ones. The plants from treated plots had lower infestation - decreasing about 5-15% superficial infestation: tan spot of barley - yellow leaf spot on cereals and leaf blotch of barley, winter wheat - leaf spot of wheat, tan spot of wheat, take-all etc., winter oil-seed rape - black leg and collar rot, potatoes - blight fungus etc. Simultaneously the effect on higher yields was observed.     

油菜细胞质雄性不育系发育进程中活性氧的代谢

为进一步认识活性氧化谢同雄性不育的联系,本文研究了油菜不同生长发育时期不育系与保持系的活性氧代谢的差异。     

Isciatica and Observation of Chloroplast DNA from the Rape and Tobacco

Chloroplast DNA (ctDNA)from the rape (Brassica napus) and tobacco (Nicotiana tabacum) has been isolated using a intact pure chloroplast lysis methed followed by discontinute sucrose gradient centrifugation and DNase treatment. Our electron microscopic observation on the chloroplast DNAs revealed clearly flowerlike configurations made up of many “petal-loops” linked together in the middle to forming one “central-loop”. The number of petal-loops per molecule varies from 5 to 50, usually about 7 or 8. The size of the petal-loops is not much different, being 1.52 ± 0.48μm and 1.28 ± 0.37μm in average length for rape and tobacco respactively. Some petal-loops appear attached to membrane protein, indicating the possibility that ctDNAs may have a similar organization as chromosome. Besides, some configurations are quite large with a total of over 50 petal-loops including 2 or 3 molecules linked together by petal-loops, and some rather small ones with a single circular molecule, the size of which is about to 1–2 petal-loops in length. Such variation in the size of ctDNA may suggest the possibility of hithly organized internal molecular arragement of the ctDNA and occurrence of intramolecular of intermolecular recombination.     

Hg对油菜叶细胞膜的损伤及细胞的自身保护作用

砂基培养50d的油菜幼苗,用不同浓度的HgCl₂溶液灌溉后,研究叶细胞膜结构与功能及细胞保护系统的变化。结果表明,0.5mg·L^-1Hg污灌叶细胞膜结构与功能未见明显变化,细胞保护系统亦无变化;浓度大于1mg·L^-1时,叶组织细胞膜脂质过氧化水平升高,膜结构损伤,膜透性增大。1～10mg·L^-1Hg污灌,组织蛋白质含量升高,SOD、POD、CAT活性表现出不同程度的升高,细胞呈现出积极性自身保护作用;50mg·L^-1Hg污灌,组织蛋白质含量下降,SOD、POD、CAT活性持续下降,细胞自身积极性保护作用消失,说明细胞自身保护系统只能在一定范围内起积极保护作用。     

油菜菌核病病斑扩展的动态模型

油菜菌核病主茎上病斑长度和面积的扩展与时间间的关系极相关,同一植株上、下部病斑扩展动态无明显差异,中、高两种肥力条件对主茎同一部位病斑扩展动态无明显影响,相对较低的湿度与病斑扩展相关不显著．     

BnFAD2、BnFAD3和BnFATB基因的共干扰对油菜种子脂肪酸组分的影响

甘蓝型油菜是一种重要的油料作物,为了改良其种子脂肪酸组分,提升其经济价值,本研究分析了油菜种子发育时期脂肪酸合成积累模式及BnFAD2、BnFAD3、BnFATB基因的表达规律,认为这3个基因在种子发育中后期(授粉后25d起)的高效表达对油酸合成积累有着重要影响。通过Napin启动子诱导对油菜植株中BnFAD2、BnFAD3、BnFATB基因进行RNAi共干扰抑制,以达到提升油酸含量的目的。试验结果表明,转基因油菜种子中BnFAD2、BnFAD3、BnFATB基因的表达受到强烈抑制,种子中油酸含量由66.76%提升至82.98%,且油脂合成的相关基因同步出现表达上调。     

麦秸与稻秸浸提液对油菜及2种靶标杂草种苗生长影响的差异性研究

采用室内培养皿生物测定的方法,测试不同质量浓度（0、0.02、0.03、0.05、0.08、0.10 g·mL^-1）麦秸、稻秸浸提液对油菜及油菜田2种常见靶标杂草野燕麦（Avena fatua Linn）、播娘蒿 ［Descurainia sophia（L.）Schur］种子萌发及幼苗生长的影响。结果表明,在供试质量浓度下,麦秸与稻秸浸提液对3种受体材料种苗生长的影响存在显著差异,二者对油菜种苗生长安全的最高质量浓度分别为0.08 g·mL^-1和0.05 g·mL^-1,可以用来开发研制油菜田肥料;在对油菜安全的质量浓度下,麦秸浸提液对野燕麦种苗生长无抑制作用;而稻秸浸提液对野燕麦种苗生长的抑制作用明显,可以用来开发研制油菜田防除野燕麦的生物抑草肥;在油菜的安全的质量浓度下,麦秸、稻秸浸提液对播娘蒿种苗生长均有很强的抑制作用,且麦秸的抑制作用强于稻秸,具有开发研制油菜田治理播娘蒿的生物抑草肥料的应用前景。