The growth of roots of perennial, Italian, hybrid and annual ryegrasses through a high-strength root medium

Abstract A test for root penetration through a wax disc of known hardness was developed and used with twenty‐five cultivars and twenty‐one breeding lines of perennial, Italian, hybrid and annual ryegrasses. After 42 days, the number of roots reaching the wax disc and the number penetrating the disc were counted. Root diameters were measured using image analysis. The proportion of root penetrations ranged from 0·06 to 0·39 across the cultivars and breeding lines, with substantial variation between replicates and cultivars. Diploid perennial cultivars had the thinnest roots, and there were no consistent differences in root diameter between perennial breeding lines, hybrid ryegrasses and Italian ryegrasses. Roots that penetrated the wax disc increased in diameter, by 0·60 on average, a few millimetres above the wax, and through the wax disc. Diameters below the wax disc were the same as those above the zone of impeded root growth. The increase was caused by an increase in size of the parenchyma cells of the root cortex. An experiment with partially and completely impeded root growth showed that impedance did not change root diameter of new roots, or the distribution of root mass between impeded and unimpeded halves of a root system for plants up to 10 weeks old.     

匙叶天南星褐腐病的检出

 匙叶天南星是华南地区近几年新引入的一种重要花卉植物,1995年秋广东省广州市和顺德市栽种引自台湾的植株发生褐腐病,导致大量死亡。通过病原菌鉴定及对病土和各种种花基质进行的一系列试验,表明该病是由Cylindrocladium spathiphyli Schoulties et al.引起;病原菌是自台湾省随种苗和介质传入大陆的。建议在进行引种种苗时严格注意对植物根和介质的检疫。     

黄瓜自根苗、嫁接苗根系活力、净光合速率和蛋白质表达差异研究

将黄瓜津优1号、津优1号与黑子南瓜的嫁接苗和黑子南瓜种在网室中的消毒泥炭钵内,用LI-6400光合系统和2D-E电泳技术分析了这3种处理的根系活力、净光合速率和蛋白质的表达差异。结果表明,黑子南瓜的根系活力强于嫁接苗黄瓜,嫁接苗黄瓜的根系活力又强于自根苗黄瓜。在光量子通量密度低于500μmol.m-2.s-1时,嫁接黄瓜和黑子南瓜的净光合速率高于自根苗黄瓜,当光通量子密度超过500μmol.m-2.s-1后,嫁接黄瓜和黑子南瓜的净光合速率则低于自根苗黄瓜。当CO2浓度低于400μmol.mol-1时,嫁接黄瓜与自根苗的光合速率相当,CO2浓度超过400μmol.mol-1后,嫁接黄瓜的光合速率超过了自根苗。黑子南瓜的光合速率在50~600μmol.mol-1的CO2浓度范围内最高,然后下降,并间于嫁接黄瓜和自根苗黄瓜之间。嫁接的津优1号黄瓜有5个蛋白质的表达量增强了,同时也产生了5个新的蛋白质。     

黑龙江春小麦根腐病流行规律与予测方法研究

小麦根腐病的流行强度受气象因子的影响很大,小麦扬花期旬平均气温10℃以上,相对湿度80％以上,病害流行起点值高。在小麦生育后期出现高温高湿的气候环境,当年根腐叶枯发生严重。小麦扬花期病情指数5％左右,当年病害流行强度1级;叶部病情指数20％左右,当年病害流行强度可达4级。据病害发生程度与小麦扬花期叶部病情以及与气象因子的相关研究结果,研制出两种予测根腐叶枯流行强度的方法,置信度90％以上,可用于指导根腐叶枯的药剂防治。     

Interactions of fungicide-insecticide combinations against Rhizoctonia solani in vitro and in soil

The inhibition of mycelial growth of Rhizoctonia solani in vitro was strongest with pencycuron, followed by tolclofos-methyl, carboxin and thiabendazole. Against cowpea seedling rot in soil infested with R. solani, tolclofos-methyl was most effective, followed by pencycuron, thiabendazole and carboxin. Of nine insecticides tested, only parathion-methyl and quinalphos suppressed mycelial growth of R. solani in vitro, although their activity was much lower than that of the four tested fungicides. The inhibition of mycelial growth by fungicide-insecticide mixtures was antagonistic in only two out of 36 combinations; it was additive in most cases or synergistic, e.g. for most mixtures of pencycuron and insecticides. Quinalphos, applied to the soil, was the only insecticide which reduced cowpea seedling rot in soil infested with R. solani. Soil application of parathion-methyl, phorate, aldicarb or carbofuran and seed treatment with phosphamidon, monocrotophos, endosulfan or dimethoate had little or no effect on seedling rot. Carboxin gave better disease control when applied to the seed already coated with phosphamidon, monocrotophos, endosulfan or dimethoate and when carboxin-treated seeds were sown in soil treated with quinalphos, parathion-methyl, aldicarb or carbofuran. Efficacy of thiabendazole seed treatment was slightly higher in the presence of insecticides, particularly dimethoate. Pencycuron and tolclofos-methyl as seed treatment gave nearly 100% disease control both in the presence and absence of insecticides. The synergistic interactions detected between fungicides and insecticides represent interesting opportunities for the control of R. solani.     

利用碳14研究杉木苗根系分泌物

对１年生杉木苗进行二氧化碳１４喂饲，同时收集苗木根系分泌的有机物质，用液闪技术进行测定。结果表明：杉木苗的光合产物在标记１ｄ后就有１．０６％运输入根部组织中，３ｄ后则为４．９０％；２０ｄ近达到２４．０４％。二氧化碳１４喂饲一结束根系就有碳１４分泌物产生；３－５ｄ后分泌量达到最高峰，以后逐渐减少。对分泌物进行分离测定表明，其中糖类占３９．５３％，有机酸占１３．８０，氨基酸占５．４５％。     

Relationship of Root and Shoot Characters in Parent, F1 and F2 Populations of Rice

The direct and indirect contributions of root characters — root length, roots/plant, fresh and dry root weight on grain yield/plant were worked out from a 7 × 7 diallel set of rice hybrids. The materials were grown in pots with four replications. Path analysis was done at genotypic level of correlation.
The grain yield/plant showed positive correlation with all the root characters in parent, F₁ and F₂ except with roots/plant in F₁ population. Fresh root weight demonstrated positive direct effect on grain yield/plant in all the three generations. Roots/plant had highly positive direct effect in F₂. Direct effects were negative in respect of root length and dry root weight in F₂ generation.     

常系数线性齐次递归关系的研究

本研究建立了常系数线性齐次递归关系的数学模型及求解理论。     

Grain Yield and Drought Resistance Indices of Oat Cultivars in Field Rain Shelter and Laboratory Experiments

Oat cultivars (n = 22) varying in origin were examined in laboratory and field tests at Svalöv and Ultuna, Sweden, in 1985 and 1986. Comparisons were made between drought resistance characteristics of juvenile plants and drought responses in yield of crops grown in field. By using automatic, movable rain shelters in combination with drip irrigation systems, both high and low irrigation regimes could be effected in the field experiments.
Black oat cultivars were more stable under water deficiency conditions, particularly on sandy soil. They possessed the highest drought resistance indices both in the laboratory and field. Modern white oat cultivars were found to be most drought sensitive.
Drought resistance index (DRI) and seminal root length (RL), as assessed in seedling stage, were strongly correlated with field drought susceptibility index (S). It is suggested that DRI and RL could be used as selection criteria to increase drought resistance of oats.     

Characterization of Pectolytic Erwinias as Highly Sophisticated Pathogens of plants

Erwinia carotovora and Erwinia chrysanthemi are the two most important soft rotting bacteria of commercially-grown plants. They are genetically diverse as is evident from polymorphisms in the pel and recA genes as well as in rrn, the ribsomal gene cluster. Subpopulations grouped into biovars, pathovars, or subspecies associated with various hosts and in different geographic regions suggest specialization in host preference and/or survival in diverse environments. Previous characterization of the pectolytic erwinias as opportunistic pathogens is being replaced by a realization that this group of bacteria exhibits a sophisticated repertoire of pathogenicity and virulence genes and regulators. The presence of an entire hrp gene cluster and associated type III secretion system, and global regulators which regulate virulence determinants such as exoenzyme production and motility, attest to a highly specialized pathogen. The fact that production of extracellular plant cell wall-degrading enzymes are coordinately activated by the diffusible signal molecule N-acyl-homoserine lactone in a population density-dependent manner may explain the occurrence of pectolytic erwinia in asymptomatic plant tissues. Transgenic plants expressing bacterial quorum-sensing signal molecules modulate this sensory system and exhibit resistance to soft rot infection. The pectolytic erwinias, being significant plant pathogens that are neither of quarantine concern nor a human health hazard while readily isolated from field sources, make an ideal model for investigating the genetic basis of plant pathogenesis and environmental fitness.