锡林河流域草地地境的划分及特征

本文在土壤与草地资源调查的基础上,本着综合性、广泛性、一致性的原则,依据地形、土属、植物群丛组把锡林河流域草地地境划分为:中丘—砂壤质碳酸盐黑钙土—线叶菊、大针茅旱生杂类草地境;中丘—中厚层黑钙土—羊草、杂类草地境;低丘—砂壤质暗栗钙土—大针茅、旱生杂类草地境;缓坡—厚层暗栗钙土—羊草、大针茅地境;平地-壤质栗钙土-大针茅地境;河漫滩-腐殖质沼泽土—苔草地境;阳坡—紧砂土—山杏、羊柴地境;阴坡—紧砂土—稠李、漏斗叶绣线菊地境;丘间低地—沙栗土—大针茅、糙隐子草地境等9个地境,并对每个地境的植被、土壤和地形特点进行了描述。     

几种蚜虫对MDMV传毒效率及其口针中病毒附着位点(VAS)的免疫荧光标记

 本研究在测定了5种蚜虫对玉米矮花叶病毒(MDMV)传播效率的基础上,采用免疫荧光(FITC)标记方法,观察到蚜虫口针中MDMV附着位点(VAS)的存在。结果发现不同蚜虫之间的传毒效率及VAS有一定的差异。其中,以麦二叉蚜(Schizaphis graminum)的传毒效率最高,达66.8%。并且其VAS也最明显,位于口针末端约50μm处。通过试验发现,尽管在VAS存在的情况下,用提纯的不含HC的MDMV进行蚜虫传毒试验,其传毒率为零。只有当HC与MDMV共同存在的情况下才可有效传播。至于蚜虫是如何释放病毒的还不清楚。根据试验结果初步认为,蚜虫对MDMV的传播是一个"识别-吸附-释放"的过程。     

安徽省稻田千金子对氰氟草酯和噁唑酰草胺的抗性及其靶标分子机制

为明确安徽省稻田杂草千金子Leptochloa chinensis对氰氟草酯和噁唑酰草胺的抗性,从安徽省12个市38个县（市、区）稻区千金子发生较严重的田块中共采集72个千金子种群,采用整株生物测定法检测其对氰氟草酯和噁唑酰草胺的抗性,筛选同时对噁唑酰草胺和氰氟草酯有疑似抗性的千金子种群并测定其对这2种药剂的抗性水平,同时利用分子生物学技术检测千金子高抗种群的乙酰辅酶A羧化酶（acetyl-CoA carboxylase,ACCase）基因是否发生抗性位点氨基酸突变。结果显示,在72个千金子种群中,13个千金子种群已对氰氟草酯产生抗性,5个千金子种群已对噁唑酰草胺产生抗性;AH-1、AH-3、AH-7、AH-34和AH-72这5个千金子种群同时高抗氰氟草酯和噁唑酰草胺,其中对氰氟草酯的抗性指数介于21.98～65.52之间,对噁唑酰草胺的抗性指数介于11.76～27.19之间;这5个种群的ACCase基因片段均在2 027位点发生氨基酸突变,色氨酸突变为半胱氨酸;此外AH-3和AH-72这2个种群在1 999位点也由色氨酸突变为半胱氨酸,表明安徽省千金子已经对氰氟草酯和噁唑酰草胺产生交...     

Biochemical mechanisms of cross-resistance to aryloxyphenoxypropionate and cyclohexanedione herbicides in populations of Avena spp.

Aryloxyphenoxypropionate (APP) and cyclohexanedione (CHD) herbicides are used extensively in the UK to control grass weeds, including Avena spp. (wild-oats). Reports of resistance to APP and CHD herbicides are a particular concern for the agricultural community. In this study, the responses of four UK Avena populations were characterized towards the APP herbicides fenoxaprop-P-ethyl and fluazifop-P-butyl, and towards the CHD herbicides cycloxydim and tralkoxydim. An A. sterilis ssp. ludoviciana population (T/41) was found to be highly resistant to fenoxaprop-P-ethyl and fluazifop-P-butyl, but did not show cross-resistance to cycloxydim and tralkoxydim. In contrast, one A. sterilis ssp. ludoviciana (T/11) and one A. fatua population (Dorset) showed partial resistance to both APP herbicides and also showed cross-resistance to the CHD herbicide tralkoxydim, but not to cycloxydim. Before this study, the biochemical mechanisms that confer resistance to the APP and CHD herbicides in UK Avena populations were unknown. Results from the present study show that an enhanced rate of metabolism of fenoxaprop-P-ethyl was found to confer resistance in the two partially resistant Avena populations (T/11 and Dorset), and the presence of an insensitive form of the target enzyme, ACCase, was responsible for target site resistance to fenoxaprop-P-ethyl and fluazifop-P-butyl in the highly resistant population T/41. Cross-resistance to the CHD herbicide tralkoxydim in the T/11 and Dorset populations was not conferred by insensitive ACCase, and was most probably caused by enhanced metabolism. This is the first report that resistance to fenoxaprop-P-ethyl can be conferred by enhanced metabolism in Avena spp.     

大岗山实验局杉木人工林可变密度收获表的编制

本文利用推广的 Richards 生长模型编制了大岗山实验局杉木人工林的可变密度收获表,在这模型中包括地位指数及密度指数。误差分析表明此表适用于该地区的杉木人工林,这种编表方法是一种较好的方法。     

林龄和立地对渭北黄土高原刺槐和油松人工林的影响

基于双因子等级模型对龄级和立地好坏两个因子对渭北黄土高原刺槐和油松人工林的主要林分参数的作用效应进行了方差分析.结果表明龄级对大部分林分参数的影响不明显,虽然龄级内林分的上层高、密度、断面积等的实际年龄加权均值趋于随着龄级的增长而增加.很多龄级内"好”和"差"立地之间,林分参数除上层高外,差异也不显著.这是因为龄级内的林分利用方法和强度差别较大导致龄级内林分参数变差大于龄级间所致.一般是立地越好利用强度越大,因而导致好的立地上林分每公顷断面积和蓄积量低于差的立地上的林分.