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81.
The effect of termites on the breakdown of Pennisetum pedicellatum straw under Sahelian conditions was studied in northern Burkina Faso during the dry and wet seasons of 1995. Litterbags were
laid on plots treated with drieldrin at a rate of 500 g a.i. (active ingredient) ha–1 to exclude termite activity and on untreated plots. Termites were the only macroscopically visible consumers which were observed
in the litterbags during the dry and wet season. In litterbags with no termites present the rate of breakdown of straw was
lower during both the dry or wet seasons than in litterbags with termites. In the litterbags with termites, much of the mulch
was taken off and replaced by termite-made sheeting. From April to September over 60% of the added material disappeared from
termite litterbags, while only 18% of the added straw disappeared from litterbags without termites. From October to December,
28% of the straw disappeared from termite-infested litterbags versus 8% from litterbags without termites. The contribution
of termites to the breakdown of straw was estimated to be over 70% for each of the two experiments. Under Sahelian conditions,
the breakdown of organic residues is strongly influenced by termites.
Received: 6 May 1998 相似文献
82.
Summary We studied the effect of three successive cuttings on N uptake and fixation and N distribution in Leucaena leucocephala. Two isolines, uninoculated or inoculated with three different Rhizobium strains, were grown for 36 weeks and cut every 12 weeks. The soil was labelled with 50 ppm KNO3 enriched with 10 atom % 15N excess soon after the first cutting. Except for the atom % 15N excess in branches of K28 at the second cutting, both the L. leucocephala isolines showed similar patterns of total N, fixed N2, and N from fertilizer distribution in different parts of the plant at each cutting. The Rhizobium strain did not influence the partitioning of 15N among the different plant parts. Significant differences in 15N enrichment occurred in different parts. Live nodules of both isolines showed the lowest atom % 15N excess values (0.087), followed by leaves (0.492), branches (0.552), stems (0.591), and roots (0.857). The roots contained about 60% of the total plant N and about 70% of the total N derived from fertilizer over the successive cuttings. The total N2 fixed in the roots was about 60% of that fixed in the whole plant, while the shoots contained only 20% of the fixed N2. We conclude that N reserves in roots and nodules constitute another N source that must be taken into account when estimating fixed N2 or the N balance after pruning or cutting plants. 15N enrichment declined up to about fivefold in the reference and the N2-fixing plants over 24 weeks following the 15N application. The proportion and the amounts of N derived from fertilizer decreased, while the amount derived from N2 fixation increased with time although its proportion remained constant. 相似文献
83.
In 12th century, the Buddhist priest Eisai brought tea ( Camellia sinensis L.) seeds to Japan from China and now tea plants are cultivated all over Japan except in the Hokkaido and Tohoku districts. The quality (reflected in the price) of Japanese green tea is affected by the nitrogen content. Consequently in tea fields, for last three decades large amounts of fertilizer have been applied to produce high quality tea. As a result, problems such as acidification of soil have been caused. It is also known that the growth of tea plants is stimulated by the addition of aluminum (Al) under acidic conditions. In this keynote address, some problems caused by excess applications of fertilizer in tea fields and the growth characteristics of tea plants related to Al are presented. 相似文献
84.
Soil compaction is of great importance in agriculture, because its high levels may adversely affect plant growth and the environment. Since mechanical methods are not very efficient and economical, using biological methods to alleviate the stress of soil compaction on plant growth may be beneficial. The objectives of this study were to: (1) evaluate the effects of soil compaction on corn (Zea mays L.) growth, and (2) test the hypothesis that applying arbuscular mycorrhiza (AM) with different origins can partially or completely overcome the stressful effects of soil compaction on corn growth under unsterilized and sterilized conditions. Corn was planted in unsterilized and sterilized compacted soils, while treated with three species of AM including, Iranian Glomus mosseae, Iranian Glomus etunicatum, and Canadian Glomus mosseae, received from GINCO (Glomales in vitro Collection), Canada. Plant growth variables and soil resistance parameters were determined. AM significantly increased root fresh (maximum of 94% increase) and dry (maximum of 100% increase) weights in the compacted soil. AM with different origins may improve corn growth in compacted soils, though its effectiveness is related to the level of compaction and also to the interaction with other soil microorganisms. 相似文献
85.
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87.
绿豆抗豆象基因PCR标记的构建与应用 总被引:5,自引:1,他引:5
采用PCR分子标记技术,对16个绿豆品种(系)进行了遗传分析。在选用的56个随机引物中,发现抗豆象品种与感豆象品种间有一定差异。根据聚类分析结果将它们分成抗豆象野生种(TC1966)、抗豆象栽培种(V2709)、抗豆象杂交后代(VC3890A2/TC1966-23)和混合类型4个大组。以绿豆抗豆象和感豆象品种及抗豆象品种×感豆象品种组合的F2群体为试验材料,利用BSA法,对抗(感)豆象品种池和一个组合F2的抗(感)豆象池进行了鉴定,获得一个共显性标记。经F2分析,在抗豆象个体中扩增出约1.79 kb的特异片段或2个特异片段(1.79 kb/1.03 kb);在感豆象个体中仅扩增出约1.03 kb的特异片段。初步认为此标记与TC1966的抗豆象基因位点紧密联锁,可用于绿豆抗豆象种质鉴定和遗传育种的分子标记辅助选择。 相似文献
88.
4种木霉对核盘菌的抑制作用 总被引:5,自引:0,他引:5
通过对峙培养以及对木霉菌(Trichoderma spp.)次生代谢物对病原菌的抑菌率进行了测定,结果表明,供试哈茨木霉(T.harzianum)、绿色木霉(T.viride)、康氏木霉(T.koningii),以及一株未知种名的木霉菌株TY(Trichoderma sp.)均对核盘菌(Sclerotinia sclerotiorum (Lib) de Bary)有明显的抑制作用.在对峙培养中,木霉菌菌落与核盘菌的菌落相向生长一定时间后,挑取核盘菌菌落内部的菌丝进行镜检,发现有木霉菌孢子存在,且核盘菌发生菌丝变形,如原生质浓缩,菌丝断裂,或菌丝消解等现象.并发现不同种木霉所产生的次生代谢物的活性不同,对核盘菌的抑制作用也存在显著差异. 相似文献
89.
90.
为降低澳洲坚果采收成本,提高采收效率,以澳洲坚果主栽品种‘HAES800’和‘HAES294’为材料,在果实成熟期喷施浓度为1.5 g/L、2.0 g/L和2.5 g/L的乙烯利溶液,对喷施乙烯利溶液后的落果情况、落叶情况和果实品质进行了研究,并对该方法的促落果效果和使用成本进行了评估。结果表明,品种‘HAES800’喷施上述浓度乙烯利溶液4周后的落果率分别达到94.10%、94.08%和93.67%,而同一时期CK的落果率仅有24.64%;品种‘HAES294’喷施上述浓度乙烯利溶液6周后的落果率则分别达到90.89%、93.17%和91.80%,而同一时期CK的落果率仅有53.27%;相比而言品种‘HAES800’对乙烯利溶液更敏感;建议在生产中品种‘HAES800’和‘HAES294’分别采用1.5 g/L和2.0 g/L的乙烯利溶液进行促落果采收;尽管喷施乙烯利会引起部分落叶,但不会对树体生长和果实品质产生影响。应用本方法可使澳洲坚果采收成本降低25.07%,具有巨大的推广应用前景。 相似文献