共查询到20条相似文献,搜索用时 109 毫秒
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C. Peter Wolk 《American journal of botany》1966,53(3):260-262
Sporulation of vegetative cells adjacent to heterocysts is prevented by detachment of the two cell types, probably without impairment of the capacity of those vegetative cells to sporulate. Apparently, therefore, heterocysts are in part responsible for the sporulation of vegetative cells attached to them. 相似文献
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云南森林植物区系研究 总被引:3,自引:1,他引:2
云南森林植物(系指木本植物)主要起源于新生代,少数古老种起源于古生代至中生代。云南森林植物区系成分极为丰富而复杂,据研究已知森林植物149科(蕨类植物1科,裸子植物10科,被子植物138科),840属,5271种。本文根据对云南森林植物15个分布区类型统计分析,证明云南森林植物区系明显富于热带性同时兼有丰富的温带成分,热带属占总属数72.12%,温带属占总属数21.87%,中国特有属在云南有46属,占云南总属数5.33%。中国特有属的三个分布中心。有两个分布中心在云南(即新特有属中心和古老特有属中心)。本文还对云南森林植物区系的地理成分起源;云南森林植物区系成分复杂、丰富之成因;云南森林植物开发利用之前景进行了研究和探讨。 相似文献
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Roblee WW 《California State Journal of Medicine》1914,12(9):387-389
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M. Abdul Hameed 《BMJ (Clinical research ed.)》1935,2(3899):576-3
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R. C. Jackson 《American journal of botany》1965,52(9):946-953
Haplopappus gracilis (Nutt.) Gray is an aneuploid species of Compositae of wide distribution in the southwestern U.S.A. and northern Mexico. Except for 2 types of supernumeraries, cytological samples from throughout its range have regularly shown 2 pairs of chromosomes. However, recent collections from a small area in south-central Arizona had 2n = 4, 2n = 5, and 2n = 6 in the same population. The 2n = 5 plants were hybrids between the 2n = 4 and 2n = 6 types. Both natural and artificial F1 hybrids show preferential disjunction from a trivalent and produce genetically balanced gametes with n = 2 and n = 3. In backcrosses of the F1 to n = 2 plants, a 1:1 ratio of 2n = 4 and 2n = 5 plants was obtained. The possible mechanisms for the evolution of n = 2 from n = 3 and vice versa are discussed. 相似文献
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<正> 灵香草的斑枯病俗称“点蜡烛”病,历来是灵香草的毁灭性病害。此病分布于广西金秀县各个灵香草产区;融水、龙胜等灵香草产地亦有此病发生。一般发病率60~70%,严重的往往达80%~90%,甚至失收。如1980年8月,金秀县外贸局为扶植生产队发展灵香草生产,无偿拨给金秀二队种苗300斤,分给社员种植。灵香草生长到高约23—27厘米时,全部病死腐烂。因此,要发展灵香草生产,必须有效地防治这种病害。 相似文献
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