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Abstract

The purpose of this study is to analyse, by means of Scanning Electron Microscopy (SEM), the validity of the typification of the pollen of Centaurea L. s.s., carried out by Wagenitz (1955) with light microscopy and based on the exine structure and sculpturing. The pollen of six species have been analyzed: one species for every type of pollen present in Italy: C. sempervirens L., C. alpina L., C. scabiosa L., C. alba L., C. montana L., C. cyanus L.

The validity of the pollen typification suggested by Wagenitz has been confirmed also at the ultramicroscopic level. The ultrastructure and the sculturing of the sporoderm are described in detail and some discrepancies, mainly due to the different potentialities offered by the two methods, are pointed out.  相似文献   

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狭义五福花科(Adoxaceae.s.s)仅含3属4种,但该科的物种分化、系统发育和分类一直存在争议。本文通过测定东方五福花和血满草的ITS(核糖体DNA内转录间隔区)序列,构建了包括狭义五福花科(4种)、广义忍冬科接骨木属、荚属以及其余4属植物在内的系统发育树。研究结果不支持狭义五福花科内根据形态学证据做出的系统发育假设四福花不是该科中最早分化出来的种;该物种与五福花属的两个物种形成一个单系群,与另一分支华福花属相对应。该科中3个物种,四福花、五福花和华福花之间的分化主要是在二倍体水平上的异域分化,而东方五福花则是通过多倍化形成的。粗略的时间估算表明这些物种之间的分化较晚,可能在第三纪末至第四纪早中期,与青池高原近期强烈隆升以及冰期气候反复变化形成的环境变迁密切相关。  相似文献   

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Ten species of Alismatales, five of Alismataceae, four of Limnocharitaceae and one of Hydrocharitaceae were studied with regard to chromosome number, chromosome morphology, and pattern of Giemsa C-bands. The genus Echinodorus had a diploid chromosome number of 22 for all species that were analyzed and a karyotypic formula of 2m + 20a. For the family Limnocharitaceae, Hydrocleys nymphoides had a diploid chromosome number of 16, Hydrocleys martii (4m + 2sm + 10a) had a diploid chromosome number of 16, Limnocharis flava had a diploid chromosome number of 20 and L. laforestii (4m + 16a) had a diploid chromosome number of 20. The only species of Hydrocharitaceae that was studied exhibited a karyotype that consisted of a diploid chromosome number of 28 and a karyotypic formula of 4m + 6sm + 4a. The distribution pattern of the C-banded karyotype in Echinodorus showed four blocks of constitutive heterochromatin in two smaller acrocentric pairs that corresponded to the heterochromatic NORs. In E. lanceolatus, 14 bands in the termini of the arms beyond the heterochromatic NORs of seven acrocentric pairs were also observed. Idiograms are presented and the karyotypic evolution patterns for the studied groups are discussed.  相似文献   

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