摘要:

We propose the first comparative study of the hypoderm in leaves ofPopulusL. based on light and transmission electron microscopy. Our results allow us to describe the hypoderm as a structural adaptation of the embryonal leaves. The sub—epidermal position of that tissue and the type of differenciation (largely vacualised cells, with thick cell walls, having in their hyaloplasme reserve lipids) indicate on homology of the leaf hypoderm with the tissues of the periderm of stems and the tissues of velamen of orchid's air-roots.

ISSN:1253-8078    

DOI:10.1080/12538078.1999.10515811

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

This study actualizes our knowledge on the flora of Togo. It is based on floristic inventory of forest patches which cover the whole costal plain of southern Togo. Most of these islands are sacred forests protected by the populations.

ISSN:1253-8078    

DOI:10.1080/12538078.1999.10515812

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

For millions of years, day and night, year after year, fruits and seeds have migrated across the globe, ensuring the survival of genera and species. And only in this way will future generations continue to do so. Plants which reproduce themselves with seeds are currently the most widespread on the planet. A thorough analysis of the “microcosm” of insects has shown that, in addition to ants, many other insects habitually transport from one place to another small seeds and fruits, less than a gram in weight, contributing in this way to the dispersal of plants. Some do so unconsciously, transporting diaspores, some of which have hooks. These attach themselves to the insect's body and later fall to the ground, allowing new plants to germinate some distance from the original plant. Other insects transport a number of seeds to underground nests—similar to ants—where these may germinate. Scarabaeoids which are found in sandy areas and live on excrement have a considerable role in this process; these insects are instrumental in the dispersal and germination of seeds, burying them with dung. It is likely that grassland termites also aidPoaceaedispersal. The study of entomochorous seeds and fruits draws attention to the fact that elaiosomes are often present and therefore; in this case, dispersal by non-Formicidaeinsects is of secondary importance.

ISSN:1253-8078    

DOI:10.1080/12538078.1999.10515813

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A new species ofColchicum (C. arenasii) having tessellated tepals is described. It is compared to other Corsican and Sardinian species of hysteranthousColchicum.The five species occurring in Corsica are keyed out. Some indications about distribution and ecology are given.

ISSN:1253-8078    

DOI:10.1080/12538078.1999.10515814

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Bulbs from two cultivars ‘Mikor’ and ‘Jermor’ ofAllium cepaL. var.aggregatumi.e. were planted in the field either in October or every month from November to April. Glyphosate, a systemic poison that moves through the vascular system, was injected into the tubular cavity of a well-developed leaf from each plant at successive dates for bulbs planted in October and on a same day for those planted from November to April. Glyphosate-induced damages indicated that vascular communication, first global in the bulb recently planted, progressively tended to be restricted to sub-units, each of them being composed of a shoot apex with the generated leaves and internodes and the adjacent adventitious roots. Thus, according to the age of the plant, the unit constituted by the original bulb was split into vegetative sub-systems, each of them being issued from the bud of the initial bulb without ontogenic priority. This deep change indicated a sequence in the developmental stages. A juvenile phase was characterised by a global vascular communication through the whole bulb. It was followed by a maturation stage corresponding to the formation of the shallot tuft, while a somatic generation composed of biological units, i.e. true entities, without any vascular exchange with the other parts of the plant, was emerging. This phenomenon may be sufficient to explain why each bud of the shallot tuft can later flower in an independent and random way.

ISSN:1253-8078    

DOI:10.1080/12538078.1999.10515815

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:1253-8078    

DOI:10.1080/12538078.1999.10515816

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:1253-8078    

DOI:10.1080/12538078.1999.10515810

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor