摘要:

Reports of 150 original chromosome counts are recorded, including reports of 22 genera and 57 species and subspecific taxa in tribe Lactuceae. Also included are first reports for 12 specific or subspecific taxa.x= 9 appears to be the ancestral base of the tribe. Chromosome numbers are known for over 85% of the genera of the tribe and the frequency of polyploidy is ca. 23%, which is about one‐half that of the angiosperms.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06129.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

Aspects of vegetative and floral morphology and anatomy of five species ofEucryphiaCav. are described. Differences in wood structure, type and complexity of petiole and leaf vascularization, presence or absence of complex abaxial cuticular protrusions on the leaves, and patterns of floral vasculature are useful in species delimitation. Anatomical data are in agreement with the inclusion of Eucryphiaceae in the Rosales near Cunoniaceae.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06130.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

Anaerobic elevation of ethylene concentration in waterlogged and non‐waterloggedHelianthus annuusL. andLycopersicon esculentumMill. was studied. A balloon method was devised to provide an anaerobic atmosphere around the intact sunflower stem. Anaerobic conditions were also produced by bubbling nitrogen into the floodwater. Ethylene concentration in the stem of waterlogged plants was higher when nitrogen was bubbled through the floodwater than when aerated, the effect being greater for the soil‐grown plants than for the sand‐cultured plants. Ethylene concentration in the stem of waterlogged plants was highest in the region exposed to anaerobiosis, and less with increasing distance or height on the non‐waterlogged part of the stems. Intact sunflower stems increased their ethylene concentration in that part of the stem which was maintained in an oxygen‐free atmosphere. The results suggest that enhanced ethylene production in waterlogged plants primarily occurs in the waterlogged part of roots and stems.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06131.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

Modern races of maize (Zea maysL.) are characterized by indurated glume and rachis tissues. The archaeological record, as well as experimental studies indicate that in North America this induration is associated with hybridization between domesticated maize and its closest wild relativeZ. mayssubsp.mexicana(Schrad.) Iltis (teosinte). Similar induration can also be introduced into maize through introgression fromTripsacum. North and South American indurated races of maize are not all closely allied morphologically. They evolved independently under domestication. Teosinte is absent from South America, butTripsacumis widely sympatric with maize from about 42 N to 42 S latitude. For these reasons it has been postulated that induration in South American races may be the result ofTripsacumintrogression. However, barriers restricting gene exchange betweenZeaandTripsacumare difficult to overcome in nature. It is maintained that indurated South American races of maize were derived from indurated Mexican races, and that the presence or absence of such induration is due to different degrees of expression by intermediate alleles of the tunicate locus.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06132.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

Morphological, developmental and cytochemical examinations were made with light and electron microscopy on the apical apparatuses of four eugymnohymenial species,Pyronema domesticum, Ascodesmis sphaerospora, Coprotus winteriandC. lacteus. Ascal tips in all four species were notably thinner walled than the rest of the ascus. Ultrastructurally, demarcation of the opercula was enhanced after staining with silver methenamine. Wide zones of dehiscence are formed in the outer layer of A.sphaerosporaandC. winteri. InP. domesticumthe outer layer of the operculum is differentially stained from the rest of the ascal wall. Wall dimensions in the multispored asci ofC. winteriare approximately three times greater than those in the eight‐spored asci of C.lacteus. The shape of the apical apparatus ofC. lateusis almost identical to that ofC. winteri. Morphological and cytochemical similarities of the apical apparatuses inAscodesmis, PyronemaandCoprotushelp demonstrate greater relationship between these taxa and support the belief that these taxa are most closely related to members of the Otideaceae and Aleuriaceae.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06133.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

The genus Ptychopetulum (Olacaceae), disjunct between South America (2 spp.) and Africa (2 spp. West Africa; I sp. Rhodesia), exhibits predominantly diploporate pollen among the West African species and predominantly triporate pollen among the South American taxa. An analysis of aperture evolution suggests two possible schemes of aperture evolution for the genus. Scheme I avers the independent origin of both triporate and diploporate apertures from a basic brevicolpate condition while scheme II proposes a basic diploporate condition in which the diploporate apertures have migrated to the equator, fused to form brevicolpi and have ultimately become reduced to pores. Pollen evidence in support of both schemes is discussed. The distribution of aperture types within the genus also suggests West Africa as the original site of aperture evolution and South America as the second area of aperture development with types traceable to West African stock.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06134.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

The branched anastomosed laticifer system in the primary body ofCichorium intybusL. originates in embryos from files of laticiferous members at the boundary between phloic procambium and ground meristem. Upon seed germination, laticiferous members develop perforations in the end walls which become entirely resorbed. Perforations also develop in the longitudinal walls of contiguous laticiferous members and from lateral connections between developing laticifer branches. Additional laticiferous members originate as procambium differentiation proceeds, and their differentiation follows a continuous acropetal sequence in leaf primordia of the plumule. In roots, laticifers closely associated with sieve tubes in the secondary phloem originate from derivatives of fusiform initials in the vascular cambium. These laticifers develop wall perforations and in a mature condition resemble laticifers in the primary body. As the girth of the root increases, laticifers toward the periphery, unlike associated sieve tubes, resist crushing and obliteration. Laticifers vary in width from about 4 to 22 μm; the widest ones occur in involucral bracts and the narrowest ones in florets. There was no evidence that intrusive growth occurs during development of the laticifer system, although such growth may occur during development of occasional branches which extend through ground tissue independent of phloem and terminate in contact with the epidermis. Presence of amorphous callose deposits is related to aging of laticifers and mechanical injury.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06135.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

Electron microscopy of sugarbeet leaves infected with the beet curly top virus confirmed earlier findings by light microscopy that the hyperplastic phloem consists mainly of sieve elements that are more or less abnormal in structure. Some parenchyma cells and occasional companion cells may be present. The hyperplastic phloem develops in the place of normal phloem and sometimes in the adjacent ground tissue and the xylem. The sieve elements vary in shape and may be haphazardly arranged. The protoplasts of the sieve elements have the usual characteristics of this type of cell. The sieve element plastids develop from chloroplasts if the hyperplasia occurs in chloroplast‐containing parenchyma cells. The cell walls have sieve areas that often are less well differentiated than those of normal sieve elements. The hyperplastic growth in the phloem of curly top diseased plants is discussed with reference to plant tumors induced by certain other plant viruses.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06136.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

A single, lateral, vegetative bud which is positioned 180° from the axil of a leaf is a generic feature ofMusa(Musaceae). Such leaf‐opposed buds occur in all ten species and five cultivars examined, representing all four sections of the genus and all groups of cultivated bananas and plantains. The bud arises relatively late and is first visible as a vascular‐free “clear zone” in the axis directly below the future bud meristem site. It is first associated with the fifth or sixth leaf primordium from the apex. A defined superficial meristem develops on the stem directly above the insertion of the leaf margins one or more plastochrons later. Normal, basically axillary, vegetative buds occur in the closely related genera:Orchidantha(Lowiaceae),Heliconia(Heliconiaceae),Strelitzia, andRavenala(Strelitziaceae). These buds arise in the axil of the first to the third leaf primordium in a manner similar to most other monocotyledons. Axillary vegetative buds also occur in the remaining families of the Zingiberales: Cannaceae, Costaceae, Marantaceae, and Zingiberaceae.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06137.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

The shoot apex ofBougainvillea spectabilisconsists of five zones: A two‐ or occasionally three‐layered tunica, a central mother cell zone, a cambium‐like zone, a rib meristem (central meristem), and a peripheral meristem. The presence of a cambium‐like zone is somewhat unusual in the apex of vascular plants, having only been reported for a few taxa. InB. spectabilisthe cambium‐like zone is consistently present throughout the plastochron and all yearly seasonal periods.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06138.x

出版商:Wiley    

年代:1978

数据来源: WILEY