摘要:

SUMMARYA study of the initial ontogeny and curvature of the ovule inChrozophora obliquaand some other euphorbiaceous taxa explains why the outer integument develops asymmetrically in bitegmic anatropous ovules. The almost simultaneous occurrence of periclinal divisions in the dermatogen of the outer integumentary primordium and funicle and the synchronous elongation of both funicle (viz. the raphe) and outer integument (antiraphe) strongly support the idea that this integument and the raphe are derivatives of the funicle. The primordium of the inner integument, on the other hand, appears to be an independent rim‐like outgrowth of the nucellar base. Therefore, inner and outer integuments are not homologous appendages from an ontogenetic point of view and the concept of ‘congenital fusion’ must be discarded as an explanation. It has also been proposed that the dividing line of nucellus and funicle is situated between the attachment zones of the inner and the outer integument. Accordingly, the term “nucellus” is to be defined as that part of the ovule which is completely surrounded by the inner integument.Both the integuments are initiated by periclinal divisions of a subdermal initial and further divisions result in the vertical growth of the primordia. The outer integument becomes multi‐layered as a result of characteristic radial divisions in the subdermal layer, and a vascular bundle differentiates at its periphery. The large, curved nucellar beak is principally of dermal origin. A hypostase differentiates below the embryo sac during prefertilization stages, whereas the development of a nucellar podium takes place only after fertilization. The caruncle consists mainly of an aerenchymatous tissue.The diagnostic value of a number of distinctive ovular features in Euphorbiaceae has been discussed; the general occurrence of a nucellar beak and especially a thick, subdermally derived and vascularised inner integument in the taxa constituting the subfamily Crotonoideae s.s. seem to indicate that this is a homoge

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1976.tb01077.x

年代:1976

数据来源: WILEY

摘要:

SUMMARYGrowth and CO2‐exchange were measured on two species in the field layer of ash coppice. Two independent methods for the measurements of photosynthesis were used: the14CO2‐method and the URAS‐method. Before coppicing the woodland plantGeum urbanumshowed its adaptation to the deciduous woodland environment: a high rate of growth and photosynthesis in the spring light phase, and an adaptation to the shade conditions in summer. The first year after coppicing,Geumshowed stunted growth and partly disappeared.Cirsium palustre, on the other hand, germinated after coppicing and demonstrated a high assimilation rate and rapid vegetative growth, which led to abundant blooming in the second year of the coppice

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1976.tb01078.x

年代:1976

数据来源: WILEY

摘要:

SUMMARYThe present paper is a sequal to similar ones dealing with populations in Belgium and France. About 80 population samples were gathered in the following areas: the southern part of the German Federal Republic, the Swiss, Austrian and (partly) Italian Alps, and northern Austria. Of these samples the occurrence of angiocarpy vs. gymnocarpy and the chromosome numbers were determined, special attention being paid to the incidence of foliar multifidy. In the Alpine region proper the large majority of the individuals is gymnocarpic. In southern Germany and Lower Austria the plants are nearly always angiocarpic, however. The distribution of the levels of ploidy is rather intricate and roughly as follows: gymnocarpic diploids occur in the southernmost French Alps, in the southern and western Swiss Alps, and in a single population in the Austrian Wachau on the NE escarpment of the Alps; gymnocarpic tetraploids in the Austrian Alps, and rather numerous hexaploids, with some angiocarpy, in the intervening border area of the central Alps. In southern Germany and Lower Austria mostly angiocarpic hexaploids were encountered, with predominantly gymnocarpic tetraploids especially in the border area between Austria and Czechoslovakia (the Bohemian Forest). In the latter region hybridisation between tetra‐ and hexaploids frequently takes place.There are correlations between this chorological pattern and certain consistent phytogeographical phenomena in the Alpine region associated with its Pleistocene geological history, such as the presence of several refugia and the so‐called Rein‐Traun gap in the central Alps. In addition it is suspected that antropogenous influences have disturbed the original situation to an appreciable extent.The degree of dissection of the leaves, as a character included in the population analyses for the first time, is present to the same extent in alpine di‐ and tetraploids (in which the leaves are more or less multifid), but in the Alpine and the German and Lower Austrian hexaploids, foliar multifidy is hardly developed. Some possible causes and plausible conclusions are discussed. The single population in the Wachau refugium contains a singularly high percentage of plants with multifid foliage and this is, among other things, the reason why this population is considered to belong to a different population complex than do the Alpine ones. In the discussion some space is devoted to difficulties that may be expected if a future, novel taxonomic classification of the complex is at

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1976.tb01079.x

年代:1976

数据来源: WILEY

摘要:

SUMMARYSomatic chromosome numbers of nineteen species of AfricanSapotaceaehave been determined. Species of the generaPachystela, Donella, GambeyaandOmphalocarpumhave 2n = 28, those ofSynsepalum(except for the polyploid speciesS. subcordatum, 2n = 112),Tridesmostemon, Autranella, Tieghemellahave 2n = 26, whereasBaillonella toxispermahas 2n = 24 chromosomes. It is concluded that 2n = 28 presents the most primitive number, whereas 2n = 26 and 2n = 24, like the polyploid numbers, are secundary.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1976.tb01080.x

年代:1976

数据来源: WILEY

摘要:

SUMMARYα‐Amyrin, esterified germanicol and β‐amyrin have been identified as major constituents ofE. pulcherrimalatex. In freshly tapped latex only a part of the latex triterpenes were synthesized from acetate and mevalonate. By feeding14C sugars or acetic acid to intact plants and subsequent analysis of tapped latex is synthesis of all the latex triterpenes could be demonstrated. Three' otherEuphorbiaspecies were studied for comparison and the results obtained are discussed. A dual mechanism of latex triterpene synthesis and a tentative model of latex particle formation is pro

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1976.tb01081.x

年代:1976

数据来源: WILEY

摘要:

SUMMARYViable tomato mesophyll protoplasts were isolated by using the non‐phytotoxic macerating enzyme PATE instead of the generally used Macerozyme. To obtain the osmotic conditions required during isolation, salt solutions, containing 2.5% (w/v) KCl and 1% (w/v) MgSO4· 7H2O, were used. From studies in different culture media it appeared that, under optimum conditions, cells regenerated a wall and divided three to four times. After about three weeks of incubation cell division stopped and cells started to degenera

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1976.tb01082.x

年代:1976

数据来源: WILEY

摘要:

SUMMARYThe anatomy of the secondary phloem ofStrephonema pseudocolaA. Chev. has been compared with that of some other representatives of the Combretaceae originating from the Ivory Coast, Africa. This is done because there exist different opinions about the systematic position of the genus. Also the anatomical wood properties of the species concerned were investigated and the results compared with those found by others. AlthoughStrephonema pseudocoladiffers fundamentally from the rest of the family, the anatomy of the secondary phloem, may be more so than that of the secondary xylem, leads us to retain the genus in the Combretaceae, but as a distinctly separate subfamily. By its bark and anatomical wood characters, the genus has some claim to be an ancestral type in the Combretaceae.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1976.tb01083.x

年代:1976

数据来源: WILEY

摘要:

SUMMARYThe total (α + β) carotene and the chlorophyll a content of fresh water phytoplancton were measured spectrophotometrically and were found to be higher during autumn and a part of the winter (100 to 200 μg/l chlorophyll a and 4 to 6 μg/l total (α and β) carotene) with maxima during December and January. From March to June the content decreased continuously from 50 μg to 20 μg (or even 10 μg/l) chlorophyll a and from 5 μg to less than 1 μg/l total carotene (α + β). The ratio of the α‐carotene to the β‐carotene content, fluctuated periodically. During January to May more α‐carotene than β‐carotene was found and during the rest of the sampling period

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1976.tb01084.x

年代:1976

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1976.tb01085.x

年代:1976

数据来源: WILEY

摘要:

G. Herklots:Flowering Tropical Climbers. 1976. Wm. Dawson&Sons Ltd., Folkestone, Kent. 4°. 194 pp., 270 fig., 16 col. pl. £ 17.5

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1976.tb01087.x

年代:1976

数据来源: WILEY