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地球上的生物,种类繁多,不论花、草、树木或者鸟、兽、虫、鱼,都是多种多样的。人类的祖先很早就知道利用和培养一些植物或动物作为食物、衣料或工具、动力等等。由于生产实践和生活的需要,人们逐渐认识了动物和植物,给它们取上名字,并进一步把它们分门别类,以便于观察和利用。这项知识的积累就成了分类学。有了分类学以后,把大量资料作了系统整理,才能更深入地进行形态、解剖、生理、遗传以及其他实验科学方面的研究。所以从科学的发展历史看,分类是生物学研究的开端,也是所有生物学家、农学家、林学 相似文献
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The Rosaceae is one of the five largest families of Xizang flora, consisting of
30 genera with 242 species, the total number of species is slightly less than those of
Compositae, Graminae, Leguminosae and Ericaceae in Xizang, amounting to 62.5% of
the total number of genera and 28% of the total number of species of the rosaceous flora
in China.
The four subfamilies of Rosaceae including primitive, intermediate and advanced
groups have been found in Xizang. These groups consist of 11 types of floristic ele-
ments, i.e. 4 genera belong to cosmopolitan, 9 genera belong to North Temperate, 3, E.
Asian-N. American, 3 Sino-Himalayan, 3 Sino-Japanesa, 2 Old World Temperate, 1
Temperate Asian, 2 Mediterranean-W. and O. Asian, 1 C. Asian, I Tropical Asian and 1
endemic to China. It is obvious that Rosaceae in Xizang comprises holarctic, Ancient Me-
diterranean and paleotropical elements, among which the temperate components are the
most dominant. The characteristics of the floristic composition of Rosaceae in Xizang
may be summarized as follows:
(1) Xizang abounds in both genera and species of the family which are diverse in
forms, including the primitive, intermediate and advanced groups, (2) The geographi-
cal elements are rather complex, mostly belonging to the temperate, among which the
Sino- Himalayan components and the elements endemic to China are dominant, (3) The
proportion of plants endemic to China and distributed in Xizang is much higher than
those endemic to Xizang itself, but there exist newly arisen species and infraspecific
forms or varieties which show that the speciation is apparently still active in Xizang.
The rosaceous flora of Xizang is a combination of old and new floristic elements, based
on the old floristic components, affected by the upheaval of the Himalayas, the differen-
tiation and speciation have been taking place in the long history.
The geographical distribution of Rosaceae in Xizang may be divided into 5 regions,
i.e. the northeastern, southeastern, southern, northwestern and northern. The rosaceous
plants are most abundant in the southeastern area, next in southern area, fewer in the
northeastern and very rare in the northwestern and northern regions. The general ten-
dency of the distribution of Rosaceae in Xizang is that the number of species gradually
decreases from the southeast to the northwest and the habit gradually changes from
trees, shrubs and herbaceous plants in the southeast to cushion-like scrubs and dwarf
perennial herbs in the northwest. These facts clearly show that the uplift of the Hi-
malayas has deeply affected the phytogeographical distribution of Xizang Rosaceae.
The rosaceous flora of Xizang has close relationships with those of the adjoring
regions, i.e. Yunnan and Sichuan. Besides, it is connected with floras of Nepal, Sikkim,
Bhutan nothern Buram and nothern India, but silghtly influenced by the Ancient Medi-
terranean flora. 相似文献
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We have described a new genus Taihangia, collected from, the south part of Taihang
Mountain in northern China. At the same time, comparative studies on Taihangia with its
related genera have been made in various fields including external morphology, anatomy
of carpels, chromosome and pollen morphology by light, scanning and transmission electron microscope. In addition, isoperoxidases of two varietier were analysed by means of polya-crylamide gel slab electrophoresis. The preliminary results are as follows:
Morphology: The genus Taihangia is perennial and has simple leaves, occasionally
with 1—2 very small reduced lobes on the upper part of petiole; flowers white, andromo-
noecious and androdioecious, terminal, single or rarely 2 on a leafless scape; calyx and cpicalyx with 5 segments; petals 5; stamens numerous; pistils numerous, with pubescent styles, spirally inserted on the receptacle in bisexual flowers, but with less number of abortive and glabrous pistils in male flowers.
In comparison with the related genera such as Dryas, Geum, Coluria and Waldsteinia,
the new genus has unisexual flowers and always herbaceous habit indicating its advanced
feature but the genus has a primitive style with thin and short hairs as compared with the genus Dryas which has long, pinnately haired styles, a character greatly facilitamg anemo-choric dissemination. The styles of Taihangia are slender and differ from those of the ge-nus Geum which are articulate, with a persistent hooked rostrum, thus adapting to epizo-ochoric dissemination to a higher degree.
The anatomy of carpels shows the baral position of ovules in the genus Taihangia like those in other related genera such as Dryas, Geum, Acomastylis, Coluria and Waldsteinia. This suggests that the new genus and its related ones are in a common evolutionary line as compared with the other tribes which have a pendulous ovule and represent a separate evolutionary line in Rosaceae. Dorsal and ventral bundles in carpels through sections are free at the base. Neither fusion, nor reduction of dorsals and vertrals. are observed. This shows that the genus Taihangia is rather primitive.
Somatic chromosome: All the living plants, collected from both Honan and Hopei
Provinces were examined. The results show that in these plants the chromosome number
is 2n= 14, and thus the basic number of chromosome is x=7. Such a diploid genus is first
found in both anemochoric and epizoochoric genera. Therefore, in this respect Taihangia is primitive as compared with herbaceous polyploid genus Geum and related ones.
Pollen: The stereostructure shown by scanning electron microscope reveals that the pollen grains of the genus Taihangia are ellipsoid and 3-colporate. There are two types of exine sculpture. One is rather shortly striate and it seems rugulate over the pollen surface; the other is long-striate. The genus Dryas differs in having only short and thick striae over the surface. The genus is similar to the genera Geum, Coluria and Waldsteinia in colpustype, but differs from them in that they all have long, parallel striae which are distributed along the meridional line.
In addition, under transmission electron microscope, the exine in the Taihangia and related genera Acomastylis, Geum, Coluria, Waldsteinia and Dryas has been shown to be typically differentiated into two distinct layers, nexine and sexine. The nexine, weakly statined, appears to consist of endoxine with no foot-layer, in which the columellae are fused, and which is thicker beneath the apertures. The sexine is 2-layered, consisting of columellae and tectum. Three patterns of tectum can be distinguished in the tribe Dryadeae: the first, in the genera Taihangia, Acomastylis, Geum, Coluria and Waldsteinia, is tectate-imperforate, with the sculpturing elements both acute and obtuse at the top and broad at the base; the second, in the genus Dryas, is semitectate, with the sculpturing elements shown in ultrathin sections rod-like and broader at the top than at the base or as broad at the top as at the base, and the third, tectate-perforate, with the sculpturing elements different in size. From the above results, the herbaceous groups and woody ones have palynologically evolved in two distinct directions, and the genus Taihangia is related to other herbaceous genera such as Acomastylis, Geum, Coluria and Waldsteinia, as shown in the electron microphotographs of ultrathin sections. The genus Taihangia, however, is different from related herbaceous genera in that the pollen of Taihangia is dimorphic, i.e. in addition to the above pattern of pollen another one of the exine in Taihangia is rugulate, with the sculpturing elements shown in the ultrathin sections being obtuse or emarginate and nearly as broad at the top as at the base.
The interesting results obtained from the comparative analysis of morphology, ana-
tomy of carpels, chromosome countings, microscopic and submicrosocopic structures of pollen may enable us to evaluate the systematic position of Taihangia and to throw a new light on evolution of the tribe Dryadeae. It is well known that the modes of dissemination of rosaceous fruits play an important role in the expansion and evolution of the family. The follicle is the most primitive and the plants with follicles, like the Spiraeoideae, are mostly woody and mesic, while the achene, drupe and pyrenarium are derived. In Rosoideae having a achene is a common feature. Particularly in the tribe Dryadeae, which is distinguished from the other related tribes by having orthotropous ovules, the methods of dissemination of fruits have developed in three distinct specialized directions: anemochory with long, plumose styles (e.g. Dryas), formicochory or dispersed by ants or other insects, with the deciduous styles (e.g. Waldsteinia and Collria),and epizoochory with the upper deciduous stigmatic part and the lower persistent hooked rostrum, an adhesive organ favouring epizoochory dissemination (e. g. Geum and related taxa). Taihangia is a genus endemic to mesophytic
forest area of northern China. Due to its narrow range and specific habit as well as pubescent styles, neither perfectly adapted to anemochory nor to epizoochory, the genus Taihangia might be a direct progeny of the ancestry of anemochory. Maintaining the diploidy and having an ntermediate sculptural type of pollen, the new genus might probably represent a linkage between anemochory and zoochory (including epizoochory and dispersed by ants).
Experimental evidence from isoperoxidases shows the stable zymograms of root and
roostoks. The anodal isozyme of T. rupestris var. rupestris may be divided into 6 bands:
A, B, C, D, E, F, and T. rupestris var. ciliata into 4 bands: A, B, C, G. The two varietiesof the species share 3 bands: A, B, C. However, D, E and F bands are characteristic of var. rupestris and G band is limited to var. ciliata. As far as the available materials are concerned, the analysis of isoperoxidases supports the subdivision of the species into two varieties. 相似文献
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蔷薇科植物的起源和进化 总被引：1，自引：0，他引：1
俞德浚 《中国科学院研究生院学报》1984,22(6):431-444
Rosaceae. consisting of about 126 genera and 3200 species, is widely distribu-
ted in warm temperate and subtropical regions of the Northern Hemisphere, while more
than half of the genera are Asiatic and more then 80% of the total number of Asiatic
occur in China (Table 1). In this paper, the origin and evolution of Chinese genera is
discussed mainly. The principal tendency of the whole family is also described from
the point of view of evolution.
First of all, the systematic position of Rosaceae in Angiospermae is reviewed. Ac-
cording to the records of paleobotany, rosaceous plants occurred first in the Tertiary,
from the early period of Eocene (genera such as Spiraea and Prunus) to the late period
of Miocene (e.g. Crataegus, Malus amd Rosa). They have quite a long history in geolo-
gical data. Where has this big and old family originated and what steps does it stand in
the long course of evolution of flowering plants? There are several opinions and ex-
planations by different authors. In this paper, a general survey of the six prevailing
classical systems (Table 2) is made to give a brief idea of the position of this family
in the Angiospermae and of the relationships between the subfamilies and also the rela-
tionships between different genera in each subfamily. At the end of this paper, an at-
tempt is made to analyse and sum up the major evolutionary tendency of the whole fa-
mily.
As generally condidered, Rosaceae originated from Magnoliales, and woody plants
of the family still hold a dominant position. For instance, subfamily Spiraeoideae con-
sists of only one herbaceous genus (i.e., Aruncus) and subfamily Rosoideae only a few
herbaceous genera. All of these herbaceous genera are derived from the closely related
woody genera of the same subfamily.
In the course of evolution of Angiospermae, Rosaceae stands at the initial to the
middle stages of development. All parts of plant body in this family are at the chang-
ing and developing stages, with carpels, fruits and inflorescences being the most active.
The primitive types in this family, such as the members of subfamily Spiraeoideae,
usually have 5 and free carpels, the number of which are either reduced to 2-1 or in-
creased to 10-numerous. They have different levels of union and are either completely
free from each other or coherent at base. The carpels usually occur on the upper part of
the receptacle, because the shapes of receptacle are variable, sometimes disk-shaped, cup-
shaped, tube-shaped or even bottle-shaped. In the last case carpels grow inside the rece-
ptacle. Thus the position of carpels has changed from superior to inferior through half-
superior.
In accordance with the development of the carpels, various kinds of fruits are produ-
ced. The primitive types of fruit are follicles, with dry, dehiscent carpels opened along
different sutures. The next step, the carpels have developed into an indehiscent, I-celled
and l-seeded fruit, the so-caned achene. In different genera, the achenes have different
coat types and appendages to facilitate dispersing the seeds. Some of the achenes grow
upon the fleshy receptacle (like strawberry) and some of them inside the fleshy rece-
ptacle (like rose). Sometimes a few carpels are united with the receptacle and develop
into a pome (like apple and pear). Another direction of the fruit development is the
single carpel with fleshy exocarp and mesocarp, and a bony endocarp, then becoming a
drupe (like peach and plum).
In addition to fleshy receptacle of thickened fruit coats, they usually have showy
colour, fragrant smell and also plenty of sugars, acids, vitamins, etc. which are edible
and attract animals and human beings to assist the dispersion of seeds.
In this family, there are various types of flower arrangements, both indefinite inflo-
rescences including raceme, umbel, corymb and panicle, and the definite inflorescence,
such as solitary flower, cyme and compound cyme. In the evolution course, they tend
to change mostly from multiflowered compound inflorescence towards few-flowered sim-
ple inflorescence, and finally becoming a solitary flower: simultaneously with the decre-
asing of number of flowers on the inflorescence, the increasing of size of petals, which
become very showy for attraction of insects so as to guarantee pollination and fertiliza-
tion of the plants concerned. Another tendency, if the bisexual flowers change to uni-
sexual, either monoecious- or dioecious-polygamous, then they form a dense spike which
is beneficial to cross pollination. The abundance, diversity, and wide range of distribu-
tion of the species and genera of Rosaceae are considered mainly resulted from their
highly developed reproductive organs. 相似文献
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