摘要:

We present the first extensive study of embryology ofAkania, the only genus of Akaniaceae (one of the 15 glucosinolate‐producing families).Akaniahas a distinctive combination of embryological features, which includes bitegmic and crassinucellate ovules; thick, multiplicative and vascularized outer integument; a Polygonum‐type embryo sac; albuminous seed; ‘exotestal’ seed coat with a palisade of columellar, thick‐walled cells and a thick and sclerotic mesotesta with the inner tissue aerenchymatous. A comparison of its embryological characteristics with those of some other groups indicates thatAkaniaclosely resembles Bretschneideraceae (another glucosinolate‐producing family) and Sapindaceae, but it retains some archaic embryological features and is best treated as a separate family in or near Sapindales, as in most modern general classifications. Based on evidence from embryological and other data, Akaniaceae appear to be the sister group of Bretschneideraceae, possibly near to Sapindales. With the data at hand, we cannot fully assess the recent suggestion that Akaniaceae‐Bretschneideraceae are a basal group

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1995.tb00471.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The stigma ofCaesalpinia pulcherrimais crateriform. The crater continues as a slit‐like canal through the style and into the ovary. Both crater and canal are lined by several layers of fusiform and thin‐walled cells which are continuous in two narrow regions in the ovary. Postanthesis and before pollination, the middle lamella of cells lining the stigmatic crater and stylar transmitting tissue undergoes dissolution. This occurs in a progression down the style with cells separating partially or wholly from neighbours. Dissolution is initiated at intercellular junctions where wall fibrils loosen and variously‐sized and ‐shaped holes appear. Cytoplasmic changes include increased dictyosome activity, increased rough and smooth endoplasmic reticulum at the periphery of cells and accumulation of electron opaque deposits at the plasma membrane. The crater fills with stigmatic fluid and the diameter of the stylar canal increases. Pollen germinates in the secretion‐filled crater, and pollen tubes grow down the style between the cells of the transmitting tissue but do not enter the canal. They emerge at the entrance to the ovary cavity and grow over one or two narrow strips of ovarian transmitting tissue cells which are present throughout the length of the ovary close to the ovules. This ensures that tubes grow in close proximity to the m

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1995.tb00472.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The systematic status ofDisa draconis(L.f.) Sw. is revised following extensive field studies of population variation in the Western Cape, South Africa. Principal component and cluster analyses revealed clear distinctions between populations from sandplain, semi‐arid and montane environments. Diagnostic characters were found in each of the population clusters indicating the existence of a species complex, rather than a single taxon as in the current taxonomy. We propose, therefore, that the nameD. draconis(L.f.) Sw. be restricted to the individuals of the sandplain populations from which the type was collected. We reinstate an earlier name,Disa harveianaLindl., to describe the montane populations which possess several autapomorphic characters. We also show that the geographical variation in spur length and flowering time within this species can be partitioned into two geographically distinct subspecies:D. harveianasubsp.harveianaandD. harveianasubsp.longicalcarataJohnson&Linder. The populations from the semi‐arid Karoo region were recognized as a distinct new species,Disa karooicaJohnson&Linder, on the basis of their peculiar petal structure. A cladistic analysis indicated that the three species forming theD. draconiscomplex form a monophyletic and relatively specialized lineage withinDisasect. Coryphaea. The revised classification also has important conservation implications asD. draconis, previously considered a common species, is now restricted to a few highly threatened populations on the west coast near Cape T

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1995.tb00473.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Knowledge of the reproductive biology of endemic plants improves our understanding of how mating system may be related to patterns of species abundance and provides a basis for the development of rational conservation programmes. In this paper we present natural population data on the floral biology and reproductive ecology of the endemic Mediterranean speciesCyclamen balearicumWillk. This is a long‐lived, diploid perennial herb which occurs in southern France in five fragmented and isolated regions and on the Balearic Islands of Mallorca, Menorca, Ibiza, Cabrera and Draponera. Our observations indicate a particularly scarce pollinator activity (rare syrphid visits) and dispersal by ants over small distances. A controlled pollination experiment in a natural population showed that in southern FranceC. balearicumis fully self‐compatible and that selfing is autonomous and probably delayed (i.e. following opportunities for outcrossing). The proximity of stigmas and anthers will favour autonomous selfing. The high pollen/ovule ratio indicates nevertheless thatC. balearicumhas a mixed mating system. Patterns of variation in stigma‐anther separation and pollen production per flower suggest that not only has the current mating system of the species evolved from an outcrossing ancestor but that due to the fragmentation and isolation of populations greater levels of selfing have evolved in southern France (and to an intermediate degree on Ibiza and Menorca). On the island of Mallorca where larger continuous belts ofC. balearicumhabitat still exist the species has floral traits indicating a more outcrossed mating system. To our knowledge this is the first paper to document such trends in floral traits in the endemic component of the Mediterranean

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1995.tb00474.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

We studied the floral and reproductive biology ofDrosophyllym lusitanicum(Droseraceae), a species endemic to the western Iberian Peninsula and northwest Morocco. Flowering lasted from March to August, peaking in April. The species is clearly homogamous, with pollen germination and stigma receptivity occurring even in preanthesis. This was reflected in the high rates of fruit set and seed set in bagged inflorescences. Fructification did not differ significantly between different pollination treatments, although we did find differences between some treatments in the numbers of viable seeds per flower and fruit. However, seed weight did not differ significantly. The importance of self‐pollination over cross‐pollination was also supported by the low percentages of fructification (24.67%) after emasculation and open pollination. Metameric deviations were seen in flowers, although this abnormality was not translated as any reproductive benefit or disadvantage (fructification, number or weight of seeds) in comparison with normal flow

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1995.tb00475.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY