摘要:

BARRETO, R. W.&DICK, M. W., 1991.Monograph ofBasidiophora(Oomycetes) with the description of a new species.The genusBasidiophorais reviewed and a key to the species provided. Within the genus,Basidiophora entosporaRoze&Cornu has the widest host range (though restricted to the Gompositae) and the widest distribution. Outside North America, it is limited to its weedy hostConyza canadensis(L.) Cronquist.Basidiophora kellermanii(Swingle) Wilson is the most distinct species, restricted to a single host,ha xanthifoliaNutt. (Compositae), occurring only in the USA.Basidiophora montanais described here, and can readily be distinguished fromB. entospora.It is a parasite ofMikania micranthaH. B. K. and was found in humid subtropical highlands of Brazil (States of Rio de Janeiro and Paraná) during a survey for weed pathogens, which was initiated with the aim of seeking potential fungal biological control agents.Mikania micranthais a very serious introduced weed in south‐east Asia and Oceania, and further work with this fungus is recommended because of its severity as a pathogen and its absence in the regions of the globe where its host is important as a we

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1991.tb00226.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

COWGILL, U. M.&LANDENBERG, B. D., 1991.The chemical compositionof Astragalus: variations within the plants over a 6‐year period.No systematic chemical examination has been carried out on seleniferous plants coexisting with non‐seleniferous ones. This paper is confined to elemental variation within the plants (12 species of seleniferousAstragalus,15 species of non‐seleniferousAstragalusand seven species of other plants) gathered from 23 sites over a 6‐year period in Colorado, Utah and New Mexico, U.S.A. Analytical procedures include X‐ray fluorescence and atomic absorption spectrometry. Only 19 elements, of 49 detected, showed significant differences in their quantities in different plant parts. Mn S, Ca, Sr and Mg concentrated in leaves; Al, Si, Ti, Cu, As, F, CI and Br accumulated in stems and K, Rb, Cs, Zn, P and Se were found in quantity in the reproductive parts. A comparison of seleniferous with non‐seleniferous species revealed that Mg, S, Mn (leaves), Se, P, K, Zn (flowers/seeds) Cu, F and CI (stems) were more concentrated in seleniferous species (P<0.0001) whereas Ca (leaves), Rb (flowers/seeds), As, Al, Si and Br (stems) were present in greater amounts in non‐seleniferous ones (P<0.0001). An hypothesis is proposed to explain the high amounts of Mg encountered in leaves of these arid region plants; according to the hypothesis some portion of the accumulated Mg functions in arid plants as a humidity stabilizer. Another hypothesis concerns the relationship observed between Se and As. It has been shown that non‐seleniferous astragali contained significantly more As than coexisting seleniferous astragali. It is proposed that As may function to time seed production in such a way that non‐accumulators have passed the full bloom stage by the time coexisting accumulators were in full bloom and volatilizing quantities of selen

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1991.tb00227.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

WANNAN, B. S.&QUINN, C. J, 1991.Floral structure and evolution in the Anacardiaceae.Carpel morphology and anatomy is investigated in 17 genera and carpellode morphology in 12 genera. There is an evolutionary sequence in the family from poorly differentiated, nearly apocarpous gynoecia towards syncarpous gynoecia with clearly defined stigmata, styles and ovaries. There has also been marked reduction culminating in pseudomonomery. The carpellodes of the male flowers appear more conservative, and provide evidence of affinities between genera with quite different fertile gynoecia. The characters have been polarized using Burseraceae as a sister group. Data from these sources, as well as from pericarp anatomy, wood anatomy and biflavonoid content indicate that the long standing intrafamilial classification into five tribes is artificial, and that the two small satellite families, Blepharocaryaceae and Julianiaceae should be included in the family. A large monophyletic group is recognized comprised of essentially four of the existing tribes (Anacardiëae, Dobineëae, Semecarpeae, Rhoëae), as well as the two satellite families. This group incorporates two subgroups of more closely allied genera. The remaining genera (mostly Spondiadeae) are very diverse, and for the present are placed in an artificial group characterised by a set of plesiomorphs. Relationships within this group must be resolved before a satisfactory taxonomy of the family can be achiev

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1991.tb00228.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

MANNINGJ. C.&GOLDBLATT, P., 1991.Systematic and phylogenetic significance of the seed coat in the shrubby African Iridaceae,Nivenia, KlattiaandWitsenia.The seeds ofNivenia, KlattiaandWitsenia,a natural alliance within Nivenioideae, are among their most distinctive features, and seed number and shape constitute at least two synapomorphies for this monophyletic lineage. In this paper we survey the structure of the seed surface of five species ofNiveniaand one each ofKlattiaandWitseniaby scanning electron microsopy (SEM), and study the development of the seed coat in a representative species of each of the three genera. Outgroups for comparison were selected from genera inside and outside the subfamily. The six genera of Nivenioideae are united in having a 3 (– 2) seriate outer integument but the shrubby genera are unique in the family in their tangentially flattened ovules which mature into depressed, flat, scutiform seeds. They display a range of variation in seed coat characters but are specialized in the subfamily and family in having a transparent outer integument. Other genera have pigmented deposits in the outer epidermis of the outer integument.NiveniaandWitseniaare further specialized in having a partially exfoliating outer integument.Klattiais unique among the shrubby genera in having deposits in the second layer of the tegmen, in retaining an intact outer epidermis of the tegmen, and in the fusiform shape of the epidermal cells and striate surface of the seed. Our results are incorporated in a cladogram that expresses our current understanding of the phylogenetic relationships of Nivenioidea

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1991.tb00229.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

BHANWRA, R. K., KAUR, N., KAUR, N.&GARG, A., 1991.Embryological studies in some grasses and their taxonomic significance.The species investigated areLolium multiftorumLam (tribe Poeae),Rostraria cristata(Linn.) Tzevlev (tribe Aveneae),Cenchrus setigerusVahl,Digitaria abludens(Roem. et Schult.) Veld, andD. ciliaris(Retz.) Koel (tribe Paniceae). Apart from the number of microsporocytes in a median longitudinal section of each anther lobe, microsporogenesis and male gametophyte development are similar. However, members of subfamilies Pooideae and Panicoideae show marked differences in structure of the ovary, ovule and post‐fertilization development.Lolium multiftorumandR. cristatavary in the structure of the dorsal ovary wall, degree of curvature in the megagemetophyte in relation to the longtitudinal axis of the ovule, and structure of the pericarp.Cenchrus setigerusis an aposporic apomict and differs markedly from species ofDigitariain this respect, in the extent of development of the inner integument and in the constitution of the dorsal ovary wall. The two species ofDigitariashow minor embryological difference

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1991.tb00230.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY