摘要:

Pododimeria, containing the brown‐spored speciesP. gallicaandP. andina, is expanded to include species with hyaline as well as brown ascospores. Two new hyalodidymous taxa,P. juniperiandP. gelatinosa, are added to the genus. Species ofPododimeriaoccur as ectocommensals on living shoots of Cupressaceae or Podocarpaceae. Although the superficial mycelium may extend into the labyrinthine chambers enclosed by the imbricated scale leaves of the host, it does not penetrate the cuticle. The tiny, black, subglobose, uniloculate ascocarps taper basally to stromatic stipes. The bitunicate asci are interspersed with pseudoparaphyses composed of broad, irregularly shaped cells that readily break apart. The thick, brown to bluish‐green ascocarp wall ofP. juniperihas a broad equatorial band of prosenchymatous cells. The ascocarp wall ofP. gelatinosais composed uniformly of subhyaline, gelatinous pseudoparenchymatous cells covered by a dark, amorphous crust.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06065.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

Sorosphaera veronicaeSchroet. is an endobiotic, holocarpic, obligately parasitic fungus presently classified in the Plasmodiophoromycetes. The ultrastructure of nuclear envelope formation in somatic nuclear division in cystosoral plasmodia was studied. The inner membrane of the nuclear envelope during prophase appears to invaginate and blebb off intranuclear membranous vesicles. The intranuclear membranous vesicles become associated with the surface of the separating chromatin in anaphase and eventually are involved in the formation of daughter nuclear envelopes within the original nuclear envelope. The sequence of nuclear envelope breakdown and reformation inS. veronicaeis noteworthy because it emphasizes alternate methods of nuclear envelope formation other than the generally considered “typical” formation described inAllium cepaL.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06066.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

Callus tissue was induced from shoot meristematic tissue and root tips of a clone of the grassAgrostis stoloniferatolerant to both zinc and copper, and from a control clone tolerant to neither metal. Growth of the callus tissue on media containing zinc and copper showed that tolerance to both metals was maintained in tissue culture. The pattern of metal uptake in tissue culture resembled uptake by whole plants in that tolerant tissue took up more metal than nontolerant tissue. Plants regenerated from callus had the same copper and zinc tolerance as the original parental clones regardless of time of growth in tissue culture and shoot or root origin of the tissue. The results support previous evidence that metal tolerance is genetically determined and acts at the cellular level.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06067.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

Seven populations ofLimnanthes albawere described for their rates of outbreeding, amount of genetic variability, and response to enforced selfing in terms of inbreeding depression. Outcrossing rates, estimated by using two genetic marker loci, varied between 43 and 97%. Heterozygosity level was found to be in the range of 12 and 27 percent, whereas percent polymorphic loci varied twofold (between 29 and 57%) among populations. Inbreeding depression was found to be significant in four of seven populations for number of flowers per plant, plant height, and seed set per flower. There was no association between observed patterns of inbreeding response and predictions from the genetic variation parameters, so that variations in outbreeding rates and consequences need a detailed quantitative verification. In populations showing no inbreeding depression, autofertility seemed to increase with inbreeding (presumably accompanied by natural selection) and to be under genetic control. This is relevant to the hypothesis on the origin of inbreeders under conditions lacking pollinators, e.g., colonization of marginal areas.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06068.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

The Cartesian diver technique has been used for measuring respiration in Protozoa, small crustaceans, insects, and in animal tissue; it can also be used to measure both respiration and photosynthesis in unicellular plants and in plant tissues. In two lichens,Peltigera caninaandEvernia prunastri, algal‐containing tissues were more than 2½ times as active metabolically as medulla. InPeltigera, cortex was slightly more active, rhizines about equally active, and apothecia about a tenth as active as medulla. Light compensation point and peak rates of apparent photosynthesis were reached at higher light intensities inEverniathan inPeltigera. In both lichens, light seemed to retard respiration in the medulla.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06069.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

Electron microscopy confirms previous light microscope observations that tobacco leaf trichomes are glandular and that there are two different types. Both the tall trichome (multicellular stalk, unicellular or multicellular head) and the short trichome (unicellular stalk; multicellular head) exhibit characteristics common to gland cells—a dense cytoplasm, numerous mitochondria, and little vacuolation. The tall trichome contains structurally well developed chloroplasts and an elaborate network of endoplasmic reticulum. The short trichome contains undifferentiated plastids and endoplasmic reticulum which parallels the nucleus and plasmalemma. Few dictyosomes are seen either in the short trichome or in the tall trichome. The short trichome appears to undergo structural changes concurrently with the appearance of secretory product within the cells. The most noticeable change is the formation of the extraplasmic space between the cell wall and the plasmalemma. Electron dense secretory product is observed between the plasmalemma and the cell wall and within the intercellular spaces.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06070.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

Wall development of tricolpate pollen of sunflower was studied by light and by scanning and transmission electron microscopy. The wall and colpi are initiated during the tetrad stage, producing a young, spinulate, two‐layered exine (ektexine and endexine) separated by a “spacer layer.” After release from the tetrads, the individual microspores round up and enlarge. The exine layers increase in thickness and complexity from sporopollenin contributed by the tapetum and microspores. During the mid‐vacuolate microspore stage, the tapetum becomes plasmodial and surrounds the developing microspores. At the vacuolate pollen stage, after the wall and colpi are completely formed, the plasmodial tapetum breaks down and releases its contents into the locule. Some of the contents are presumably utilized by the pollen to make storage reserves while other components, such as lipids and proteins, fill the spaces within the pollen wall exine. Pollen wall ontogeny provides a scheme of terms for mature composite walls in general. The various events associated with microsporogenesis in sunflower are compared with those reported in other pertinent studies.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06071.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

Time lapse photographs were analyzed for curvature, κ, of the plumular hook as a function of distance from the apex,s, of seedlings of lettuce.Lactuca sativacv ‘Grand Rapids,‘ during hook maintenance (red light) and hook opening (white light). Curvature of the inner edge of the photographic projection of the hook increases from 0.14 mm–1near the apex to 12.7 mm–1at the hook bisector (about 1 mm from the apex) and decreases to approximately zero below the hook (2 mm from the apex). Using concepts from fluid dynamics we relate growth rates to curvature changes. For a material element of stem cross section located atswe predict thatM(s,o)−M(s,i)=∂∂t[ln(1+κω)]+u(s)⋅∂∂s[ln(1+κω)]whereM(s,o)andM(s,i)are the relative elemental growth rates at the outer and inner edges of the hypocotyl cross section,wis element width,tis time, andu(s)is velocity of departure ofsfrom the apex. During hook maintenance ∂[ln(1 + κw)]/∂tis approximately zero if the apex is taken as origin. As each hypocotyl element is displaced from the apex it becomes increasingly curved; then, after displacement past the hook bisector, the element straightens. Growth rates, determined by measurements of the displacement of epidermal hairs, show the pattern expected from the equation: On the apical side of the hook, relative growth rates of the outer edge exceed growth of the inner edge,M(s,o)>M(s,i), while on the basal side of the hook.M(s,o)

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06072.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

Nutritional, hormonal, and environmental control of chamise (Adenostoma fasciculatumH.&A.) shoot growth was investigated. In vitro culture of shoot tips demonstrated that 0.18 M sucrose was required for optimum apical growth. Cytokinin (benzyladenine) promoted shoot growth at otherwise growth‐limiting sucrose concentrations and induced uptake of sucrose from the basal medium. Abscisic acid inhibited growth of cultured shoot tips induced by high sucrose concentration or cytokinin. In the field, inhibition of shoot growth was a function of water stress. These studies indicate that the effects of water stress on chamise shoot growth may be mediated by changes in carbohydrate, cytokinin, or growth inhibitor levels at the shoot apex.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06073.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

The sizes, shapes and zonations of the shoot apical meristems of 22 species of cacti were examined. This family was chosen because of its great diversity of habits; the more primitive members are nonsucculent. leafy trees and more advanced members are highly specialized “leaf‐less” stem‐succulents. By combining these measurements with those already in the literature, a sample of almost 70 species was obtained. Apical meristems range in size from only 80 μm in diam in some species to as much as 1.500 μm in diam in others. The shape ranges from being flat to almost hemispherical. Despite the great range in size and shape of the apical meristems, or the range in the morphologies of the leaves and stems which are produced by the meristems. all apices had the usual zonation: tunica, central mother cells, peripheral zone, and pith‐rib meristem. The sizes of each of the zones. expressed either as the number of cells per zone or expressed as a percentage of the whole apex. were highly variable. The variation in apical dimensions and zone sizes occurred both phylogenetically and ontogenetically. and this has been interpreted to indicate that the morphogenetic mechanisms which control apical size and zonation are easily modified, both during the development of individual plants and during the evolution of new species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06074.x

出版商:Wiley    

年代:1978

数据来源: WILEY