摘要:

The present work deals with growth eccentricity and reaction anatomy in horizontal branches ofPseudowintera colorata(Raoul) Dandy. Growth promotion is distinct and occurs on the lower (abaxial) side of inclined branches in the manner common to gymnosperms. Neither compression wood nor tension wood was found either on the upper or on the lower side of the investigated branches. The cells of the wood to the lower side show some differences from those of the upper side. The lower‐side tracheids are longer, wider, possess thicker walls and have a higher microfibril angle than those of the upper side. The lower‐side rays are less high but wider (because of a greater number of larger cells) than those of the upper side.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06115.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

Eight isolates ofDraparnaldiafrom a variety of freshwater habitats were grown in unialgal, defined culture. The morphological responses of these isolates to different daylengths, light intensities and temperatures are described. The phenotypic expression ofDraparnaldiais markedly modified by all three factors. The interaction of these environmental variables was highly significant, and it is not possible, in most cases, to describe or predict the morphological appearance ofDraparnaldiaby referring to one of these parameters in isolation. The adaptive significance of phenotypic plasticity inDraparnaldiais discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06116.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

Morphological features of nutlets of all members of the genusLimnantheswere examined by light and scanning electron microscopy (SEM). Eight distinct nutlet types are recognized on the basis of presence or absence, size, shape, density, and color of tubercles and associated filamentous or globular background structures. Some taxa (e.g.,L. macounii, L. bakeri)display only one nutlet type, some (e.g.,L. floccosa floccosa)have different types in different populations, and others (e.g.,L. alba, L. striata)have two or more types within populations. Four classes of nutlets are designated as subtypes on the basis of their forms varying between the eight types recognized. The relationships among various taxa on the basis of nutlet types are schematically diagrammed and compared with other classification schemes. Results suggest that the proposed details of nutlet morphology should be considered in an identification key. Preliminary evidence indicates that certain highly sculptured (tuberculate) nutlet types with large surface areas occur more often in wetter habitats and that variation in this trait in differentLimnanthesspecies might be adaptively associated with geographical distribution patterns.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06117.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

An earlier report of the presence ofAlnus‐type nitrogen‐fixation root nodules onArctostaphylos uva‐ursi(bearberry) has been re‐examined. Nodular structures, externally resembling those of alder, were observed at four locations in eastern North America and in northern Scotland. No endophytes could be found in these structures and repeated assays by the acetylene reduction technique failed to demonstrate their ability to fix dinitrogen in North American material. The structures, in microscopic section, possessed typical bud morphology, could be sprouted in a moist chamber and produced shoots under stressed conditions in the field. The suspected 'nodules' are probably latent buds, serving to re‐establish bearberry plants following damage.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06118.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

The tissues of the sporocarp ofMarsilea vestitaundergo profound changes during development. Early in development, the cells of the peripheral tissues, epidermis, hypodermis and layers of the transitional zone between the hypodermis and more internal tissues contain prominent vacuolar bodies. As development proceeds, these vacuolar bodies disappear. Prominent amyloplasts are found only in the guard cells and in the cells of the transitional zone. Later in development the cells of the hypodermis divide periclinally forming two layers which differentiate as macrosclereids. The cells of the outermost layer of the transitional zone differentiate as osteosclereids. Internally, the cells of the sorophore accumulate large amounts of mucilage in the central vacuoles. The peripheral cytoplasm ultimately degenerates leaving just hygroscopic mucilage. The mucilage carbohydrate contains the sugars, rhamnose and arabinose. In the young sorus, only the spore mother cells and the cells of the indusium contain amyloplasts. By the time of meiosis, there is a massive accumulation of starch in the receptacle, stalk and jacket but not in the tapetum of the sporangia. Late in development, the starch disappears and the mega‐ and microspores become coated with carbohydrate.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06119.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

In the young sporocarp ofMarsilea vestita, the sorophore tissue consists of vacuolate parenchymatous cells. The vacuoles contain electron‐dense bodies which disappear as the cells enlarge. During the differentiation of the sorophore cells, there are three phases of polysaccharide accumulation. During the first phase, speroidal carbohydrate bodies accumulate in vesicles and vacuoles of the peripheral cytoplasm. Globular carbohydrate bodies which are interconnected by strands of polysaccharide appear in the central vacuole during the second phase. The third phase begins with the appearance of strands of polysaccharide radiating out into the central vacuole from the tonoplast. As the sorophore cells mature, the central vacuoles become filled with this fibrous polysaccharide. The cytoplasm ultimately degenerates leaving behind dispersed globular carbohydrate and fibrous polysaccharide. When the mature sporocarp is scarified and placed in water, the hygroscopic polysaccharide in the sorophore cells expands and stretches the cell walls. As a result, the sorophore is transformed into a long column many times its original length.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06120.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

The fluorescent boundary across the stalk of an antheridium ofPolytrichumappears as a distinctive, secondary wall layer in electron micrographs. Lamellations of electron‐dense and ‐lucent materials cause this layer to resemble the “suberized lamellae” of root endodermis and leaf bundle sheaths in grasses. The cells of the stalk below the boundary are especially rich in lipid droplets, whereas those in the base of the antheridium, above the boundary, have markedly fewer and smaller lipid droplets and abundant rough endoplasmic reticulum often in loosely parallel arrays. Cytological differences develop before the boundary appears, so that the distinctive wall layer is secreted by protoplasts that are already specialized morphologically. During maturation of an antheridium there is a secretion of a fluid into a space that forms at the bottom of the sperm chamber. However, the cells surrounding this fluid show no special morphological adaptations that would seem to relate to secretion.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06121.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

Organogenesis in alfalfa callus (Medicago sativaL. cv. ‘Regen S’) has been obtained by the transfer of callus from an induction medium containing growth regulators to a regeneration medium lacking growth regulators. The transfer of callus from induction medium containing high levels of 2,4‐D and low levels of kinetin to regeneration medium resulted in the formation of shoots. Conversely, the transfer of callus from induction medium containing low levels of 2,4‐D and high levels of kinetin resulted in the formation of roots. The pattern of organogenesis on regeneration medium was modified by the nutritional composition of that medium. When Blaydes medium supplemented with inositol and yeast extract was employed as regeneration medium, root organogenesis was inhibited. Root organogenesis was not inhibited by either Shenk and Hildebrandt medium or Gamborg's B5 medium. Shoot formation occurred on all of these media. A survey of the in vitro organ‐forming capacity of 14 genotypic clones from the cv. ‘Regen S’ was conducted. The capacity to form organs differed quantitatively among the clones analyzed. A more detailed analysis of a highly responsive clone (RA3) and a poorly responsive clone (RA5) revealed no significant qualitative difference in their organogenic responses.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06122.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

In crosses involving a polyploid myxamoebal clone. CR 2‐25*, F1plasmodia and myxamoebae display a variety of unexpected ploidy levels as indicated by nuclear DNA measurements. Genetic analyses of the F1generations reveal either complete elimination of certain genetic markers or greatly skewed segregation ratios. On the basis of these two kinds of evidence, it is assumed that chromosome elimination occurs at some stage (or stages) following karyogamy between parental nuclei. The possible significance of polyploidy in relation to myxomycete speciation and evolution is discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06123.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

The immunocytochemically observed intracellular redistribution of phytochrome as a function of its molecular form is described by utilizing color photomicrography. The reversible change from a diffuse to a discretely localized distribution following photoconversion of the red‐absorbing Pr form to the far‐red‐absorbing Pfr form observed with etiolated oat (Avena sativaL., cv. Garry) coleoptile parenchyma cells is not seen with etiolated wheat (Triticum sativumL., cv. unknown), barley (Hordeum vulgareL., cv. Harrison), or rye (Secale cerealeL., cv. Balbo). Whether redistribution in these latter cases does not occur or is below the limit of detection is not known. Upon continuous actinic irradiation, phytochrome, which is discretely localized as Pfr, rapidly disappears by both immunocytochemical and spectral assay. However, after about 90 min irradiation, a new association of phytochrome with nuclei is evident which is more pronounced after 4 or 8 h of irradiation. With longer irradiation times there is a total loss of antigenically detectable phytochrome at the resolution employed in these experiments.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb06124.x

出版商:Wiley    

年代:1978

数据来源: WILEY