摘要:

Floral nectary development and nectar secretion in three species ofPassiflorawere investigated with light and electron microscopy. The nectary ring results from the activity of an intercalary meristem. Increased starch deposition in the amyloplasts of the secretory cells parallels maturation of the nectary phloem. Large membrane‐bound protein bodies are observed consistently in phloem parenchyma cells, but their function is presently unknown. The stored starch serves as the main source of nectar sugars at anthesis. Plastid envelope integrity is maintained during starch degradation, and there is no evidence of participation of endoplasmic reticulum or Golgi in the secretion of pre‐nectar. It is concluded that in these starchy nectaries granulocrine secretion, commonly reported for floral nectaries, does not occur.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07789.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

Chromosome counts and observations of reproduction for 55 taxa of Cactaceae indicate that polyploidy is correlated with self‐fertility, adventive embryony, profuse branching, and vegetative reproduction. Six genera (Blossfeldia. Cleistocactus, Frailea, Pelecyphora, Rebutia, andStrombocactus) and 35 species or varieties are reported here for the first time. Preliminary observations of pachytene and diplotene indicate that these stages may be more useful in chromosome recognition than mitotic stages. Secondary association at metaphase I and II is interpreted as a retention of homologue association at interphase I and II (interkinesis). During meiosis of certain species, Feulgen negative bodies are present. The production of an abnormal premeiotic division is suggested as a mechanism for polyploid origin.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07790.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

The biomass, density, age structure, and dominance patterns of the tree and shrub populations in hardwood swamps of the New Jersey Pine Barrens are described and contrasted with each other. The total biomass of individual swamps ranges from 92,000 kg/ha to 194,000 kg/ha, depending on the age of the stand. These biomass values are similar to those reported for southern hardwood swamps. The Pine Barrens swamps are distinguished by very large populations of ericaceous and other shrubs, which range up to 13% of the total above‐ground biomass. The tree populations, composed principally ofAcer rubrum, Nyssa sylvaticaandMagnolia virginiana, are even‐aged;Aceris strongly dominating, with a minimum of 73% of the biomass, and species richness is associated with the availability of different microhabitats. The shrub populations, by contrast, are all‐aged, with the dominance patterns among the species and the stand biomasses varying with the degree of flooding of the stand. Differences in size and growth rate among the shrub species parallel their evident response to the flooding gradient. The shrub stratum has lower species richness than the comparable southern swamps and floodplains, but ranges up to higher biomass values.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07791.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

The in toto pattern of the floral vasculature inKoeberliniaZucc, is distinctive. The median vascular trace to each sepal is concrescent with the antesepalous stamen trace forming a trace complex. Each petal trace is concrescent with the nearest antestaminal trace, and this common trace is in turn concrescent basally with the common basal supply to the adjacent sepal margins. The ventral carpellary bundles and the ovular traces of the two carpels are arranged for part of the ventral carpellary system into an essentially continuous hollow stele‐like cylinder and many of the ovular vascular supplies originate from this strand. All vascular concrescences are congenital. Comparisons of the morphological and floral vasculature characters ofKoeberliniawith those of its various putative allies revealed that there are no substantial reasons for linkingKoeberliniawithCanotia, Celastraceae, Rutaceae, Simaroubaceae, or Zygophyllaceae. The in toto floral vascular structure ofKoeberliniais closely similar to that of the Caryophyllaceae and dissimilar to that of the Capparaceae. Several qualitative characters of the secondary xylem ofKoeberliniadiffer from those of the Capparaceae, yet certain important ones are similar. Many of the morphological characters ofKoeberliniaare similar to those of the Capparaceae as well as the Caryophyllaceae, yet certain critically important ones strongly indicate a relation ofKoeberliniato the Capparaceae: occurrence of myrosin cells, capparaceous pollen, capparaceous ovular characters. To includeKoeberliniawithin either of these families is unwise, but the writers are inclined to retainKoeberliniain a monogeneric family within the larger Capparales.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07792.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

A technique for the partial purification of α‐amylases from latex ofEuphorbia heterophylla, E. marginata, andE. tirucalliis described. The enzymes were found to be similar to other higher plant amylases using the criteria of molecular weight, pH characteristics, kinetics, number of isozymes, and blue value‐reducing value patterns. Carbohydrases other than α‐amylases were not detectable in latex. The amylases were employed to examine their capacity to digest latex starch grains which are common components of the laticiferous cell in this genus. Laticifer starch grains are not susceptible to in vitro amylolysis. Removal of the starch grain membrane with Triton X‐100, damaging the grain, or treating the grains with α‐amylases from diverse biological sources had little effect upon hydrolysis. Grains incubated with pullulanase followed by α‐amylase caused a slight but significant increase in hydrolysis of raw laticifer starch grains. These studies indicate that the nonarticulated laticifer inEuphorbiais acul de sacfor certain primary and secondary metabolic products and that the indigestible and morphologically complex starch grains in the latex have evolved to function in a secondary role within the laticifer.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07793.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

The effects of light, temperature, and salinity on growth, net CO2exchange and leaf anatomy ofDistichlis spicatawere investigated in controlled environment chambers. When plants were grown at low light, growth rates were significantly reduced by high substrate salinity or low temperature. However, when plants were grown at high light, growth rates were not significantly affected by temperature or salinity. The capacity for high light to overcome depressed growth at high salinity cannot be explained completely by rates of net photosynthesis, since high salinity caused decreases in net photosynthesis at all environmental conditions. This salinity‐induced decrease in net photosynthesis was caused largely by stomatal closure, although plants grown at low temperature and low light showed significant increases in internal leaf resistance to CO2exchange. Increased salinity resulted in generally thicker leaves with lower stomatal density but no significant differences in the ratio of mesophyll cell surface area to leaf area. Salinity and light during growth did not significantly affect rates of dark respiration. The mechanisms by whichDistichlis spicatatolerates salt appear to be closely coulpled to the utilization of light energy. Salt‐induced leaf succulence is of questionable importance to gas exchange at high salinity in this C4species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07794.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

Cell division patterns in germinating spores of severalThelypterisspecies were studied using light microscopy of sectioned material and scanning electron microscopy. All species exhibited the same basic germination pattern, characterized by an asymmetric cell division of the spore parallel to the equatorial plane to delimit a proximal rhizoid, followed by a perpendicular division of the basal cell to form the protonemal cell. While spore‐germination patterns appear to be a potentially useful taxonomic character in some groups of ferns, the homogeneity in this character exhibited by the thelypteroid group impairs its usefulness in the taxonomy ofThelypteris.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07795.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

Succession of chaparral shrubs was studied for the first 4 years after fire on the four major slope faces at three elevations in southern California. Although total cover fluctuated from year to year, shrub cover increased annually through the third year. There was little or no increase in shrub cover between the third and fourth years. Four years after fire the shrubs covered 55% ground surface at the highest elevation site but only 28% at the lowest elevation site. Shrub cover was similar between slope faces with one exception; at the lowest elevation site shrub cover was twice as great on the north and east‐facing slopes as on the south and west‐facing slopes. Post‐fire recovery of shrubs was by seedlings and/or resprouts.Yucca whippleiwas an exception in that it did not resprout once the aboveground parts were killed nor did seedlings establish after fire, however the aboveground parts of manyY. whippleisurvived the fire. Species which reproduced entirely by seed did so in the first post‐fire year from soil‐stored seed with the exception ofCeanothus greggiiat the highest elevation site. This species was entirely absent the first year after fire but abundant in the second year. Species producing both resprouts and seedlings varied from site to site in the proportion of resprouts:seedlings. Between 83–100% of the post‐fire populations ofCercocarpus betuloides, Arctostaphylos glandulosa, andXylococcus bicolorwere resprouts whereas 12–13% ofCeanothus tomentosuswere resprouts. ForAdenostoma fasciculatum, resprouts constituted 27–54% of the population at the lowest elevation and 65–94% at the highest elevation; whereas, theQuercus dumosapopulation was 100% resprouts at the lowest elevation and 31–67% resprouts at the highest elevation. Data are presented on the height of resprouts and seedlings for all species at the end of the first post‐fire year.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07796.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

A stereological, morphometric study of the ultrastructure of subapical cells, xylem parenchyma, and cortical chlorenchyma ofEchinocereus engelmanniishows that each of these cell types has a unique organellar composition. The cells of any of these tissues are unique not only in vacuolation (which is visible at the light microscope level), but also in the nucleus/cytoplasm ratio and the concentrations of mitochondria, chloroplasts, and dictyosomes. Furthermore, the differences between each of these cell types were large and statistically significant. It had previously been found that the cells of each zone of the shoot apical meristems ofE. engelmanniiare different from those of the other zones, but the present study suggests that, considering the large ranges of structure possible in the nonapical cells of this species, the apical meristem variation should be considered as only a minor difference and that the meristem zones are really quite similar to each other.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07797.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

Ring width chronologies from 127 black birch trees in the northeastern United States were used to study age dependent and spatial patterns in growth. The trees sampled show no evidence for increasing stability of growth with age, as measured by the year‐to‐year variance and autocorrelation. Large scale spatial patterns were studied using trees sampled from five localities separated by distances of 40 km to 325 km. Cluster analysis based on the last 30 years of growth is able to assign a tree to its locality of origin with approximately 80% accuracy. However, the degree of correlation between these chronologies does not decline as a function of the distance of separation of the localities. Fine scale patterns were studied using chronologies from 46 birches lying within a 50‐m x 60‐m plot. Strong neighborhood effects could not be detected in the rate of growth, the variance of growth, or the between‐tree correlation. Dry‐site trees, however, were found to be growing significantly faster and with less variability than wet‐site trees. The results suggest that very local factors are important determinants of growth and dominate the environmental structure perceived by mesic forest trees.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07798.x

出版商:Wiley    

年代:1981

数据来源: WILEY