摘要:

This study is concerned with the determination of the shoot and root inducing effects of kinetin (K) and naphthaleneacetic acid (NAA) on shoots ofthe fishtail fern (Nephrolepisfalcata formafurcans) in sterile tissue culture. The data shows that K is the major factor involved in maximal shoot production. The NAA is not essential. Specific concentrations ofNAA must be present with specific concentrations of K for maximal root production. At the same time, the data also demonstrate that shoots on media containing no NAA but with K concentrations of 5× 10−7and 10−6M produced as many roots as with any other NAA concentration. The data can be used as a guide to rapid commercial propagation of fishtail fern, and demonstrate that media available commercially for Boston fern multiplication will induce maximal shoot production in fishtail fern.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12425.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

The principal contributors of biologically fixed N in natural grassland ecosystems appear to be asymbiotic bacteria and heterocystous cyanobacteria. The environmental factors of light, moisture, and temperature play important roles in the magnitude of the N2‐fixation activity. Biological N2‐fixation was measured in the Elizabeth's Prairie section of the Lynx Prairie Preserve, Adams County, Ohio, during 15 site visits beginning 29 March through 8 November 1980. In situ N2‐fixation activity was measured using the acetylene‐reduction technique. The percentage cover of cyanobacterial colonies (Nostocsp.) was determined using Point‐Frame Analysis. Soil and air temperatures and soil water potentials also were measured. Intact soil cores with a surface cover ofNostocwere collected and returned to the laboratory to quantify the effect of decreasing water potential on the N2(C2H2)ase activity ofNostoc.The N2(C2H2)ase activity ofNostocon the intact soil cores displayed a linear response of approximately 10% decrease in N2(C2H2)ase activity per one bar decrease in soil water potential. The cyanobacteria contributed almost all of the biologically fixed N at the site until late June. From late June through to mid September, heterotrophic diazotrophs played the major role in the N2‐fixation activity. These changes are attributed to fluctuations inNostocsp. colony cover, temperature, and soil water potentials. Extrapolation of the measured rates, and assuming an average of 10 hr per day of activity,Nostocsp. is shown to have contributed 4.60 ± 1.17 kg N ha−1yr−1. Heterotrophic diazotrophs contributed an estimated 3.19 ± 1.18 kg N ha−1yr−1. The total biological N2‐fixation for the site was calculated at 8.2 ± 2.55 kg N ha−1yr−1, from additional measurements which estimated total diazotrophic activity of the site. These rates of N2‐fixation are among the highest reported for temperate grassland habitats.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12426.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

The vascular system for the two lodicules in a floret ofDactylis glomerataL. was studied in serial sections. The floret stele contained a few modified tracheary elements and xylem transfer cells enveloped by a phloem of squat sieve‐tube members and intermediary cells. A single sieve tube and associated phloem parenchyma exited the right and left sides of the stele and upon nearing the base of each lodicule branched and formed the minor veins of the lodicule. The minor veins underwent limited branching and anastomosing to form a small three‐dimensional system which described an arc during its ascent in the adaxial portion of each lodicule. The sieve tubes in the minor veins extended halfway up the lodicule and contained short sieve‐tube members with transverse, slightly oblique, or lateral simple sieve plates. The associated phloem parenchyma cells were intermediary cells, companion cells, and less intimate parenchyma cells. Intermediary cells terminated the minor veins and touched the distal ends of the terminal sieve‐tube members, which lacked distal sieve plates. Although the transverse area of the sieve‐tube members remained constant up the lodicule, the transverse area of the associated phloem parenchyma fluctuated.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12427.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Field assays of N2(C2H2)ase activity were performed with intact nodules from a pure alder site (alder) and a mixed alder‐aspen site (aspen). Assays were performed between 12 June and 12 August 1980 and in May 1981. N2(C2H2)ase rates are expressed as g N g nodule oven‐dry wt−1hr−1(g N g−1hr−1). Diurnal N2(C2H2)ase activity showed an increase in both sites between 0600 and midday, then decreased to a low by 1800. Nighttime activity in the May 1981 assay was approximately 25% of the daytime peak. Mean (±SE) 1200 hr N2(C2H2)ase activity (μg N g−1hr−1) for all sizes in the alder stand rose from 24.56 ± 6.56 on 12 June to 73.96 ± 28.37 on 26 June and declined to 9.20 ± 2.56 by 12 August. In the aspen stand activity decreased from the 12 June rate of 21.81 ± 4.59 to 3.64 ± 1.87 on 24 July but then increased to 30.00 ± 7.39 by 12 August. Based on diurnal assays, the seasonal mean N influx (μg N g−1hr−1) is statistically higher (P0.05) in the alder stand with a value of 26.70 compared to 14.63 in the aspen stand. Small size class shrubs had significantly higher (P<0.05) N2(C2H2)ase activity (μg N g−1hr−1) in diurnal assays than medium or large class shrubs. The estimated mean (±SE) N2(C2H2)ase activity (mg N g−1season−1) for all sizes was 44.4 ± 18.6 in the alder stand compared to 16.2 ± 5.2 in the aspen stand. Nodule excavations showed the g shrub−1in the alder stand to be 16.48 ± 10.29, 38.57 ± 12.34 and 29.11 ± 7.15 for small, medium and large size shrubs and 12.73 ± 3.23, 28.21 ± 4.36 and 56.45 ± 16.23 for respective sizes in the aspen stand. Seasonal N influx was 4.69 kg ha−1in the alder stand and 0.84 kg ha−1in the aspen stand, representing 17.9% of the alder stand. Nitrogen feedback inhibition from uric acid‐N influx and allelochemic interference from aspen are discussed as explanations for the differences in N influx in the two stands.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12428.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Somatic and meiotic chromosomes of one plant ofAnthurium warocqueanumJ. Moore and its selfed offspring were analyzed. The parent showed 2n =30 + 3B in both somatic cells and pollen mother cells. The B chromosomes divided normally in somatic cells, but meiotic associations of Bs varied. Three configurations of three B chromosomes were observed at metaphase I of parent meiosis: one trivalent, one bivalent and one univalent, or three univalents. The number of B chromosomes in offspring ranged from 0 to 6, indicating their transmission from both male and female gametes. Offspring with two B chromosomes appeared in greatest frequency. It was hypothesized that both male and female gametes of the 3 B parent frequently contained one B chromosome through the normal distribution of the bivalent Bs at meiosis and the elimination of the univalent B chromosome due to lagging. Examination of pollen mother cells of offspring also revealed irregular behavior of B chromosomes. With a high number of B chromosomes, normal A chromosome bivalent formation seemed to be reduced. No phenotypic effects of B chromosomes were observed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12429.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Recruitment and mortality ofSpartina alternifloratillers and culms were estimated from measurements of live standing crops at Wallops Island, Virginia. Stands of tall and medium form grass produced from 452 to 1,227 tillers m−2yr−1. Those tillered in spring lengthened into culms their first year, while those tillered in late summer and fall may have overwintered and lengthened into culms their second year. Biennial growth was most prevalent in tall formSpartina.Fifty‐six to sixty‐one percent of all tillers died before lengthening into culms. Of the remainder, 9 to 56% died as culms before the time of flowering. Sixty‐three percent of the surviving culms of tall formSpartinaflowered, compared to only 14 to 23% in medium form. Mortality of tillers and culms removed 16 to 35% of the annual production ofSpartinabiomass from live standing crops before the time of flowering.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12430.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Two adjacent populations ofP. lanceolatawere observed to have different rosette morphologies and apparently, capacities for vegetative reproduction. Plants growing in an open, sunny habitat were clumped while those found growing in a periodically shaded habitat, only developed as single rosettes. Representative genotypes from each population were cloned from leaf cuttings and propagated in controlled‐environment facilities. Growth and vegetative reproduction were measured under two contrasting irradiances to determine whether the differences seen in the field were primarily genetic or environmentally induced. These studies indicated that each population was adapted to the light regime most similar to that prevailing in its natural habitat. The clumping in the open population was the result of a greater capacity for vegetative reproduction.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12431.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Microelectrodes were used to study the oxygen concentration withinMyrica galeL. nodules. Low oxygen concentrations were found only in the region of the mature, nitrogen‐fixing endophyte, and appeared to correspond to clusters of infected host cells. The oxygen concentration in the remainder of the nodule was much higher. Interconnected intercellular air spaces were demonstrated by infiltration with India ink. Infiltration of the spaces with water greatly reduced oxygen concentration throughout the nodule, indicating that they function in supplying oxygen to the infected cells and remainder of the nodule. These results differ from those found previously for soybean nodules and provide evidence that legume and actinorhizal nodules have different mechanisms for protecting nitrogenase from oxygen.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12432.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

As part of a continuing study of sieve elements in primitive angiosperms, a study of this cell type was undertaken inLiriodendron tulipifera.A typical ontogenetic sequence was observed in which synthetic processes such as wall thickening are followed in time by cellular lysis of nucleus, ribosomes, microtubules, vacuoles, and dictyosomes. This lysis is selective in that certain cellular components (e.g., the plasmalemma) remain unaffected. Concomitant with lysis is the formation of sieve‐area pores from plasmodesmata. Comparison of pore size on end and lateral walls indicates that the use of the term “sieve tube” rather than “sieve cell” to describe these elements is appropriate.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12433.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Equisetum scirpoidesMichx., propagated from a single clone, was grown in a controlled growth chamber at 24 ± 1 C under a photoperiod of 16 hr light/8 hr darkness. The apical cell of aerial vegetative shoots gives rise to derivatives (merophytes) in a helical sequence. Each newly formed merophyte divides anticlinally to form two superposed cells that are parallel to a lateral face of the apical cell. Radial longitudinal divisions then take place in the two superposed cells. Shoot tips were fixed every 2 hr for 24 hr to determine the mitotic index of the apical cell, six subjacent cells, and the remaining cells above the level of leaf initiation. Average mitotic indices for the 24‐hr period were 3.9%, 3.9%, and 7.0%, respectively. The results indicate that the apical cell is quite active mitotically; there was no clear evidence of endopolyploidy in cells of the shoot apex, young leaves or in the developing cortex, based upon cytophotometric measurements of DNA content.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12434.x

出版商:Wiley    

年代:1983

数据来源: WILEY