摘要:

We investigated the photoperiodic regulation of aging inAnagallis arvensisL. propagated by cuttings. Short‐day (SD) conditions caused the persistence of juvenile forms and vegetative growth, as well as high rooting capacity and a high RNA content, through successive vegetative multiplications. SD + 1 long day (LD) every 15th day induced reproductive growth but allowed the persistence of a high rooting capacity and high RNA content through vegetative multiplications. LD conditions caused the persistence of the reproductive stage, the progressive loss of rooting capacity, and a decrease of RNA content. The longevity of the clones seems to be connected to the photoperiodic effects which induce indeterminate growth (SD) and/or determinate and reproductive growth. The loss of propagation capacity and the decrease of RNA content can be considered as indexes of aging not only in plants but also in clones.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05995.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Carpospores and tetraspores germinate and the germlings develop similarly. A prostrate holdfast of regular or irregular outline is formed if the spore makes direct contact with the substrate. If not, rhizoids grow from the few‐celled germling unilaterally in no apparent relation to light or gravity, forming a prostrate holdfast if they encounter a solid substrate, and, in any case, eventually an erect shoot of different anatomy. Tetrasporophytes have been grown to reproductive maturity from single spore cultures in the laboratory. The ontogeny of the procarp and subsequent postfertilization events are described from field material. Only a single putative male plant was found when plants bearing procarps were numerous at Plymouth. Evidence from this study and from other reported observations places in doubt the expected role of fertilization in the diphasic, cytological alternation ofChondrus.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05996.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Growth and reproduction were examined periodically through a full year at four stations located in a dense population ofChondrus. Growth rates of germlings and of mature plants reach a maximum in late summer and a minimum in winter, paralleling temperature. At the time of maximum growth, nitrate is at its lowest seasonal concentration. Ammonia, however, is available and apparently utilized. Fronds are smaller but more numerous at −3 m MLW than at −6 m MLW and deeper and regrow from holdfasts with twice the original density after removal. Large fronds are torn off by storms at lesser depths. The average weight and density varies with season and possibly with depth.Chondrusat Plymouth is similar to populations investigated elsewhere in average density of plants per unit area, but the average weight per unit area was approximately twice that reported for other populations. Presence or absence of sori gives a false picture of reproductive periodicity because at some seasons most sori are empty or contain non‐viable spores. Carposporic reproduction reached a sharp maximum in October. Tetrasporic reproduction did likewise, with an additional lesser peak in May. At the time of greatest reproductive intensity, approximately half of all mature plants were shedding spores. Spores settle, germinate, and produce germlings successfully on initially sterile surfaces; no prior macroscopic or microscopic successional events are required. Seasonal composition of associated flora and epiphytes ofChondrusare discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05997.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Plasmodial extracts of 45 isolates ofFuligo septica(L.) Wiggers selected from diverse geographical areas were subjected to acrylamide disc electrophoresis. Profiles for ten enzymes and general protein were determined. Profile variability among isolates occurred. Indices of similarity calculated for each isolate indicated that the variations of the yellow and white plasmodial isolates fell within different ranges. Determination of the total range of variation for the species must wait on the analysis of more white isolates. The extreme sensitivity of disc electrophoresis in detecting color forms suggests it can be useful as a tool in myxomycete taxonomy.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05998.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Cell walls prepared from onion bulbs were found to exhibit an affinity for Ca++. The adsorption of this ion was enhanced by the action of pectin methylesterase. It was confirmed that Ca++reacts with two COO“ groups and the corresponding affinity constant, K, was found to be: log K = 4.25. The action of pectin methylesterase had no effect upon K. The cell walls, as prepared, had 25 % of the total COO−groups occupied by Ca++, 14 % by Mg++, and 39 % by H+. Treatment with acidified ethanol removed all of the metallic cations. K+and Mg++could displace Ca++from the cell walls. At concentrations from 10−3to 3 times 10−3m it required from 4.9 to 13.2 moles of Mg++to displace one mole of Ca++. For K+it required 80 moles to displace 1 mole of Ca++at K+concentrations from 0.65 × 10−2to 1.6 × 10−2M.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05999.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

HawaiianMetrosiderosis a highly polymorphic complex that is distributed throughout the six major islands of the Hawaiian Island chain from tropical climates near sea level to altitudes up to 8,500 ft with frost. Its populations extend continuously over many areas with average annual precipitation ranging from 30 to 450 in. and with diverse edaphic and topographical features. The Hawaiian forms are probably all derived from one or a very small number of ancestral introductions that arrived within the last 20 million years by longdistance dispersal. Seeds collected from diverse altitudinal sites on the islands of Hawaii and Maui and grown under uniform greenhouse conditions at Honolulu show evidence of ecotypic differentiation along altitudinal gradients. Seedlings from these islands separated by 50 miles of ocean show parallelism in their altitudinal differentiation in plant height and leaf size, but with strongly overlapping variation from site to site.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb06000.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Thalassia testudinum(Turtle Grass), a marine monocot which grows completely submerged, differs from intertidal and other halophytic angiosperms in that it has no specialized saltsecretory glands. Osmoregulation appears to be accomplished by the epidermal leaf cells which have highly invaginated plasmalemmas with numerous mitochondria situated in the interdigitations. The ultrastructure and proposed mode of secretion are similar to that of the salt‐marsh monocotSpartina, but differ from that found in dicots. Evidence is presented to show why monocots are the only angiosperms which have adapted to a completely marine environment.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb06001.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Natural and synthesized hybrids ofCeratopteriswere investigated to determine the effect of hybridization on the genetic system. Studies indicated that the hybrids exhibited massive spore abortion and pairing abnormalities at meiotic prophase, characteristic of “sterile diploids and triploids” reported in hybridization studies of other fern genera. However, a small percentage of viable spores also was produced by the hybrids. Cytological investigations indicated the presence of previously unreported meiotic adaptations that allowed the production of unreduced spores and reduced spores exhibiting chromatid heterozygosity. The reduced spores allow haploid gametophytes to form heterozygous zygotes in spite of intragametophytic selfing. The unreduced spores were shown to be responsible for the fertility of the “sterile” hybrid and allowed the subsequent production of up to three generations of sporophytes. The literature suggests that these meiotic adaptations are present in other fern genera and may play a significant role in evolution through hybridization.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb06002.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

The mean chiasma number per cell was 11.44 ± 0.04 in 489 cells. Due to chiasma failures, the ring‐of‐twelve chromosomes may be broken into two or three chains. Cells with four or more chains were not observed. All six possible two‐chain situations and eight different threechain situations were found. All possible lengths of chains from one to all twelve chromosomes were found, with “chain”‐of‐one inordinately frequent. The overall mean number of chromosomes in 273 chains in 188 cells is 8.26 ± 0.31 and 5.38 ± 0.31 among 154 chains in the 69 cells that had two or more chains. The mean number of chains per cell among these 188 was 1.45 ± 0.13. In 73 cells, 113 chiasma failures were found to be distributed at random among the twelve chromosome arm positions. The absence of association either between length of arm or between presence‐absence of secondary constriction and frequency of chiasma failure support the generally accepted theory that, inRhoeo, synapsis and crossing over are restricted to small terminal segments on all chromosomes.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb06003.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Effects of low temperatures on cell ultrastructures of three grass species were studied.Secale cerealeL.,Cynodon dactylon(L.) Pers., andPaspalum notatumFlugge seedlings were given treatments of −5, 0, 10, or 25 C for 3 days and then evaluated for cellular response. Electron micrographs showed chloroplasts to be the most sensitive organelle in all three species, with the temperateSecaleplastids responding differently than plastids from the subtropical and tropical species. Rough endoplasmic reticulum increased, but dictyosome numbers decreased in all species as treatment temperatures were lowered to 0 C. Mitochondria expanded slightly at reduced temperatures, but with little difference detected between species. The study indicated that the various cellular components of these species responded differently to reduced temperatures, with the species differing mainly in degree of response.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb06004.x

出版商:Wiley    

年代:1973

数据来源: WILEY