摘要:

The morphological responses of 28 shrub and 109 herbaceous species buried by 5–20 cm of tephra (volcanic aerial ejecta) from Mount St. Helens were examined after 1 year of burial. All shrub species produced adventitious roots in the tephra but the extent of roots varied greatly; three shrub species produced extensive rhizomes in the tephra. Most herbaceous species moved perennating buds into the tephra. Upward movement was accomplished in many ways, including upward growth of normally long rhizomes, accelerated elongation of normally short rhizomes, and development of perennating buds on aerial shoots that penetrated the tephra. Nineteen herbaceous species failed to move their perennating buds into the tephra; many of these are forest-dwelling members of the Liliaceae. Herbaceous plants representing a wide range of morphological types successfully penetrated tephra deeper than 12 cm; other species representing the same morphological types failed to penetrate deep deposits. A range of plasticity in several attributes of growth form appeared following burial.

ISSN:0008-4026    

DOI:10.1139/b85-293

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The burial of plants is seldom studied but is potentially important in some ecosystems. For each of eight herbaceous species, about 10 individuals that survived burial by 7 – 15 cm of tephra were totally excavated during both 1981 and 1982. The long rhizomes ofAchlys triphylla,Clintonia uniflora, andSmilacina stellatagrew upward at an angle, so that 7% of rhizome and 3% of root dry weights were in the tephra in 1981; these values increased to 23 and 19%, respectively, in 1982. Burial reduced the number of shoots produced by each plant. Stolons ofRubus lasiococcusgrew straight up and then spread across the tephra surface, although few roots were produced in the tephra. Plants ofArnica latifoliaquickly moved rhizomes and roots into the tephra; 50% of underground dry weight was in the tephra by 1982. In two species with short rhizomes (Tiarella trifoliataandValeriana sitchensis) there was an altered growth form; the rhizome elongated rapidly straight up to the tephra surface. The corm ofErythronium montanumwas not relocated upward and it produced no roots in the tephra.

ISSN:0008-4026    

DOI:10.1139/b85-294

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The Alaskan taxonCarex jacobi-peteriHultén (Cyperaceae:Primocarex) is shown to be a synonym ofCarex pyrenaicaWahlenb. ssp.micropoda(C. A. Meyer) Hultén. The inclusive taxon is more variable and has a wider range than previously believed. It should not be considered threatened or endangered in Alaska.

ISSN:0008-4026    

DOI:10.1139/b85-295

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The different growth patterns of the beech tree are described from a morphological and architectural point of view in the first part of this paper. In about 10 years, individuals can achieve various forms, according to the growth pattern. About thirty architectural variations are examined in the second part of this study; they reveal a surprising diversity within the species. In seedlings, the interindividual variations confer upon small beeches distinct "social status." In a regeneration, the silviculturist distinguishes individuals as well and poorly grown. This distinction into categories can henceforth rely on an architectural basis. Light and genetics have an important influence on the architecture of young beeches.

ISSN:0008-4026    

DOI:10.1139/b85-296

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The pattern of14C assimilate distribution was studied inAralia nudicaulisL. to determine the extent of physiological integration among individual shoots in a clone. The experiments showed that most of the carbon assimilated by an individual shoot remained within that shoot after 24 h. Most of the carbon exported by a shoot was translocated basipetally into the rhizome section adjacent to the shoot. While the rhizome basipetal to a shoot was a major storage organ, the roots and new rhizomes adjacent to a shoot had the highest specific activity. Changes in the normal translocation pattern were observed when one shoot was shaded before an adjacent shoot was labelled. There was an increased amount of carbohydrate translocated from an unshaded shoot to the root and rhizome components adjacent to a shaded shoot. The changed pattern of translocation after disturbance indicated the potential for physiological integration among shoots within a clone.

ISSN:0008-4026    

DOI:10.1139/b85-297

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Arsenate treatment of plant cell cultures can effectively kill growing cells while sparing quiescent cells. This growth-lethal property provides a basis for counterselective enrichment of conditional-lethal mutants by arresting their growth (under nonpermissive conditions) prior to exposure to arsenate which will kill many of the growing wild-type cells. We have used reconstruction experiments to optimize the enrichment of an adenine-requiring auxotroph (Ad1) from mixtures of predominantly wild-type cells. Substantial enrichment (>50-fold) was achieved by reducing the phosphate concentration, lowering the titers of cells in the culture, and using feeder plates to recover colonies after treatment. Unfortunately, these improvements have not resulted in the isolation of new, stable auxotrophs from mutagenized cultures at much higher rates than by nonselective means. Possible reasons for the discrepancy between theory and practice are discussed.

ISSN:0008-4026    

DOI:10.1139/b85-298

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The development of the endosperm of castor bean seed from its initial free nuclear state through to the end of maturation is presented. An investigation of the pattern of reserve accumulation in the endosperm at the light microscopy level revealed that the accumulation of soluble and insoluble storage proteins, and of phytin, does not occur simultaneously in all cells of the developing storage organ. Rates of reserve accumulation also vary among regions of the endosperm. Storage protein and phytin accumulation are initiated in a region midway between the periphery and central lumen of the endosperm by the early cotyledon stage of seed development. Afterwards, reserve deposition occurs more intensely in the proximal and more peripheral regions than in the distal and internal regions. A wave of reserve accumulation, or protein body maturation, proceeds from the more peripheral and the proximal regions to the more internal and distal regions as development continues. The last cells to complete reserve deposition are those in regions lying close to the endosperm lumen (into which the cotyledons have expanded) and the outermost two cell layers of the endosperm.

ISSN:0008-4026    

DOI:10.1139/b85-299

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

An intact mature epidermis precluded formation of approach grafts of stems of five angiospermous species. When the epidermis was excised, unsclerified cortical tissue exhibited tissue responses resulting in wound closure, including cell dedifferentiation and redifferentiation into callus tissue. Removal of the epidermis from both partners resulted in a graft union. Cortical callus tissue proliferated and coalesced to bind the partners. None of these responses associated with grafting or wound closure occurred in either epidermal or subepidermal tissue in intact partners. Whereas cortical cells adjacent to a cut region reacted in a similar way to those underlying the cut, neighboring epidermal cells were usually unaltered. This developmental quiescence of epidermal cells is a unique characteristic, useful in studies of epidermal differentiation and determination.

ISSN:0008-4026    

DOI:10.1139/b85-300

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Seed numbers and the species composition of seed banks (germinable seeds) from a marsh adjacent to the Great Salt Lake were compared among five vegetation types prior to a drawdown, during a drawdown, and prior to fire, after fire, and after restoration of normal water levels. Substrate samples were processed in the greenhouse under submersed and moist soil treatments to simulate the two germination conditions found in the field. After the fire, seed movement into the different vegetation types was also estimated. Numbers of germinable seeds were not depleted during the drawdown, possibly owing to increased salinity and the presence of standing vegetation. Fire had little effect on seed banks and subsequent seedling response. In general, seed banks were not affected by disturbance (e.g., burning, drawdown). The movement of seeds into the different vegetation types indicated that seed ingress could be important when one considers potential vegetation change. Seed banks of open water sites contained few germinable seeds when compared withScirpus lacustris,S.maritimus,Distichlis spicata, andTyphaspp. sites. Open water sites were devoid of vegetation and had few physical barriers, and seeds continued to move (air, water) across these areas until a barrier was reached, e.g., sites with vegetation.

ISSN:0008-4026    

DOI:10.1139/b85-301

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Canonical variates analysis was used to compare the effects of fertilization on the concentrations of five mineral elements (N, P, K, Ca, and Mg) in young shoot tissues of six tundra plant species of three different growth forms. There were two specific objectives: (i) to determine whether it was possible to describe meaningful dose–response relationships in a multivariate response to fertilization, and (ii) to determine the multivariate effect of N plus P fertilization in comparison with the effects of N or P added alone. The results showed that low levels of N–P–K fertilization caused a shift in multivariate nutrient content that was intermediate between the control values and the shift caused by high fertilization, and in the same direction as the latter. In a June harvest, the effect of N plus P fertilization was very similar to the effect of N fertilization alone. However, in August the N plus P effect was dominated by the response to P alone. In all of the analyses, the fundamental similarities and differences among unfertilized plants of each species and growth form were maintained under fertilization.

ISSN:0008-4026    

DOI:10.1139/b85-302

出版商:NRC Research Press    

年代:1985

数据来源: NRC