摘要:

Movement and distribution of [14C]sucrose was studied in snapdragon flowers cultured on sucrose solutions in relation to the timing and extent of the characteristic reduction of nectar yield by 1AA, the question of whether IAA acts in the nectary cells or by reducing sugar movement to the nectary, and competition for sugar between nectaries and other tissues.There was a 50% reduction in accumulated nectar yield in flowers treated with IAA within 18 h; thereafter, the capacity to secrete nectar was virtually abolished. Within 6 h, IAA caused a significant increase in the incorporation of14C into protein. Most of the14C activity lost to nectar in flowers treated with IAA was recovered in the ethanol-soluble materials and protein of the flowers. Radioactivity continued to accumulate in the secretory tissue after secretion had stopped. The percentage reduction in nectar by IAA was not diminished under conditions of minimal growth and sugar transport distance. It was concluded that IAA acts on the secretory process in the nectary cells rather than on movement of sugar to the nectary.The influence of differences in sugar supply appeared mainly in the distribution of14C activity between peduncles and nectar: as sugar supply was increased, a smaller percentage remained in the peduncles and a larger percentage was secreted. The secretory process competed strongly with floral tissues for sugar even when the latter were undersupplied.

ISSN:0008-4026    

DOI:10.1139/b78-065

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Observations on a population ofHieracium piloselloidesVill. in an old-field habitat revealed two distinct microsites on which seeds might land, bare soil and moss-covered areas. Regular monitoring of newly emerged seedlings on both microsites revealed that the seeds could germinate as soon as they are shed and that emergence of the seedlings coincided with rainfall, forming distinct emergence flushes. The number of emergences and losses recorded on the bare soil sites always exceeded those which occurred on the moss-covered microsites. The greatest losses of seedlings from the population occurred in periods of low rainfall. The mortality in six seedling cohorts was also followed on these plots. Similar patterns of survival were shared by most of the bare soil cohorts and by all cohorts of moss-covered soil, but the decline in the bare soil cohorts was always more rapid. The number of seeds available in the natural seed rain is estimated to be 40 190 seeds/m2. To this, a total of 120 000 seeds/m2were added artificially in marked plots, and from the recorded emergences, the establishment success of seedlings was estimated at less than 1%. It is suggested that in terms of monthly microclimatic variation, both types of microsite may be of value in contributing to the apparent stability of the population.

ISSN:0008-4026    

DOI:10.1139/b78-066

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The taxonomy ofSuaedaspp. occurring in Canada has been studied. It is concluded that four species are present:Suaeda moquinii(Torrey) Greene,S. calceoliformis(Hook.) Moq.,S. maritimaL., andS. rolandiiI. J. Bassett & C. W. Crompton sp.nov.Suaeda moquinii(2n = 18) is only known from the badlands of Saskatchewan and Alberta;S. calceoliformis(2n = 54) is widespread across Canada;S. maritima(2n = 36) is mostly present along the Atlantic coastline;S. rolandii(2n = 90) is found only in Quebec, New Brunswick, and Nova Scotia.Suaeda maritimaspp.richiicomb. nov. is rare in eastern Canada. Several names applied to these taxa are discussed.

ISSN:0008-4026    

DOI:10.1139/b78-067

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Cell enlargement and tissue differentiation have been examined using the leaf plastochron index (LPI) as a measure of developmental stage inCatharanthus roseus(L.) G. Don. Observations were made from plastic-embedded, 2-μm serial sections and measurements were made using a microprojector. At the earliest stages examined, six cell layers are present; periclinal divisions in the third abaxial layer give rise to seven cell layers at maturity. The initial six layers are similar in size, shape, and staining characteristics but palisade cells are slightly elongated. Relative rates of change in leaf length are high during early stages before LPI 1.0 whereas relative rates of change in leaf thickness increase after LPI 1.0 largely because of continuing high rates of change in palisade cell height. The predominant plane of enlargement in palisade mesophyll is perpendicular to the predominant plane of enlargement in spongy mesophyll. Relative rates of change in cell height in upper epidermis are higher than in lower epidermis throughout most of the period of development and absolute rates of change in cell size in upper epidermis are always higher than in lower epidermis. Formation of intercellular space in mesophyll seems well correlated with rates of change in cell width in developing dermal layers. These observations show how the rate, duration, and direction of cell expansion in each tissue type results in the histology of the mature leaf.

ISSN:0008-4026    

DOI:10.1139/b78-068

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The morphology and awn anatomy of the large-glumed species ofStipaoccurring in Canada were examined. Numerical analysis of the data indicates thatS. sparteavar.sparteaandS. sparteavar.curtisetaare very distinct taxa differing not only in many of their quantitative characters but also in nodal pubescence, ligule shape, and pubescence of the leaf margin. It is proposed that they be treated as separate species,S. sparteaandS. curtiseta. Some evidence was found for differentiation withinS. sparteas.s. but it was deemed insufficient for the recognition of infraspecific taxa.Stipa comatavar.comataandS. comatavar.intermediaare very similar in all morphological characters examined. Cross sections of their distal awn segments do, however, show consistent distinguishing characters; those of var.intermediaare more heavily lignified and tend to be square in outline compared with those of var.comata. Although similar to each other, cross sections of the varieties ofS. comataare distinct from those ofS. sparteaandS. curtiseta. The possibility that certain specimens were hybrids betweenS. comatavar.comataandS. curtisetawas explored and rejected. Distribution maps and a key to the accepted taxa are given.

ISSN:0008-4026    

DOI:10.1139/b78-069

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

In black walnut sapwood, ethylene production,in vitro, near the heartwood boundary peaks early in the dormant period and is low while the cambium is active. In black cherry, ethylene production in the heartwood–sapwood transition zone peaks during the middle to the late growing season and is greater than in the middle and the outer sapwood during early dormancy. In walnut,in vitroperoxidase (EC 1.11.1.7) activity near the heartwood boundary peaks during the late growing season to the early dormant period and is greater than in the adjacent sapwood regions. In both species, ethylene production correlates with peroxidase activity.In vivotyrosinase (EC 1.10.3.1) and peroxidase activities are relatively high near the heartwood boundary during dormancy. Laccase (EC 1.10.3.2) is absent from the heartwood boundary region. Total nitrogen levels reach a minimum during the dormant period. General phenological biochemical trends suggest that in both species dormancy is a time of major heartwood formation. Heartwood formation in walnut apparently is minimal when cambial activity is greatest. Walnut phenotypes that differ in heartwood-formation class, a measure related to sapwood–heartwood ratio, also differ in sapwood peroxidase activity. In cherry sapwood, ethylene production and total nitrogen are related to heartwood formation class.

ISSN:0008-4026    

DOI:10.1139/b78-070

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The Scholander–Hammel pressure bomb has been used to measure ontogenetic and seasonal changes in π0(the osmotic pressure of the symplasm at zero water potential), πp(the osmotic pressure of the symplasm at ‘incipient plasmolysis’), ϵmax(the bulk elastic modulus near maximum turgor), and a number of other water relations parameters in single leaves ofAcer saccharumand several species ofPopulusand in shoots ofTsuga canadensisandPicea abies. In newly emerged leaves ofAcer, Populus, andPicea, π0, πp, and ϵmaxare all small but rise rapidly with leaf development. These parameters stabilize at a maximum value or slowly increase with progress in season. InAcer, ϵmaxdeclines shortly before senescence. In developing leaves, the water content reaches a maximum before the soluble solutes; this accounts for the low values of π0and πp.InTsugaπ0cycles through an annual maximum in winter and a minimum in summer. These changes may correlate with frost hardiness.

ISSN:0008-4026    

DOI:10.1139/b78-071

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Light microscopical observations of living germ tubes and infection structures of cowpea rust were combined with an ultrastructural study to show that a nucleolus was present in the interphase nucleus at all stages of development from uredospore germination through to new uredospore formation. Vacuolate nucleoli were common in germ tubes but only nonvacuolate nucleoli were observed at other stages of fungal development. When grown on oil-containing collodion membranes, germinating uredospores, germ tubes, appressoria, and infection hyphae without haustorial mother cells all contained nucleoli composed primarily of nongranular material. Predominantly granular nucleoli were observed in developing uredospores and all parasitic stages in the leaf after the formation of the first haustorial mother cell. However, the fact that granular nucleoli were also seen in a membrane-grown infection hypha after haustorial mother cell formation suggested that the host was not required to stimulate the resumption of nucleolar activity. Electron-opaque patches, presumed to be condensed chromatin, were most prominent in the nucleoplasm of haustorial mother cells and virtually absent in germinating uredospores and germ tubes. The significance of this observation is discussed. A reduction in nuclear volume was observed in living material prior to cytokinesis in the appressorium and the substomatal vesicle. Evidence suggested that this reduction was produced by the expulsion of part of the nucleoplasm, plus the nucleolus,duringmitosis rather than before as suggested for other rusts. Nuclei of haustorial mother cells and haustoria were also smaller than those in intercellular hyphae but the mechanism by which this was achieved could not be determined.

ISSN:0008-4026    

DOI:10.1139/b78-072

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Changes in dry weight and N, P, K, Na, Ca, Mg, Al, and Fe content were studied over a 525-day period in decomposingTypha glaucaandScirpus fluviatilisshoots. SubmergedTyphalitter decomposed more rapidly than submergedScirpuslitter, losing 50% of its original dry weight in 325 days whileScirpuslitter still retained 62% of its original dry weight after 525 days. Major pathways of mineral flow from standing litter were (1) leaching during the first few weeks after shoot death and (2) fragmentation and litter fall during the rest of the study. Mineral losses from fallen litter were mainly due to leaching or to excretion by microbial populations associated with the litter. Microbial uptake (N, P) and adsorption (Ca, Al, Fe) were important processes in the fallen litter. After 525 days, as a result of the combined action of mineral uptake and release,Typhalitter had net releases of N (71 kg/ha), P(10 kg/ha), K (123 kg/ha), Na (94 kg/ha), Ca (41 kg/ha), and Mg (25 kg/ha) and net accumulations of Al (21 kg/ha) and Fe (20 kg/ha).Scirpuslitter, during this same period, had net releases of N (10 kg/ha), K (9 kg/ha), and Na (11 kg/ha). All other minerals increased in decomposingScirpuslitter: P (8 kg/ha), Ca (55 kg/ha), Mg (5 kg/ha), Al (13 kg/ha), and Fe (11 kg/ha). At the end of the study, the calculated combined dry weight of undecomposed standing and fallen litter had decreased by only 20% inTyphalitter and 14% inScirpuslitter. Most of the biomass and minerals were in the fallen litter.

ISSN:0008-4026    

DOI:10.1139/b78-073

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A freshwater isolate ofStichococcus bacillarisNaeg. (strain UTEX 314) was evaluated for its ability to grow, photosynthesize, and osmoregulate over a wide range of salinity. The growth and photosynthetic measurements indicate that it is a euryhaline organism. Studies of the soluble organic metabolite pools showed that the steady-state levels of two solutes varied with salinity; sorbitol (a polyol) and proline (an amino acid). Intracellular proline levels increased from 0.002 to 0.28 Mover the salinity range of 0 to40%c whereas the sorbitol level increased from 0.10 to 0.52 M. The level of total amino acids (excepting proline) remained relatively constant. No single amino acid of this group exceeded an intracellular concentration of 0.04 M. The changes in the concentrations of these solutes accounted for at least 75% of the required increase in intracellular osmolality in cells following adaptation to high salinity media. Sorbitol and proline are very soluble, nontoxic, and are efficient osmotic solutes. These properties make them ideal solutes for osmoregulation.

ISSN:0008-4026    

DOI:10.1139/b78-074

出版商:NRC Research Press    

年代:1978

数据来源: NRC