摘要:

The flowers are tetracyclic, pentamerous, and hypogynous. The ovary of the bicarpellary syncarpous gynoecium is bilocular at the base and unilocular towards the apex or bilocular towards the base and apex and unilocular in the middle. The sepals are three traced and the origin of the sepal traces is peculiar inPittosporum heterophyllumandP. rhombifolium. The petals and stamens are one traced. The heteromerous flowers ofP. revolutumstand apart in perianth and androecial characters. The carpels are three traced except inP. phyllarioides, where they are five traced. There is adnation of traces between petals, stamens, and gynoecium and this precedes the external fusion. Judging from the position of the ventral bundles, the placentations can be described as parietal, anatomically parietal, or both in different parts of the ovary. A true nectariferous disc is lacking. The basal peripheral portion of the ovary resembles the disc, showing deep-staining cells, and it is devoid of any vasculature.

ISSN:0008-4026    

DOI:10.1139/b82-232

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Mirabilis hirsuta, a fugitive prairie plant species, occurs only on disturbances (mounds) resulting from the foraging activity of badgers on the Cayler Prairie Preserve in northwestern Iowa, U.S.A. Seedling survivorship and later competitive success are predicated upon the root's rapid extension to and occupation of a moisture-retentive layer of buried vegetation which forms the base of these disturbances. Seed size, which varies from <2 to >6 mg, is a predictor of the likelihood of establishment success through effects upon germination and seedling vigor. Regressions indicated that germination increased by 10.2% per milligram increase in seed weight, leaf area of 30-day-old seedlings increased by 47.8 mm2/mg seed weight, and dry weight biomass of these seedlings increased 40.2 mg/mg seed weight. Germination also occurred more rapidly with heavier seeds. Differences in seedling growth with increases in seed size are largely due to the capital provided by initial food reserves. The instantaneous rate of increase in seedling biomass is nearly identical for seeds of all different weights. Absolute growth rates of seedlings are thus proportional to seed size, at least through the establishment phase. These results are of demographic importance because droughts frequently begin in early summer on this prairie.

ISSN:0008-4026    

DOI:10.1139/b82-233

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

A new genus,Stilbotulasnella, with the single speciesStilbotulasnella conidiophora, is described from material collected in Hawaii. The distinguishing features of the genus are (i) copious production of blastic conidia; (ii) scattered tulasnellaceous basidia; (iii) germination of conidia and basidiospores by budding; (iv) dolipore septa without parenthesomes. Conidia ofS. conidiophoraare blastic annelidic, dikaryotic; they are produced on mononematous conidiophores or conspicuous synnematous to sporodochial conidiomata. The basidiospores germinate by repetition, by germ tube, or by budding.

ISSN:0008-4026    

DOI:10.1139/b82-234

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The flower ofAmelanchier alnifoliaNutt. (Maloideae) exhibits a polyandric androecium and a syncarpous, pentalocular, inferior ovary. Each of the five locules contains two ovules. The vascular system of the floral tube is composed of 10 major bundles in addition to numerous, secondary branches. Carpel vasculature consists of one dorsal and two ventral bundles with secondary traces in addition to an ovular trace from each ventral bundle. Although there is no core line, the approximate boundary between what has been interpreted as floral tube and carpel may be discerned. Numerous mitoses, substantial increases in cell diameters, and intercellular space formation contribute to the ultimate size and shape of the mature fruit. Fruits are mature approximately 38 days after petal drop. The mature fruit does not exhibit an extensive sclerenchymatous endocarp and, therefore, it differs from the more typical pomaceous fruits.

ISSN:0008-4026    

DOI:10.1139/b82-235

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

For pollen types whose morphological characters overlap markedly, it is often helpful to be able to estimate the proportions of each type present in a sample of pollen grains. Several numerical methods of estimation have been proposed in recent years. This paper criticizes some procedures that are based on the identification of each pollen grain, rather than the direct estimation of proportions. A class of maximum likelihood models is described and illustrated by the analysis of eight samples ofPiceapollen from late Quaternary profiles in eastern North America. The maximum likelihood approach provides an indication of the precision of the estimates, a point considered to be important.

ISSN:0008-4026    

DOI:10.1139/b82-236

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Chromosome numbers of putative wildAster lanceolatus×lateriflorushybrids were found to be either 2n = 40 or 2n = 48. A comparison of the morphology and chromosome numbers of the putative hybrids, their likely parental species, andA. ontarionisfrom Ontario revealed that the hybrids were morphologically and cytologically intermediate betweenA. lanceolatusandA. lateriflorus. The 2n = 40 hybrids were similar toA. ontarionis(2n = 32) but lacked the characteristic leaf pubescence of that species. At one site on the Bruce Peninsula 14A. lanceolatusplants (2n = 64), 13A. lateriflorusplants (2n = 32), and one hybrid (2n = 48) were collected and compared in detail. The hybrid was more likeA. lanceolatusthan the 2n = 40 hybrids from other sites where theA. lanceolatusparents were 2n = 48. The similarities between the putative hybrids andA. ontarionissuggest that this species arose via a hybridization event betweenA. lanceolatusandA. lateriflorus. Alternative origins are nonetheless possible and these along with the nomenclature ofA. lanceolatusare reviewed.

ISSN:0008-4026    

DOI:10.1139/b82-237

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Mung beans (Vigna radiata) were grown in the field, and measurement of leghaemoglobin and nitrogenase activity of root nodules during plant growth showed a maximum 30 days after sowing, i.e., just when flowering began. Mung beans were also grown in hydroponic cultures with varying amounts of nitrate nitrogen and harvested at 30 day s. The extent of root nodulation, leghaemoglobin accumulation and nitrogenase activity in the nodules, and plant dry weights were found to be maximal at a low concentration (0.5 mM) of nitrate. Dry weights of shoots and roots (exclusive of nodules) and total chlorophyll content of leaves were also increased more by this low concentration than at higher concentrations of 1–3.5 mM. Nodule formation, including leghaemoglobin content and nitrogenase activity, declined with increased nitrate levels. At the highest nitrate levels studied (4.5 and 5 mM) no nodules were formed, but the shoot and root dry matter increased markedly. It is evident from the results that a minimal amount of nitrate nitrogen is essential for efficient symbiotic nitrogen fixation.

ISSN:0008-4026    

DOI:10.1139/b82-238

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

A modelling technique for penetration of solar radiation into clumped vegetation canopies is described. It combines Monte-Carlo simulation to determine ray pathlengths through individual plant canopy envelopes with exponential attenuation along these rays. The technique is applied to a hillside forest of randomly located and sized jack pine trees. Scattering effects are incorporated and the model output is compared with field measurements. The results depend on the shape of the tree outline. Attenuation is less rapid with downward cumulative leaf area index than in a randomly dispersed canopy.

ISSN:0008-4026    

DOI:10.1139/b82-239

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Equations were developed for estimating total aboveground phytomass from structural dimensions of individual stems involving 17 tree and shrub species in the understory of second-growth Appalachian oak forest stands in southwest Virginia. All possible combinations of three functional forms of the equation (linear, allometric, and exponential) and three independent variables (basal area, stem height, and crown area), singly and in combination, were tested. The linear model, with stem basal area as the independent variable, provided the best fit to the data for 15 of the 17 species. The exceptions were the blueberries (Vaccinium stamineumandV. vacillans) where crown area performed better than basal area as the independent variable. With respect toVaccinium vacillans, in particular, only 35% of the variation in aboveground phytomass could be accounted for using all three independent (structural) variables, which suggests a pattern of growth substantially different from the other species studied. Stratified sampling of stems involving broad height classes appeared to favor the application of linear models over nonlinear models.

ISSN:0008-4026    

DOI:10.1139/b82-240

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Populations ofRumex crispuswere sampled from eastern North America and Europe. The relative amounts of genetic variation and plasticity were examined, using 58 plant characters. About 61% of the total variation occurring in the experimental plants was accounted for by plasticity. The remaining 26% and 13% occurred within populations and among widespread populations, respectively. At the local level, there was little difference between variation occurring within genotypes and that within families (between maternal siblings). This suggests that the species is predominantly inbreeding. The majority of genetic variation occurs within populations at both the local and species' range levels.It was concluded that the species has large amounts of both flexibility and genetic heterogeneity. This adaptive strategy enables the species to survive under a very wide range of environmental situations and largely accounts for its becoming one of the most widely distributed plants in the world.

ISSN:0008-4026    

DOI:10.1139/b82-241

出版商:NRC Research Press    

年代:1982

数据来源: NRC