摘要:

We investigated the changes in amounts and patterns of phenotypic plasticity which have arisen in the Texas annualPhlox drummondiiduring domestication. Character means and plasticities were compared for five populations: a wild population, three cultivated varieties (a Tall cultivar and two Dwarf cultivars), and a population of an escaped Tall cultivar naturalized in Texas. To measure plasticity, we scored the responses of 10 characters to six treatments and analyzed both the amount and direction of plastic response. Wild plants are phenotypically distinct from the Tall and Escaped cultivar and from the two Dwarf cultivars. Despite its substantial phenotypic divergence from the Wild population, the Tall cultivar's plasticity has changed little during domestication. Traits most strongly correlated with fitness show the least change in their plasticities. The two Dwarf varieties have very similar plasticities, despite strong phenotypic divergence from the Tall population and despite the fact that they were derived from different Tall lines. This suggests that indirect selection on phenotypic plasticity related to selection for the Dwarf habit has resulted in the characteristic plasticity of the Dwarf lines. The Escaped cultivar has substantially different plastic responses from those of the Wild or cultivated populations.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13428.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

A chemical survey of pollen lipids was carried out to examine the composition of pollenkitt in relation to that of whole pollen and to evaluate the possible role of pollenkitt as the principal carrier of chemical cues used by flower visitors. Investigated pollen was collected from 69 angiosperm species (28 families) in California. Lipid extracts of pollenkitt and of the internal portion of pollen were analyzed for each species using thin‐layer chromatography. Neutral lipids (energy storage and essential oil constituents) were most diverse in pollenkitt, while polar lipids (mostly membrane constituents) were found almost exclusively in the internal pollen fraction. Patterns in neutral lipid compositions suggest that pollenkitt may provide pollen with species‐specific odors. Yellow pigments were observed in pollen of most species, with carotenoids predominating in pollenkitt and flavonoids in the internal fraction. Phenolic and heterocyclic nitrogen compounds were found in the lipid extracts of several species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13429.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Investigations of the growth of anthers and ontogeny of pollen grains ofOryza sativa(rice) IR‐30 were undertaken for the purpose of 1) providing a set of growth measurements and 2) describing stable cytological features of anther and pollen development. Correlations exist between elongation of the floret and growth parameters of the anther such as its length, width, fresh and dry weights and cytological stage of pollen development. In the early ontogeny of the anther, hypodermal archesporial initials divide periclinally to form primary parietal cells and primary sporogenous cells. Each of the latter divides twice mitotically to generate four microspore mother cells, which undergo meiosis. The anther wall is formed by anticlinal and periclinal divisions of the primary parietal cells as well as of cells surrounding the primary sporogenous cells. Subsequent cytological features in the development of anther and pollen grains of rice have much in common with anther and pollen developmental biology of other members of Gramineae.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13430.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTCaespitose and cold‐tolerant plants ofParthenium ligulatum(Jones) Barneby (Asteraceae) from a native population in the Uinta Basin, Utah, were uprooted, potted, and transferred to a greenhouse in California. Approximately two years after transfer, the plants flowered and subsequently were crossed to diploid guayule (Parthenium argentatumGray), the rubber‐bearing species, native to the state of Durango, Mexico. Only female guayule × maleP. ligulatumcrosses produced F1hybrids. Only crosses involving guayule as female parent and F1plants as male parents produced backcross (BC,) plants. Hybrid plants were variable with respect to their growth habit, inflorescence, and leaf shape. Both parents and F1hybrids had 2n= 36 chromosomes. Unlike the parents, however, meiosis was irregular in the hybrids which showed a range of 0–5 and an average of 2.1 univalents at metaphase I. Hybrids averaged 0.87 laggards at anaphase I and 0.83 micronuclei at the tetrad stage. The crossability of guayule andP. ligulatum, the high degree of chromosome pairing of the F1hybrids, and the production of BC1plants indicate that the two species are related in spite of their distinct morphological and ecological differences. This study suggests that the cold‐tolerance trait ofP. ligulatummay be transferred to guayule through interspecific hybridization followed by backcrossing. The development of cold‐tolerant guayule cultivars is expected to expand the areas of guayule production beyond that of the Chihuahuan desert and similar climates.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13431.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

The characteristic of heteromorphic inflorescences in some mimosoid legumes such asNeptuniais a puzzling one which can be approached developmentally. Each spicate inflorescence ofNeptunia pubescensincludes three types of flowers: perfect in the upper half, functionally male just below the middle, and sterile or neuter at the base. Developmental studies of the inflorescence show that order of initiation of bracts on the inflorescence is acropetal, but that order of subsequent development of flowers is both acropetal and basipetal on the axis. Bract growth and initiation of the axillary floral apices at the base are inhibited or retarded, while those in the middle and upper levels continue development without interruption. The three types of floral primordia are similar during initiatory stages of organ formation and through early development. At mid‐development, differences arise in floral symmetry, petal form, stamen form, and size and shape of the carpel. The functionally male flowers become strongly dorsiventral and zygomorphic while the other two morphs remain actinomorphic or nearly so. Heteromorphy arises from a combination of early suppression of organogeny plus mid‐stage innovations of zygomorphy and lateral expansion of stamen primordia. These divergent developmental pathways in one inflorescence can be interpreted in part using Gould's concept of heterochrony: changes in timing of developmental events to produce different structures. Other changes inNeptuniacannot be explained by this concept, however; such changes as omission of processes (i.e., meiosis) in some organs, or addition of processes not normally present (i.e., blade formation in stamen primordia which become staminodia). It is becoming evident from work on this and other legume flowers that actual loss of organs is rare, compared to initiation followed by suppression or modification.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13432.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Ten conifer species were grown in an unshaded greenhouse at the University of Maryland under 3 levels of biologically effective ultraviolet‐B radiation. Ultraviolet‐B radiation was supplied by Westinghouse FS‐40 sunlamps and effective daily doses were 0, 12.4, and 19.1 kJ m–2. During the irradiation period, seedling growth and the development of stress symptoms were monitored. After 22 weeks of irradiation, seedlings were harvested and morphological characteristics analyzed. Visual symptoms included needle discoloration and stunting in three of the ten species tested. Seedling height was significantly reduced by supplemental UV‐B inPinus contorta(lodgepole pine),Pinus resinosa(red pine), andPinus taeda(loblolly pine). Biomass increased inPicea engelmannii(Engelmann spruce).Abies fraseri(Fraser fir),Pinus edulus(pinyon pine), andPinus nigra(black pine) were unaffected by UV‐B while biomass reductions exceeding 5% were observed in all other species tested. These deleterious effects occurred despite the presence of morphological characteristics which would tend to reduce UV‐B effectiveness. Generally, the effects of supplemental UV‐B dose were less for those species native to higher elevations, implying the presence of natural adaptations to UV‐B.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13433.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Because homosporous pteridophytes (Psilotophyta, Arthrophyta, most Microphyllophyta and Pteridophyta) produce bisexual gametophytes, it was maintained that high levels of inbreeding would characterize these plants. Electrophoretic evidence was used to estimate the frequency of intragametophytic selfing inEquisetum arvense(Arthrophyta). A total of 669 samples from 17 populations was examined from western North America. Although some populations exhibited as many as seven or eight genotypes, 10 populations were each characterized by only a single genotype; eight of these populations were heterozygous for one or more loci. For most populations, estimates of intragametophytic self‐fertilization are 0.000, indicating that virtually all matings involve different gametophytes. Genetic data corroborate predictions based on earlier field and laboratory investigations ofEquisetumgametophytes. These detailed studies demonstrated that in many species, includingE. arvense, gametophytes are initially either male or female; only later and in the absence of fertilization do some gametophytes become bisexual. Our findings join a growing electrophoretic data base which demonstrates that homosporous pteridophytes are not highly inbreeding as previously suggested.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13434.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

It has been established that the number of isozymes (different forms of an enzyme encoded by different gene loci) is highly conserved in diploid angiosperms and gymnosperms. In contrast, allopolyploid angiosperms display an increase in isozyme number due to the addition of divergent genomes. Lycopods (Microphyllophyta) are an ancient lineage of vascular plants having very high chromosome numbers. It has been maintained that lycopods acquired these high chromosome numbers through repeated episodes of polyploidy. Despite high chromosome numbers, however, lycopod species having the lowest chromosome numbers within genera possess the number of isozymes typical of diploid seed plants for all enzymes examined except triosephosphate isomerase. There is, therefore, no genetic evidence from enzyme electrophoresis for polyploidy in these plants. These results are comparable to findings for other homosporous pteridophytes including the ferns (Pteridophyta) and horsetails (Arthrophyta). Alternative hypotheses for widespread genetic diploidy in homosporous pteridophytes are 1) repeated cycles of allopolyploidy followed by gene silencing; 2) repeated cycles of autopolyploidy, which would result in duplicated, but not divergent genes for isozymes; 3) initiation of these lineages with relatively high chromosome numbers.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13435.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Homosporous pteridophytes are characterized by the production of free‐living, potentially bisexual gametophytes. Because of the close proximity of archegonia and antheridia on the same thallus, it has been assumed that high rates of intragametophytic self‐fertilization would predominate in natural populations of homosporous pteridophytes. Using enzyme electrophoresis we determined sporophytic genotype frequencies for natural populations of three lycopod species,Lycopodium clavatum, L. annotinum, andHuperzia miyoshiana.Based on these genotype frequencies and the estimation procedures of Holsinger (1987), the estimated rates of intragametophytic selfing in these species are extremely low. Estimated selfing rates were greater than 0.000 in only two of 13 populations ofL. clavatum, one of six populations ofL. annotinum, and one of four populations ofH. miyoshiana.Despite the potential for intragametophytic self‐fertilization, the gametophytes of these three lycopod species predominantly cross‐fertilize, although the mechanism(s) promoting intergametophytic matings are unknown. These results are similar to those obtained for homosporous ferns andEquisetum arvense.It is therefore clear that most homosporous pteridophyte species investigated do not exhibit high rates of intragametophytic self‐fertilization; in contrast, intergametophytic matings predominate.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13436.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

The effects of inoculation with vesicular‐arbuscular mycorrhizal fungi on nonmycotrophic (plants which do not form a mycorrhizal association) colonizing annuals and on mycotrophic perennials were investigated in southwestern Wyoming. A subsoil containing no initial mycorrhizal inoculum was used, and seeds of the later successional perennials were planted. The annuals were removed from one‐half of the sampling quadrats to test for the interaction of competition and mycorrhizae on the perennials. During the third and fourth years of succession, the density and percent cover ofSalsola kali, the most abundant nonmycotrophic annual, decreased by one‐half to one‐third with inoculation. Mycorrhizal hyphae and spores were found in the rhizosphere ofS. kali, with only occasional (1–2% of the root length) penetration of hyphae into the cortex. There were no differences in tissue phosphorus and nitrogen concentrations or water relations of inoculated vs. uninoculatedS. kali.The planted grasses, allAgropyronspecies, had no significant increase in density or percent cover with inoculation. The percent root infection ofA. smithiiwas 5–30%. Grass density and percent cover was greatest whereS. kaliwas present, suggesting facilitation of grass establishment by annuals on this harsh, windy site. However, grass density was lower where 5.kalidensity was lower following inoculation. Mycorrhizal fungi were hypothesized to hasten the rate of succession on other sites. On this site where facilitation is an important process, inoculation of early seral plants and their subsequent decline may slow primary succession in the early years.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13437.x

出版商:Wiley    

年代:1988

数据来源: WILEY