摘要:

Botanists have long been aware of the floristic similarities between eastern Asia and eastern North America. Most who have considered this classic disjunction pattern have suggested that it arose through range disruption of a flora that was once more widely distributed in the Northern Hemisphere. There is less agreement on the timing of this process, with suggestions ranging from the Paleocene to the Neogene. In this study, molecular markers from two different plant genomes were used to assess the degree of genetic divergence between the two interfertile, morphologically similar species of the genusLiriodendron, i.e.,L. tulipiferaandL. chinense.Resulting molecular divergence estimates were translated into approximate dates of separation, independent of evidence from the fossil record. Allozyme data (Nei's genetic identity = 0.434) suggested a divergence time of 10–16 million years before present, whereas sequence divergence in the plastid genomes (1.24%) led to an estimate of approximately 11–14 million years before present. A review of the paleobotanical literature indicated that the fossil floras that included, or might have includedLiriodendroncould not have survived in Beringia after the late Miocene and the onset of southward‐migrating Arctic air masses on the North American continent. This interpretation suggests a minimum time of separation of approximately 13 million years before present. Thus, both molecular data sets and the paleobotanical evidence concur in suggesting a divergence time of 10–16 million years before present. Interspecific compatibility and relative morphological stasis must have, therefore, persisted from at least the late Miocene. We emphasize the need for similar studies in other genera, especially those that have both a reasonable Tertiary fossil history and extant species in mesic temperate refugia in Asia, Europe, and western as well as eastern North America.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb11376.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

The stage of pollen development at the time of anther culture is an important factor in the production of haploids. The objectives of the current study were to develop a staining procedure for peanut (Arachis hypogaeaL., ssp.hypogaea)microspores, to describe and document the stages of microsporogenesis in peanut, and to confirm a previous report concerning correlations of peanut floral bud shape with stage of microspore development. A staining procedure using propionic carmine provided adequate staining of pollen mother cells, microspores, and pollen. Pollen mother cells and microspores could easily be differentiated by their size and cell wall structure. Plants grown in a controlled environment were found to have highly synchronized microspore development, both within an anther and among anthers contained in the same bud. In addition, floral bud shape was confirmed as a reliable indicator of anther stage in peanuts.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb11377.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

The reproductive biology of a tropical palm swamp community, called morichal in the Venezuelan Central Llanos, was studied. Of the 128 woody and herbaceous species of plants recorded, 99 (77.34%) were hermaphrodites, 25 (19.53%) were monoecious, and four (3.13%) were dioecious. The morichal is characterized by a low number of species with obligate cross‐fertilization. The frequencies of species with different breeding systems in a subsample of 26 species showed that eight (30.77%) were self‐incompatible, 14 (53.85%) were self‐compatible, and four (15.38%) were agamospermous. Ten of 14 self‐compatible species were autogamous. Regardless of the self‐incompatibility level estimated, seed and fruit set were greater in self‐fertilized flowers than in hand‐pollinated flowers in three of the nine self‐incompatible species. These results are related to the facts that: 1) the relative isolation of the plant population limits the gene flow among similar communities and enforces the intrapopulation pollen flow; 2) the overlapping flowering patterns and infrequent and unspecialized pollinators may be enforcing self‐compatibility and agamospermy; 3) self‐compatibility is the rule among short‐lived species in the morichal; and 4) three out of four agamospermous species are of the Melastomataceae family.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb11378.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

Arborescent stem succulents in tropical and subtropical deserts depend on scarce and uncertain rainfall. Gas exchange and the diurnal acidity fluctuation of bark and ephemeral leaves were measured under both dry and moist soil conditions inFouquieria columnaris(cirio or boojum tree) andPachycormus discolor(torote bianco or elephant tree) and in stems of the columnar cactusPachycereus pringlei(cardon) in the Central Desert of Baja California, Mexico. Results demonstrated that ephemeral leaves were the only site of exogenous CO2 assimilation inF. columnarisandP. discolor; there was no measurable gas exchange across the green photosynthetic bark. The pattern of gas exchange inF. columnarisandP. discolorwas consistent with that of C3 plants.P. pringleiwas shown to be a typical Crassulacean acid metabolism plant on the basis of acid fluctuations and gas exchange. Chlorophyll fluorescence studies of the green bark ofF. columnarisandP. discolorindicated that this tissue is photosynthetically functional, and that CO2 assimilation can rise above the compensation point under high CO2 concentrations, such as may occur within the plant. The green photosynthetic bark of these species may be an adaptation for surviving prolonged drought and may function to recycle endogenous respiratory CO2, thus maintaining the plant's energy reserves and permitting rapid production of leaves in response to infrequent rains.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb11379.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

Rotational‐fit methods were used to examine shape variation in oak leaf morphology by reference to a set of 14 landmarks for each leaf. Within‐tree, between‐tree, and between‐species variations were examined. Generalized least‐squares and generalized resistant‐fit analyses revealed patterns of landmark variation that could be related to leaf architecture. The two species (Quercus palustrisandQ. velutina) did not illustrate the same patterns of within‐tree variability nor did they reveal similar degrees of between‐tree variability. Incorporating an affine transformation algorithm resulted in little insight in some comparisons but suggested strong uniform shape change in other comparisons (especially between species). Resistant‐fit mean square statistics were equally variable 1) in upper vs. lower crown samples within trees, 2) between trees within each species, and 3) between species. In addition, resistant‐fit mean square statistics were found to be a poor measure of similarity, whether derived by comparison to a single reference object or by way of pairwise comparisons. Fundamental species differences in leaf shape are suggested by relationships among particular sets of landmarks, although overall shape differences cannot be explained fully by these analyses.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb11380.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

The pollen brush commonly is referred to as a “bearded” or “pubescent” style in taxonomic literature and traditionally is taken to be an aggregation of trichomes on the distal end of the style, and occasionally including the stigma. We present data that support the taxonomic utility of the pollen brush but define it more specifically as a dense aggregation of erect trichomes emanating from the style (not stigma or ovary) and functioning in secondary pollen presentation. We recommend avoiding such vague terminology as bearded or pubescent styles as these refer not only to the pollen brush but also to ciliate and penicillate stigmas and ciliate styles. The latter three conditions have some taxonomic use, and since their occurrence is not necessarily correlated with the presence of a pollen brush, they should be distinguished from it. We estimate that the pollen brush has arisen independently in the following eight taxa: 1)CrotalariaandBolusia(Crotalaraieae), 2) subtribe Coluteinae (Galegeae), 3)TephrosiasubgenusBarbistyla(Millettieae), 4)Adenodolichos(Phaseoleae subtribe Cajaninae), 5)Clitoria(Phaseoleae subtribe Clitoriinae), 6) the subtribe Phaseolinae (Phaseoleae), 7) theRobiniagroup (Robinieae), and 8) the tribe Vicieae. Its hypothesized homology within each of these groups is supported by a cooccurrence with other taxonomic characters, both morphological and molecular.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb11381.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

The perennial herbaceous species,Antennaria rosea, is a large, morphologically diverse, polyploid agamic complex that is widespread in the cordillera of western North America. The species consists of triploid and tetraploid, nonpseudogamous, gametophytic apomicts. Populationsof A. roseaare gynoecious, consisting almost entirely of pistillate clones. Clonal diversity among 63 populations ofA. roseawas studied over a large portion of its range. Isozyme electrophoresis utilizing four polymorphic enzyme systems detected 192 multilocus genotypes among the populations. Populations ofA. roseatend to be composed of one or a few genotypes (range 1–11; mean 3.5), and these genotypes usually occur in only one or a few localized populations. Geographic patterns of clonal diversity may be a result of frequent genesis of new clones in populations that occur in areas where sexual relatives ofA. roseadonate compatible pollen to facultatively sexual apomicts. Populations from previously glaciated regions tend to have fewer clones per population than those from unglaciated portions of the range.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb11382.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

We examined the effect of ovule position within the ovary on the probability of seed maturation, on seed weight, and on progeny performance in the outbreeding legumePhaseolus coccineus.Ovaries ofP. coccineuspossess six linearly arranged ovules (ovule position one = stylar end). We found that in both 1987 and 1988, ovule position had a significant effect on the probability of seed maturation under field conditions. In 1987, ovule positions one. two, and three had a higher probability of maturing seeds than the three most basal ovule positions. In 1988, the probability of producing a mature seed in ovule position one was more similar to the three most basal ovule positions than to ovule positions two and three. The position of the ovule in the ovary had no significant effect on seed weight in 1987, but it had a significant effect in 1988. Overall, seeds from ovule positions one, two, and three tended to produce heavier seeds than the three most basal ovule positions. The effects of ovule position on progeny performance were determined in a greenhouse and a field study. In the greenhouse study, we found no significant overall effect of the position of the ovule that produced the seed on progeny performance. In the field study, we did find a significant ovule position effect on several measures of reproductive performance as well as an overall effect on reproductive performance. In addition, we found a significant interaction between ovule position and number of seeds per fruit. Progeny from the stylar end of the fruit outperformed the progeny from the peduncular end in fruits containing many seeds, whereas there were no significant differences between progeny produced in the stylar and peduncular ends of fruits containing few seeds. Causes of position effects are unknown but hypotheses abound.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb11383.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

Inflorescence ontogeny and morphology of thedetmutant ofPisum sativumL. were investigated using scanning electron microscopy. This mutation causes the production of a limited number of axillary flowers followed by the formation of an apparent terminal flower slightly offset from the vertical. Our study indicates that the apparent terminal flower arises from an axillary meristem. The terminal meristem senesces and differentiates hairs, forming a rudimentary stub in the same manner as axillary meristems of conventional (Det) anddetplants. Thus the dramatic effect of thedetgene on inflorescence architecture results from early apical arrest rather than conversion of the terminal meristem to a flower as implied by the symboldet.This mutant will be valuable in elucidating regulation of apical arrest.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb11384.x

出版商:Wiley    

年代:1990

数据来源: WILEY

摘要:

Crinum erubescens(Amaryllidaceae), a water‐dispersed herbaceous perennial occupying the margin between land and freshwater lakes and swamps in Panama, produces seeds of highly variable size (0.1–66.5 g). Seeds were grown under conditions mimicking natural habitat types (water; saturated, undrained soil; moist, drained soil; and drained soil, saturated every third day) to determine whether either small or large seeds perform better in some habitats. Time to germination and percent germination are not related to seed size in any habitat type. Small seeds are less likely to survive in water, but not in other habitat types. Growth is positively associated with seed size in all habitat types and is greatest in saturated soil. Unlike studies with terrestrial plants, the benefits of having a large seed are demonstrated in the absence of competition.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1990.tb11385.x

出版商:Wiley    

年代:1990

数据来源: WILEY