摘要:

MioceneLiriodendroncarpels, whole fruiting structures and leaves from Clarkia and Oviatt Creek sites in northern Idaho are preserved as imprints and compressed fossils in soft lacustrine clays. The isolated carpels are indistinguishable from those described asL. hesperiaBerry from the Spokane Latah flora. Fruit aggregates from the type Clarkia and Oviatt Creek localities and leaves from three Clarkia sites are considered to be within the range of variation of the single speciesL. hesperia.Comparisons were made regarding leaf architecture, lower leaf epidermal structures, leaf flavonoid and steroid analysis, morphological features of receptacles and carpels, and the venation pattern of carpels of the fossil material to the two extant species,L. tulipiferaL. (native to southeastern United States) andL. chinenseSarg. (native to southeastern Asia). Leaf architecture features analyzed by standard statistical and canonical tests and marginal venation patterns near the base of leaves suggest thatL. hesperiais more similar toL. tulipifera, whereas the size dimensions of lower epidermal cells and the common presence of two sterane compounds imply thatL. hesperiais more similar toL. chinense.The fossil species, however, is a distinct taxon indicated by statistical discriminant and canonical tests, leaf base shape, often smaller epidermal cell dimensions, and the shape of round receptacle carpel scars. Both the fossil and the two livingLiriodendronspecies are associated with comparable mixed mesophytic floras.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13463.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Spergula arvensisL. (Caryophyllaceae) is a cosmopolitan weedy annual that exhibits a genetically based seed coat polymorphism in which two primary seed types, papillate (P) and nonpapillate (NP), are produced. This study examined germination response of the two morphs and seedling emergence in Pacific coast populations. Germination behavior was complex and variable among populations and between seed morphs. Seeds from some populations exhibited greater temperature sensitivity and/or differentiation between morphs. Freshly produced seeds from grassland and ruderal populations were strongly dormant at the time of dispersal, in contrast to seeds from cultivated or summer‐wet populations. In San Francisco Bay area populations, germination and seedling emergence was largely simultaneous, following the first substantial fall rains.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13464.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

An analysis of 60 populations ofOenotherasects.Gauropsis, Hartmannia, Kneiffia, Paradoxus, andXylopleurumshowed that 29 flavonols and 4 glycoflavones were present among 19 of the 20 species studied in these five sections. The four glycoflavones, representing the first report for this class of compounds forOenothera, were present only inO. canescens, a highly specialized and isolated species within the genus. The most closely related species,O. dissecta, had a flavonoid profile more similar to species of sect.Hartmanniaand sect.Kneiffia.The most striking feature of the analysis is that roughly 70% of the known flavonoids in the family were found in the group of sections studied. The large number of compounds in this one lineage ofOenotheracontrasts sharply to the relatively low numbers found in most other genera of the family. Further, the occurrence of glucuronides and sulfates withinOenotherais restricted to these sections. Each species examined had a unique flavonoid profile, exceptO. deserticolaandO. multicaulis(both sect.Hartmannia) which had identical profiles. This finding contrasts sharply with the uniform profiles of other sections ofOenotheraand other genera in Onagraceae, such asEpilobiumandLudwigia.By contrast,O. havardii, a phyletically isolated species of the monotypic sect.Paradoxus, had only five flavonol glycosides, compared with 11–19 compounds in the other species. Based on morphological and seed anatomical data,O. havardiiis only distantly related to sects.Gauropsis, Hartmannia, Kneiffia, andXylopleurum, although along with sect.Lavauxia, it appears to represent the sister group to them. Overall, with the exception ofO. havardiiandO. canescens, the flavonoid profiles support the hypothesis recently suggested by seed anatomy that these four sections are more closely related to each other than any one of them is to another section of the genus.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13465.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Patterns of interfertility for intersectional hybridizations inGauraare generally consistent with current taxonomic hypotheses regarding the sectional division of the genus. Crossability is generally lower for intersectional crosses than for intrasectional, interspecific crosses. Average intersectional cross‐success ranged from 0–14% among the eight sections, and a total of 54 intersectional hybrids were produced from 1,872 intersectional pollinations. Low rates of capsule‐set and no intersectional hybrids were produced byG. mutabilis(sectionGauridium), an early offshoot of a primitive ancestor ofGaura.Two species of sectionXerogaurathat are regarded as relicts of the primitive ancestor of all otherGaurashowed low averages for cross‐success, but did produce hybrids in combination with three relatively advanced sections (Campogaura, Stipogaura, Pterogaura). Low capsule‐set and no intersectional hybrids were produced byG. parviflora(sectionSchizocarya). Extreme morphological specialization for autogamous reproduction has been accompanied by reproductive isolation ofG. parviflora.Only three hybrids resulted from crosses usingG. coccinea(sectionCampogaura), a polyploid complex. Each successful cross pairedG. coccineawith a putative progenitor, either a species of sectionXerogauraorG. villosaof sectionStipogaura.Hybrids ofG. coccineawith odd ploidy number showed reduced pollen staining. Species ofStipogauraproduced only three hybrids, one each in combination with species of sectionsXerogaura, Campogaura, andPterogaura. Gaura drummondii(sectionXenogaura) registered the highest average cross‐success despite being a tetraploid. All 25 hybrids ofG. drummondiiresulted from crosses withG. suffulta, and were triploids that showed reduced pollen staining. Intersectional crosses fail to support the hypothesized relationships ofG. drummondiieither toG. coccineaor to species of sectionStipogaura.SectionGauraproduced moderate averages of cross‐success, but all 20 hybrids resulted from crosses withG. suffulta.Fifty of the 54 intersectional hybrids were descended from a species of sectionPterogaura.Crosses that usedG. suffultaas one parent produced 49 of these hybrids. Four hybrids were from crosses withG. macrocarpa(sectionXerogaura), and the remaining 45 were due to the recurrent success of crosses that pairedG. suffultaas maternal parent with eitherG. drummondiior a species of sectionGaura.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13466.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Greater needle packing (number of needles per unit stem length) among shoots ofPicea engelmannii(Parry ex. Engelm.),Abies lasiocarpa([Hook] Nutt.), andPinus contorta(Engelm.) collected at sun‐exposed locations resulted in leaf temperatures (T1) that were well above air temperature (Ta) and which were closer to optimum for maximum photosynthesis under field conditions. Maximum photosynthesis in these species occurred at leaf temperatures well above mean maximum Taduring most of the summer growth period. An approximate doubling in needle packing on sun shoots of these species, however, led to an estimated temperature enhancement of daily photosynthetic carbon gain of 21 to 36% compared to estimations assuming T1= Tafor the entire day. Elevated T1due to needle packing may lead to substantial increases in summer carbon gain for conifers experiencing cold‐limited, short growth seasons.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13467.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Salicornia europaeaL. (Chenopodiaceae) is an annual succulent halophyte that lacks leaves, is photosynthetically active over its entire surface, and branches in a predictable manner. A computer model based on that of Niklas and Kerchner (1984) was used to generateS. europaea‐like branching patterns. The model was used to predict the morphology ofS. europaeathat could maximize light interception and minimize the total bending moment. The optimal branching pattern generated by the computer corresponded very closely to the form ofS. europaeafound in late‐successional populations. The progression of model forms from the least efficient (lowest total projected surface area and highest bending moment) to the most efficient (highest projected surface area and lowest bending moment) parallels the observed phenotypic changes in morphology ofS. europaeaover the course of succession in New England salt marshes. Based on computer simulations, we conclude that morphological changes in the branching patterns ofS. europaeaduring succession correspond to alterations of shape capable of coincidentally maximizing the interception of light and minimizing the total bending moment.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13468.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Young floral buds of a male sterile stamenless‐2 (sl‐2/sl‐2) mutant of tomato were cultured, at the sepal primordia stage, in a liquid Murashige and Skoog medium containing either benzylaminopurine (BAP) or gibberellic acid (GA3) or both. In the basal medium (BM), the buds initiated petal and stamen primordia only and they showed limited development. In buds grown in BM supplemented with 10–6M BAP, all types of organ primordia were initiated but the petals remained small and the stamens and carpels were immature. Well‐developed flowers with a normal complement of floral organs were, however, produced in a medium containing both BAP (10–6M) and GA3(10–7M to 10–5M). The development of stamens was variable and ranged from the complete absence of microsporogenesis to the formation of abnormal pollen. Gynoecium development was normal and ovules with megaspores were produced in the ovary. The results show that male sterility in the sl‐2/sl‐2 mutant can be expressed in vitro and that GA3is essential for the in vitro growth and development of all the floral organs of this mutant.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13469.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

The potential for interspecific genetic exchange was examined by monitoring flowering patterns, pollinator movement, and gene flow among experimental populations of the Texas gourd (Cucurbita texana) and cultivars ofCucurbita pepo.While flowering patterns and pollinator movement tended to maximize self‐pollination and local gene exchange, movement of effective pollen exceeded 1,300 m. This movement, mediated by the solitary beeXenoglossa strenuaand monitored by tracking allozyme variants, produced interspecific hybrids in 5% of the progeny from experimental plants. Interspecific gene exchange occurred in either direction with either species serving as staminate or pistillate parent. No obvious constraints to gene flow among plants representingC. texanaand distinctive cultivars (vars.ovifera, medullosa, melopepo) ofC. pepowere detected. Genetic exchange among different species and cultivars is enhanced by the foraging behavior ofXenoglossa.Multiple visits to either staminate (pollen carryover) or pistillate (multiple pollinations) flowers often result in the deposition of mixed pollen on receptive stigmas. The wild type (C. texana) can donate and receive effective pollen when growing under both weedy and natural conditions. The observed lack of interspecific reproductive isolation supports treatment of cultivars and wild types as a single species and, in conjunction with available data concerning temporal/geographical relationships among bees, squash, gourds, and humans in eastern North America, suggests the possibility of long‐term genetic interaction between wild types and domesticates.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13470.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

In this paper we examine some ecological consequences and phenotypic correlates of flower size variation in wild radish,Raphanus sativus.Mean corolla diameter varied significantly among individuals within natural populations ofR. sativusin California. On the average, almost 40% of flower biomass was allocated to corolla tissue. In field experiments, pollinator visitation increased significantly with corolla size. Large flowers also accumulated more nectar when pollinators were excluded from plants. In three populations, corolla size was positively correlated with allocation to pollen per flower (either anther weight or pollen grain number), but there was usually no phenotypic relationship between corolla size and several measures of female allocation (ovule number per flower, proportion fruit set, and total seed mass per fruit). Plants growing in the field produced fewer large flowers per unit of stem, and stem biomass was negatively related to corolla size for plants grown under controlled greenhouse conditions. Male and female fitness may covary differently with allocation to attractive floral features in species such asR. sativus, where seed production is often limited by resources rather than by pollen.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13471.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Theories of sex allocation make a number of predictions about the relationship between male and female resource investment in flowering plants and realized fitness. Testing these predictions requires quantitative information on costs and benefits associated with various allocation patterns. These data are difficult to obtain even in experimental settings, and may be impossible to obtain in many natural populations. Experimental studies of pollination and female reproduction in plants have been facilitated by the qualitative distinction between resource and pollen limitation of seed set. Here, we present an analogous model for studying relationships between pollinator visitation, pollen production, and pollen export. For animal‐pollinated species where seed production is resource‐limited, maternal fitness may be enhanced by conserving resources rather than investing in secondary attractive structures. In contrast, pollen export is likely to increase with increasing allocation to advertisements and rewards, at least until anthers are stripped of pollen.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb13472.x

出版商:Wiley    

年代:1988

数据来源: WILEY