摘要:

Current systems of estimating gene segregation in autotetraploids usually are based on two extreme methods: chromosome segregation with absolute centromere linkage, or maximum equational segregation with crossing over always occurring between the centromeres and marker genes. The hiatus between the two methods is unacceptable quantitatively, and segregation of thedgene in tomato shows that neither method predicts an acceptable fit. We present a new meiotic configuration (MC) method of analyzing tetrasomic inheritance in autotetraploids that allows more accurate estimations of all intermediate types of segregation. The method is based on a maximum of two chiasmata per bivalent and four per quadrivalent. The theoretically expected numbers of bivalents and chain and circle quadrivalents are derived first. Chromosome frequencies from these configurations are then used to determine relative contributions from each configuration to the gamete genotypes by way of newly developed tables for gene segregation in various autotetraploid genotypes. The large sample sizes from classic 4xtomato (Solanum lycopersicumL.) data are used to demonstrate the stepwise method of calculating gamete genotypes, and the method gives acceptable fits for the data tested. The interspecific tetraploid hybridSolanum lycopersicum×S. pimpinellifoliumhad good fits to expected autotetraploid segregation, supporting its autoploid nature and the fact that taxonomic rank should not be a consideration in designating categories of polyploids. Autotetraploid allozyme segregation data for several genes in one genus of another family had acceptable and usually better fits to the MC expectations than to the standard methods.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12756.x

出版商:Wiley    

年代:1996

数据来源: WILEY

摘要:

Mutants affected in flavonoid (tt4) or sinapate ester (fah1) biosynthesis were used to assess the relative importance of these phenolic UV photoprotectants inArabidopsis.Flavonoid and sinapate ester absorption was more specific for UV‐B than major nonphenolic chromophores in crude extracts. A new method of evaluating phenolic UV‐B attenuation was developed using fluorescence analysis. When excited by UV‐B, sinapate ester containing leaves and cotyledons had enhanced sinapate ester fluorescence and reduced chlorophyll fluorescence relative to those without sinapate esters. Although fluorescence analysis gave no evidence of UV‐B attenuation by flavonoids, enhanced chlorophyll and protein loss were observed upon UV‐B exposure in flavonoid‐deficient leaves, suggesting they have another mechanism of UV‐B protection. The hydroxycinnamates have been largely ignored as UV‐B attenuating pigments, and the results indicate that greater attention should be paid to their role in attenuating UV‐B.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12757.x

出版商:Wiley    

年代:1996

数据来源: WILEY

摘要:

Distinctions in floral ontogeny among three segregate genera (Cassiasensu stricto,Chamaecrista, andSenna) ofCassiaL. support their separation. In all species studied, the order of floral organ initiation is: sepals, petals, antesepalous stamens plus carpel, and lastly antepetalous stamens. Sepal initiation is helical in all three genera, which however differ in whether the first sepal is initiated in median abaxial position (Senna), or abaxial and off‐median (Cassia javanica), a rare character state among legumes. Order of petal initiation varies: helical inSennavs. unidirectional inCassiaandChamaecrista.Both stamen whorls are uniformly unidirectional. Intergeneric ontogenetic differences occur in phyllotaxy, inflorescence architecture, bracteole formation, overlap of initiation among organ whorls (calyx/corolla inCassia;two stamen whorls inChamaecrista), eccentric initiation on one side of a flower, anther attachment, anther pore structure, and precocious carpel initiation inSenna.The asymmetric corolla and androecium inChamaecristaarise by precocious organ initiation on one side (left or right). The poricidal anther character can result from differing developmental pathways: lateral slits vs. sealing of lateral sutures; clasping hairs vs. sutural ridges; terminal pores (one or two) vs. none; and clamp layer formation internally that prevents lateral dehiscence. Genera differ in corolla aestivation patterns and in stigma type. Convergence is shown among the three genera, based on intergeneric dissimilarities in early floral ontogeny (floral position in the inflorescence, bracteole presence, position of the first sepal initiated, order of petal initiation, asymmetric initiation, overlap between whorls, anther morphology, and time of carpel initiation) resulting in similarities at anthesis (showy, mostly yellow salverform flowers, heteromorphic stamens, poricidal anther dehiscence, bee pollination, and chambered stigma).

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12758.x

出版商:Wiley    

年代:1996

数据来源: WILEY

摘要:

Vascular system development in sepals, petals, and sepaloid petals was compared in wild‐type andcrinkled petalmutant plants ofClarkia tembloriensis.Patterns of vascularization in cleared whole mounts were visualized and traced under both brightfield and polarizing illumination. Wild‐type sepals exhibited a basipetal pattern of maturation, with tracheary elements maturing relatively rapidly. Mature sepals had three primary veins with numerous secondary veins. In contrast, wild‐type petals exhibited an acropetal pattern of maturation, with tracheary elements maturing relatively slowly. The mature petals had only one primary vein with numerous secondary veins. Sepaloid (crinkled) petals combined characteristics of both wild‐type sepals and wild‐type petals. They exhibited a basipetal pattern of development and a relatively rapid maturation of the tracheary elements characteristic of wild‐type sepals. Venation architecture incrinkled petalmutants showed a single primary vein with numerous secondary veins, similar to wild‐type petals. Thecrinkled petalmutant fits the definition of a homeotic mutant in that the petal has assumed characteristics of the sepal. However, homeotic transformation from petal to sepal is incomplete since the crinkled petal still retains many of the characteristics of wild‐type petals.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12759.x

出版商:Wiley    

年代:1996

数据来源: WILEY

摘要:

Low levels of genetic variability are common for a number of geographically restricted plants: these data are consistent with theoretical expectations that small populations should be genetically depauperate. However, in some species, high levels of variability have been found in rare species.Allium aaseaeis a rare, narrow endemic in the foothills of the Boise Front of southwestern Idaho. Genetic variation in the rare endemicA. aaseae, and nearby populations of the more common species,A. simillimum, was examined with randomly amplified polymorphic DNA (RAPD) data. Eight populations ofA. aaseaeand six populations ofA. simillimum(three near the range ofA. aaseae, and three distant populations) of 25 individuals each were examined for this analysis. Genetic diversity as determined with RAPD markers of both species examined in this study is largely found within and not among populations. Levels of genetic diversity are high, especially for a narrow endemic species such asA. aaseae.Proportion of RAPD loci polymorphic was high in both species, although slightly higher in the more commonA. simillimum.Because these higher levels of genetic variability run counter to theory, alternative explanations beyond population size must be invoked to explain the levels of genetic diversity found in this study. Possible explanations are (1)A. aaseaeis only recently derived fromA. simillimum, (2) hybridization betweenA. aaseaeandA. simillimumis occurring, (3) multiple origins ofA. aaseae, (4) populations ofA. simillimumincluded in the analysis are allA. aaseae, (5)A. aaseaeandA. simillimumare conspecific, and (6) an artifact of RAPD data.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12760.x

出版商:Wiley    

年代:1996

数据来源: WILEY

摘要:

Genetic structure within a population ofSilene albawas studied using a chloroplast DNA (cpDNA) and six allozyme polymorphisms. A 20 × 65 m area was sampled by constructing a 5 × 5 m grid and determining the genotype of the plant nearest to each grid node. Analysis of the spatial distribution of genotypes by Moran'sIand join‐counts showed a significant degree of association of like cpDNA haplotypes (I= 0.52,S.N.D. =2.55) but a random or slightly repulsed distribution of allozyme genotypes. A second sample was taken by collecting all individuals from within a 1‐m wide transect established along the perimeter of the grid. Genotype and allele frequencies were calculated by grouping individuals from arbitrary 3‐m intervals along the transect, and analyzed by Wright'sFstatistics. TheFstvalue calculated for cpDNA (0.875) differed markedly from that based on all allozymes (0.027). Taken together, the results suggest that in this population gene flow in the maternally inherited cpDNA is limited by restricted seed dispersal, whereas gene flow in the nuclear DNA based allozymes is more pervasive owing to the added effects of pollen dispersal. The utility of cpDNA polymorphism for the study of fine‐scale gene flow is discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12761.x

出版商:Wiley    

年代:1996

数据来源: WILEY

摘要:

Pollination biology of 41 plants species of 21 families blooming in the forest understory was investigated in a lowland mixed diplerocarp forest in Lambir Hills National Park, Sarawak. Among these species, 29 species (71%) were pollinated by bees, four (10%) by nectariniid birds, three by small dipterans, and others by moths, butterflies, syrphid flies, wasps, and beetles. The 29 bee‐pollinated species consisted of five distinct pollination guilds: ten species pollinated by medium traplining bees (twoAmegillaspecies), nine by small traplining bees (three halictid and a xylocopine species), two by stingless bees and beetles, seven by stingless bees, and one by megachilid bees. The bees constituting the first two guilds were shade‐loving, swiftly flying, long‐tongued trapliners. Proboscis lengths of these pollinators correlated with flower depth of the host plant. Pollination systems in the forest understory were distinguished from that in the canopy by the prevalence of specific interactions, the number of traplining solitary bees, and lack of pollination systems by mass‐recruiting eusocial bees, largeXylocopabees, thrips, bats, and wind. These characteristics are largely similar between the Palaeotropics and the Neotropics through convergence of nectarivorous birds (spiderhunters vs. hummingbirds) and traplining bees (Amegillavs. euglossine bees).

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12762.x

出版商:Wiley    

年代:1996

数据来源: WILEY

摘要:

We studied various aspects of the fruiting biology ofCornus sanguinea(Cornaceae), a fleshy‐fruit‐producing deciduous shrub, in four populations in northwest Spain. One population was studied over a 5‐yr period (1989‐1994), and the remaining populations in 1994 only. Fruit‐set level varied among years (range 11‐18%) and among populations (range 8‐22%), but was in all cases low. Within plants, fruit‐set level did not vary significantly among inflorescences, indicating that inflorescence fruit set is independent of inflorescence position and inflorescence, phenology. To investigate the function of surplus flowers, we carried out flower removal experiments. Inflorescence fruit‐set level was unaffected by removal of up to =75% of flowers. These results suggest thatCornus sanguinearegulates its fruit‐set level via plasticity in the number of fruits aborted: if flower mortality has been high, fewer fruits will be aborted. Within the inflorescence, surplus flowers thus act as insurance against flower loss.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12763.x

出版商:Wiley    

年代:1996

数据来源: WILEY

摘要:

We report on two field experiments that were conducted in 1991 and 1992 at the South Coast Extension and Research Center, Irvine, CA, to study the incidence of multiple paternity in the common bean (Phaseolus vulgarisL.). Hypocotyl color and shikimate dehydrogenase (Skdh) isozymes were used as genetic markers. The white‐seeded cultivar ‘Ferry Morse 53’ (FM 53) was used as the female parent. This cultivar is homozygous recessive (pp) for hypocotyl color. The pollen source parents were three homozygous dominant (PP) purple‐hypocotyled, black‐seeded cultivars. Three cultivars, ‘ICA Pijao,’ G4459, and the maternal parent FM 53, are of Mesoamerican origin and homozygous for the fast (F) allele at theSkdhlocus. The other cultivar, Black Valentine, is of Andean origin and is homozygous for the slow (S) allele at theSkdhlocus. Overall, 6 125 pods were obtained from 57 and 111 plants harvested individually in 1991 and 1992, respectively. All progeny, 28938 seeds, were scored for hypocotyl color at the seedling stage. The purple‐hypocotyled seedlings were genotyped for theSkdhlocus to identify their pollen parents. Multiple paternity was identified in all the pods with hybrid seeds (i.e., those of intercultivar crosses) at 5.8% and 8.1% in 1991 and 1992, respectively. All multiply sired pods produced both nonhybrid and hybrid seeds. As many as three successful fathers per pod were identified, but the number of markers limited measuring higher levels of multiple paternity. Most multiply sired pods (≈70%) were filled by nonhybrid seeds plus a single hybrid seed. Ovule position effect within multiply sired pods was inferred from the nonrandom distribution of hybrid seeds within a pod. On average, hybrid seeds occurred more frequently in ovules in position 7 (most basal) and in position 1 (most stylar) than in ovules in the middle positions of the pod.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12764.x

出版商:Wiley    

年代:1996

数据来源: WILEY

摘要:

The development of staminate and pistillate flowers in the dioecious tree speciesPistacia veraL. (Anacardiaceae) was studied by scanning electron microscopy with the objective of determining organogenetic patterns and phenology of floral differentiation. Flower primordia are initiated similarly in trees of both sexes. Stamen and carpel primordia are initiated in both male and female flowers, and the phenology of organ initiation is essentially identical for flowers of both sexes. Vestigial stamen primordia arise at the flanks of pistillate flower apices at the same time functional stamens are initiated in the staminate flowers. Similarly, a vestigial carpel is initiated in staminate flowers at the same time the primary, functional carpel is initiated in pistillate flower primordia. Differences between the two sexes become apparent early in development as, in both cases, development of organs of the opposite sex becomes arrested at the primordial stage. Male flowers produce between four and six mature functional stamens and female flowers produce a gynoecium with one functional and two sterile carpels.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12765.x

出版商:Wiley    

年代:1996

数据来源: WILEY