摘要:

The pollen morphology of 32 species of the genusViciawas studied using scanning and transmission electron microscope (SEM and TEM). The interstitia of the pollen of the examined species were found to be either regular columellate, irregular columellate, or granular. The granular pattern was recognized to be apomorphy against the columellate patterns in the tribe Vicieae by comparison with the pollen in the tribes Vicieae, Cicereae, Galegeae, Hedysareae, and Trifolieae. The group ofViciaspecies having the apomorphy was congruent with that having a known apomorphy of the pistil character. This group with such synapomorphies may be monophyletic, though it is treated as polyphyletic in the present infrageneric system ofVicia.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12792.x

出版商:Wiley    

年代:1996

数据来源: WILEY

摘要:

CrataegussectionDouglasiiexhibits variation in stamen number per flower typical for the genus throughout North America. To understand the developmental basis for this variation we studied the early floral ontogeny of the three taxa in sectionDouglasii: C. douglasii(both Pacific northwest and the upper Great Lakes basin),C. rivularis, andC.suksdorfii. Crataegus suksdorfii, like all known diploidCrataegus, has ≈20 stamens; the two other taxa have ≈10 stamens, a condition associated only with polyploidy. In all taxa petal primordia and a whorl of five pairs of stamen primordia develop from five common primordia. The 10‐stamen∗∗∗ condition results from loss of two whorls of five stamens that are subsequently formed inC. suksdorfii.Loss of these two whorls in the 10‐stamen taxa is the result of neither a smaller floral apex at initiation, nor a smaller flower at anthesis. Stamen number variability, particularly inC. douglasiiandC. rivularis, is the result predominantly of fewer than two stamen primordia developing between adjacent petal primordia. Pollen production inC. douglasiiis half that inC. suksdorfiibecause of the reduction in stamen number. The results are presented and discussed in terms of morphogenetic explanations of meristic variation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12793.x

出版商:Wiley    

年代:1996

数据来源: WILEY

摘要:

Studies were conducted evaluating germinability states in giant foxtail(Setaria faberii)embryos, as well as surrounding tissues (hull, caryopsis), with germination assays. Further, seed age, fascicle arrangement, flowering patterns, and elongation in the inflorescence were evaluated. Both qualitatitive and quantitative morphological observations of the hull and the caryopsis were revealed by precisely determined fertilized spikelet age from anthesis until after seed abscission. Red coloration of the placental pad at ≈ 11 d after anthesis is probably a morphological indicator of physiological maturity. Germinability of giant foxtail embryos changed with development. Four qualitatively different types of embryo germination were observed during development of the seed: early disorganized callus growth at the basal, coleorhizal end of the embryo; germination of immature embryos with shortened and thickened axes; germination of the scutellum; and germination and growth of the coleoptile and coleorhiza in embryos aged 7 d after anthesis and older. Axis‐specific embryo germinability was also observed. Inhibition of the embryo could be localized to the coleoptile, the coleorhiza, or both. These studies provide evidence for a complex model of germinability regulation based on the independent, asynchronous actions of the embryo, caryopsis, and hull compartments, as well as on their dependent, synchronous action. These studies provide evidence for a dynamic, developmental model of giant foxtail germinability regulation resulting in phenotypes with a wide range of germinability shed from an individual panicle. These diverse germinability phenotypes are found at all stages of development, but particularly when the seed is shed and the soil seed bank is replenished.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12794.x

出版商:Wiley    

年代:1996

数据来源: WILEY

摘要:

There is increasing interest in using somatic embryogenesis to meet the demand for high quality seedlings. However, in vitro production of propagules on a large scale depends on the optimization of the maturation and germination steps promoted by desiccation and subsequent imbibition of the embryo, respectively. It is therefore important to characterize zygotic and somatic embryos in terms of their water relations. Bound water, elastic modulus, osmotic potential at full turgor, and relative water content at turgor loss point were determined for somatic and zygotic embryos of western larch and loblolly pine and somatic embryos of white spruce at two developmental stages. These water relations parameters were derived from water‐release curves obtained by suspending tissue samples in sealed vials over unsaturated NaCl solutions of known water potential. There was little difference in water relations parameters among species but marked stage dependency for bound water and elastic modulus. The amount of bound water was lowest in western larch somatic embryos (0.02‐0.07) and highest in zygotic loblolly pine embryos (0.10‐0.18). Elastic modulus ranged from 2.5 to 6.2 MPa in somatic embryos but varied between 1.4 and 1.8 MPa in zygotic embryos. The osmotic potential was lower in somatic embryos than in their zygotic counterparts. Our results show that water relations parameters are remarkably conservative across species but that, within a given species, these parameters are stage specific. It would seem, therefore, that desiccation protocols might be developed for a given developmental stage and applied across a range of species without the confounding effects of differences in water relations parameters.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12795.x

出版商:Wiley    

年代:1996

数据来源: WILEY

摘要:

Sixteen accessions of the xerohalophyte,Atriplex canescens(Pursh.) Nutt., differing in tendency to accumulate Na or K in leaf tissues, were compared for salt tolerance in a greenhouse study. Plants were grown along a salinity gradient from 72 to 2017 mol/m3NaCl measured in the root zone. Growth rates (RGR) were negatively affected by salinity for all accessions. Initial leaf levels of Na (measured before exposing plants to saline solutions) were positively correlated with subsequent RGR's of accessions on the salinity gradient (r= 0.60 ‐ 0.88,P<0.05 across salinity levels), whereas initial leaf K levels were negatively correlated(r= ‐0.68 to ‐0.85,P<0.01 across salinity levels). Varietieslinearis(S. Wats.) Munz andgrandidentatumStutz&Sanderson had greater tendency for Na accumulation, lower tendency for K, and higher growth rates on saline solutions than var.occidentalis(Torr.&Frem.) Welsh&Stutz accessions. Within var.occidentalisaccessions, RGRs were negatively correlated with initial leaf levels of K but not Na. Postexposure leaf Na and K levels were not strongly correlated with RGR's. All accessions responded to salinity by increasing their uptake of Na, which is the primary mechanism of osmotic adjustment to salinity in this species. It is suggested that differences in tendency to accumulate Na or K amongA. canescensgenotypes are related to their specialization for saline or xeric habitats, respectively.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12796.x

出版商:Wiley    

年代:1996

数据来源: WILEY

摘要:

A progeny of the native Florida cycadZamia integrifoliagrown from seeds planted in 1986 was monitored until 1995 to record mortality and the nature and time of expression of primary and secondary sex characters. In addition to gender‐specific cone morphologies, males and females differed in secondary sex characters such as age at first cone production, frequency of cone production, mean cone numbers in second and later coning episodes, and, in older plants, mean leaf and branch numbers. Gender differences expressed themselves at different stages in the life history: their nature and extent varied during the years following sexual maturation. By 1995, 46% of the plants in the progeny had died, most of them before producing cones. Prior to 1988 the mean leaf number of plants that died did not differ from that of survivors, but the mean leaf number of plants dying between 1988 and 1989 was 0.4 times that of the survivors during that period, suggesting reduced vigor prior to death. Mean age at first cone production was 5.8 yr for males and 6.6 yr for females. Mean dry masses of individual male cones increased between the first and second coning episodes, but not between the second and third coning episodes. Mean dry masses of the entire cone crop of individual males increased through the third coning episode due to an increase in mean cone number per episode, but mean cone number was unchanged between the third and fourth coning episodes. Mean dry mass of unpollinated female cones did not change between the first and second coning episodes; mean cone numbers did not change between the first and third coning episodes. After the first coning episode, males produced higher mean cone numbers than females. By 1995, the mean dry mass of an individual male's cone crop was greater than that of a female. Coning frequency of males was 1.7 times greater than that of unpollinated females, suggesting a gender difference in the genetic control of coning frequency. Coning frequency of females pollinated 1 or 2 yr previously was reduced compared with that of unpollinated females. Cone production did not affect subsequent leaf production by either gender. Mean leaf numbers increased in some years and not in others. Mean leaf numbers of males and females did not differ prior to cone production. After cone production mean leaf numbers of males were greater than of females. Mean age of males producing first branches was 6.3 yr, with a mean of 2.5 first branches per plant. Mean age of females producing first branches was 7.7 yr, with a mean of 2.5 first branches per plant. By 1995 the mean branch number of males was 5.7 per plant and of females was 2.7 per plant. Between 1993 and 1995 the mean branch number of males and females increased incrementally, but mean leaf numbers did not change. In early years of branching, leaf number increased with branch number; higher mean leaf numbers of males of an age class thus reflected their earlier branching. Males produced first cones earlier than females. Since branch production was associated with cone production, higher branch numbers of males in an age class reflected their earlier first cone production. In 1995 the sex ratio of known males and females in the progeny was 1:1, with a few individuals not having produced cones by that year.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12797.x

出版商:Wiley    

年代:1996

数据来源: WILEY

摘要:

Sarracenia jonesiiandS. oreophilaarc insectivorous perennial plants of the southeastern United States. Both pitcher plant taxa arc rare and endangered. Allozyme diversity was assessed for eight of the ten extant populations ofS. jonesiiand 14 of the 35 remainingS. oreophilapopulations. Genetic diversity was low and comparable for both species (Hes= 0.086 and 0.082 forS. jonesiiandS. oreophila, respectively). Mean population genic diversity(Hep)was 0.061 forS. jonesiiand 0.060 forS. oreophila.Estimates of genetic diversity were typical of those commonly associated with endemic species. Small populations of each species and geographically disjunct populations tended to maintain less genetic diversity. Indirect estimates of gene flow were comparable forS. oreophila (Nm= 1.62) andS. jonesii (Nm= 1.07).

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12798.x

出版商:Wiley    

年代:1996

数据来源: WILEY

摘要:

The evolution of distyly from tristyly has occurred repeatedly, especially in the Lythraceae. However, the evolutionary forces involved remain unclear since species exhibiting transitional stages between tristyly and distyly have rarely been studied. The self‐compatible, wetland perennialDecodon verticillatus(Lythraceae) may provide this transitional variation since populations commonly lack style morphs, particularly the mid‐styled (M) morph. In dimorphic populations lacking the M morph, anthers positioned at the mid level in both the long‐ (L) and short‐styled (S) morphs have lost their target stigma, setting the stage for either evolutionary repositioning of mid‐level anthers to increase pollen export to L and S stigmas, or increased variability in mid‐level anther position resulting from relaxed selection. We examined these two hypotheses by comparing floral morphology in eight dimorphic and ten trimorphic populations from throughout the species’ range. We found no evidence that loss of the M morph has led to evolutionary modification of mid‐level stamens. While mid‐level stamens of the S morph were 11.0 ± 4.0% (mean ± 1 SE) longer than those of the L morph in dimorphic populations, divergence in stamen length between morphs occurred to the same extent (10.4 ± 2.0%) in trimorphic populations and cannot be attributed to the absence of the M morph. Analyses of variability using median ratio tests revealed no difference in the variability of mid‐level stamen length between dimorphic and trimorphic populations. Mid‐level stamens were not more variable than long‐ and short‐level stamens within dimorphic populations. The consistent divergence in mid‐level stamens between the L and S morphs may reflect morph‐specific differences in the optimal position of mid‐level anthers for maximizing cross‐pollination and avoiding self‐fertilization.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12799.x

出版商:Wiley    

年代:1996

数据来源: WILEY

摘要:

Opportunities for selfing through geitonogamy are possible if more than one flower within the same clone, inflorescence, or floral unit is open at the same time. In a total of 200 inflorescences in two natural populations ofIris versicolor, flowers were observed and classified daily on the basis of anther dehiscence and stigma receptivity. Analysis of the flowering phenology demonstrated that (1) protandry limits opportunities for autogamy, (2) flowers mature sequentially within a floral unit (defined as a cluster of flowers borne on a single branch within an inflorescence), preventing the opportunity for geitonogamous fertilization between flowers of the same floral unit, and (3) 77% of all flowers had no opportunity to be pollinated by another flower within the same inflorescence. Both the number and the proportion of flowers with opportunities for geitonogamy increased with the number of flowers open in each population, and opportunities for geitonogamy also increased with the number of floral units within inflorescences. These morphological and phenological controls suggest that when selfing occurs in this species, it is most likely to occur between flowers on different inflorescences within the same clone. Since the organization of whole inflorescences in space is determined primarily by rhizome placement, clonal architecture may play an important role in mating system regulation in this species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12800.x

出版商:Wiley    

年代:1996

数据来源: WILEY

摘要:

The consequences of selfing and outcrossing inDatura stramonium, a colonizing annual species, were experimentally assessed in terms of the fecundity of maternal plants and the performance of their progeny. Selfed and cross‐pollinated plants were produced through controlled crosses and were then planted in their native environment. We recorded size at establishment, final height, number of branches, fruits, total biomass, and resistance to herbivores for each plant. Natural selection was measured for plant size and resistance to herbivores in both types of plants. Seed production (fecundity) was higher for fruits developed from outcrossing than for fruits derived from selfing. Among‐family differences were detected for seed mass, but these were not related to mating system. No differences in germination, plant size, and fruit number were found between the two mating systems. Damage produced by two herbivores,Epitrix parvulaandSphenarium purpurascens, ranged from 0 to 95% of total leaf area; however, there were no differences in resistance to both herbivorous insects either among families or between mating systems. Plant survival through the whole season was similar for plants of both types of crossing. The direction and magnitude of phenotypic selection for each trait were similar for both types of progeny. Directional selection to increase plant size and reduce resistance toE. parvulawas detected, while no selection was detected for resistance to 5.purpurascens.Curvilinear (stabilizing/disruptive) and correlational selection modes were not detected for any trait. Inbreeding depression coefficients were all statistically indistinguishable from zero, except for seed number per fruit. The inbreeding depression coefficient for seed number was high and close to 40%, suggesting that evolution toward complete selfing may be prevented in this population ofDatura stramonium.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1996.tb12801.x

出版商:Wiley    

年代:1996

数据来源: WILEY