摘要:

We have developed a diagnostic method to screen rapidly for plant species potentially capable of biparental inheritance of plastid DNA using the DNA fluorochrome 4′,6‐diamidino‐2‐phenylindole (DAPI) in conjunction with epifluorescence microscopy. Pollen shed from 235 plant species (including about 50 of agronomic importance) representing 80 families were screened. Putative plastid DNA was detected in the generative and/or sperm cells of pollen from 26 genera (43 species) representing 15 families. Plastid DNA was not detected in the generative or sperm cells of pollen from 192 plant species, thereby strongly suggesting that these species have only maternal inheritance. Our cytological diagnosis corroborated the known genetic evidence in 42 plant species and conflicted with the genetic reports in five species, which are discussed. The data suggest that biparental inheritance of plastids is rare; overall, it may occur in about 14% of flowering plant genera, examples of which are scattered among 19% of the families examined. This methodology also readily reveals whether pollen is bi‐ or trinucleate.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11219.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Measurements of light variation among leaves within crowns of fivePiperspecies were compared with estimates of spatial variation in light within understory, forest edge, and clearing habitats to estimate the extent to which crown structure contributes to variation in leaf light environment. Daily photon flux density (PFD) varied greatly within and among crowns. Coefficients of variation for daily PFD among sensors within a single crown ranged from 26 to 79%. Within a single crown located in a clearing, the range in daily PFD among leaves was nearly as great as the range over the entire sample of plants. In the understory, localized sunfleck activity contributed to a high degree of spatial variation in instantaneous and total PFD among leaves within individual crowns. Much of the microsite variation in sunfleck activity, however, reflected environmental conditions within the understory habitat. Within an array of sensors placed next toPipercrowns in the understory, correlations were poor for light sensors spaced only 0.2 m apart, and only 8% of the variance in light readings was explained by measurements made 0.5 m away. In the clearing habitats, microsite heterogeneity among leaves was more strongly influenced by leaf positions within crowns and leaf angles than by spatial heterogeneity within the habitat.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11220.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Shoots ofPentadenia orientandinaexhibit varying degrees of anisophylly, ranging from pairs of equal‐sized leaves to pairs of large ventral and small dorsal leaves. In this study we compare phyllotaxis, leaf expansion, and accompanying histological changes in extremely anisophyllous shoots of this species and in isophyllous shoots of the related species,P. crassicaulis.InP. orientandina,decussate phyllotaxis is modified at leaf initiation, and angles of leaf insertion appear to be further changed during leaf expansion. In both species, leaf primordia of a pair are not distinguishable at inception, suggesting an equivalent developmental potential. InP. orientandina,size differences between ventral and dorsal leaves become significant at the P2 or P3 stage, coincident with lamina initiation. Minute dorsal leaves are arrested in their development at the P3 stage and mature without differentiation of multiple epidermis, stomata, mesophyll and most vascular tissue. Variation in dorsal leaf structure inP. orientandinaemphasizes the plasticity of leaf development in this facultatively anisophyllous species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11221.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

The organization and differentiation of primary vascular tissue in isophyllous shoots ofPentadenia crassicaulisand facultatively anisophyllous shoots ofP. orientandina(Gesneriaceae) were compared using serial reconstructions and quantitative methods. Despite clear differences in shoot symmetry, both species are vascularized by four sympodia, with trilacunar, split‐lateral nodal anatomy. Leaf trace tracheary element number and diameter reflect leaf size differences inP. orientandina:these parameters are significantly greater in the large ventral leaves than in the small dorsal leaves. The median and lateral traces of ventral leaves of this species have a similar number of tracheary elements of equal diameter, while there are significantly more tracheary elements in the median than lateral traces of dorsal leaves. The pattern seen inP. crassicaulisis similar to that seen in the dorsal leaves ofP. orientandina.In both species, protoxylem development anticipates differences in mature shoot vasculature. Changes in tracheary element number during ontogeny precede or are approximately coincident with changes in leaf size. These results suggest that the facultative expression of leaf size differences inP. orientandinais associated with opportunistic development and differentiation of the lateral trace.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11222.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Hyphae, sporocarps, and structures which appear to represent arthroconidia are described from silicified peat deposits of Triassic age from Antarctica. Sporocarps with a single ostiole possess a multilayered wall with internally produced aseptate appendages that ornament the sporocarp surface. The primitive features exhibited by this fungus, together with previously described sporocarps, provide evidence for the existence of a group of fungi that may be ancestral to modern Ascomycotina.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11223.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Scanning and transmission electron microscopy of pollen grains of 29 species, representing the ten extant genera of Cycadales, has provided valuable insight into their relationships. Pollen grains of these taxa are boat‐shaped, monosulcate, and bilaterally symmetrical. They range from narrowly to widely elliptical or subcircular when viewed distally, and have an exine surface of psilate, foveolate, or fossulate. Pollen wall ultrastructure of Cycadales is typically tectate with alveolate∗∗∗spongy exine. The nexine is laminated in all genera. Nexine 1 (footlayer) is present in most species as a thin and often discontinuous layer. There is consistent variation in thickness of the sporoderm layers among the genera but relative uniformity within them. Pollen characteristics are well correlated with macro‐ and micromorphological features, chromosome numbers, geographical distribution, and postulated pollination mode. A close affinity betweenEncephalartos, Lepidozamia,andMacrozamiais recognized. Pollen characteristics of the genusBoweniashow some similarity with those of the latter group. Except for two species ofMacrozamiawhich are narrowly elliptic, all of the genera have widely elliptic pollen and share a psilate exine surface and the thinnest sexine with nearly identical arrangement of alveoli. Pollen grains of the species in the genusDioonexhibit a unique morphology but are more similar toStangeriathan they are to those of taxa in Zamiaceae. The circular outline of the grains and the foveolate exine surface are characters shared by these two genera, but several morphological features distinguishDioonfromStangeria. CeratozamiaandZamiashare a widely elliptic shape, foveolate exine surface and nearly identical sexine, as well as morphological features and chromosome numbers. They differ fromMicrocycasin sexine thickness, gross morphology and chromosome numbers. The pollen grains ofCycas circinalisandC. revolutadiffer in size and structure of the sexine from all other genera and from each other, substantiating their distinct subgeneric delimitations.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11224.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Multiple resonance frequency spectra (MRFS) provide a rapid and repeatable method for determining the flexural stiffness and modulus of elasticity, E, of segments of plant stems and leaves. Each resonance frequency in a spectrum can be used to compute E, and removal of the distal portion of an organ produces characteristic shifts in spectra dependent upon the geometry of an organ. Hence, MRFS can be used to quantitatively determine the extent to which a particular leaf or stem morphology can be modelled according to beam theory. MRFS of flower stalks ofAllium sativumL. are presented to illustrate the technique. The fundamental, f1,and higher resonance frequencies, f2… fn,of stems and the ratios of f2/f1f3/f1,and f3/f2increase as stalk length is reduced by clipping. The magnitudes of these shifts conform to those predicted from the MRFS of a linearly tapered beam. Morphometric data confirm this geometry in 21 flower stalks. Based on this model, the average modulus equals 3.71 × 108± 0.32 × 108N/m2, which compares favorably with values of E determined by static loading (3.55 × 108± 0.22 × 108N/m2) and is in general agreement with ultrasonic measurements (3.8 × 108to 4.4 × 108N/m2). Data indicate that determinations of E from a single resonance frequency are suspect, since each resonance frequency yields slightly different values for E. Statistical evaluations from all the frequencies within a MRFS are more reliable for determining E and testing the appropriateness of beam theory to evaluate the biomechanical properties of plants.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11225.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

The influence of age on chloroplast structure and photosynthetic light response ofRhododendron maximumL. was studied in three different microhabitats. The three microhabitats constituted a gradient of low, intermediate, and high irradiance levels. The most dramatic change in chloroplast structure with increasing age was the proliferation of the number and size of plastoglobuli. The magnitude and age specific rate of chloroplast occlusion by plastoglobuli increased in habitats with higher irradiance. Photosynthetic responses to light differed among the age categories of leaves. Light saturated photosynthesis and quantum yield decreased as leaves aged. However, in high light environments the rate of reduction of quantum yield or light saturated photosynthetic rate was more rapid than in the low light environment. The quantity of plastoglobuli increased in association with reduced light reaction capacity. The presence and abundance of plastoglobuli inR. maximumchloroplasts and their association with reduced photosynthetic performance indicates that the photosynthetic apparatus of theR. maximumchloroplast is sensitive to photodestruction by high irradiance: commonly a winter phenomenon in these environments.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11226.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

The dispersal of the chasmogamous, aerial cleistogamous, and subterranean cleistogamous seeds ofAmphicarpaea bracteatawas examined. The chasmogamous and aerial cleistogamous seeds are ballistically dispersed. Chasmogamous seeds were dispersed farther than the aerial cleistogamous seeds due to the height advantage of the chasmogamous pods. There was no difference in the firing angle or the initial velocity of the seeds discharged from the two aerial pod types. The subterranean cleistogamous seeds are “dispersed” the shortest distance by the elongation of runners. Differential dispersal of the three types of seeds may be a factor involved in the evolution of cleistogamy inA. bracteata.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11227.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

The microdistribution of a beach plant,Cakile maritima,was examined relative to patches of an introduced beachgrass,Ammophila arenaria.Sampling was done with belt transects oriented parallel to the beachfront to minimize the influence of physical factors along the land/sea gradient. NoCakileindividuals were found withinAmmophilapatches, and a 3–4 m wide zone of decreased abundance occurred outside of patch borders.I hypothesized that this microdistribution was due to foraging behavior of deer mice,Peromyscus maniculatus,which nest inAmmophilapatches and forage outward from them. Manipulative experiments using fruits and seedlings ofCakileconfirmed that herbivory was higher inside patches and in border areas. Seedlings protected from herbivory by wire cages survived and grew equally well both inside and outside ofAmmophilapatches, demonstrating that differences in other habitat factors were not of major importance in determiningCakilemicrodistribution. Herbivory by mice was concluded to be of primary importance in determining the microdistribution ofCakilerelative toAmmophila.Rodent herbivory may influence microdistributions of beach plants along the land/sea gradient, and may also be partly responsible for decreased plant species richness often observed inAmmophila‐dominated areas on the West Coast.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11228.x

出版商:Wiley    

年代:1988

数据来源: WILEY