摘要:

The floating, stoloniferous plant,Eichhornia crassipes, has high rates of productivity and rapidly invades new sites. Because the transport of carbon among connected ramets is known to increase the growth of clonal plants, we asked whether there is intraclonal carbon transport inE. crassipes.Because net photosynthesis ofE. crassipesis significantly higher at high levels of atmospheric CO2, we also asked if high CO2can change patterns of carbon transport in ways that might modify clonal growth. We exposed individual ramets within groups of connected ramets to14CO2for 15–45 min and measured the distribution of14C in the group after 4 days of growth at 350, 700, 1,400, or 2,800 μ11−‐1CO2. At 350 μ1 1−‐1CO2, a parent ramet exported approximately 10% of the14C that it assimilated to its first rooted offspring ramet. The offspring exported a similar percentage of thel4C it assimilated toward the parent; two‐thirds of this14C was retained by the parent, and one‐third moved into new offspring of the parent. In all ramets, imported carbon moved into leaves as well as roots. At the higher levels of CO2, the percentage of assimilated carbon exported from a parent ramet to the leaf blades of its first offspring was lower by half. High CO2had little other effect on carbon transport.E. crassipesmaintains bidirectional transport of carbon between ramets even under uniform and favorable environmental conditions and when external CO2levels are very high.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb11425.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

The structure of the secondary pulvinus ofRobinia pseudoacaciahas been examined together with ultrastructural features of motor cells both in open and closed pulvini, to identify ultrastructural changes associated with leaflet movement. Pulvini have a central vascular core bordered by thick‐walled collenchyma cells, which in turn are surrounded by several layers of cortical parenchyma cells. Cortical motor cells exhibit ultrastructural features similar to those reported in homologous cells of other pulvini. The vacuolar compartment contains two kinds of vacuoles: nontannin vacuoles, which change both in number and size during leaflet movement, and tannin vacuoles, which may act as an ion reservoir. No differences in wall thickness were found between flexor and extensor motor cells. Thick walls of collenchyma cells show numerous pits with plasmodesmata through which the phloem parenchyma cells and the inner cortical motor cells are connected. Tannin vacuoles and calcium oxalate crystals are common inclusions of phloem parenchyma cells. The tissue arrangement and the occurrence of pits with plasmodesmata in the central cylinder cells provide evidence of symplastic continuity through the central cylinder between the extensor and flexor regions of the motor organs. The greater amplitude ofRobinialeaflet movements may be related to the extension of motor regions, the scarcity of lignification in the central vascular core, and the thin flexor walls.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb11426.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

Many mosses occur both on and off serpentine soils, but experiments designed to test whether serpentine populations of widespread species display genetic adaptations for growth on serpentines have not been reported. Toward that end, two populations of the moss,Funaria flavicans, were grown on nutrient media varying in nickel and chromium concentration and in the ratio of magnesium to calcium. Three haploid siblings from each of five sporophytic families from the two populations were grown on five experimental media. There was no evidence that serpentine plants were more tolerant of nickel, chromium, high magnesium/calcium, or high nickel combined with high magnesium/calcium. In fact, plants from the nonserpentine population produced more protonemal growth than the serpentine plants on every medium except the control, on which plants from the two populations were indistinguishable. Large differences in nickel tolerance among haploid sib families (families of meiotic progeny derived from the same sporophyte) from the nonserpentine site provided evidence of genetic polymorphism in that population.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb11427.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

The relationship of differences in life history traits among genotypes to competitive ability is not well known for most clonal plants. It has been hypothesized that genetically identical clones will compete more intensively than genetically distinct clones. The perennial grassAmphibromus scabrivalvis, which produces basal corms and cleistogamous seeds enclosed by leaf sheaths, exhibits pronounced clonal growth via rhizome and ramet production. In a controlled greenhouse experiment, clones of four genotypes of this species were grown under three regimes: alone in the absence of competition, paired with a clone of the same genotype (intraclonal competition), and paired with a clone of a different genotype (interclonal competition). There were differences in some biomass measures and in ramet and corm production among the four genotypes grown in the absence of competition. All genotypes showed a significant reduction in total biomass under both intra‐ and interclonal conditions, indicating that competition had occurred. For three of four genotypes, biomass allocation to corm increased under competition, while allocation to cleistogamous seeds was constant or increased slightly. Although some genotypes in specific interclonal combinations were less affected by competition than in intraclonal combinations, there was no support for the contention that the effects of competition were more intense for genetically identical clones.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb11428.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

A technique using micronized metal powders was developed for both general labeling of pollen and marking of individual pollen grains. After labeling, pollen flow is analyzed by the use of backscatter scanning electron microscopy and X‐ray microanalysis. To test the efficiency and efficacy of the technique, we assessed differences in pollen distribution inSolanum rostratum, an enantiostylous species with dimorphic anthers which are putatively feeding and pollinating anthers. Pollen from each set of anthers was labeled using different micronized metal powders. We could not confirm the differentiation of functional anthers inS. rostratum.This technique provides an efficient and convenient method for tracking pollen movement within and between flowers, and anthers within a single blossom can be differentially marked.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb11429.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

To test whether sharing of resources occurs among connected ramets of the tall goldenrod,Solidago altissima, we examined the extent of clonal integration for nutrients. In a greenhouse experiment, two‐ramet clones were grown in a triad of connected pots so that nutrients could be supplied to either sister ramet or to their old rhizome (mother rhizome). Mother rhizomes and their associated roots shared nutrients with daughter ramets; however, any nutrient sharing that occurred between sister ramets was too little to significantly affect their growth. In addition, sister ramets not only competed for nutrients through parental connections, but larger ramets inhibited the growth of smaller ramets. We suggest that, for tall goldenrod, a clonal growth strategy in which nutrients are not shared among sister ramets may increase genet fitness by reducing the rhizome production of ramets in poor‐nutrient microsites. Consequently, the genet would produce relatively fewer ramets in unfertile areas and make better use of heterogeneous nutrient resources.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb11430.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

Douglas fir (Pseudotsuga menziesii[Mirb.] Franco) ovules were used to study male gamete formation, insemination of the egg, and free nuclear and cellular proembryo development. Two male nuclei form as the pollen tube either reaches the megaspore wall or as it enters the archegonial chamber. No cell wall separates them. They are contained within the body‐cell cytoplasm. A narrow extension of the pollen tube separates the neck cells and penetrates the ventral canal cell. The pollen tube then releases its contents into the egg cytoplasm. The two male gametes and a cluster of paternal organelles (plastids and mitochondria) migrate within the remains of the body‐cell cytoplasm toward the egg nucleus. Microtubules are associated with this complex. The leading male gamete fuses with the egg nucleus. The zygote nucleus undergoes free nuclear division, but the cluster of paternal organelles remains discrete. Free nuclei, paternal and maternal nucleoplasm, maternal perinuclear cytoplasm, and the cluster of paternal organelles migrate en masse to the chalazal end of the archegonium. There, paternal and maternal organelles intermingle to form the neocytoplasm, the nuclei divide, and a 12‐cell proembryo is formed. The importance of male nuclei or cells, the perinuclear zone, and large inclusions in cytoplasmic inheritance are discussed in the Pinaceae and in other conifer families. This completes a two‐part study to determine the fate of paternal and maternal plastids and mitochondria during gamete formation, fertilization, and proembryo development in Douglas fir.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb11431.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

There are numerous reports that cortical cells senesce in young, otherwise healthy main roots of cereals, including corn. These are based on apparent absence of nuclei in root segments or transverse sections after acridine‐orange staining. Senescence is said to progress from the outer to the inner cortex basipetally from the root tip, except cells around branch bases where nuclei always stain. We studied axile roots of soil‐grown cereals using various methods to detect nuclei primarily in longitudinal sections. No senescence marked by nuclear loss was found in healthy‐looking intact cortices. Cortical cells of mature corn roots remained alive except where aerenchyma developed. No cortical death had occurred in barley, wheat, or oat seminal roots in 15‐,17‐, and 20‐day‐old plants, respectively, but cortical cells in older regions of seminal and nodal roots did collapse and slough off, but with no evidence for earlier loss of nuclei. Failure to detect acridine‐orange‐stained nuclei may not indicate that cells are senescent, and can be an artifact caused by sectioning method and wall impermeability. The effectiveness of other methods for evaluation of root cell vitality is discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb11432.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

Septa from metabasidia and clamp connections of the heterobasidiomycetous sedge parasiteKriegeria eriophoriwere studied with light and electron microscopy. Septa from clamp connections subtending probasidia were reconstructed from serial sections. Septa at clamp connections are perforated by multiple, simple pores, while metabasidial septa possess single, central swellings which probably represent pores occluded by wall material. The occurrence of multiperforate septa in the fungi is reviewed. The septal morphology ofK. eriophoriis compared to that of simple‐septate heterobasidiomycetes, and the systematic and functional implications are discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb11433.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

Leaves ofSonchus oleraceus(Asteraceae) were examined with the electron microscope to determine plasmodesmatal frequencies and other structural features relating to the collection of photoassimilate and its subsequent loading into minor veins. Few plasmodesmata occur between mesophyll cells, which contain chloroplasts that are sometimes connected to both the plasmalemma and the tonoplast by membranous tubules. The minor veins consist of tracheary elements, sieve‐tube members, vascular parenchyma cells, and companion cells. The latter two cell types are transfer cells, with some of the fingerlike wall ingrowths in companion cells being traversed lengthwise by plasmodesmata. The frequencies of plasmodesmata at the mesophyllbundle sheath boundary and within are higher at some interfaces than at corresponding interfaces in nine other species, including some that previously had been characterized as loading assimilate via the symplast. It is thus premature to designate all species containing transfer cells in their minor veins as loading assimilate only via the apoplast.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb11434.x

出版商:Wiley    

年代:1991

数据来源: WILEY