摘要:

Restionaceae are characterized by Polygonum‐type development, a well‐developed hypostase, the presence of starch grains in the mature female gametophyte, and a thick nucellus that is uniseriate at the micropylar end.Flagellaria indicadiffers in these characters. In general, proliferation of antipodals occurs in South African taxa of Restionaceae but not in Australasian taxa. The presence of multiplied antipodals is the usual condition in the allied family Poaceae, but the sporadic occurrence of this character in Restionaceae cannot be used to support the view that the two families are sister groups.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11258.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

The quantitative and qualitative changes in the contents of foliar secretory cavities during development ofTagetes erectaCV. Moonshot plants were determined. Separation of the secretory components by HPLC yielded three major compounds, subsequently identified by mass spectroscopy, UV spectra, and cochromatography as indole, piperitenone, and piperitone. Comparison of extracts from isolated cavities vs. lamina without cavities showed that in all cases the components were absent from lamina tissues. The quantities of indole and piperitone, in general, increased as the plants developed up to the stage of early flowering, when there was a reduction in total content. At late flowering, the amounts of these components, once again, increased. Concomitantly, the amount of piperitenone decreased during plant development. At all ages studied, indole comprised at least 99% of the total secretion product. This is the first report of the secretory components being restricted to the cavities.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11259.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Seeds of pokeweed (Phytolacca americanaL.), an underinvestigated species, were studied to determine optimal conditions for laboratory germination. Soaking seeds in acid solutions prior to sowing increased rates of germination. Concentrated (conc) H2SO4was more effective than conc NO3or conc HCl acids. Physiological evidence from seed germination studies suggests that autotoxicity, or intraspecific inhibition, exists in pokeweed, a species known to possess several biologically active compounds. Seed germination was investigated in the laboratory with aqueous extracts of vegetative and reproductive structures of the plant. The presence of extracts from most plant parts correlated with reduced or no germination by seeds of its own species, whereas the presence of distilled water correlated with high percentages of germination by control seeds. Whether diluted with water by 5‐fold (20% v/v) or undiluted, juice of pokeweed fruits completely inhibited the laboratory germination of pokeweed seeds. Also, extracts of freshly harvested mature leaves, stems, and immature fruits inhibited seed germination. However, results with root extracts, obtained from a single individual, depended more on concentration, since the highest concentration (50% v/v) inhibited germination, and lower concentrations (10 and 20% v/v) increased germination percentages over control samples. Results with extracts of juvenile leaves correlated with neither inhibition nor promotion of germination. Thus, except for juvenile leaves and the root, most extracts of the pokeweed plant inhibited seed germination with more mature structures exerting more inhibition and less mature structures exerting less or no inhibition. The ecological implication of autotoxicity is that seeds are more dispersed through time and space. In regard to seed germination by other species, especially those taxa known to possess biologically active compounds, these and other results suggest that the phenomenon of autotoxicity might be more widespread than previously suspected.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11260.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Fire acts as a strong flowering stimulus forHypoxis sessilisandHypoxis wrightiiin southern Florida. Flowering intensity reaches a peak during the period 6–12 weeks postburn. Thereafter, reproductive activity decreases and follows a seasonal pattern with maximum intensity observed during the summer months. Some plants in each population are reproductively active throughout the year. In addition to increasing reproductive intensity, fire also influences the morphology of the inflorescence. Those inflorescences produced shortly after the burn are larger, more likely to have two flowers, and have chasmogamous flowers. Within three weeks after the start of flowering, all flowers produced by the plants are cleistogamous. Inflorescence size decreases soon afterward. Easy recognition of the two species is hampered by this morphological plasticity, but they retain enough distinguishing characteristics in southern Florida to be considered separate species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11261.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

The phenology of pollen release and pollen capture byPistacia verawas studied in the field and laboratory respectively. Inflorescences ofPistacia verawere examined in a wind tunnel to determine whether the behavior of airborne conspecific pollen around receptive flowers differed as a result of changes in the shape and size of the inflorescence. In addition, the behavior of unclumped (single) and clumped pollen grains was studied to determine differences in the probability of their capture. Wind speeds within a commercial orchard during pollen shedding averaged 0.9–2.2 m/sec and atmospheric pollen concentrations were highest between 0900–1100 hr MST. Each of three stages in inflorescence development (defined on the basis of the number of exserted stigmas) was examined under identical ambient airflow conditions with equal concentrations of airborne pollen (1,000 grains/m3). The general pattern of pollen grain motion involves direct inertial collision by windward surfaces and by sedimentation of pollen onto leeward surfaces; clumped pollen rarely sedimented onto leeward surfaces. Small changes in ambient wind speed (0.5 m/sec to 1.0 m/sec) produced significant changes in the pattern of pollen motion around inflorescences and altered the number of pollen grains captured by leeward surfaces. Thus, wind pollination inP. verais affected both by windspeed and by the shape or size of flower clusters. Differences in the behavior of clumped and unclumped pollen result from their inertial properties and responsiveness to local changes in the direction and speed of airflow. Unclumped pollen has a higher probability of being captured by leeward surfaces. The apparent insensitivity of pollen motion to differences in inflorescence size may ensure equitable pollination during the acropetal development of flowers.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11262.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

We studied the perennial vinePassiflora incarnataLinnaeus (Passifloraceae) in Alachua County, Florida, from May to August 1983 to determine the breeding system and investigate seasonal changes in phenotypic gender of individual plants.Passiflora incarnatais an obligate outcrosser, incapable of self‐fertilization. The major pollinators were carpenter bees (Xylocopasp.). The proportion of flowers setting fruit was not limited by pollinator service, but the weight of individual fruits and number of seeds/fruit was increased over naturally pollinated flowers by manually performing cross‐pollination. Morphological differences in style position among flowers caused some flowers to function primarily as males and others to function as hermaphrodites. Although some of the flowers that functioned as males set fruit when manually cross‐pollinated, the proportion of these male flowers capable of setting fruit was lower than the proportion of hermaphroditic flowers setting fruit when manually cross‐pollinated. Further, some male flowers had atrophied ovary and styles and were completely incapable of setting fruit.Passiflora incarnatais thus functionally andromonoecious. The relative production of male versus hermaphroditic flowers varied among individuals and over the course of the flowering season. Unmanipulated plants in the population became increasingly male‐biased in floral sex ratios as the reproductive season progressed. We attempted to modify phenotypic gender in experimental plants by limiting the ability of plants in some treatment groups to set fruit. Treatment groups significantly affected production of hermaphroditic flowers, but production of male flowers was not affected by treatment. Treatment did not significantly affect fruit weight, number of seeds per fruit or the percentage of hermaphroditic flowers that successfully matured fruit. These results suggest that andromonoecy inP. incarnatais a mechanism for adjusting allocation of reproductive effort to male and female function, and that maternal investment in this species is regulated primarily by varying production of hermaphroditic flowers.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11263.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

We examined the effect of defoliation on gender expression and fruit set in a north‐central Florida population of the andromonoecious vine,Passiflora incarnata, during the 1984 flowering season. At three times during the flowering season (May, June, July), the leaves adjacent to flowers at four stages of development were removed, and subsequent sex and fate of each flower were determined. Defoliation affected gender of the flower by significantly decreasing the probability that the styles of the flower would deflex and the flower would thus function only as a pollen donor. Flowers were sensitive to defoliation at any stage before anthesis, though the sensitivity appeared to decrease in the most mature category of flower buds. Fruit set of hermaphroditic flowers remained unaffected by defoliation, but the probability of fruit set and gender expression were significantly influenced by the time of the flowering season. We conclude that the local photosynthate environment determines flower gender inPassiflora, but branch or entire plant photosynthate resources can compensate for local resource fluctuations and play an important role in fruit set and flower bud abortion. The sexual lability ofPassiflora incarnataappears to be an adaptation to uncertain resource levels at a fine scale, caused by nearby developing fruits and the possibility of herbivore defoliation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11264.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Microtubule arrays associated with simultaneous cytokinesis in the coenocytic microsporocytes ofLonicera japonicaandImpatiens sultaniwere studied by indirect immunofluorescence. The future division planes are not predicted prior to meiosis by either a preprophase band of microtubules or cytoplasmic lobing. Cleavage planes appear to be determined by position of the four haploid nuclei and the development of postmeiotic microtubule systems. Perpendicular second division spindles inLoniceraresult in tetrahedrally arranged tetrads while parallel spindles inImpatiensresult in tetragonal arrangement. Immediately following meiosis bands of microtubules, the secondary spindles, develop between both sister and nonsister nuclei. These arrays give way to systems of microtubules that radiate equally from each of the four nuclei in the coenocytic sporocyte. Simultaneous cytokinesis is initiated by centripetal wall deposition at the periphery of the sporocyte and proceeds along planes marked by interaction of the opposing arrays of nuclear‐based microtubules.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11265.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Eucharis, Caliphruria, andUrceolinaform a monophyletic group of petiolate‐leaved, Neotropical Amaryllidaceae ecologically specialized to the understory of primary tropical rain forest below 2,000 m elevation. Pollen morphology of the three genera is surveyed. Pollen grains of all species ofEucharis, Caliphruria, andUrceolinaare boat‐shaped elliptic, monosulcate, heteropolar, and bilateral in symmetry. Exine sculpturing is semitectate‐columellate and reticulate in all species examined. A transformation series in reticulum coarseness and pollen grain size is described. The large pollen grain with coarse reticulum of mostEucharisspecies is considered ancestral. The fine reticulation ofCaliphruriais considered derived and the exine morphology ofUrceolinais intermediate. Both of these genera have medium‐sized pollen grains. Exine dimorphism common to allUrceolina, but rare inEucharisandCaliphruria, may be symplesiomorphous among those taxa exhibiting this morphology. The three genera are largely uniform in pollen grain ultrastructure, with completely ektexinous exines. Pollen grain size inEucharisis not closely correlated with style length. Several wide‐ranging species show considerable intraspecific variation in pollen size. Parallelisms in pollen grain evolution among related tribes of Neotropical Amaryllidaceae are discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11266.x

出版商:Wiley    

年代:1988

数据来源: WILEY

摘要:

Tuckermannopsis pinastriis a lichen species found commonly on rocks and tree branches in boreal and alpine habitats in the northern United States. Members of this species produce three yellow‐pigmented phenolic compounds: usnic, pinastric, and vulpinic acids. The objective of our study was to quantify the variation in concentration of the latter two of these compounds in relation to substrate factors, chlorophyll content, and thallus size. Using high‐performance liquid chromatography, we analyzed 120 thalli ofT. pinastricollected randomly from a single large population located at Spruce Knob, West Virginia. Although individuals were sampled from both tree and rock substrates that differed markedly in light intensity, these environmental factors were not correlated with observed variations in vulpinic or pinastric acid concentrations. Instead, compound concentrations were correlated most closely with thallus size, with small rather than large thalli having the highest concentrations of the two compounds. Small thalli did not have higher concentrations of chlorophylls than large thalli, however, which suggests that the rate of production of secondary compounds by the fungus inT. pinastriis independent of algal biomass. Inasmuch as lichen secondary compounds serve a defensive role against microorganisms and herbivores, our results suggest that small, juvenile thalli are better defended than more mature thalli.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1988.tb11267.x

出版商:Wiley    

年代:1988

数据来源: WILEY