摘要:

The strangler figs,Ficus pertusaandF. trigonata, are abundant in the seasonally flooded palm savanna (llanos intermedio) near Calabozo, Venezuela. The most common host tree for the hemiepiphytic figs is the palmCopernicia tectorum; nearly half of the palms support either an epiphytic or a ground‐rooted fig. During their epiphytic stage the figs are rooted behind the palms' marcescent leaf bases. Material trapped behind the leaf bases is higher in organic matter, nitrogen, magnesium, and potassium than soil from the ground near the palms. The suggestion that nutrient availability to epiphytes is high is supported by the observation that concentrations of several nutrients, including N, P, and K, are significantly higher in epiphytic leaves than in tree leaves. Figs retain access to the epiphytic medium by producing upwardly growing (apogeotropic) roots that remain attached in the host palm's crown long after the fig has become firmly rooted in the ground. Although upward growing roots are expected to be more important in nutrient than water uptake, there are no obvious differences in the xylem anatomy of upward and downward growing fig roots. Terrestrial roots of fig trees are generally infected with vesicular‐arbuscular mycorrhizae, but the epiphytic roots of the same individuals are not infected.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15056.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

Anatomical and physiological responses to drought stress were compared in twoMicroserisspecies differing in DNA content and originating from contrasting habitats relative to water availability (M. bigelovii, DNA = 2.6 pg nucleus–1, more xeric;M. laciniata, DNA = 6.8 pg nucleus–1, mesic). Leaf mesophyll cell volume was positively correlated with DNA content and negatively correlated with tissue elasticity, i.e., low ϵ̄ and thin cell walls. Drought stress increased leaf tissue elasticity (lower ϵ̄, thinner cell walls). Cell volume, cell wall thickness, cell number, and leaf area were decreased most by drought stress inM. laciniata.Osmotic adjustment with a 20% increase in total solutes (mostly amino acids) after stress was observed in both species, but their estimated contribution to the change in osmotic potential was larger inM. bigelovii.These findings indicate that theMicroserisspecies studied respond to low water availability by maintaining turgor with 1) small cell volumes, 2) elastic tissues (low ϵ̄, thin cell walls), and 3) osmotic adjustment. Both enhanced tissue elasticity and small cell volume appear to be inherent characteristics inM. bigeloviiand drought‐induced responses inM. laciniata.These data are compatible with the hypothesis that natural selection may influence DNA content through differential sensitivity of cell growth to environmental stress.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15057.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

Generic delimitation in the Triticeae has long been problematical because the extensive hybridization in the group is not readily accomodated in a hierarchical classification. The genomic genera of Löve (1984) are one solution, but fully one‐third of them are polyphyletic, incorporating 2 or more genomes. The suggestion that the tribe be considered a single genus (Stebbins, 1956) is theoretically defensible—the genus would be strictly monophyletic—but probably impractical. This paper presents a cladistic analysis of the tribe that differs from previous analyses in that it uses only strictly monophyletic (monogenomic) groups as terminal taxa; hybrids (heterogenomic groups) are shown as reticulations. Monophyletic groups can then be delimited to minimize the number of polyphyletic genera. A classification incorporating genomic information is derived from the phylogeny.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15058.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

The development of the inflorescence and flowers are described forGymnotheca chinensisDecaisne (Saururaceae), which is native only to southeast China. The inflorescence is a short terminal spike of about 50–70 flowers, each subtended by a small bract. There are no showy involucral bracts. The bracts are initiated before the flowers, in acropetal order. Flowers tend to be initiated in whorls of three which alternate with the previous whorl members. No perianth is present. The flower contains six stamens, and four carpels fused in an inferior ovary containing 40–60 ovules on four parietal placentae. Floral symmetry is dorsiventral from inception and throughout organ initiation. Floral organs are initiated in the following order: 1) median adaxial stamen, 2) a pair of lateral common primordia which bifurcate radially to produce two stamen primordia each, 3) median abaxial stamen, 4) a pair of lateral carpel primordia, 5) median adaxial carpel, 6) median abaxial carpel. This order of initiation differs from that of any other Saururaceae previously investigated. The inferior ovary results from intercalary growth below the level of stamen attachment; the style elongates by intercalary growth, and the four stigmas remain free. The floral structure ofGymnothecais relatively advanced compared toSaururus, but its assemblage of specializations differs from that of eitherAnemopsisorHouttuynia, the other derived genera in the Saururaceae.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15059.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

PermineralizedLepidostrobusspecimens were examined from the Westphalian A of England, Westphalian B (Breathitt) of the Appalachian Basin, and the Westphalian D (Desmoinesian) of the Illinois Basin and Western Interior Coal Region to correlate species of the dispersed spore genusLycosporawith source cones and cone types (“species”) with parent plants. Based on 51 specimens ofLepidostrobus oldhamiussensu Balbach, three cone types, producing three species ofLycospora, are recognized.Lycospora pellucidaoccurs in smaller diameter cones with a prominently coronate stele; cones are associated withLepidophloios harcourtiifrom the Westphalian A‐B.Lycospora pusillaoccurs in larger diameter cones with a small “pith” containing elongate, sclerified, tanniferous cells from Westphalian D coal balls. Secretory cells also are present in sporophyll trace sheaths and in subarchesporial parenchyma pads in sporangia. The suggested plant source isLepidodendron hickii. Lycospora granulataoccurs in large cones with a large “pith” composed of thin‐walled parenchyma; no secretory cells were observed in the “pith,” sporophyll traces, or subarchesporial pads. These cones are associated withLepidophloios halliifrom the Westphalian D. Association ofLycosporaspecies with source lycopods increases the possibilities of paleoecological interpretation using microspores from Carboniferous coals.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15060.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

The fagaceous genusTrigonobalanusas recently treated includes 3 species, two in Malaysia and Southeast Asia and a single species in Colombia, South America. Character analysis suggests that the genus as currently circumscribed is paraphyletic, without synapomorphies to unite the three species. Each of the three species is a morphologically distinct relict of a group that probably was ancestral to the modern generaQuercusandFagus.Each of the three species also has at least one autapomorphy which is unique within Fagaceae. Analysis of cupule morphology in Fagaceae provides an interpretation of evolution in cupules which differs substantially from Forman's interpretation. We interpret trigonobalanoid cupules as indicative of an ancestral type of inflorescence within Fagaceae. This inflorescence type is a dichasial structure in which the outermost axes are cupular valves, but the degree of branching and subsequent number of fruits are variable. Following this model, a strict relationship exists between valve number and fruit number as seen in cupules ofTrigonobalanus(valves = fruits + 1). Fossil evidence is consistent with our interpretation of the phylogenetic position of the trigonobalanoids. We propose to segregate the three species ofTrigonobalanusas three monotypic genera; two of these require names which we provide here:FormanodendronandColombobalanus.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15061.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

Fossil evidence of Fagaceae from the Paleocene/Eocene boundary of western Tennessee is described and discussed. These fossils include a newly discovered pistillate inflorescence and dispersed fruits of subfamily Castaneoideae as well as a taxon that resembles modern trigonobalanoids (pistillate inflorescences and dispersed mature fruits). Fossil staminate catkins with fagaceous pollen, which we suggest may be conspecific with the trigonobalanoid infructescences, are also found at the locality. Two distinct types of fagaceous leaves are present at the locality. The reproductive structures are the oldest megafossils unequivocally assignable to Fagaceae and represent the oldest remains of subfamily Fagoideae and the oldest megafossil remains of Castaneoideae. In addition, the fossils provide insights into the chronology of diversification, biogeography, and phylogeny of Fagaceae. The trigonobalanoid remains may also provide insights into the timing and circumstances of the evolution of wind pollination in Fagaceae.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15062.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

The proexine that forms within the callosic envelope before the end of the microspore tetrad period is thick (about 1μm) and exceptionally complex. It has components equatable with tectum, columellae, and a nexine that includes lamellar zones. All these components persist in the exine although late in development they become difficult to recognize because this exine is reduced in thickness, apparently by stretching, to a maximum of 0.2μm.Strelitziais an example of an exine template, with receptors for sporopollenin, that is not maintained during development. TheStrelitziamicrospore surface changes from an exine like that on an interaperture sector to the channeled intinelike system common for the apertures of pollen grains. The exine on sterile grains gives what may be a rare view of a stabilized immature exine. The mature exine on viable pollen grains resembles this early exine only in the most impressionistic way. Tapetal cells go through at least one cycle of hyperactivity, dedifferentiation, mitosis, and then again hyperactivity before they finally decline.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15063.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

6(5)carboxyfluorescein (6(5)CF), a polar fluorescein with an apparent pK of 6.3, was introduced, as a pH 6.3 solution, into the apoplast of lamina or petioles of mature soybean leaves. Freehand sections were prepared at various times and immediately observed with a fluorescence microscope. 6(5)CF‐associated fluorescence appeared in all sink organs, from shoot apex to roots. It was strictly confined to the phloem regions, even after 4 days. Its transport into young leaves ceased at approximately the time they underwent sink‐to‐source transition. It was never transported between two leaflets of the same leaf. Its transport was interrupted by phloem destruction. All these transport characteristics were highly reproducible, and were paralleled by those of14C transport after application of (14C)sucrose to leaf surfaces. In contrast with 6(5)CF, fluorescein was transported between mature leaves, and between leaflets of the same leaf. It was not restricted to phloem, and often appeared in the xylem region. These results indicate that 6(5)CF can be used to monitor phloem sap translocation in real time, in short‐ and long‐term experiments.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15064.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

Plants ofAcomastylis rossiiwere treated over a three‐year period with artificial acid mists of pH 2.5, 3.5, or 4.5 prepared with sulfuric acid or nitric acid. Treatments were made in the field twice weekly for eight weeks during each of the three growing seasons. Significant decreases in the percentage of plants flowering were noted in each year of the study in plants treated with sulfuric acid mist at pH 2.5. Significant decreases in flowering with sulfuric acid at pH 3.5 and in leaf number with sulfuric acid at pH 2.5 and 3.5 occurred in the third year of treatments as well. Some individual plants flowered in one, two, or three of the years, indicating that new floral primordia were being produced during the treatment period. Plants that flowered produced viable, germinable seeds. No effects of nitric acid mists were noted during the study period. Treatments with citrate buffer solutions (pH 6.2) used to determine if the plants were responding to sulfate independently of pH showed no significant differences for any of the measurements taken. The observed decreases in flowering are apparently a sulfuric acid effect and are not attributable to hydrogen ions or sulfate ions independently of each other. Experiments with plants that had visible floral buds indicate that plants aborted the floral structures in response to direct contact of buds with solution from the acid mists. The growth form of the plants enhances contact by causing pooling of the solutions on top of the developing buds in pockets formed by the basal leaves.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb15065.x

出版商:Wiley    

年代:1989

数据来源: WILEY