摘要:

Forty‐one chromosome counts are reported for 29 species of the flora of the Juan Fernandez Islands, Chile. Counts are provided for the first time forAzara(Flacourtiaceae),Cuminia(Lamiaceae),Dysopsis(Euphorbiaceae),Raphithamnus(Verbenaceae),Robinsonia(Asteraceae) andUgni(Myrtaceae). New species counts are inDendroserisandErigeron(Asteraceae),Eryngium(Apiaceae),Escallonia(Saxifragaceae),Haloragis(Haloragaceae),Libertia(Iridaceae),Myrceugenia(Myrtaceae),Pernettya(Ericaceae),Peperomia(Piperaceae),Spergularia(Caryophyllaceae), andWahlenbergia(Campanulaceae). The level of recent polyploidy and aneuploidy in the chromosomally known flora is each estimated conservatively at 6%. Almost all of the endemic lineages appear to have evolved at the same ploidy level from their polyploid mainland relatives. Furthermore, there is no evidence for chromosomal evolution by euploidy or aneuploidy within endemic genera. The level of ancient polyploidy in the endemic Juan Fernandez flora is estimated to be 66%. This high level correlates with the idea that many of the woody endemics (comprising nearly one‐half of the woody species in our chromosomal sample) have been derived paedomorphically from herbaceous perennial mainland ancestors in temperate, orogenetically active, Andean regions, in which high levels of polyploidy would be expected.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06415.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Onoclea sensibilisgametophytes grown on agar, unsterilized soil or ashed soil without the addition of antheridiogen developed antheridia after the notch meristem was formed. There was a linear increase in maleness through time on all three media. Antheridial production on agar was delayed nearly 3 wk. Agar had a significantly higher proportion of females than ashed soil or unsterilized soil. It was concluded that agar is an inappropriate medium for experiments on the mechanism of sexual development inOnocleagametophytes.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06416.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Excised pea embryonic axes were cultured on mineral salts plus various carbon sources. Growth continued for at least 3 wk, as measured by increased length, fresh and dry wt, sugar content, andβ‐amylase activity. The optimum sucrose concentration for elongation and fresh wt accumulation was 5% (w/v), although dry wt and sugar content increased in cultures containing 10 to 20%. Comparable growth was observed for axes cultured on 2% sucrose, glucose, fructose, or maltose.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06417.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Several methods were used to test the hypothesis thatα‐amylase activity in pea stem tissues is regulated by catabolite repression. The presence of various exogenous sucrose concentrations had little effect upon the accumulation and subsequent loss of enzyme activity in excised embryonic axes. Comparable results were observed for glucose, fructose, and maltose, and mixtures of sucrose and glucose. While growth and sugar accumulation was increased by culturing the axes in liquid medium, the activity was not reduced. Therefore the results of each procedure were inconsistent with the initial hypothesis. Preliminary experiments also demonstrated the lack of influence of sugars upon the in vitro activity of peaα‐amylase.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06418.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Root growth rate was studied inLemna gibbaL. (strains Gl and G3) andL. minorL. in relation to low energy red and far‐red light treatments. Far‐red treatments inhibited growth rate; inhibition was abolished upon subsequent treatment with red light. These effects can be observed after an 18‐hr growth period. This red/far‐red photoreversible response suggests that root growth inL. gibbaL. andL. minorL. is under phytochrome control.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06419.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Cochleanthes lipscombiaeis pollinated by large male and female euglossine bees. The flowers lack pollinator rewards, but attract bees searching for nectar. The euglossines extend their long tongues and crawl into the gullet‐flower. The bees probe the back‐swept lateral sepals for nectar. Pollination occurs as a pollinarium laden bee backs out, deposits pollinia on the stigma, and obtains a new pollinarium load by dislodging the anther. Some related orchid species have similar morphological characteristics as those essential to the pollination mechanism ofC. lipscombiae. These features may have taxonomic significance at the generic level.Cochleanthes lipscombiaemay be a floral mimic of a sympatric legume, but may also receive exploratory visits by bees searching for food resources. The latter may be young, recently emerged naive bees, or individuals seeking new nectar hosts during a period of rapid host species turnover.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06420.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

North American species of the grassDanthoniabear distinct chasmogamous and cleistogamous flowers. Four taxa occurring in North Carolina (D. compressa, D. epilis, D. sericea, andD. spicata) were examined for variation in the degree of cleistogamy. The flowering culms bear a single terminal panicle consisting of 4 to 12 spikelets of chasmogamous flowers. In each leaf axil, at the nodes of the flowering culm, is a single spikelet of cleistogamous flowers completely surrounded by the leaf sheath. The percentage of cleistogamous flowers produced on any culm depends on the number of chasmogamous and cleistogamous spikelets and the number of flowers in each type of spikelet. All four characters vary among the taxa examined.Danthonia compressaproduces, on the average, 50% cleistogamous flowers;D. spicata, 25% cleistogamous flowers;D. sericeaandD. epilis, 5% cleistogamous flowers. The degree of cleistogamy inD. spicatais associated with certain habitat features. Populations from mountain sites, disturbed sites, and non‐woodland sites produced higher percentages of cleistogamous flowers than did populations from piedmont, undisturbed, and woodland sites, respectively. Grazing may favor increased cleistogamy because cleistogamous flowers are produced lower on the plant. In North Carolina, the most frequently grazedDanthoniataxa also produce the highest percentage of cleistogamous flowers.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06421.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Sympatric populations ofPedicularis oederi, P. cystopteridifolia, andP. groenlandicaon the Beartooth Plateau (Montana) were obligately dependent onBombuspollinators. Their corolla colors were mutually distinct to insect vision, but their nectars had identical sugar components. Analysis of corbicular pollen loads of pollinating insects indicated a high degree of polylecty. Queen/worker ratios of pollinators on plant species corresponded to the parallel phenological sequences of plant blooming and insect caste development. The total number of individual pollinators of eachBombusspecies on all plants was directly related to the number of plant species it pollinated, but a comparable relationship between the number of pollinators on a plant species to the number ofBombusspecies pollinating it was not found. Morphological and behavioral correspondence of floral mechanisms and pollinators form an integral part of the general pattern of coadaptive evolution of the floral ecology ofPedicularisin North America known from previous studies. Reproductive isolation betweenPedicularisspecies in this study is attributed to internal barriers. Wide overlaps of blooming seasons, proboscis lengths of bumblebee species and castes, and pollinator species onPedicularisspecies suggest resource sharing, rather than resource partitioning or competition for resources among plant and insect species and individuals.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06422.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Water chemistry and titratable acidity and malic acid levels inIsoetes howelliileaves were sampled every 6 hr from plants in a seasonal pool and an oligotrophic lake. Plants in the seasonal pool showed a diurnal fluctuation of ~ 300 μequivalents titratable acidity g−1fresh wt; daytime deacidification was 75% complete by noon and nighttime acidification was 45% complete by midnight. Late in the season after the pool had dried, emergent leaves showed only a very weak tendency to accumulate acid at night. Plants from the oligotrophic lake had a diurnal change of ~100 μeq g−1fresh wt, daytime deacidification was only 45% complete by noon but nighttime acidification was 80%complete by midnight. Water characteristics were distinctly different between these two systems. In the seasonal pool there were marked diurnal changes in temperature, pH, oxygen and carbon dioxide. Free‐CO2levels were an order of magnitude greater in the early morning than in the late afternoon. In contrast, the conditions in the oligotrophic lake showed no marked diurnal fluctuation, though total inorganic carbon levels were extremely low relative to other aquatic systems.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06423.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Chromosome numbers were determined for 86Anthuriumspecies. Fifty‐one of these were newly determined with counts ranging from 2n= 24 to 66 and 30 being the most common. All knownAnthuriumchromosome numbers were summarized, and 43 taxonomic changes were made in the previous reports to reflect current taxonomy. In terms of somatic chromosome numbers, the numbers form four polyploid series of 20–40–60, 24–30–48–84, 28–56 and 30–60–90–ca. 124. Paleoaneuploidy, polyploidy and B‐chromosomes are basic features of the genus, but subsequent recent aneuploidy is not. The exact nature of chromosome evolution inAnthuriumremains to be elucidated.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06424.x

出版商:Wiley    

年代:1983

数据来源: WILEY