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Results for “Ranunculus”

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114 records · Page 7Linked to original sources
PubMed2006

Growth onset, senescence, and reproductive development of meadow species in mesocosms exposed to elevated O3 and CO2.

We studied the effects of elevated O3 (40-50 ppb) and CO2 (+100 ppm) alone and in combination on the growth onset, relative chlorophyll meter values, and reproductive development of meadow species grown in ground-planted mesocosms using open-top chambers. The 3-year study was conducted in the summers of 2002-2004. Elevated O3 decreased the early season coverage of plant communities and delayed the flowering of Campanula rotundifolia and Vicia cracca. The relative chlorophyll meter values of Fragaria vesca leaves were decreased by O3. Ozone also reduced the overall number of produced flowers, but as far as individual species were concerned, O3 had significant effects only on Campanula rotundifolia. In the case of Fragaria vesca, O3 decreased the fresh weight of individual berries. The effects of CO2 were less pronounced, and CO2 generally did not ameliorate the negative effects of O3. Changes in reproduction may affect the long-term fate of the whole community.

Agrostis↗
PubMed2003

Inhibition of the gravitropic bending response of flowering shoots by salicylic acid.

The upward gravitropic bending of cut snapdragon, lupinus and anemone flowering shoots was inhibited by salicylic acid (SA) applied at 0.5 mM and above. This effect was probably not due to acidification of the cytoplasm, since other weak acids did not inhibit bending of snapdragon shoots. In order to study its mode of inhibitory action, we have examined in cut snapdragon shoots the effect of SA on three processes of the gravity-signaling pathway, including: amyloplast sedimentation, formation of ethylene gradient across the stem, and differential growth response. The results show that 1 mM SA inhibited differential ethylene production rates across the horizontal stem and the gravity-induced growth, without significantly inhibiting vertical growth or amyloplast sedimentation following horizontal placement. However, 5 mM SA inhibited all three gravity-induced processes, as well as the growth of vertical shoots, while increasing flower wilting. It may, therefore, be concluded that SA inhibits bending of various cut flowering shoots in a concentration-dependent manner. Thus, at a low concentration SA exerts its effect in snapdragon shoots by inhibiting processes operating downstream to stimulus sensing exerted by amyloplast sedimentation. At a higher concentration SA inhibits bending probably by exerting general negative effects on various cellular processes.

Acetic Acid↗
PubMed2005

Biogeographic interpretation of splits graphs: least squares optimization of branch lengths.

Although most often used to represent phylogenetic uncertainty, network methods are also potentially useful for describing the phylogenetic complexity expected to characterize recent species radiations. One network method with particular advantages in this context is split decomposition. However, in its standard implementation this approach is limited by a conservative criterion for branch length estimation. Here we extend the utility of split decomposition by introducing a least squares optimization technique for correcting branch lengths that may be underestimated by the standard implementation. This optimization of branch lengths is generally expected to improve divergence time estimates calculated from splits graphs. We illustrate the effect of least squares optimization on such estimates using the Australasian Myosotis and the Hawaiian silversword alliance as examples. We also discuss the biogeographic interpretation and limitations of splits graphs.

Boraginaceae↗