Library

Notes: Abstract The growth habit of the rosette plant Plantago lanceolata is highly variable, and many vegetative and reproductive traits co-vary. At one end of the range plants have relatively few but long and erect leaves, form few daughter rosettes, and produce a limited number of large spikes, with relatively heavy seeds. Plants at the other end of the range have the opposite characteristics. This suite of characters was shown to correlate with the height of the vegetation in mid-summer. The causes for this association between different traits were investigated in different experiments, with the following results:〈list xml:id="l1" style="custom"〉Plants from two contrasting habitats both react strongly to light intensity and the red to far-red (R/FR) ratio of the ambient light. Light intensity mainly affected plant size, whereas light quality affected the growth habit. Populations differ in their mean response rather than in the level of plasticity (i.e., slope of the reaction norms). Experiments show that genetic factors (population effects), R/FR ratio, and hormone treatments (GA or CCC) have similar effects on morphology, and are largely additive and interchangeable.Ten different populations were grown in a common garden, so that the genetic (clonal) correlation within populations, and their bivariate phenotypic means could be compared. Trait combinations which deviated in the same direction (both higher of both lower than the mean over all populations) on average had positive clonal correlations within populations, whereas combinations which deviated in opposite directions had negative correlations.Artificial selection on leaf length, performed under a high or a low R/FR ratio showed clear responses to selection, with heritabilities around 0.4. Correlated responses were found in many other traits, and genetic correlations were similar to the trait associations for the means of different natural populations. Correlated responses to selection depended on environmental circumstances. Under a high R/FR ratio (sun) evidence for a size/number trade-off was found for leaf length and leaf number. Under a low R/FR ratio, however, a trade-off between leaf length and leaf quality was found.In conclusion, the trait associations that are so characteristic for the growth habit in Plantago lanceolata are probably due to differences in hormone levels or activities. Genes and environmental factors affect growth habit in similar ways, by tapping into this regulatory mechanism. In the field, selection can lead to concerted changes in the mean of different traits, but changes in plasticity will be slow.

Notes: Zusammenfassung Zusammenfassend läßt sich feststellen: 1. Thyreotropes Hormon ist hitzeempfindlich und nicht ultrafiltrierbar durch eiweißdichte Ultrafeinfilter. KH.-Stoffwechselhormon im Ultrafiltratp H 5,3 ist thermostabiler, es zeigt sich jedoch bei längerem Erhitzen ein starker Verlust der Wirksamkeit (blutdrucksteigernde Wirkung). 2. Ultrafiltrate vorher thyreotrop wirksamer Extrakte lassen keine Wirkung auf die Schilddrüse im Meerschweinchentest erkennen. 3. Die glykogerimobilisierende Wirkung des thyreotropen Hormons, die regelmäßig nur nach mehrfacher Injektion nachweisbar ist, ist ebenso wie die Wirkung auf den Blutzucker rein thyreogen bedingt. Es besteht die Möglichkeit, daß sich in thyreotropen Präparationen geringe Mengen einer blutzuckersteigernden und glykogensenkenden Substanz befinden, die auch im Ultrafiltrat dieser Präparationen ihre Wirksamkeit behalten. Die bei Verwendung von Ultrafiltraten aus wässerigen HVL.-Acetontrockenpulverextrakten beobachteten Veränderungen im KH.-Stoffwechsel (Senkung des Leberglykogens, Steigerung des freien und gebundenen Blutzuckers, antiinsulare Wirkung) sind auf ein besonderes Stoffwechselhormon zurückzuführen. 4. Dem thyreotropen Hormon fehlt eine antiinsuläre Wirkung, Insulinwirkungsintensität und -dauer wird durch größere Dosen verstärkt. 5. Die Wirkung des Stoffwechselhormons ist auch beim thyreodektomierten Tier nachweisbar, während thyreotropes Hormon jede Wirkung vermissen läßt.

Notes: Abstract Plants from a sun and shade population were grown in two environments differing in the ratio of red to far-red light (R/FR ratio). A low R/FR ratio, simulating vegetation shade, promoted the formation of long, upright-growing leaves and allocation towards shoot growth, whereas a high R/FR ratio had the opposite effects. The increase in plant height under the low R/FR ratio was accompanied by a reduction in the number of leaves. Population differences in growth form resembled the differences between plants grown in different light environments: plants from the shade population had rosettes with long erect leaves, whereas plants from the sun population formed prostrate rosettes with short leaves. Plants from the shade population were more responsive to the R/FR ratio than plants from the sun population: the increases in leaf length, plant height, and leaf area ratio under a low R/FR ratio were larger in the shade population. However, differences in plasticity were small compared to the population difference in growth form itself. We argue that plants do not respond optimally to shading and that developmental constraints might have limited the evolution of an optimal response.