Entwicklungsphysiologie

An acidic (Fs) and a nearly neutral (Fn) protein fraction were extracted from the chromatin of calf thymus and pea seedlings. Both fractions are able to combine with protein-free DNA to form a complex, which, however, has a lower thermal stability than a DNA-histone complex. Fs and Fn inhibit root initiation in a similar manner as histone, actinomycin-D, streptomycin and 5-bromouracil do when these substances are applied to regenerating pea epicotyls during different times after culture initiation.Oxidized and thermally denaturated Fs and Fn inhibit root initiation less than untreated proteins do. Furthermore the treated proteins act in a more specific way on special steps of development such as root differentiation or root growth. In a very similar manner inhibition of root regeneration is also restricted to special developmental steps by treatment of Fs or Fn with small amounts (1 μg/ml) of IAA, GS or KI at pH≧8. With increasing acidity of the chromatin proteins treatment with IAA diminishes the inhibition of root growth, whereas root differentiation is preserved.The results support the suggestion that acidic and neutral proteins of the chromatin may act as regulators of DNA-activity as histone does. During IAA-induced root formation Fs acts as an antagonist to histone, because these two protein fractions are specialized in their action by IAA treatment in a contrary manner.

Hemmung der Wurzelneubildung durch saure und neutrale Kernproteine

Fellenberg

1969

Kennzeichnung der Bildung und Alterung von Wurzeln in Callus-und Organ-Kulturen von Daucus carota durch die Aktivit�t der Glutamatdehydrogenase

Werner

Gogolin

1970

In callus tissues of Daucus carota rhizogenesis was influenced by addition to the cultures of solutions with different kinetin concentrations (0-0.1-0.5-2 mg/l) and a constant auxin content (1 mg/l). In these cultures the specific activity of glutamate-dehydrogenase (E.C. 1.4.1.2.), aspartate-aminotransferase (E.C. 2.6.1.1.), isocitrate-dehydrogenase (E.C. 1.1.1.42) and of acid phosphatase (E.C. 3.1.3.2.) was determined. Before root initiation can be seen morphologically in tissues grown on low kinetin concentrations, the specific activity of glutamate-dehydrogenase increases to more than three times the level found in cultures with no subsequent root initiation, whereas the specific activity of the other three enzymes changes far less. Total soluble protein measured as percentage of fresh weight remains nearly the same in all callus cultures. The activity of the same enzymes was measured in liquid grown roots of Daucus carota during a period of ageing of 130 days. During this time, the specific activity of glutamate-dehydrogenase is reduced to 1/10 of the value found in growing roots, whereas the activity of the other three enzymes is reduced only to 1/2 or to 1/3 of this value. Therefore, the state of senescence and the capacity for further growth can be characterized by the specific activity of the glutamate-dehydrogenase in the roots. The changes in the specific activity of glutamate-dehydrogenase in callus tissue and in the roots do not depend on inhibitory substances in the cell-free extracts.

Ausl�sung der Bl�tenbildung bei der Langtagpflanze Hyoscyamus niger im Kurztag durch 2-Thiouracil

Eichhoff¹,

Rau²

1969

Aqueous solutions of 2-thiouracil (TU) were applied selectively either to the growing point or to the leaves of the long-day plant Hyoscyamus niger in order to determine whether this antimetabolite has an effect on the synthesis of the floral stimulus in the leaves. Applications to the growing point were made by means of a small glass tube covering the shoot apex; application to the leaves was performed by vacuum infiltration. In all experiments all leaves except the three youngest fully expanded leaves and the 8-10 youngest primordia were removed before application. Plants were recorded as having initiated flowers when flower primordia were visible under a dissection microscope 5 weeks after the experiment.TU was inhibitory to photoperiodic induction by long-days of 16 hours when applied to the growing point during the second 8 hours of the daily photoperiod. A concentration of 5·10(-3) M of TU fully suppressed flowering without significant inhibition of leaf primordia increment; however, leaves developing from treated primordia had reduced leaf blades. These results are in agreement with findings already published by other investigators.However, when the leaves were infiltrated by TU, the antimetabolite did not inhibit photoperiodic induction but on the contrary initiated flowering even under short-day conditions. This effect was investigated in more detail by repeated daily infiltrations of TU-solutions in concentrations of 10(-5)-10(-2) M during the second part of an 8 hour photoperiod up to 5 following days. Even after one single infiltration of a 10(-4) M solution 18% of the treated plants were flowering; the percentage of flowering plants increased with increasing concentrations of TU and number of days of application up to approximately 80%. In no case was a flower initiation of 100% obtained. Leaves developing from primordia after infiltration of the leaves with TU have reduced and deformed leaf blades, indicating that TU is transported to the shoot apex to some extent.Some possible explanations of this inductive effect of TU were tested experimentally. Oxygen uptake of the leaves was not decreased and the respiratory quotient was not affected by TU. Photoperiodic induction is not stimulated by low concentrations of TU when applied to the growing point. Infiltration of the leaves by solutions of 2,4-dinitrophenol (10(-4) M) and sodium azide (10(-3) M) had no inductive effect under short-day conditions; a single complete defoliation (except for the 8-10 youngest primordia) is also not inductive. Under short-day conditions additional leaves remaining on the plant that were not infiltrated by TU decreased the percentage of flowering plants but did not fully suppress flower initiation.From these results it is concluded that TU does not act by inhibition of particular metabolic processes concerned in flower initiation or by inhibition of the synthesis of an inhibitor. We suggest that application of TU may lead to synthesis of a floral stimulus in the leaves under short-day conditions also.