Notizen: An attempt was made to identify some of the hormonal factors that control adventitious root formation in our Prunus avium micropropagation system in order to improve rooting in difficult-to-root genotypes. Changes in endogenous contents of free polyamines were determined at intervals during auxin-induced rooting of shoot cultures. Accumulation of putrescine and spermidine peaked between days 9 and 11. Spermine was only present in traces, Exogenously supplied putrescine or spermine (50-500 μM), in the presence of optimal or suboptimal levels of indolebutyric acid (IBA), had no effect on rooting percentage or root density, except for spermine at 500 μM. At this external concentration spermine caused a substantial accumulation in both free spermine and putrescine. The use of several inhibitors of polyamine biosynthesis, namely α-difluoromethylornithine (DFMO), α-difluoromethylarginine (DFMA), dicyclohexylammonium sulphate (DCHA) and methylglyoxal-bis-guanyl-hydrazone (MGBG) alone or in combination in the 0.1 to 5 μM range, resulted in an inhibition of rooting that was partially reversed by the addition of the corresponding polyamine. Cellular polyamine levels were significantly reduced by DFMO and DFMA but not by DCHA and MGBG, Labeled putrescine incorporation into spermidine increased somewhat in the presence of the ethylene synthesis inhibitor aminoethoxyvinylglycine (AVG). A system based on [3,4-14C]methionine incorporation was used to measure ethylene synthesis by the in vitro cultured shoots. Label incorporation was drastically reduced by 10 μM AVG and increased 3.5-fold in the presence of 50 μM IBA with respect to controls (no IBA). Labeled methionine incorporation into spermidine increased to some extent when ethylene synthesis was inhibited by AVG. Adding the ethylene precursor 1-aminocyclopropane-l-carboxylic acid (ACC) to the rooting medium significantly inhibited rooting percentage; AVG caused the formation of a greater number of roots per shoot but delayed their growth. Supplying the shoots with both compounds resulted in an intermediate rooting response, in which both rooting percentage and root density were affected. These results indicate that polyamines may play a significant role at least in some stages of root formation. The polyamine and ethylene biosynthetic pathways seem to be competitive but under our conditions, the enhancement of one pathway when the other was inhibited, was not dramatic. Although IBA promoted ethylene synthesis, AVG, which drastically reduced it, also promoted root formation. Thus, the auxin effect on root induction cannot be directly related to its ability to enhance ethylene synthesis.

Notizen: Ornithopus sativus Brot.), a cool-season annual forage legume adapted to acid soils. Serradella was established on a Dystric Eutrochrept soil with pH 5.4 in Mabegondo, northwestern Spain, for three consecutive years (1990–1992). Shoot samples were taken at approximately biweekly intervals in the spring and summer following autumn seeding, and were separated into stems, leaves, and seed pods. Dry matter (DM) accumulation, crude protein (CP), acid-detergent fiber (ADF), and in vitro organic matter digestibility (IVOMD) were determined for each plant part at each stage. Average annual DM production at initial flowering was 5.1 Mg ha-1, and the CP, ADF, and IVOMD concentration were 163, 279, and 750 g kg-1, respectively. The rates of nutritive value decline with age coincided with a reduction in leaf-to-stem ratio (from a range of 1.91 to 2.85 at vegetative stage to 0.2 at ripe seed stage) and appear lower than the rates reported for other legumes, possibly because of the long indeterminate flowering period. We concluded that the nutritive value parameters of serradella indicate that this legume has a forage quality comparable to other leguminous crops and, if seeded in double-cropping systems (as is done in some Atlantic coastal areas of southern Europe, where it is harvested around initial flowering), it can provide forage of good quality.