Arno Tietz

Effect of abscisic acid on the transport of assimilates in barley

The effect of abscisic acid (ABA) on assimilate transport in barley was investigated in two parallel experiments. First, the effect upon [14C]sucrose transport from the flag leaf to the ear of a single ABA application made at different stages of growth of the fruits was investigated; the effect was measured 24 h after treatment. Second, the effect of a single application of ABA made at the same stages of growth as above on grain weight of the mature plant was investigated. In both types of experiments ABA was applied once to the ear of different plants as an aqueous solution (10-3–10-5 M), one to five weeks after anthesis. [14C] sucrose was applied by means of agar blocks. Parallel to these experiments, the endogenous content of ABA was investigated in the developing grains. When ears were treated with ABA two or four weeks after anthesis, an increase of up to 70% in the 14C-transport from the flag leaf to the ear was observed within a 24-h period after treatment (short duration experiments). At these growth stages the endogenous concentrations of ABA were low. In sharp contrast, ABA, especially in a concentration of 10-3 M, decreased 14C-import from the flag leaf when applied three weeks after anthesis. At this stage the endogenous ABA content had reached its maximum. Long duration experiments with a single application of ABA to the car two weeks after anthesis resulted in a marked increase of weight per thousand kernels. ABA applications made earlier or later than two weeks after anthesis either reduced the grain weight or had no effect. It is concluded that ABA is involved in the regulation of assimilate transport from the leaves to the grains, possibly by influencing the unloading of sieve tubes in the ears. Promotion or inhibition of assimilate import by exogenously applied ABA may depend on the developmental stage of the grains and on the endogenous ABA level.

Further Investigations on the Occurrence and the Effects of Abscisic Acid in Algae

Summary After abscisic acid (ABA) had been detected in the green alga Stigeoclonium a much wider occurrence of the hormone in other green algae e.g. Dunaliella parva, Chlamydomonas reinhardii, Ulva lactuca, Draparnaldia mutabilis and Chara foetida could be demonstrated by combined GC-MS. The effect of exogenously applied ABA in the concentration range of 10 -7 -10 -5 M on batch cultures of Stigeoclonium cf. tenue was rather small. 3 weeks after application, a slight reduction of growth was caused by ABA, and in some cases, senescence was promoted. In order to investigate the effects of salt stress on endogenous ABA levels batch cultures of Dunaliella parva (halotolerant ecotype) and Draparnaldia mutabilis (halophobe ecotype) were treated with various NaCl-concentrations. When 85.5 mM NaCl were added to the culture medium the ABA concentration of Draparnaldia cultures increased to the tenfold within a week. On the contrary, in Dunaliella the ABA level is lowest at 1.5 M NaCl. This salt concentration is regarded optimal for e.g. photosynthesis of Dunaliella .

Nachweis von Abscisinsäure in Wurzeln

Twenty-day-old pea roots were extracted with methanol. Abscisic acid could be detected in the root extract by use of UV- and ORD-spectra.SummaryTwenty-day-old pea roots were extracted with methanol. Abscisic acid could be detected in the root extract by use of UV- and ORD-spectra.

Sterin-Glukoside: Eine gruppe pflanzlicher wirkstoffe mit biphasischer dosiswirkungskurve

Summary Earlier investigations had demonstrated that steryl-glucosides may stimulate growth in the Avena coleoptile bioassay ( Kimura et al., 1975). As it was now possible to obtain synthetic substances in larger amounts, the effects of sitosteryl-, campesteryl-, stigmasteryl- and cholesteryl-glucosides were tested over a wide range of concentrations on the growth of Avena -coleoptiles, on the germination of cress seeds ( Lepidium sativum L.) and on the H + -efflux of protoplast suspensions prepared from leaves of Vicia faba L. Avena -assay: concentrations from 0.4 to 200 ppm of steryl-glucoside were tested, in some cases with the addition of 1 ppm IAA. Fig. 2 shows that the dose response curves were mostly biphasic and that the 4 substances tested yielded similar results. Addition of IAA did not markedly change the shape of the curves in relation to the behavior of the control. To explain such dose response curves it is necessary to postulate a multisite system at the site of action, which might be the outer cell membrane. Germination: the percentage of germination was not markedly affected by steryl-glucosides applied in the same concentrations as in the Avena -assay. However the lengths of shoots and roots of 3 days old cress seedlings revealed dose response curves similar to those obtained in the Avena coleoptile test (Fig. 4). Protoplasts: if the mode of action of steryl-glucosides is similar to that of IAA, it must be possible to demonstrate a H + -efflux at the cell membrane. Therefore steryl-glucosides (40 ppm) were applied to a protoplast suspension containing 0.35 M D-mannitol and pH changes were recorded continuously. The results show that already 1.5 hours after application a marked drop in pH was detectable, whereas the pH of the control increased slightly over a period of approximately 7 hours. As the solutions appear to be slightly buffered, it must be born in mind that H + -efflux begins before the first changes can be measured. Addition of 10 −4 M IAA accelerates the efflux of H + , whereas 10 −4 M 2,4-dinitrophenol applied 1 hour prior to the application of the steryl-glucosides inhibits acidification (Fig. 6). As sterols are probably involved in the structure of biological membranes, it is concluded that steryl-glucosides and IAA may act in a similar manner at the outer cell membrane, inducing changes in permeability and hydrogen-ion secretion. It may be that steryl-glucosides or sterols themselves are a kind of secondary messenger affected by hormones, for example by IAA.

Abscisinsäure und Keimlingswachstum

Summary Pea seedlings were cultivated in tap water, which contained mineral nutrients and abscisic acid (ABA). In some cases, GA 3 was applied to the shoot apex (0.5 μg/plant). In the beginning of application, ABA (0.1 and 1 mg/l) promotes shoot growth. Later on it is inhibitory. 2 mg/l ABA always retard shoot growth. The interaction between ABA and GA 3 often shows a synergistic effect that means, ABA intensifies the growth promotion resulting from GA 3 treatment. Ether extracts from 16 days old pea shoots, treated with 2 mg/l ABA, contain about 43 % more ABA than from untreated controls. The longitudinal growth of roots is inhibited by ABA, but the number of lateral roots and of root hairs is increased. Concentrations of 1 or 2 mg/l ABA form roots looking yellowish, stunted, and rather thick.

Der Einfluß von Licht auf Wachstum und Abscisinsäuregehalt der Erbsenwurzel

Summary Roots of pea seedlings, growing in a water culture, were illuminated by white fluorescent lamps. One or two weeks after the beginning of illumination, the roots were analysed morphologically, the content of endogenous abscisic acid (ABA) was determined by means of gas liquid chromatography, and the results were compared with those of control roots growing in the dark. It could be demonstrated that in most cases light causes an inhibition of longitudinal growth of the roots. The absolute number of lateral roots decreased, however, in relation to the length of the main root, the number of laterals was increased one week after illumination. The diameter of roots growing in the light was greater than the diameter of the controls (dark-grown roots). The quantitative determination of the abscisic acid content showed that light causes a marked increase of the ABA-concentration in roots: Since application of synthetic ABA (T ietz 1973) causes similar effects as the illumination of roots, it is concluded that ABA is at least partly involved in the light-dependent morphological changes of root growth.

Veränderungen im Gehalt von Abscisinsäure und Indol-3-essigsäure sowie der Chloroplastenfarbstoffe in Pisumkeimlingen durch Gibberellinsäure

Twelve-day old pea seedlings were treated with gibberellic acid (GA3). The hormone was applied to the apical bud in quantities of 0.05, 0.5, and 5 μg in 5 μl droplets.After 2 and 4 days the contents of indoleacetic acid (IAA) and abscisic acid (ABA) of the apical parts (apical bud including the 5th internode) and of the basal parts (3rd and 4th internode and leaves) were estimated by means of paper chromatography of ether extracts and bioassay with avena coleoptile segments. In addition, the contents of ABA were checked by spectropolarimetric measurement.Apical parts of the gibberellin treated plants contain more IAA, basal ones less IAA than the untreated controls. On the other hand, the contents of ABA are higher in basal parts and lower in apical parts. Only the seedlings treated with 5 μg GA3 and analysed after 2 days do not follow this rule. Their apical parts contain not only more IAA but also more ABA than the untreated plants, and their basal parts contain more IAA than the controls.It is concluded, therefore, that GA3 causes changes not only in the contents of these hormones but also in the distribution of hormones within the plant.Moreover, GA3 decreases the contents of chlorophyll a and b and of the carotenoids. The changes in carotenoid contents do not seem to be related to the changes in abscisic acid contents.SummaryTwelve-day old pea seedlings were treated with gibberellic acid (GA3). The hormone was applied to the apical bud in quantities of 0.05, 0.5, and 5 μg in 5 μl droplets.After 2 and 4 days the contents of indoleacetic acid (IAA) and abscisic acid (ABA) of the apical parts (apical bud including the 5th internode) and of the basal parts (3rd and 4th internode and leaves) were estimated by means of paper chromatography of ether extracts and bioassay with avena coleoptile segments. In addition, the contents of ABA were checked by spectropolarimetric measurement.Apical parts of the gibberellin treated plants contain more IAA, basal ones less IAA than the untreated controls. On the other hand, the contents of ABA are higher in basal parts and lower in apical parts. Only the seedlings treated with 5 μg GA3 and analysed after 2 days do not follow this rule. Their apical parts contain not only more IAA but also more ABA than the untreated plants, and their basal parts contain more IAA than the controls.It is concluded, therefore, that GA3 causes changes not only in the contents of these hormones but also in the distribution of hormones within the plant.Moreover, GA3 decreases the contents of chlorophyll a and b and of the carotenoids. The changes in carotenoid contents do not seem to be related to the changes in abscisic acid contents.Zusammenfassung12 Tage alte Erbsenkeimlinge erhielten je 5 μl einer wäßrigen GA3-Lösung (0,05, 0,5 und 5 μg GA3) zwischen die jüngsten Blätter. Nach 2 und 4 Tagen wurden die Sproßspitzen und die im Wachstum nicht beeinflußten Sproßbasen getrennt auf ihren Gehalt an Indol-3-essigsäure (IES) und Abscisinsäure (ABS) untersucht.In Sproßspitzen von gibberellinbehandelten Keimlingen ist ein im Vergleich zu unbehandelten Kontrollpflanzen erhöhter IES-Gehalt nachweisbar, während die basalen Sproßteile weniger IES enthalten. Der Abscisinsäuregehalt ist dagegen in den Sproßspitzen gibberellinbehandelter Keimlinge verringert, in den Basen erhöht. Eine Abweichung von dieser Regel ergibt sich bei Keimlingen, die 2 Tage nach Applikation der für das Wachstum überoptimalen Gibberellinmenge 5 μg untersucht wurden. Diese enthalten in apikalen und basalen Teilen sowohl mehr IES als auch mehr ABS im Vergleich mit Kontrollpflanzen.Gibberellinsäure bewirkt auch eine Verminderung des Chlorophyll-und Carotinoidgehaltes. Ein Zusammenhang zwischen der Veränderung des Carotinoidgehaltes und des Abscisinsäuregehaltes wurde nicht gefunden.

Die Wirkung von Gibberellinsäure und Abscisinsäure auf den Gehalt an Chloroplastenfarbstoffen bei Erbsenkeimlingen

Summary Five-day old pea seedlings, growing in a water-culture, were treated with abscisic acid (ABA) via the roots and with gibberellic acid (GA3) on the shoot apex. The hormones were applied alone or in combination. When the seedlings were 13 days old the shoots were extracted and the chloroplast pigments checked by means of a spectrophotometer. ABA and GA3 both decrease the contents of chlorophyll a and b and of the carotenoids. The combination of the two hormones shows a synergistic effect.

Verlagerung von 14C-Saccharose aus den Kotyledonen von Helianthus-Keimlingen unter Einfluß von Abscisinsäure

Summary The influence of apical applications of abscisic acid (ABA) on the translocation of 14 C-sucrose from the cotyledons was investigated in sunflower seedlings. It could be demonstrated that 10 −4 M ABA induced a significant reduction of 14 C-content in apical plant sections near the ABA application site (repulsion). On the other hand, 10 −6 M ABA, especially with intact plants, caused the opposite effect (attraction). From the results it is concluded that ABA, depending on concentration, may influence the transport of sucrose within the plant by affecting sink capacity and/or the unloading of sieve tubes.

Zwergwuchs und Abscisinsäure

Summary Extracts from actively growing parts of dwarf rice plants (stem apex and basal parts of the leaves) contained a higher amount (up to 50 %) of abscisic acid (ABA) than those from tall plants. The ABA content of the leaf blades did not show significant differences. Application of various concentrations of ABA either to etiolated rice coleoptile sections or to intact green rice seedlings growing in a water culture revealed a different sensibility to ABA of dwarf and tall plants. Therefore it is concluded that dwarfism not only depends upon the endogenous amount of gibberellins. The content of inhibitors as well as the sensibility of the plant to them may also play a certain role.