Levels of Endogenous Indole-3-acetic Acid in Achenes of Rosa rugosa during Dormancy Release and Germination

Abstract

ABSTRAC1Indole-3-acetic acid (IAA) in highly purified extracts of rose achenes (Rosa rugosa var rubra) was quantified by means of ion-pair reversephase high performance liquid chromatography with spectrofluorimetric detection. Changes in IAA content were determined during a 14-week 4°C stratifiation, which leads to dormancy breakage, and during subsequent germination at 17C. IAA was also determined in achenes stratified in parallel at 17°C, which does not induce release from dormancy. IAA decreased during the first 2 weeks of stratification both at 4C and at 17°C. IAA remained low during the remaning 12 weeks of stratification at 4°C, whereas it continued to decrease in achenes kept at 17C. An immediate increase in IAA during germination was followed by transients in the IAA level. The results suggest that IAA is without a regulating role in dormancy release although it seems to be involved in the germination process.Hormonal regulation of dormancy breakage and germination are believed to be affected by an interplay between endogenous promotors and inhibitors. As these two processes commonly overlap each other in time, it may be difficult to judge if the observed hormonal changes are linked to one or the other process. Rose achenes, however, seem to be a suitable study material, since the period during which embryo dormancy is broken is well separated from the subsequent germination period (16), which is blocked by germination inhibitors (8). In two recent studies from our laboratory, changes in the levels of cytokinins and ABA in achenes of Rosa rugosa have been reported. A transient increase of cytokinin-like substances appeared early during cold stratification and another during germination suggesting that they are involved in both processes (9), whereas ABA was shown to play only a passive role, if any, in the regulation of dormancy release and germination (16). The present report describes changes in IAA levels in the same material and discusses its role in these processes.There are reports suggesting that IAA is involved as an inhibitor in the regulation of dormancy whereas the effect of auxin on germination has long been in dispute. Decreases in the levels of auxins in apple seeds during a time course were strikingly similar to those of growth inhibitors during cold stratification (10 IAA diminishes both in cold and warm stratified embryos of Acer platanoides and have suggested that there is more direct relationship between IAA content and germination-growth than between IAA content and dormancy breakage (17). For these reasons, the possible role of IAA in these processes is controversial. The purpose of the present investigation was to determine the dynamics of IAA during cold stratification at 4°C and during germination induced by transfer to 17°C after a 14-week stratification period. Controls were conducted in parallel at 17C, which does not break dormancy. As preliminary experiments with the indolo-a-pyrone method gave low yields of IAA, a more sensitive method, HPLC with fluorescence detector, was a...

Dynamics of abscisic acid and indole-3-acetic acid during the early-middle stage of seed development in Rosa hybrida

“…Tilberg (1984) quantified IAA by reverse-phase, ion-pair high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) in mature R. rugosa var. rubra seeds during 14 weeks of stratification.…”

Development of a Rapid LC-DAD/FLD Method for the Simultaneous Determination of Auxins and Abscisic Acid in Plant Extracts

“…Limited knowledge on endogenous auxin quantitation in the genus Rosa, for comparison purposes, was found in the literature. Tillberg 48 obtained a concentration of 0.08 μg/g of 2 in mature seeds.…”

Rosa rugosa Thunb. ex Murray

“…However, the decrease in abscisic acid concentration was even bigger in achenes imbibed and kept at 17 °C (Tillberg 1983). Concentration of indole‐3‐acetic acid, the most important auxin, decreased rapidly during cold stratification, and remained at low levels, but showed a similar pattern as abscisic acid (Tillberg 1984). During germination the indole‐3‐acetic acid concentration fluctuated, but it appeared low when germinability was increasing.…”

“…Julin‐Tegelman (1983) and Tillberg (1983, 1984) presented studies of endogenous inhibitors and promoters during dormancy release and germination on the same seed material ( R. rugosa var. rubra ).…”

“…Julin-Tegelman (1983) and Tillberg (1983) completed the studies of Jackson & Blundell (1963) by showing that even excised embryos need at least 3 weeks of chilling (at 4 °C) to show some germination (5 weeks chilling for 100% germination to appear), and that control achenes kept at 17 °C showed no germination. Julin-Tegelman (1983) and Tillberg (1983Tillberg ( , 1984 presented studies of endogenous inhibitors and promoters during dormancy release and germination on the same seed material (R. rugosa var. rubra).…”