Carlina acaulis L. (fam. Asteraceae) is perenial herbaceous plant which grows on dry and rocky habitats up to 2000 m in South Europe. In Serbia, it is most frequent in western parts of the country. Leaves are set in rosette and the stem grows up to 40 cm in height. The fruit is dark yellow coloured achene, 5 mm in length. The rhizome is large and vertically set in the ground. It is considered to be medicinal plant because of inuline (up to 20%), essential oils and thanins that it contains.

In vitro culture was established using immature zygotic embryos. Bud multiplication was satisfactory on MS medium supplemented with BAP 1 mg/l, and IAA 0.2 mg/l. Maximal rooting of buds was obtained after short cultivation (4-8 days) on auxin-supplemented media. Number of roots was highest if NAA was used, while root length was highest on IAA supplemented medium. Plantlets were treated under light or dark conditions either with gibberellic acid, or ancimidol, a potent inhibitor of gibberellin biosynthesis. In all experiments the concentration of BAP was constant - 1 mg/l. Under light conditions untreated plantlets were in rosette form without stem i.e. with extremely short internodes. Under same light conditions, GA3 - treated plantlets showed dose dependent stem increase in length, reaching maximum at GA3 concentration of 10^-4 M. This effect was correlated with average number of internodes. In darkness, stems were elongated, but in presence of ancimidol they were significantly shorter. The inhibitory effect of the growth retardant on stem elongation could be completely overcome by addition of GA3.

The obtained data suggest that stem elongation, of stemless Carlina, is under strong light-control mediated by gibberellins.