Effect of different media and of a CO2-ENRICHED atmosphere on growth of lilac (Syringa vulgaris L.) vitroplants

Lilac (Syringa vulgaris L.) is an ornamental shrub for which clonal varieties must be propopagated vegetatively. So, industrial in vitro multiplication is sought in place of the expensive method of grafting. For some clones, the behaviour of vitroplants is not controlled properly and makes the multiplication difficult due to the vitroplant's insufficient elongation. Here, we focus first on the influence of eight different mineral formulations upon growth and multiplication rates of lilac vitroplants. Secondly, the effect of an atmospheric CO 2 enrichment is studied. Growth is estimated by both the height of the axis and by multiplication rates. Lindemann et al. (LGD, 1970) and Gresshoff and Doy (DBM2, 1972) media appeared to be unsuitable for lilac in vitro culture. Best results were obtained with the Murashige and Skoog (1962) and the Kao and Michayluk (1975) formulations as regards multiplication rates. Vitroplants cultured on the Kao and Michayluk, the De Greef and Jacobs (DGJ, 1979) and the Shenk and Hildebrandt (1972) media, showed similar average heights, but morphological differences led to lower rates of multiplication in the case of De Greef and Jacobs and Shenk and Hildebrandt. For 36-day vitroplants placed in a CO 2 -enriched atmosphere, a significant positive effect was always recorded. In the case of plants cultured on the Murashige and Skoog and the Kao and Michayluk media, the CO 2 treatment resulted in a multiplication rate of 8 and 9 respectively. For vitroplants on the De Greef and Jacobs, the Shenk and Hildebrandt and Gamborg B5 (1968) media the multiplication rate was 4.5 (against I to 3 for control).