CLONAL PROPAGATION OF ENDANGERED NATIVE PLANTS RHODODENDRON CHAPMANII GRAY, TAXUS FLORIDANA NUTT., AND TORREYA TAXIFOLIA ARN. (MICROPROPAGATION, IN VITRO/TISSUE CULTURE, PLANT PROPAGATION, WOODY ORNAMENTALS).

摘要

Clonal propagation utilizing conventional and micropropagation techniques was investigated for three endemic and endangered Florida plant species, Rhododendron chapmanii Gray, Taxus floridana Nutt. and Torreya taxifolia Arn. This is critical for their preservation since these species exist in limited numbers but have high ornamental value which has threatened their survival due to illegal collection.;Torreya and Taxus cuttings could be easily propagated when treated with 2,000-4,000 mg/l IBA. However, cuttings taken from lateral branches demonstrated strict plagiotropic growth. Best rooting and growth of Torreya cuttings (20%) occurred following treatment with 4000 mg/l IBA. Taxus cuttings rooted best (67%) following treatment with 2000 mg/l IBA.;Shoot-tip cultures (3-5 cm long) of Taxus and Torreya developed only 2-3 lateral shoots, apparently from preformed buds. Cultured "embryonic shoots" from expanding vegetative buds failed to produce multiple shoots. Excised embryos did not germinate following liquid culture to leach inhibitors. Micro- and megasporangia did not grow or differentiate in culture.;The most promising technique for Torreya involved application of cytokinins (4 weekly sprays with 100-200 mg/l BA or 2-i-P) to seedlings before culture. Newly stimulated axillary shoots developed additional shoots and multiple "bud-masses" when cultured on WPM with BA (1 mg/l) and NAA (0.01 mg/l). These were slow to develop but could be subcultured with additional growth of multiple shoots. No rooted plantlets were obtained.;Micropropagation of R. chapmanii was investigated using shoot-tip cultures. An average of 7.6 fold increase in lateral shoots was achieved for three additional Stage II multiplication cycles on low salts Woody Plant Medium (WPM) with 2-i-P (10 mg/l) and adenine sulfate (80 mg/l). Microcuttings rooted in 4-6 weeks when direct-stuck into autoclaved 1:1:1 (v:v:v) Canadian peat:vermiculite:perlite medium in covered flats. A 5 second quick-dip in 1000 mg/l IBA (20% EtOH + 80% H(,2)O) increased survival and rooting of microcuttings. Inoculation of plantlets with the mycorrhizal fungus, Pezizella ericae increased survival and growth when plantlets were established in a less than optimal soil-less medium (1:1 v:v Fired montmorillonite clay:Canadian peat) but not in MetroMix-500.