Micropropagation of Stewartia pseudocamellia

Abstract

Single-node explants were excised from shoots of actively growing, 2-year-old seedlings of Stewartia pseudocamellia Maxim. (Japanese stewartia) on three dates associated with specific stock plant growth stages. Following surface sterilization, explants were placed on agar-solidified Woody Plant Medium (WPM) containing either no growth regulators or N-(3-methyl-2-butenyl)-1H-purin-6-amine (2iP) at 5.0 or 10.0 ppm (24.6 or 48.2 μM) or 0.025 or 0.05 ppm (0.11 or 0.23 μM) N-phenyl-N-1,2,3-thiadiazol-5-ylurea (TDZ). The most frequent budbreak was noted for explants placed on media containing 2iP at either concentration. Explants cultured at the softwood stage had less contamination and greater budbreak than explants taken from more mature stem tissue. In another study, the three distal, axillary nodes of each shoot were excised at 4-day intervals for 28 days beginning 52 days after stock plants were potted following cold storage at 7C (44F). Explants were surface sterilized and placed on WPM supplemented with 10 ppm (49.2 μM) 2iP either alone or in combination with 3 ppm (8.6 μM) gibberellic acid (GA3). Neither GA3 nor node position influenced budbreak frequency or shoot elongation. Days after potting (stock plant growth stage) influenced frequency of budbreak and shoot elongation with the optimal period for explant collection being 56 to 72 days after stock plants were potted. Elongated shoots (one microcutting per explant) were produced on both media. Microcuttings ≥10 mm (0.4 in) were rooted using ex vitro procedures and acclimatized to greenhouse conditions.