Effects of Shading and Fertilizing of Mother Plants, and NH4+ : NO3- Ratio in the Medium on In Vitro Organogenesis of Stock (Matthiola incana R. Br.)

The effects of shading and fertilizing pre-treatments of mother stock (Matthiola incana R. Br.) plants and NH4+ : NO3- ratio in the medium on in vitro micropropagation through leaf and hypocotyl explants were investigated.1. In leaf explant culture, (1) shoot formation was enhanced when 'Ginshio' explants were taken from the mother plants grown under 75% shading and 1/2 strength Ootsuka liquid fertilizer. In 'Yukimatsuri' shoot formation was inhibited by shading mother plants grown in 1/2 and 1/4 strengths of Ootsuka fertilizer. (2) Reducing NH4+ : NO3- ratio in the medium promoted shoot formation in both cultivars.2. In hypocotyl explant culture, (1) shading mother plants for two weeks after sowing resulted in less shoot formation in both cultivars. (2) Addition of NH4+ to the medium, by which the ratios of NH4+ : NO3- were adjusted to 1 : 10 and 1 : 2 in 'Littlejem Yellow' and 'Yukimatsuri' respectively, enhanced shoot formation and increased the number of shoots per explant. The highest rate of shoot formation was 85% in both cultivars.3. Most shoots regenerated from leaf and hypocotyl explants appeared vitrified. Vitrified leaves, unlike normal ones, (1) had higher moisture content; (2) were larger; and (3) had poorly developed vascular bundles and palisade tissues. The stomata of vitrified leaves were frequently located above and below the epidermal cell layer and distributed irregularly.