Highly efficient in vitro rooting of Nyctanthes arbor-tristis Linn.-A medicinally important woody shrub, by auxins and root promoting agents

Silver nitrate and phloroglucinol induced enhanced in vitro rooting was achieved on Nyctanthes arbor-tristis Linn., a woody aromatic medicinal shrub. The frequency of rooting varied from 0 to 86.66% for different treatments with various concentrations and type of growth regulators as well as solid and liquid nature of nutrient medium. Modified MS liquid medium augmented with IBA at 2 mg/l was found to be the most effective among different auxins, which showed highest (70%) per cent root induction with a mean of 4.23±0.19 roots per shoot within 21 days of culture, while the maximum length (4.6±0.19 cm) of root was recorded with 3 mg/l of IAA. Liquid medium fortified with various concentrations of different auxins was superior to solid culture in terms of per cent root induction, mean number of roots per shoot and mean root length. An enhanced rooting frequency (83.33 and 86.66%) with a statistically greater mean number of roots per shoot (6.9±0.1 and 7.2±0.07) with average length of 5.0±0.06 cm and 5.2±0.09 cm were obtained on inclusion of 2.0 mg/l AgNO₃ and 9.0 mg/l PG, respectively, to modified MS basal medium containing optimal concentrations of IBA (2.0 mg/l) or IAA (3.0 mg/l). After a period of four weeks, the well rooted plantlets were transferred to pots containing a mixture of sand: soil: vermicompost (1: 1: 1) and hardened for six weeks before their field transfer with almost 92% survival rate.