In vitro Mass Propagation and Gren House Establishment of Munronia pinnata (Wall) Theob. (Binkohomba)

Abstract

Munronia pinnata (Wall). Theob is a valuable medicinal plant which is widely used in Ayurvedic medicine in Sri Lanka. Due to over exploitation and low percentage of seed germination of M. pinnata it has become necessary to adopt ex situ conservation methods via in vitro propagation techniques. The objectives of this study was mass propagation, greenhouse establishment and comparison of in vitro propagated plants with seed raised plants. Callus cultures were initiated from different explant types such as apical buds, nodal segments, petioles, petals and leaf discs in Murashige and Skoog (MS) medium supplemented with 1.1 mg L 1 2,4- dichlorophenoxy acetic acid (2,4-D) and 0.5 mg L 1 benzyl amino purine (BAP) at 25 ± 1°C in complete darkness. Leaf discs (6.0 mm) showed significantly higher calli production (mean fresh weight 0.167± 0.04 g) than other tested explants. The best growth regulator combination for callus initiation was 1.1 mg L"12,4-D and 0.3 mg L"1 BAP which produced a mean of 0.30 ± 0.06 g callus while other treatments produced lesser amount of callus. Leaf discs taken from first fully opened leafs, produced the highest amount of callus (0.06 ± 0.01 g) and a decreasing trend was observed with increased maturity of the leaf. Tissues along the midrib area have a higher potential to give high yield of callus. Shoot proliferation was higher (32.9 ± 2.2) in MS medium containing 3.0 mg L 1 naphthalene acetic acid (NAA) and 3.0 mg L 1 BAP. Light intensity at 3000 lx showed significantly higher number of shoots (33.4 ± 2.84) than other tested light intensities. Half MS minerals supplemented with 0.2 mg L"1 indole acetic acid (IAA) was the most effective treatment for root induction (75%) with the highest mean root length (15.05 ± 0.5 mm) and 3.15 ± 0.03 of mean number of roots. A suitable potting mixture for acclimatization was determined using different ratios of compost and sand. Higher percentage of survival (60%) was achieved with compost: sand 1:3. When morphological features of seed raised plants were - compared with tissue cultured plants, mean height increment was higher in seed raised plants while mean number of leaves washigher in tissue cultured plants and branching habit was observed only in tissue cultured plants. A comparison of physiological parameters between the two types of plants showed that the rate of photosynthesis was higher in tissue cultured plants whereas stomatal resistance was higher in seed raised plants.