Vegetative propagation of some selected mangrove species from Negombo estuary, Sri Lanka
K.H.W.L. DE SILVA* AND M.D.AMARASINGHE
Mangrove forests are degraded and threatened worldwide, due to anthropogenic events. Mass production of planting material and successful germination of seeds are essential processes in rehabilitating these degraded mangrove forests. The present work was carried out to determine the efficacy of using propagule cuttings in mass production of plant materials and to determine the potential of using non mangrove soils to establish propagule cuttings for ornamental purposes. In addition air layering and stem cutting techniques were also tested for the mangrove propagation. Propagation of Rhizophora apiculata, by propagule cuttings, treated with root promoting hormones is feasible and it was possible to produce three saplings from one propagule. Indole Butyric Acid (IBA) (1000 ppm) was the best hormone concentration for inducing roots and IBA (1500 ppm) was the best for inducing shoots from propagule cuttings of R. apiculata. Air layering and stem cutting were performed with Avicennia marina and R. apiculata but none of the species was able to generate roots and therefore these vegetative propagation methods cannot be used for mass propagation of these mangrove species. Optimum growth medium and period of nursery care for mangrove saplings of R. apiculata, Ceriops tagal and Bruguiera sexangula were studied and the results revealed that best growth performance was in mangrove soils, i.e. 4.15 cm/ 4weeks for R. apiculata, 3.75 cm/ 4weeks for B. sexangula and 0.56 cm/ 4 weeks for C. tagal, while mangrove soils mixed with sand produced the second best growth for C. tagal and B. sexangula. Seedlings grown on terrestrial soils showed the lowest growth rate for all three mangrove species. However, no significant difference (P < 0.05) exists in growth rates of mangrove seedlings when grown in different growth media, indicating they can be grown with terrestrial soil for ornamental purposes. Potting media consisted only of mangrove soils as well as mangrove soils (1): sand (1), terrestrial soil alone and mangrove soil (1): terrestrial soil (1) can be used as nursery growth media for R. apiculata and C. tagal.