GROWTH AND ROOT ARCHITECTURAL PERFORMANCE OF NEEM AND MAHOGANY TREE SAPLING UNDER WATER STRESS CONDITION

Abstract

An experiment was conducted at the Agroforestry Research Field of HSTU to find out the responses of shoot morphology and root architecture of Azadirachta indica (neem) and Swietenia macrophylla (mahogany) seedlings to water stress. The experiment was done from February to August 2019. There were four treatments; namely- 100% watering, 50% watering, 25% watering and no water except rainwater (control). Neem and mahogany seedlings were collect from a Government nursery. The experimental design was RCBD with three replications. Before applying the water stress treatment, initial data of the transplanted seedlings were recorded in February 2019. Results showed that shoot height of neem and mahogany seedlings increased after transplanting in the field and polybag i.e. from 3 to 6 months of transplantation in different water regimes. The highest shoot height was record in 50 % watering regime and 100 % watering regime in field and polybag respectively of both neem and mahogany. In addition, the lowest was find in control after six months of transplanted ion in all condition. Similar results were obtain for the root collar diameter, number of branches, sturdiness ratio and central root length. In case of biomass allocation, shoot and root dry biomass of neem and mahogany seedlings increased in all the treatments compared to water stress condition. In case of biomass, allocation of neem and mahogany seedlings, the highest shoot dry biomass was obtained in 100 % water after six months in polybags and 50 % water after six months of transplantation in field condition and the highest root dry biomass was obtained in 100 % and 50 % watering regime after four month of transplantation in polybags and field respectively. All other treatments varied due to level of water stress condition. In all case, though mean diameter of FOLRs (First Order Lateral Root) increased except control but this diameter did not vary significantly over time. However, after 3 months mean length of FOLR did not vary significantly but it varied after 4 and 6 months. Finally, after six months, the full stressed seedlings showed highest length of FOLR(s) and the 100% watering regime showed lowest length. Increasing the length of FOLRs with the sacrifice of their diameter might be the adaptive mechanism of neem and mahogany seedlings in water stress condition. There was no seedling mortality after 3 and 4 months but mortality was recorded after 6 Months of transplantation of neem and mahogany seedlings. The highest survival percentage was obtained in 100 %, 50 % and 25 % water regime after 3, 4 and 6 months of transplantation in polybags and in 100 % and 50 % water regime after 3, 4 and 6 months of transplantation in field condition. From the overall results it can be concluded that neem and mahogany seedlings can be established in water stressed condition with ensuring at least 50% additional water supply in the field and polybags at their early stages