ROOT ARCHITECTURE AND SHOOT MORPHOLOGY OF NEEM (Azadirachta indica A.Juss) SEEDLINGS IN WATER STRESSED CONDITION

Abstract

An experiment was conducted in the Agroforestry Research Field of HSTU to find out the responses of shoot morphology and root architecture of Azadirachta indica (neem) seedlings to water stress. The experiment was done from March to October 2015. There were four treatments; namely- 100% watering, 50% watering, 25% watering and no water except rain water (control). Neem seedlings were collected 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 April 2015. Results showed that shoot height of neem seedlings increased after transplanting in the field i.e. from 3 to 6 months of transplantation in different water regimes. The highest shoot height was recorded in 100 % watering regime (45.33 cm) and the lowest was found in control (31.0 cm) after six months of transplanted ion. Root collar diameter also varied among different water levels. The highest root collar diameter after six months of transplantation was found in 100% water level (5.67mm) and the lowest was recorded in control. Similar results were obtained for the number of branches, sturdiness ratio and central root length. In case of biomass allocation, shoot and root dry biomass of neem seedlings increased in all the treatments compared to water stress condition. Highest shoot dry biomass was recorded in 50% water level followed by 100 % water and the lowest was recorded in 25 % and Control watering regimes. Same result was found in total dry biomass. But root dry biomass, shoot to root ratio and quality index did not vary significantly after six months of transplantation. The number of first order lateral root (FOLRs) did not vary among the watering treatments after 3, 4 and 6 months but the same increased after 4 to 6 months than their earlier number in all the water levels except water stress (control) condition. Though mean diameter of FOLRs increased except control but this diameter did not vary significantly over time. There was no seedling mortality after 3 months but motality was recorded after in 4 and 6 Months of transplantation of neem seedlings. Though 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 str essed 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 seedlings in water stress condition. Survival rate neem seedlings did not change in 100% and 50% watering regimes over time but it decreased sharply in stressed seedlings (20% survival rate ) followed by 25% watering regime (95% survival rate) due to water stress condition after 6 months. From the overall results it can be concluded that neem seedlings can be established in water stressed condition with ensuring at least 50% additional water supply in the polybags at their early stages.