Root growth potential and seedling morphological attributes of narra (Pterocarpus indicus Willd.) transplants

The lack of simple and reliable nursery grading practice to assess quality of planting stocks led to the failure of many reforestation projects in the Philippines. Thus, it is important to develop a mechanism to evaluate nursery seedling quality and performance prior to field planting. The study was conducted to evaluate two measures of root growth potential (RGP; number and length of new roots) as seedling performance attributes of narra (Pterocarpus indicus Willd.), one of the most valuable native reforestation species in the Philippines. RGP was determined in response to three different soil moisture regimes (50, 75 and 100% of field capacity). Effects of these treatments on height, rootcollar diameter, stem diameter, length of taproot, shoot biomass, root biomass, total biomass, root:shoot ratio and seedling quality index were also investigated. Measurements were made on 7, 14 and 21 days after transplanting. The experiment was laid out using a completely randomized design. RGP and length of taproot were significantly affected by moisture treatment at 7 days. High RGP and longer taproots were observed in soil at 50% of field capacity. Increased stem diameter, shoot biomass, total biomass and quality index were observed in the reduced soil moisture condition at 7 and 14 days. Results confirm that narra is capable of producing new roots in response to reduced soil moisture on a relatively short period of time. This response would enable narra plants to counteract transplanting shock thereby ensuring their survival in the nursery. Correlation analysis of new root counts and length measurements revealed a strong positive correlation with each other. Thus, either will provide a good estimate of RGP in narra.