Effects of Seed Pretreatment, Substrate Types and Water Stress on Germination and Growth of Dalbergia melanoxylon (Guill. & Perr.)

Abstract

Dalbergia melanoxylon (Guill. &Perr.) is an important species providing significant socio-economic and ecological services. Despite its importance, D. melanoxylon is facing increasing to anthropogenic pressure and climate change. This study aimed to evaluate the effects of seed pretreatment, substrate and water stress on germination and seedling growth of D. melanoxylon . A split-plot experimental design with three factors (seed pretreatment, substrate and water stress) and three replications was established. Pretreatment (dehulled “D” and non-dehulled seeds “ND”), substrate (3/3 sand “SB1”; 2/3 sand + 1/3 potting soil “SB2”; 1/3 sand + 2/3 potting soil “SB3”) and water stress (Watering every day “ST0”, every three days “ST3”, every seven days “ST7”and every ten days “ST10”) were the factors and modalities considered in this study. Results showed that dehulled seeds (25.86 ± 9.99%) significantly improved germination rate compared to non-dehulled seeds (11.16 ± 2.41%). The pure sand substrate (3/3 sand) gave the highest germination rate, and the combination of dehulling with pure sand achieved the best performance (41.96 ± 8.36%). For growth and biomass parameters, substrate SB2 recorded the highest values for diameter (0.21 ± 0.08 cm), height (10.65 ± 2.75 cm), leaf number (12.21 ± 2.56), aerial dry biomass (4 ± 1.75 g) and root dry biomass (9 ± 2 g). For the response to stress, the ST10 recorded the lowest values of diameter (0.16 ± 0.03 cm), height (7.02 ± 0.87 cm), leaf number (5.97 ± 3.26), aerial (2.5 ± 1.49 g) and root (7.5 ± 2.5 g) dry biomass. ST7, ST10 and SB1 produced the lowest growth values across all parameters (diameter, height, and leaf number). Overall, these findings provide essential insights to guide conservation and reforestation strategies by identifying optimal germination, growth, and adaptation conditions for D. melanoxylon .