Germination Comparison of Eight Exotic and Native Forest Tree Species at Different Salt Concentration Levels

Abstract

Salt-affected areas are problem worldwide and Thailand is not exceptional. Salinity tolerant trees with deep root system can control the level of salty water table to be as deep as the root zone and not coming up to the soil surface. Plant growth and development begin with germination which is an important process especially at salt-affected areas. Therefore, this study aimed at comparing the germination percentage and salt tolerant ability in seeds of 8 tree species including Acacia mangium, Leucaena leucocephala, Xylia xylocarpa, Buchanania siamensis, Peltophorum dasyrachis, Albizia lebbeck, Dalbergia cochinchinensis and Eucalyptus camaldulensis under sodium chloride solution at 0, 4, 8, 16, 25 and 40 dS/m. Completely randomized design with 4 replications of each species and salt levels was conducted. Seeds were considered to germinate when their roots were exposed to the naked eye. Seed germination was counted daily for 30 days.  When salt levels increased, total seed germination percentage decreased while the day to germinate increased. Most seeds germinated well at salinity level less than 16 dS/m. E. camaldulensis germinated the highest with value of 73.67% following by A. mangium and D. cochinchinensis with the values of 65.50% and 59.33% respectively. Most species required about 2 - 15 days to germinate. However, when salt concentrations were at 40 dS/m, seeds required 2 - 5 times to germinate. Salinity concentration that reduced germination by 50% (EC₅₀) was used to indicate the most salt tolerant seeds which A. mangium, (30.86 dS/m), B. siamensis (26.37 dS/m) and Albizia lebbeak were the most salt tolerant in this study.