Effect of Seed Treatments on Germination of Teak (Tectona grandis Linn. f.).

Teak (Tectona grandis) is one of the most important commercial timbers in Costa Rica. Plantations are established from seeds, and poor germination is a common problem for growers that have been related to the thick a mesocarp and a hard endocarp of the fruit (drupe). The objective of this research was to study the effect of several temperature and humidity treatments on teak germination. Drupes without mesocarp from lots with high (70 %), medium (60 %) and low (40 %) germination were used, and seed viability was confirmed by tetrazolium test. Pre-sowing seed treatments were used to improve seed germination: CIGRAS protocol (T1), soaking the drupes in water 4 (T2) and 6 (T3) days, heating the drupes in humid heat 2 (T4), 4 (T5) and 6 (T6) days, heating in hot water for 2 (T7), 4 (T8) and 6 (T9) days, and control (T10) that did not receive any treatment. CIGRAS protocol consists in making a little fissure in the drupe and soaking the fruit 24 hours in a gibberellic acid solution at 100 mg l^-1 concentration. There was no difference between T1 and T10; and T2 and T3 reached lower germination. No significant differences were found among humid heat treatments (T4, T5 and T6) and CIGRAS protocol or between CIGRAS protocol and control. Pre-treatments T7, T8, and T9 showed lower germination values and with greater exposure time germination was negatively affected. T6 increased germination in the low germination lot by 10 %. According to this study low teak germination of lots could be improved with hot humidity because this treatment allows the entrance of more water through the mesocarp to the seed.