Mixed Effect of Provenance and Stand Age on the Germination of Teak ( Tectona grandis ) Seeds in Ghana

Abstract

Teak (Tectona grandis L. f.) plantations developers in Ghana have difficulty in selecting teak seeds from ecological sources and maternal ages that could guarantee optimum germination rates. To fill this knowledge gaps and contribute knowledge on germination characteristics of teak seeds in Ghana, we studied the effects of age of the maternal tree, the ecological zone of the mother tree, and the combination of the two on germination rates of teak seeds. We collected teak seeds from 10, 15, and 20-year-old healthy teak stands in the Savannah Zone (SZ), Transitional Zone (TZ), and the High Forest Zone (HFZ) of Ghana for this study. Fifty seeds from each maternal age for each ecological source were pretreated and sown in nine replicates using a completely randomized design in a factorial experiment with 2-factor treatment combination (age and ecological source). Our findings show that germination rate of seeds from the three maternal ages in the SZ was not different. The SZ also recorded the lowest overall germination rate among the three ecological zones studied. In the TZ, germination rate was not different between 10 years (47.33%) and 15 years (45.33%) maternal stands but both were significantly (p<0.01) higher than 20 years old (34.22%) maternal stands. The TZ recorded intermediate overall germination rates, which are higher than SZ but lower than HFZ. Germination rate was not different between 15 years old (88.00%) and 20 years old (94.44%) in the HFZ but was significantly (p<0.05) higher than 10 years old (41.56%). Moreover, the HFZ recorded the highest overall germination rate among the three ecological zones studied. Our findings further show that seed source (ecological zone), the age of the maternal teak tree, and the interaction of both, have significant (p<0.01) effects on germination rate of teak seeds. More importantly, the effects of age of maternal tree on germination rate was found to be dependent on the ecological zone in which it is located as same maternal age trees recorded different germination rates in different ecological zones. Interaction plot of age and the ecological zone of maternal teak plant produced the highest germination rate at the combination of HFZ with 15 and 20-year-old teak stands. We recommend that teak plantation developers in Ghana select teak seeds from 15 years and above in the High Forest Zone for optimum germination rates.