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Germination and Storage of Dyera Costulata Hook. f. and Macaranga gigantea Mull. Seeds
Thesis Abstract:
Good physiological quality of seeds such as high germination percentage and vigor are the most important factors to be considered in the production of high quality tree seed for commercial plantations. This study aimed to enhance the germination and storage condition of commercially important tree seeds, Dyera costulata Hook.f. and Macaranga gigantea Mull. It intended to develop tetrazolium test for rapid detection of seed viability. Paper, sand, soil, forest soil, coconut husk, and paddy husk were the germination media tested for best germination. Three storage conditions (refrigerated at 10 and 20ºC, and ambient at 30ºC.), four storage periods (0, 31, 89, and 181 days), and three plant growth hormones (GA3, BAP, and kinetin) at four concentrations (0.1, 0.2, 0.5, and 10 mg/L) were used to determine the best conditions for storage and growth promoter for both D. costulata and M. gigantea seeds. In addition, three germination media (sand, soil, and forest soil) and light regimes (25, 55, and 75% relative light intensity) were tested to find out the best condition for seedling growth.
Results of the study indicated that the best germination medium for both tree seeds was sand, followed by forest soil and soil. The best temperature for storage was at 20°C giving from 85 to 97 percent seed viability. However, storage of more than 89 days reduced the germination rate when stored at 10 and 20°C, and more than 30 days if stored at 30°C. Among the three types of hormones, GA3 at 10 mg/L was found to be the most effective at 65 percent viability for germination and 74 percent viability when combined with excised seedcoat. Among the concentrations used, application at 10 mg/L gave the overall best result for all the hormones in enhancing the germination process.
The study also found that buried seeds had better germination rate than freshly collected seeds. Overall, hormone treatment using GA3, BAP, and kinetin at various concentrations was found to enhance germination rates of M. gigantea seeds. GA3 at 10 mg/L was the better treatment for germination even when combined with excised seedcoat that gave 74 percent viability. It was found that growth was significantly better at 75 percent light in forest soil condition.
Comparison of the anatomical structures of buried seeds and fresh seeds of M. gigantea were carried out using scanning electron microscopy (SEM). Results indicated that the buried seeds had thinner pericarp, full endosperm, and better developed embryonic axis compared with fresh seeds. Differences in buried seeds and fresh seeds were evident to their pericarp thickness (357.6 and 308.7 μm), respectively. Differences were also evident within the radicle area where structures from fresh seeds were not as well organized as those of buried seeds.