Effect of Drupe size Grading on in Vivo and in Vitro Germination and its Dormancy Mechanism of Teak (Tectona grandis Linn. F)

The effect of drupe size on in vivo and in vitro germination and its dormancy mechanism in teak have been studied in this paper. Teak drupes were size graded to five categories namely very large with more than 15 mm, large with 13 to <15 mm, medium with 11 to <13 mm, small with 9 to <11 mm and very small with less than 9 mm of diameter. Under in vivo pot culture condition very low germination percent of drupes was observed. It was observed that very large size drupe had highest 100 drupe weight, 100 true seed weight and seed filling capacity, but it was negatively correlated with in vivo germination of teak drupes. When true seeds isolated from the drupes were grown under in vitro condition in half strength MS medium the germination percent was significantly increased up to 54.1. True seeds obtained from small size graded drupes recorded highest germination per cent in MS media. This showed that the drupe size did not play major role in the germination and early growth in teak. Very small size graded drupes have low seed filling capacity, and it leads to decrease the germination percent. Poor germination of drupes showed the presence of mechanical and physiological dormancy in drupes. Similarly, the presence of morphological and embryo dormancy in teak may limit the true seed germination potential to 54.1 per cent. In addition, in vitro germination of true seeds will be a promising approach to obtain large number of saplings in teak.