Characterization of Larix kaempferi seeds selected by near-infrared spectroscopy for germination and post-germination growth in nursery containers

Demand for nursery stock of Japanese larch (Larix kaempferi) is growing. Containerized seedlings are expected to meet this demand. However, the conventional methods are labor intensive and time consuming because one-year-old bare-root seedlings are transplanted to containers. In this study, we selected seeds using a spectroscope and examined two propagation methods, direct sowing on nursery container (direct sowing) and sowing on a small plug tray followed by transplantation to a container (plug transplant), to shorten the nursery period of 2 years. Germination rate increased in the selected seed when compared with the unselected seed (χ² test). The days to germinate (DtG) shortened with the use of heavier seeds, and the one-year-old seedlings grew taller as the DtG decreased. However, transplantation from plug trays had negative effects (generalized linear model (GLM) and analysis of variance (ANOVA). On the other hand, large volume cell had positive effects on root collar diameter (GLM and ANOVA). The results revealed that the nursery periods were shortened by using large volume cell, irrespective of the seedling type (direct sowing or plug transplant).