Seed dormancy and after-ripening requirements of Indian lac tree (Schleichera oleosa Lour. Oken)

Abstract

ABSTRACT After-ripening (AR) is a time and environmental regulated process which determines the germination potential of the dry seeds. The after-ripened seeds swell after absorbing water and initiates metabolic activity linked to the germination process. Such after-ripening process is not studied in detail in Schleichera oleosa species. Therefore, an experiment was designed to assess the effect of different pretreatments on seed dormancy and AR patterns in the seeds of S. oleosa. The seeds were subjected to various pre-treatments, viz., mechanical scarification, scarification + Gibberellic acid (GA3, 0.02% and 0.05%), scarification + KNO3 (0.02% and 0.05%) for 24 hours. Further, the seeds were desiccated at four levels (10, 12, 14 and 16%) of intact seed water content (SWC) and were kept at either uncontrolled ambient room temperature or controlled constant temperatures (22°C, 25°C and 28°C), and their germination was tested fortnightly for 60 days. The results revealed that S. oleosa possess combined physical+ physiological dormancy and soaking of scarified seeds in GA3 solution (0.05%) for 24 hours showed the maximum germination percentage (80.0%), vigour index (721.4), and mean germination time (6.6 days). Results also indicated that AR process under optimum conditions (25°C, 16% SWC and 60 days) can increase germination percentage up to six times (81.25%) as compared to freshly collected seeds (12.5%) in the species. These findings can be utilized for developing the seed germination protocol with the aim to devise the propagation techniques and conservation programme for the species.