Abstract:

The characteristics of seed dormancy and germination of Pinus bungeana were studied with naked embryos (seed capsule and endosperm were excised off) and embryos with whole or partial endosperm of the seeds either non-pretreated or low temperature stratified. Naked embryos were cultured separately on agar-solidified media containing different concentrations of sucrose or on filter-paper bridge. Embryos with whole or partial endosperm were cultured on filter-paper bridge. For naked embryos of the seeds without pretreatment, radicles could emerge on culture system of neither filter-paper bridge nor agar media supplemented with low concentrations of sucrose; 20% of the radicles could germinated on media containing 3.0% of sucrose, the germination rate tended to rise when sucrose concentration in range of 3%～5.5%, the highest germination proportion (Gp) could reach 40% and the germination index (Gi) were 6.5%·d^-1. The remainder 60% of embryos could not germinate even when sucrose concentration of the media was higher than 6%. For the non-pretreatment seeds cultured on filter-paper bridge, 92% or 74.7% Gp was obtained as embryos with whole or two-third to half of endosperm. No growth of radicle except hypocotyl elongation was found of embryos with 1/3 part of endosperm, and naked embryos still in dormancy except the rapid hypocotyl elongation, which could culture on either one matrix experimented. For embryos pretreated by cold stratification for 36 days or GA₃ immersion, naked embryos could germinate on agar media containing lower concentrations of sucrose (0.2% or 0.4% respectively),and 90% of Gp was obtained on media supplemented with 3.0% of sucrose after stratification, 60% of Gp was got on media with 4.0%～5.0% sugar after GA₃ treatment, and Gi was 26.3%·d^-1 or 7.5%·d^-1 respectively. 70% of naked embryos germinated at the third day, but embryos with intact endosperm germinated at 40%, 10%, 10%, 10%, 0% and 30% separately from the fourth to ninth day. From these results we inferred that the embryo was of property of dormancy, but its hypocotyls were not. The testa permeability was not the main factor to inhibit embryo germination, embryo germination did need enough sucrose supply and was regulated by its endosperm.

Key words: Pinus bungeana, Embryo dormancy, Embryo culture, Endosperm, Low temperature stratification, GA₃ treatment