摘要：This study was conducted to determine the optimum period to collect loblolly pine (Pinus taeda L.) cones that contain embryos with the greatest capacity to produce embryogenic callus for establishing somatic embryogenesis. Cones were collected from trees at the University of Arkansas Agricultural Experiment Station, Fayetteville, in 1991 during four consecutive months: May, June, July, and August. Seeds were extracted and disinfected in 70% ethanol for 1 min, 50% Clorox for 20 min, followed by four water rinses. Seed coats were removed, and embryos were cultured on DCR medium adjusted to pH 5.7 and supplemented with 3 mg/L 2,4-D, 0.5 mg/L 6-BAP, 30 g/L sucrose, and 6 g/L agar. Callus was induced and maintained in the dark at 20 ± 5 C. Embryos collected in May failed to proliferate; however, 55%, 88%, and 66% of the embryos cultured produced callus from June, July, and August collections, respectively. Suspension cultures were initiated from pine callus and maintained for over 6 months in MSG medium for subsequent investigation of the conversion of embryogenic complexes into mature embryos and eventually into plantlets. Evidence for embryogenesis was observed with double-staining techniques.
