VARIABILITY IN MATURATION AND GERMINATION FROM WHITE SPRUCE SOMATIC EMBRYOS, AS AFFECTED BY AGE AND USE OF SOLID OR LIQUID CULTURE

The yield of morphologically normal Stage 3 somatic embryos of white s pruce [Picea glauca (Moench) Voss], and subsequent germinability, was affected by culture age and use of solid and/or liquid culture growth conditions. Of the conditions that were compared, best results were ob tained with cultures up to 3 yr old that had been continuously grown i n liquid medium. Such material yielded up to 374 morphologically norma l Stage 3 embryos per g f. wt. inoculum, when routinely pretreated usi ng a 1 wk 2,4-dichlorophenoxyacetic acid-free period before maturation . By comparison the continual use of solid culture conditions resulted in lower yields (5/g f. wt. inoculum), and the use of solid medium in combination with liquid medium showed a greater affect of age on the production of normal Stage 3 embryos (348/g f. wt. at 1.5 yr dowm to 1 9/g f. wt. at 3 yr) over the age range tested, In the absence of cultu re pretreatment, the oldest liquid cultures yielded only 44 normal Sta ge 3 embryos/g f. wt. inoculum, and the comparable solid to liquid cul tures yielded 1.3/g f. wt. inoculum. The number of aberrant Stage 3 em bryos in older cultures was reduced as a result of culture pretreatmen t; for example, in the oldest liquid cultures these represented 83% of the Stage 3 embryo population without pretreatment and 45% with pretr eatment. Normal Stage 3 somatic embryo yield and germination character istics (radicle and epicotyl development) were informative in distingu ishing among the conditions studied. Germination characteristics were especially important when maturation responses were incapable of disti nguishing among age classes.