CARBOHYDRATE REQUIREMENTS FOR THE DEVELOPMENT OF BLACK SPRUCE (PICEA-MARIANA (MILL) BSP) AND RED SPRUCE (P-RUBENS SARG) SOMATIC EMBRYOS

Different carbohydrates were investigated for somatic embryo development of black spruce and red spruce. They were testcd in a basal maturation medium consisting of Litvay's salts at half-strength containing 1 g l-1 glutamine, 1 g l-1 casein hydrolysate, 7.5-mu-M abscisic acid, and 0.9% Difco Bacto-agar. A comparison of different sucrose concentrations showed that 6% was optimal for embryo development. Among the nine carbohydrates tested, sucrose, fructose, glucose, maltose, and cellobiose supported embryo development while arabinose, mannitol, myo-inositol, and sorbitol did not. A comparison of sucrose, glucose, and fructose at three concentrations showed that the general pattern of response for both species followed concentration expressed as a percentage, independent of the molarity of carbohydrate in the medium. Interspecific differences were observed concerning carbohydrate requirements. For red spruce, 6% fructose was found best for embryo development, while no such preference was observed for black spruce. No significant difference was observed in the number of embryos produced with 6% sucrose or 3% sucrose plus an equimolar concentration of either mannitol, sorbitol, or myo-inositol in the maturation medium, suggesting that the effect of the carbohydrate on the maturation was partly osmotic.