Effect of temperature on needle anatomy and transpiration of Piceamariana after bud initiation

Abstract

Six-month-old black spruce (Piceamariana (Mill.) B.S.P.) container seedlings were placed in either a cool (18 ± 4: 6 ± 4 °C, light:dark) or a warm (26 ± 3: 18 ± 2 °C, light:dark) hardening regime for 12 weeks after bud initiation to assess the effects of temperature on needle maturation and transpiration. Stomatal transpiration was greater in warm-hardened seedlings than in cool-hardened seedlings. Cuticular transpiration was found to be greater in cool-hardened excised shoots than in warm-hardened shoots. Needle cuticle thickness increased in seedlings exposed to both warm and cool temperatures, however, cuticular growth after bud initiation was greater in the warm-hardening regime.