Influence of the Irradiance on Carbohydrate Content and Rooting of Cuttings of Pine Seedlings (Pinus sylvestris L.).

Seedlings of Pinus sylvestris L. were grown for 6 weeks at an irradiance of either 8 or 40 watts per square meter in a controlled environment room. Cuttings from these plants were rooted in tap water for 75 days at either 8 or 40 watts per square meter. The photoperiod was 17 hours.During the first 30 days of the rooting period quantitative changes in carbohydrates were recorded in cuttings from the different treatments. The carbohydrate contents of the cuttings were mainly regulated by the irradiance during the stock plant stage and generally a higher carbohydrate level was found in cuttings from stock plants grown at 40 watts per square meter.The irradiance during the rooting period had only minor effects on the time course of root formation, whereas the irradiance during the stock plant stage did influence the subsequent root formation. Cuttings from stock plants grown at 8 watts per square meter rooted faster and with higher frequency than those from stock plants grown at 40 watts per square meter. These results are discussed in relation to the mentioned irradiance effects on carbohydrate content.