Development of photosynthetic ability of hybrid walnut plantlets during acclimatization

Growth, carbohydrate content and gas exchange were studied in hybrid walnut plantlets (Juglans nigra n degrees 23 x Juglans regia) during acclimatization in a growth chamber. The acclimatization was conducted during 28 days at 28/25 degrees C (day/night temperature). During the first seven days, respiration was higher than photosynthesis (gas exchange calculated on a daily basis); growth and maintenance processes appeared to be chiefly supplied by the carbohydrates which were stored in the callus and roots during the in vitro phase. From day 8 to day 28, the daily balance of gas exchange was positive; the plantlet was autotrophic for carbon. In spite of that: the carbohydrate content of the plantlet was very low at the end of the acclimatization phase.