CARBOHYDRATE RESERVES AND CO2 BALANCE OF HYBRID WALNUT (JUGLANS-NIGRANO-23 X JUGLANS-REGIA) PLANTLETS DURING ACCLIMATIZATION

Morphological and physiological characteristics of hybrid walnut plant lets were studied during acclimatisation in growth chambers. The study was conducted on two clones, M41 and D152. At the end of the in vitro phase, D152 had produced more adventitious roots but less leaves than M41, M41 accumulated more soluble sugars and starch than D152, During acclimatisation, the greatest increase in growth occurred in root len gth, regardless of the clone studied, However, the dry matter and carb on contents were always higher in M41 than in D152. The morphology of rooted plantlets differed markedly from that of young seedlings, Durin g the first 7 days of acclimatisation, the balance of CO2 exchange on a daily basis was negative (respiration was dominant), During this per iod, the carbohydrates which accumulated chiefly in the roots and call us during the root development phase were used for growth and maintena nce processes, The balance of CO2 exchange (on a daily basis) became p ositive after this heterotrophic phase, The new leaves formed during t he acclimatisation phase appeared to be actively involved in the acqui sition of autotrophy, At the end of the acclimatisation phase, the car bohydrate content of all organs was very low and the plantlet was depe ndent on photosynthesis. The capacity of hybrid walnut clones to survi ve the acclimatisation phase is discussed. (C) Elsevier Science B.V.