CHANGES IN RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE OXYGENASE AND PHOSPHOENOLPYRUVATE CARBOXYLASE ACTIVITIES AND (CO2)-C-14 FIXATION DURING THE ROOTING OF STRAWBERRY SHOOTS IN-VITRO

The potential for carbon fixation was investigated in in vitro strawbe rry (Fragaria x ananassa Duch. Kent) shoots 5, 10 and 28 d after trans fer to a rooting medium. The activities of ribulose-1,5-bisphosphate c arboxylase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC) and th e time of (CO2)-C-14 fixation were investigated. Five days after trans fer, Rubisco activity was low but was increased two-fold after 28 d. I n contrast PEPC activity was highest at 5 d and declined to about 0.4- fold by day 28. The rate of (CO2)-C-14 fixation was similar at 5, 10, and 28 d after transfer. However, a more rapid incorporation of (CO2)- C-14 into amino acids was observed at 5 than 10 or 28 d after transfer . These results suggest that strawberry shoots undergo a progressive t ransition from heterotrophic to autotrophic carbon fixation during the ir rooting and that PEPC plays an important role in sustaining carbon fixation and amino acid synthesis during the first few days after thei r transfer to rooting medium.