Cytokinins and mineral nutrition in Actinidia deliciosa (kiwi) shoots cultured in vitro

Benzyladenine (BA) uptake and metabolism, zeatin-type cytokinins and residual macronutrients in the culture medium were measured after 0, 0.5, 1, 2, 8 and 16 hours of culture in Actinidin deliciosa explants cultured in liquid medium using cellulose plugs as support of the explants. At the end of the culture period, low percentages of hyperhydric shoots were found. During the first 30 min of culture the amount of BA in the culture medium dramatically decreased. 8-[C-14] BA was rapidly metabolized by rootless shoots of kiwifruit cultured in liquid medium and it could be the reason of the low percentage of hyperhydric shoots. The levels of zeatin-type cytokinins remained constant during the first 16 h of culture, which could suggest that BA acts per sea and not through endogenous cytokinins in the development of kiwifruit explants. Ammonium and phosphate were mainly uptaken during the first hours of culture and these ions were the most consumed at the end of the culture period (35 days). MS medium could be too rich for the culture of kiwifruit in liquid medium except for phosphate which concentration should be even increased.