THE EFFECT OF SUCROSE ON THE DEVELOPMENT OF HYBRID WALNUT MICROCUTTINGS (JUGLANS-NIGRA X JUGLANS-REGIA) - CONSEQUENCES ON THEIR SURVIVAL DURING ACCLIMATIZATION

We studied the effect of sucrose concentration in the root-development medium on the formation of adventitious roots and survival of microcuttings during acclimatization in 2 interspecific hybrid walnut (Juglans nigra n degrees 23 x J regia) clones. Sucrose increased the rooting percentage (fig 1), the number of adventitious roots (fig 2A) and the dry-matter content (table I) per rooted shoot. These effects were due to the energy properties of sucrose rather than to its osmotic function. High sucrose concentrations in the root-development medium (> 20 g.l(-1)) resulted in a high soluble carbohydrate content in the plantlets (fig 3), mainly located in roots and callus. The 2-clones showed different capacities in rooting and growth. Survival of microcuttings during acclimatization was not directly influenced by the sucrose concentration (fig 5) but was correlated with the number of adventitious roots (fig 6A) as well as with the number of leaves (fig 6B) present at the time of transfer to the growth chamber for each individual plant.