MOBILIZATION OF STORAGE MATERIALS THROUGH THE IN VITRO ROOTING OF WALNUT (JUGLANS REGIA L.) COTYLEDONS
Through the rooting process, some parenchymatic cells became elongated and after 5 days of culture, they appeared nearly empty of storage materials. These type of cells were surrounding the other small and isodiametric cells with a slower degradation of reserve contents, which remained highly stained and constituted nodules of organization that will give place to new roots. These facts were not observed in cotyledonary portions cultured in no rhizogenic conditions.
Quantification of ribose as indicator of total RNA content, showed an increase that preceded root initiation.
Portions pretreated with an inhibitor of polar transport of auxins (TIBA), only showed a delay of reserve degradation and RNA expression. However, with an inhibitor of protein synthesis (cycloheximide) these events were accompanied by a new tissue organization; individualized chains of cells were formed and their association gave place to the formation of root nodules.
All the results that were correlated with root expression, seemed to occur according to three rooting phases: i) Induction phase, with an increment of RNA contents related to the beginning of reserves degradation and also related to the presence of auxins in the culture medium; ii) Initiation phase, characterized by the formation of the cellular nodules with a specific distribution of the reserve materials, and a decrease of RNA at the initial levels; iii) Manifestation phase, where storage materials remained only in cells associated to vascular bundles and areas involved in the formation of new roots, and with no variation in the total RNA content.