ANATOMICAL INVESTIGATION ON WALNUT SHOOTS AFTER IBA APPLICATION

The present research aimed to investigating the effect of IBA on young growing shoots of 'Hartley' walnut mother plant, when indole-3-butyric acid is applied on plastic tapes directly on the shoots. Ten-year-old trees has been severly pruned during the winter of 1986 in order to obtain the development of vigorous shoots in the following spring.

Applied to the shoots were black tapes made of 1 inch wide PVC; they were prepared using differents concentrations of IBA solution in acetone (500, 1000, 2000 ppm) crystallized at room temperature. IBA was attached to the tapes simply by leaning them on glass plates holding the solutions.

For each treatment 16 shoots were treated by applying the tapes on to the third sub-apical bud. Untreated shoots were taped without IBA treatment, and shoots without tape were also used.

The observations that have been carried out focused on growth, bending, and anatomical changes of the shoots. After 5 weeks the shoots were harvested, fixed in Karpetcenko solution, and finally cut in order to obtain thin slices that were stained with safranin and fast green for microscopic observations.

The results shows that the treatment with tape but without IBA did not influence the tissue, neither in macro or microscopic observations. The tape treated with IBA induced a growth reduction and bending effect proportional to the IBA concentration. The microscopic analysis showed relevant changes in the tissue structure. An interesting observation has been the presence of anomalous parenchymal rays; some meristematic cells develop from the rays to the cambial zone and under the cortex giving rise to root primordia. This effect seems to be particulary evident on shoots treated with 1000 ppm IBA.

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