ADVENTITIOUS ROOTING IN CHESTNUT - AN ANATOMICAL INVESTIGATION

The effects of girdling and etiolation on the anatomical structure and adventitious rooting of hybrid chestnut (Castanea sativa X Castanea crenata) cultivar 'Marigoule' shoots are reported and discussed. The treatments were: (1) shoot girdling (2-3 cm above stool-insertion point); (2) etiolation (covering stoolbed with soil); (3) girdling and etiolation; (4) untreated control. Only the shoots of treatment (3) formed adventitious roots (70% rooting). Etiolation induced no substantial differences in shoot anatomy in comparision with the control, except for a greater accumulation of starch grains. The two girdling treatments stimulated cell division and growth, particularly evident in the swelling of the cortex just above the girdle, and the production of multi-seriate xylem rays, especially notable in treatment (3). This latter treatment also evinced diminished shoot-tissue differentiation compared with treatments (2) and (4), and poorly differentiated cortex sclerenchyma cells, which were arranged not as rings but in irregularly shaped groupings. Root primordia in the early formation stages were found next to the multi-seriate xylem rays in the youngest phloem of the treatment (3) shoots. These findings indicate that root formation occurs over a fairly lengthy period and is associated with anatomical changes in the involved shoot zones. The effects of etiolation and girdling in treatment (3) could not be separated, suggesting their synergistic influence on rooting in chestnut.