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 c renata) cultivar 'Marigoule' shoots are reported and discussed. The tr eatments were: (1) shoot girdling (2-3 cm above stool-insertion point) ; (2) etiolation (covering stoolbed with soil); (3) girdling and etiol ation; (4) untreated control. Only the shoots of treatment (3) formed adventitious roots (70% rooting). Etiolation induced no substantial di fferences 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 swell ing of the cortex just above the girdle, and the production of multi-s eriate xylem rays, especially notable in treatment (3). This latter tr eatment also evinced diminished shoot-tissue differentiation compared with treatments (2) and (4), and poorly differentiated cortex sclerenc hyma cells, which were arranged not as rings but in irregularly shaped groupings. Root primordia in the early formation stages were found ne xt to the multi-seriate xylem rays in the youngest phloem of the treat ment (3) shoots. These findings indicate that root formation occurs ov er a fairly lengthy period and is associated with anatomical changes i n the involved shoot zones. The effects of etiolation and girdling in treatment (3) could not be separated, suggesting their synergistic inf luence on rooting in chestnut.