THE EFFECT OF LEAF SOURCE AND DEVELOPMENTAL STAGE ON SHOOT ORGANOGENIC POTENTIAL OF SWEETGUM (LIQUIDAMBAR-STYRACIFLUA L) LEAF EXPLANTS

Leaf explants harvested from shoot proliferating cultures and intact plants of Liquidambar styraciflua 'Variegata' were placed on solidified Woody Plant medium supplemented with 0.1 mg 1-1 (0.5-mu-M) naphthaleneacetic acid and 2.5 mg 1-1 (11.1-mu-M) benzyladenine to initiate shoot meristems directly. Leaves from intact plants produced over 4 times more adventitious shoots than leaves from in vitro shoots and had a greater tendency to form shoots on the lamina. The relative developmental age of leaf tissue used dramatically influenced the shoot organogenic response observed for leaf explants from intact plants of L. styracifua 'Variegata' and 'Moraine'. Leaves that were either 20% or 50% of full size and still actively expanding were superior to other developmental stages for shoot organogenesis. As developmental leaf age increased throughout the period of leaf expansion, the number of shoots forming on the petiole stub remained constant, whereas shoot formation on the lamina increased 8 fold. Shoots derived from 'Variegata' leaves rooted well and grew normally as plants. Differences in rooting ability and plant size could be detected between groups that had been separated according to explant source (in vitro vs. intact plant) and the location of shoot formation (petiole vs. lamina).