EFFECTS OF THERMAL WOUNDING, SHADING AND EXOGENOUS AUXIN ON SOME SPROUTING RESPONSES OF COAST REDWOOD SEEDLINGS

The effects of wounding, shading, and indole-3-acetic acid (IAA) on sp routing responses were examined in coast redwood (Sequoia sempervirens D. Don (Endl)) seedlings. In August, two-year-old seedlings were give n one of three thermal wounding treatments made with a blowtorch at th e stem base. After 8 months, the heat-wounded seedlings were decapitat ed above the burl and IAA (0.00% to 1.00% by weight in lanolin) was ap plied to the cut surface every week for 8 weeks. Throughout the 8-week hormone treatment, the decapitated seedlings were subjected to one of three shading treatments (no shade, 70% shading and complete darkness ). At the beginning of June, sprouts were harvested from each stump an d measurements made of the length of the tallest sprout, number of spr outs, dry weight of all sprouts, and mean dry weight per sprout. All s prouting parameters showed negative responses to IAA. Shading decrease d sprout number and sprout dry weight. Wounding increased maximum spro ut length and dry weight per sprout but decreased the number of sprout s. Only the 2-way interaction between IAA and wounding was not signifi cant for any of the responses.