Studies on the Effect of Growth Regulators on Growth and Tracheid Characters of Pinus caribaea Seedlings

Pot culture experiments were conducted with the seedlings of Pinus caribaea. Morelet var.hondurensis is to study the effect of different growth regulators on height aad diameter growth and tracheid characters. Gibberellic acid, Indole acetic acid and Indole butyric acid were given at 10, 100 and 1000 ppm concentrations. Studies reveal that except IAA 1000 ppm all the other growth regulator treatments have enhanced the height growth. Gibberellic acid at 1000 ppm has given best height growth, whereas, the best diameter increment has been obtained under IAA 10 ppm. Tracheid length variations among different treatments are highly significant. The longest tracheids were formed under GA 1000 ppm. No significant variations have been observed for tracheid and lumen diameter, but wall thickness results have shown significant differences among different treatments in the middle region.