EFFECTS OF GIBBERELLIC ACID ON GROWTH OF ANTIRRHINUM MAJUS ’UTAH WHITE’ IN A CARBON DIOXIDE-ENRICHED ENVIRONMENT

Abstract

Snapdragon seedlings (Antirrhinum majus ’Utah White’) were benched in two adjoining greenhouse compartments. A randomized-block design including three concentrations of gibberellic acid (GA3) and a distilled water control was employed in each compartment. Treatments were replicated three times. Treatment of snapdragon seedlings with GA3 significantly increased the length of inflorescences, the overall height of the plants at maturity and the fresh weight of the tops when the plants were grown in a carbon dioxide-enriched atmosphere. Treatment hindered root development and reduced chlorophyll content of leaves in relation to dry weight. Plants grown in an atmosphere containing 0.09% CO2 had longer inflorescences, were taller, had greater fresh weight and more chlorophyll at each level of treatment with GA3 than such plants grown in an atmosphere containing 0.03% CO2. However, these comparisons were considered significant only for total height (control) and fresh weight of tops (0, 10 and 50 μg/ml GA3). Whereas GA3 at 10 μg/ml reduced length of roots proportionally in both levels of CO2, higher concentrations of GA3 continued to give significant reduction only under the higher level of CO2.