Giberellic Acid in the Expansion of the Thermal Range of Lettuce Seeds

Lettuce presents an increasing demand, which makes necessary the expansion of the areas destined to its planting. Temperature is a limiting factor, because it acts directly on germination, where changes and adjustments in the hormonal balance, mainly of gibberellin (GA) and abscisic acid (ABA), occur. The objective of this study was to evaluate if the treatment of seeds with gibberellic acid is capable of mitigating the damages caused by high temperatures. The seeds were submitted to germination test, first count, percentage of abnormal seedlings and analysis of shoot and root growth. The treatments consisted of seven concentrations of gibberellic acid (control—not treated with GA, 25 mg L-1, 50 mg L-1, 75 mg L-1, 100 mg L-1, 125 mg L-1, 150 mg L-1) and three constant temperatures (25, 30 and 35 °C). The germination and first count, when submitted at 25 and 30 °C presented an increase up to 50 mg L-1 of GA, while at 35 °C the growth was constant up to 125 mg L-1 of GA. Treatment with GA increased root and shoot length. Giberelic acid mitigated the damage caused to lettuce seeds when subjected to temperatures above the optimum.