Effects of Osmotic Water Stress and Gibberellic Acid on Initial Growth of Oak Seedlings

Abstract

Red and white oak seeds were treated and untreated with gibberellic acid (GA) and then watered with graded polyethylene glycol 400 solutions to simulate various soil water stress conditions. Seedling growth decreased as the osmotic potential of the soil solution decreased from −1/3 bars to −4 bars to −8 bars (the low, moderate, and high osmotic stress conditions, respectively). Seedling dry weights at high stress condition averaged only 11% of seedling dry weights at low stress condition. At high stress condition, shoot growth was more suppressed than root growth. White oak roots grew somewhat better than red oak roots at high stress condition.Treatment of seed with GA prior to germination stimulated stem elongation and number of leaves per plant but inhibited formation of lateral roots and other aspects of shoot and root growth, especially among white oak seedlings. The GA-stimulated stem growth observed at the low stress condition was completely suppressed at moderate and high stress conditions. GA-white oak seedlings appeared to be less tolerant of soil stress than untreated seedlings.