| 'Grand Rapids' lettuce (Lactuca sativa L.) was grown in nutrient culture in five controlled environment chambers during three separate months to determine environmental uniformity in space and in time. Environmental conditions were designed to replicate those used in the base-line studies by the American Society for Horticultural Science Growth Chamber Committee. Significant variation in growth occurred both in space (among chambers) and in time (among months). The variation in time was greater than the variation in space. Variation within chambers was not significant. Environmental factors affecting biological variability are discussed. The described procedures and plant growth data are recommended for use as an environmental bioassay.; Using these controlled environments, the effect of root zone temperature on young tomato plants (Lycopersicon esculentum Mill.) was evaluated. Growth rates were measured at root zone temperatures of 15, 20, 25, and 30(DEGREES)C in a near optimum foliar environment. Growth was severely restricted at 15(DEGREES)C. Analysis of xylem exudates revealed hormonal differences among plants grown in different root zone temperature treatments. Fifteen (mu)M additions of GA(,3) to nutrient solution increased specific leaf area, total leaf area, and growth. Gibberellic acid-induced growth stimulation was more profound at 15(DEGREES)C than at 25(DEGREES)C. |
