Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: 3/14/2007
Publication Date: 7/14/2007
Citation: Taylor, M., Nelson, P., Frantz, J. 2007. Impact of flower removal and light and temperature stresses on acidification of nutrient solution by geranium (pelargonium x hortorum bailey). HortScience. Scottsdale, AZ, July 16-19, 2007. Interpretive Summary:
Technical Abstract: The cause of sudden substrate pH decline by geranium (Pelargonium x hortorum Bailey) is unknown. Published reports indicate that this response can be influenced in other plants by temperature and light extremes. The first of five experiments compared plants with all flowers removed to plants that were allowed to flower. Experiment 2 compared plants grown at 4 light levels (105, 210, 450 and 1020 µmol•m–2•s–1). Experiment 3 compared plants grown at 4 temperatures (14/10, 18/14, 22/18 and 26/22º C day/night). Experiment 4 was a repeat of experiment 1 and experiment 5 was a factorial combining the 3 highest light levels and the 3 highest temperature levels. Plants allowed to form flowers had a final substrate pH of 6.3 compared to 5.7 for plants where flowers were removed. With increasing increments of temperature, substrate pH declined from 6.8 to 4.6 and with increasing light intensity from 6.1 to 4.8. There was no effect of flower removal in experiment 4. Light and temperature had no consistent effects in experiment 5 throughout 46 days after planting with most pH values remaining in the acceptable range of 5.6 to 6.1. By 60 days, temperature treatments began to segregate with pH being highest in the low temperature treatments and lowest, down to 5.5, in the highest temperature treatments. High temperature stimulated geranium acidification in both experiments, with the effect more severe in the first experiment. The flowering and high light effects were not duplicated in the second trial. This indicates that an additional factor is involved in expression of the light, temperature, and flowering control of acidification.