Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 1, 1998
Publication Date: N/A
Interpretive Summary: Much plant research is done with plants that are grown in pots. Pot experiments are especially attractive in drought studies because the amount of soil moisture available to the plants can be closely regulated. There are, however, indications that decreasing pot size can result in decreasing rates of plant growth. The objective of this study by Agricultural Research Service scientists in Gainesville, FL, was motivated by the experimental question of whether plant response to drying soil would also be influenced by the size of the pot in which the plants were grown. Corn and soybean plants were studied in pots ranging in size from 2.3 to 16.2 L. The growth of well-watered plants of both species were clearly decreased with decreasing pot size. The response of transpiration rate to the relative soil water content as the soil dried was, however, equivalent across all pot sizes. These results indicated that pot size was not an important experimental variable in studying the physiological response of plants to drying soil.
Technical Abstract: Many experiments are conducted in greenhouses or growth chambers in which plants are grown in pots. Considerable research has shown that pots can have a limiting effect on overall plant growth. This research was undertaken to examine the effects of pot size on transpiration rates of maize (Zea maize L.) and soybean (Glycine max L.)plants undergoing drought stress. Maize plants were grown in 2.3, 4.1, 9.1 and 16.2 L pots and soybean was grown in the three larger pots. For each pot size, plants were divided into two watering regimes, a well-watered control and a water-deficit regime. For both maize and soybean, and in both watering regimes, there was a reduction of shoot dry weight and total transpiration with decreasing pot size. Although a longer time was required to reach the same fraction of transpirable soil water (FTSW) with increasing pot size, there were no significant differences among pot sizes in the FTSW point at which transpiration began to decline (FTSW approximately 0.31 for maize and approximately 0.35 for soybean). These results indicated that, regardless of pot size or plant size, the overriding factor determining transpirational response to drought stress was soil water content.