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A Thermoelectric Method for Determining the Rate of Water Movement in Plants¹

ABSTRACT

A thermoelectric method is described for the measurement of stream flow rates in the stems of plants. It has a definite advantage in that repeated measurements can be made on the same plant without damage to it. The method is quite simple and usually requires about 15 minutes for each measurement.

By subjecting cotton plants to different environmental conditions such as temperature, humidity, and wind velocity, it was found that the rate of water uptake and movement in the stem dropped from 114 cm./hr. to 76 cm./hr. when the wind velocity was changed from high to low. A temperature of approximately 99°F. and 20% relative humidity was maintained in both cases. With no wind movement but having a temperature of 82°F. and 62% relative humidity, the rate of water movement for the same plant was 38 cm./hr.

Present data show that this method is well adapted for indicating the effects of micro-climate, soil moisture availability, and soil aeration upon the rate of water uptake and movement within intact plants. In addition, it has other uses which will be of interest to both the soil scientist and plant physiologist.

¹ Contribution of the Texas Agr. Exp. Sta., College Station and Weslaco, Tex. The work reported in this paper is in partial fulfillment for the Ph.D. degree at the Agricultural and Mechanical College of Texas, College Station, Tex. Presented before Div. I. Soil Science Society of America, St. Paul, Minn. Nov. 10, 1954.

² Associate Soil Physicist, Lower Rio Grande Valley Exp. Sta., Weslaco, Tex. (Formerly Graduate Assistant, Department of Agronomy and Texas Agr. Exp. Sta.), Professor of Agronomy, A. and M. College of Texas, and Superintendent, Lower Rio Grande Valley Exp. Sta., Weslaco, Tex., respectively.

Received for publication November 1, 1954.