A CRITICAL STUDY OF THE COBALT CHLORIDE METHOD OF MEASURING TRANSPIRATION

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Abstract
The major objective of this study was to determine of a C0Cl2 technic could be used to measure absolute rates of transpiration, with a view to possible appln. of the method in field studies. The standard of comparison was gravimetric water loss from small potted plants. Requirements for adequate sampling and statistical analysis were met. Test plants were Nicotiana tabacum, Pelargonium zonalee, Lycopersicum esculentum, Quercus velutina. and Q. alba. Results obrained indicate that quantitative data can be obtained with the CoCl2 procedure, but these data show no consistent relationship with gravimetric observations. Good agreement between the 2 methods was obtained occasionally, but frequently the results were very divergent. The CoCl2 technic apparently measures some unidentified determinant of transpiration which can vary independently of the total moisture loss as measured gravimetrically. Potted plants which appear quite similar may differ significantly in their transpiration rates as measured gravimetrically. CoCl2 tests on different leaves show a high order of variability.

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