Measuring Water Potential (Activity) from Free Water to Oven Dryness

Autor:	Herman H. Wiebe
Rok vydání:	1981
Předmět:	Hygrometer Water activity Physiology Chemistry Psychrometric constant Psychrometrics Analytical chemistry Plant Science Thermocouple Environmental chemistry Genetics medicine Slurry Dryness Relative humidity medicine.symptom
Zdroj:	Plant Physiology. 68:1218-1221
ISSN:	1532-2548 0032-0889
DOI:	10.1104/pp.68.6.1218
Popis:	Water activities (potentials) in plant materials were measured over the range from free water to oven dryness with a Spanner thermocouple psychrometer. In a two-step procedure, water was first condensed on the thermocouple junction for several minutes. The sample was then inserted under the wet thermocouple and the maximum psychrometric cooling was measured in about 10 seconds. Calibration was with saturated salt slurries of known water activities. Psychrometric cooling was a nearly linear function of the water activity and of the negative log of the water potential. The psychrometric cooling to water activity relationship agreed with wetbulb temperature depression to relative humidity relationships given in tables. Water activities of wheat grains and leaves decreased sharply in a curvilinear fashion as their water contents decreased. Some problems of the procedure are discussed.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::6cacf11d7cb64c45fc62e6b4ea02402f https://doi.org/10.1104/pp.68.6.1218 Zobrazit plný text záznamu