Conditions of carbonic anhydrase extraction and activity measurement should be adapted to plant species and to tissues of plants. Different extraction and reaction media have been compared in ten different tree species in order to define the best conditions for carbonic anhydrase activity measurement. Bias and variability of differences in measured values were analysed according to Bland and Altman method. A comparison of titrimetric method with the traditional electrometric method of

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... of CA activity in the ten species revealed that the measures were in agreement justifying the use of both methods for measurement of the enzyme activity interchangeably. Use of Tris-HCl buffer, 0.1 M (pH 8.3) allowed for a better stabilization of the enzyme during extraction and estimation. Use of potassium phosphate, sodium borate and veronal buffers is discouraged during extraction of the enzyme as the enzyme activities varied with species. Titrimetric method was found to be better over the electrometric method since change in colour appeared to be a better indicator of the end point of the reaction than measurements using a pH meter.