DETERMINING OPTIMUM PH AND EC LEVELS FOR EXTENDED VASE LIFE OF CUT ROSA 'FREEDOM', 'CHARLOTTE', AND 'CLASSY'

Abstract

Cut Rosa L. 'Freedom', 'Charlotte', and 'Classy' stems were subjected to solutions of various pH and electrical conductivity (EC) levels. Increasing solution pH decreased vase life. Solutions with an initial pH of 3.1 to 4.0 produced the longest vase life, averaging 13.2 days, when the buffers citrate-borate-phosphate, bis-tris propane-citrate, or their individual components were combined with HCl, NaCl, or NaOH. Solutions with an initial pH of 6.1 to 6.3 produced a vase life averaging 11.6 days and those with a pH of 7.3 to 8.2 produced a vase life averaging 9.8 days. Despite the use of buffers, the solution pH increased by an average of 1.5 at termination of vase life when HCl was added, decreased by 0.7 when NaOH was added, and decreased by 0.5 when NaCl was added. A 2 hour treatment in high pH solutions had no effect on vase life. Increasing pH was correlated with reduced water uptake. The overall solution that produced the longest vase life had a low pH, 3.1 to 4.0, and an EC of 1.0 to 1.3 dS·m -1 . Although 'Freedom', 'Classy', and 'Charlotte' responded differently to the various treatments, the optimum solution composition was nearly the same. In solutions where both initial pH and EC varied, initial pH accounted for 30 to 54% of variation in vase life (average 44%) and initial EC accounted for 18 to 48% of variation (average 36%). In all cases, final pH and EC were not as strongly correlated with vase life as initial pH and EC.