Optimum pH Value for Improving Postharvest Characteristics and Extending Vase Life of Rosa hybrida cv. Tereasa Cut Flowers

This experiment was conducted on cut Rosa hybrida L. (cv. Tereasa) during two summer seasons; 2015 and 2016 at the laboratory of the Ornamental Horticulture Department, Faculty of Agriculture, Cairo University. Stems of cut Rosa flowers were dipped in five different pH solutions; 3.0, 4.6, 5.6, 6.6 and 7.0 in the presence of 2% sucrose. The pH values were adjusted through using 0.2 M Na2HPO4 and 0.1 M citric acid. The results revealed that, the maximum values of vase-life and in turn the water uptake (4.54 ml/g) which was highly correlated with vase life duration, over the two seasons, was recorded with solution pH 3.0 followed by pH 4.6. Also, the lowest significant reduction in flower fresh weight was recorded with pH 3.0. The highest mean count of total spores forming bacteria in vase solution was recorded at pH 6.6, whereas the lowest was obtained with pH 3.0. Increasing pH level negatively influenced Rose flowers longevity through increasing free total amino acid as well as reducing total sugar and total chlorophyll and anthocyanin concentrations. Whereas, pH 3.0 was able to maintain a higher osmotic potential of cells through enhancing the total sugar and the total chlorophyll and anthocyanin concentrations which were in conformity with enhancing antioxidant enzymes, i.e. superoxide dismutase (SOD) and catalase (CAT) activities in leaves. In conclusion, decreasing the solution pH enabled the cut Rose flowers to maintain higher osmotic potential, delaying senescence and enhancing flowers longevity.