HYDRAULIC CONDUCTIVITY IN FLOWER STEMS OF ROSA CV. POLO WITH DIFFERENT LENGTH

Abstract

Flower stem length is a quality criterion in cut roses (Rosa hybrida L.). Cutoff sectional area and water absorption in long stems are larger than in short stems. Thus, a short stem has a small xylem area, which might restrain water flow and tissue hydration, and reduce life in a flower vase (VL). Therefore, this study describes xylem vessels characteristics and their relationship with water conductivity capacity, and how they influence VL in long (50 cm), medium (35 cm) and short (25 cm) stems of Polo rose. Vulnerability indexes, relative hydraulic conductivity, and water flow in stem fractions, floral unity and VL were calculated. Comparison between xylem diameter in short, medium and long stems showed values of 4.41, 12.4 and 12.51 µm, respectively. In the same order, vulnerability indexes were 0.14, 0.83 and 1.29; while relative hydraulic conductivities were 898, 25,269 and 19,628, respectively. In regard to physiological traits, shorter stems also registered reduced flow and consumption in both stem fractions and floral units. VL in long and medium stems was 11.4 and 10.6 d, compared to only 7.3 d in short stems. It was concluded that short diameter xylem vessels with reduced hydraulic conductivity have a negative influence on tissue hydration and VL.