Genotypic and phenotypic differences in fresh weight partitioning of cut rose stems : implications for water loss

In vase life studies, cut flower fresh weight is often recorded, but mass distribution is not. Here, we addressed the variation in mass distribution among the different cut flower organs, and assessed its role in water relations. In the first part of the study, excised leaves, flower, and stem were exposed to desiccation. Water loss (per fresh mass) of both flower and stem was low, relatively constant over time and comparable between the three studied cultivars. Instead, water loss (per fresh mass) of leaves was initially much higher, and decreased upon desiccation due to stomatal closure. Leaves had the greatest contribution to cut flower water loss, while this contribution was different among the tested cultivars. Similar findings were obtained following evaluation of the contribution of leaves, stem, and flower to cut flower transpirational water loss under conditions where water supply was not limiting. A strong correlation between the leaf weight loss in the desiccation experiment and the length of vase life was found. Low evaporative demand during vase life evaluation increased vase life, and alleviated vase life differences between cultivars. Instead, high evaporative demand during evaluation shortened vase life, and increased the noted differences in vase life between cultivars. In the second part of the study, fresh weight partitioning was assessed within and among cut rose cultivars. Among eight cultivars, same weight flowering stems may have over 11% difference in leaf weight. In conclusion, cultivar differences in transpirational water loss between cut flowers of the same weight may be attributed to variations in both stomatal characteristics and mass partitioning to the leaves.