Effect of drought stress on shoot growth and physiological response in the cut rose ‘charming black’ at different developmental stages

To investigate the responses of the cut rose ‘Charming Black’ to drought stress at different growth stages, we defined five stages of flowering and shoot development defined from initiation of the axillary bud to full complement of the floral parts. Drought stress was applied from earliest bud break (stage 1) to floral bud appearance (stage 5). After the stage of treatment, irrigation was restored to normal levels. Results showed that rose plant growth was not only influenced by the environment but also by different stages of floral bud appearance. The stem length as well as the time it took to reach different stages of rose development was influenced by the applied irrigation and supplemental lighting conditions. Drought stress did not have negative effects on the quality of the flower at stage 1. Drought stress reduced the vegetative growth phase and promoted flowering in the early stages (2–3), and significantly decreased shoot length, shoot weight and leaf area. However, at the stage prior to flower appearance (stage 5) drought stress was more severe. The most damage was accompanied by malformed floral buds that had shorter petal length and distorted petals. Furthermore, photosynthesis was negatively affected by drought stress at stage 5, even after re-irrigation, for which this negative effect could not be compensated.