LEAF PHOTOSYNTHESIS, FLOWER RESPIRATION AND FLOWER LONGEVITY OF POT ROSES INFLUENCED BY CULTIVAR AND GROWING ENVIRONMENT

Photosynthesis and flower respiration were investigated on single-stemmed plants of Rosa L., cultivars Meiferjac, Ruijef and Ruirosora, grown in controlled environment growth chambers simulating summer-like and winter-like greenhouse growing conditions. When the flower on each plant reached developmental stage 2, one group of plants was placed under a simulated interior environment at 21 ^oC under 15 μmol·m^-2·s^-1 from cool-white fluorescent lamps for postharvest evaluations. Photosynthesis and flower respiration evaluations were performed under laboratory conditions at 23 ^oC, using a LI-COR 6400 Portable Photosynthesis System. Flower respiration was determined under dark conditions by enclosing the whole attached rose flower, at development stage 2, into the 6400-05 LI-COR Conifer Chamber. The same pattern of differences was observed for flower respiration and flower longevity when comparing growing environments for each cultivar. Plants of cultivar Meiferjac and Ruijef exhibited greater flower longevity and lower flower respiration under summer as compared to the winter growing environment. Plants of cultivar Ruirosora exhibited similar flower longevity and similar flower respiration in both environments. Higher maximum photosynthetic assimilation rates were found for plants grown under the winter environment versus summer with no differences among cultivars.

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