Studies on development and maintenance of photosynthetic capacity in leaves of assimilation shoots in rose

Roses are widely cultivated in greenhouses. In rose cultivation, the basal shoots emerging in the early stage of growth are artificially bent down as assimilation shoots to effectively catch sunlight, and then the shoots that emerge successively are cut and used for rose products. This 'shoot-bending' (or 'arching') cultivation technique leads to a higher yield and high quality of the flowering shoot. This study investigated: I) the growth of photosynthetic organs in assimilation shoots, and II) development and senescence of photosynthetic capacity in assimilation shoots. To form assimilation shoots having higher photosynthetic capacity, low temperature (LT) is better than high temperature (HT). The optimum temperature for photosynthesis was approximately 20degC for LT grown leaf, and approximately 30degC for HT grown leaf. Decrease in photosynthetic rate with senescence of leaves was closely related with Rubisco content and nitrogen content, but less related with chlorophyll content. After leaf expansion, leaf nitrogen content greatly decreased in HT, and it was suggested that the photosynthetic rate greatly decreases if the temperature of bent assimilation shoots is high. The number of days necessary for flowering and the quality of cut rose depended on the temperature during growth. However, it is shown that fewer days are necessary for flowering and the quality of cut rose is better for assimilation shoots grown in LT than in HT.