Training system affects whole canopy photosynthesis of the greenhouse roses (Rosa hybrida 'Habari').

Greenhouse rose canopy management by means of different types of training systems can strongly affect the rate of whole plant photosynthesis. Investigating this, we developed 5 various kinds of arching technique to evaluate their possible effect on the both entire plant photosynthetic capacity and its variations within the canopy leaf layers. Canopy of the rose plants (R. hybrida ‘Habari’) were divided into four vertical intervals, assigning 3 intervals for upright shoots and one for bent section of the canopy. Leaf area of each interval was determined using a simple relationship linking the area of leaves to their length. A portable photosynthesis measurement system was used to measure the rate of gas exchange and incident light within different layers of the canopy. Chlorophyll content of each layer was determined spectrophotometrically by extracting in 80% acetone. Results showed that training system significantly affected leaf area and photosynthetic rate, while incident light and chlorophyll content did not differ significantly among different training systems. Training system ‘T.S. 1-1’ indicated the lowest photosynthesis rate and leaf area in comparison to the other systems. Canopies trained by the method of ‘T.S. 3-3-2’, T.S. 5-1’ and ‘T.S. 5-3’ indicated the highest leaf area and correspondingly higher photosynthetic capacity. Bent layer of the canopy exhibited the maximum rate of the photosynthesis among all the layers and accounted for about 40% of the whole plant photosynthetic rate. Total chlorophyll as well as chlorophyll a and b decreased with canopy depth, showing a possible degradation as a result of leaf aging along the flower shoot.