The contribution of bent canopy to crop growth in cut rose (Rosa hybrida L.)

MSc-thesis abstract (submitted 31 August 2017): Shoot-bending technique has been widely used in greenhouse cut-rose (Rosa hybrida L.) production all over the world due to cut-rose quality improvement. However, how the bent canopy affects light interception and photosynthesis of the whole canopy is still unclear.
In this research, rose cultivar Red Naomi was used to investigate the effects of bent canopy on upright shoot growth and the contribution of bent canopy to whole canopy light interception and photosynthesis.

Upright shoot architectural parameters, dry mass and partitioning, leaf photosynthetic properties and light distribution
along upright and bent shoots were measured. Furthermore, the contribution of bent canopy to whole canopy photosynthesis was
estimated using the big leaf model.

Rose plants with more bent shoots produced significantly greater dry mass in organs of stem, leaf and flower per upright shoot. However, plants with fewer bent shoot allocated a larger proportion of assimilates to leaf and flower at the expense of the fraction of assimilates allocating to stem.
Longer and thicker upright shoot, larger leaf area, greater average leaf angle, higher growth rates of leaf, stem and flower were found in plants with more bent shoots.

The relative contributions of bent canopy to whole canopy light interception and photosynthesis were decreasing with new upright shoot growth and then stayed stable when upright shoots were fully-developed. During the first two weeks of new upright shoots growth, bent canopy contributed over 50% to canopy light interception and photosynthesis because of little shading by the upright shoot as well as low photosynthesis from upright shoot. When upright shoots were fully-grown, bent canopy contributed around 20% to the light interception of the whole canopy.
Bent canopy in plants with one bent shoot and three bent shoots contributed about 15% and 25% of the total photosynthesis, respectively.

Keywords: Rosa hybrida L.; Bent shoot; Growth; Light interception; Photosynthesis