Dry Matter Production and Fruit Sink Strength Affect Fruit Set Ratio of Greenhouse Sweet Pepper
Masaru Homma, Takafumi Watabe, Dong-Hyuk Ahn, Tadahisa Higashide
Abstract
We investigated the relationships among the fruit set, dry matter production, and source-to-sink ratio of sweet pepper ( Capsicum annuum ) plants grown in a greenhouse. We quantified daily fruit sink strength per stem (st) at m days after transplanting (SST m_st ) by modeling the fruit growth curve. The daily total dry matter production (TDM m_st ) was calculated and defined as the source strength. During an experiment lasting ≈250 days, the fruit set ratio [number of fruit harvested/number of flowers (FSR m )] decreased significantly with increases in both the weekly average SST m_st from 9 days before anthesis (DBA) to 13 days after anthesis (DAA) and the weekly average fruit number (FRN m_st ) from 9 to 1 DBA. FSR m increased significantly with increases in both the weekly average TDM m_st from 1 to 13 DAA and the weekly average source-to-sink ratio [source strength/fruit sink strength (SSR m_st )] from 5 DBA to 13 DAA. During the whole experimental period, significant positive correlations with FSR m were observed for TDM m_st and SSR m_st , and significant negative correlations with FSR m were observed for SST m_st and FRN m_st . FSR m increased until approximately the time when the weekly average SSR m_st at 1 to 7 DAA (anthesis to 156°C⋅d −1 ) ranged from 1.0 to 4.0; then, it showed a saturation curve at SSR m_st values more than 4.0 ( R 2 = 0.81). These results suggest that it is possible to moderate the fluctuations in sweet pepper yield by monitoring the SSR m_st and the number of fruit set.