Unraveling Light Spectrum Effects on Fruit set in Sweet Pepper

Summary

Fruit set, the percentage/number of flowers successfully developed into fruits, is a crucial component for crop production. Sweet pepper has a generally low fruit set. Moreover, sweet pepper fruit set fluctuates over time in a long-term production, which causes unstable product price and labor demand. This PhD thesis investigated whether light spectrum influences fruit set in sweet pepper. Climate chamber studies shows that additional far-red light reduces fruit set, compared to plants grown under LEDs without far-red. However, additional far-red enhances fruit set when sweet pepper plants were cultivated in greenhouses, under sunlight, as in commercial production. This suggests the effect of far-red depends on other conditions. This thesis also shows that high ratios of blue to red light reduces fruit set. The physiological mechanisms underlying the effect of far-red and blue to red light ratios on fruit set were investigated and discussed in this thesis.