We studied the effect of shade on the phenology, growth, berry yield, and chemical content of two common blueberry species (Vaccinium myrtilloides and V. angustifolium) in Northwestern Ontario. We hypothesized that high shade would delay vegetative and reproductive phenology and decrease berry yield by increasing resource allocation to vegetative vs. reproductive growth, whereas moderate shade would increase berry phenolic content and antioxidant capacity. We subjected transplanted blueberry plants to a controlled shade treatment and evaluated plant phenological events, vegetative and reproductive growth, berry phenolics, and antioxidant capacity. High shade caused an earlier leaf maturation in V. myrtilloides, delayed flowering in V. angustifolium, and prolonged fruit maturation in both. The berry yield of both species decreased with increasing shade. High shade reduced the berry phenolic content and antioxidant capacity, especially in V. myrtilloides. We concluded that shade shifts species-specific vegetative and reproductive phenology, leading to a difference in resource acquisition, resulting in lower berry yield and antioxidant activity.
Keywords: antioxidant capacity; black shading net; blueberry; chemical content; light intensity; phenology; plant physiology; reproductive response; vegetative growth.