Photosynthetic Performance and Growth-related Traits of Petasites japonicus under Different Shading Conditions

초록

P. japonicus, a perennial herbaceous plant widely consumed as a vegetable in Korea, requires optimized light management during summer cultivation to ensure stable growth and high-quality yield. This study aimed to evaluate the photosynthetic response and quality traits of P. japonicus under varying shading conditions. Light response curves were measured using a portable gas exchange system and analyzed using three nonlinear regression models: Exponential, Rectangular Hyperbola, and Non-rectangular Hyperbola. Among these, the Exponential model showed the highest predictive accuracy (R2 = 0.9970), suggesting it captures the gradual saturation pattern of photosynthesis. Physiological parameters such as net photosynthetic rate (Pn), dark respiration rate (Rd), light compensation point (LCP), and light saturation point (LSP) decreased significantly with increasing shading intensity, indicating reduced light utilization efficiency under deep shade(95%). In contrast, the 55% shading treatment resulted in the highest fresh weight and leaf area, suggesting improved photosynthetic productivity under moderate shading. However, leaf hardness significantly decreased with higher shading, indicating a trade-off between yield and textural quality. Leaf color analysis revealed that RGB and HSV values were sensitive to shading levels, with Value (V), red (R), and saturation (S) values declining as shading increased. These results suggest that P. japonicus exhibits a shade-tolerant growth strategy, with moderate shading improving biomass and leaf expansion while deep shading suppresses photosynthesis.

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