Insights into the changes in leaf functional traits of Aralia elata grown under different shading treatments

Aralia elata is a traditional medical plant endemic to China, and its young leaf buds have important potential edible value. However, its optimal cultivation conditions are poorly understood. Here, we determined the effects of shading on the leaf trait morphology and physiology of A. elata. Plants were exposed to four shading intensities (20%, 35%, 50%, 60%, and a control grown in no shading) for three growing stages (30, 40, and 50 d). Leaves from three canopy positions (Top, Central, and Bottom) were sampled to asses morphological, physiological, and photosynthetic functional traits. The 50% shading treatment was found to increase the height of A. elata. Antioxidant enzyme activity, such as that of peroxidase (POD) and catalase (CAT), together with the relative conductivity (REC) were lower under 50% and 60% shading. Chlorophyll content was highest at 3.15 mg & BULL;g(- 1) under the 50% shading treatment. Meanwhile, the maximum quantum efficiency (Fv/Fm) of photosystem II, quantum efficiency of electron transfer (YII), and photochemical quenching (qP) were all higher under 50% and 60% shading, while non-photochemical quenching (NPQ) was lower. In addition, antioxidant enzyme activity, chlorophyll content, Fv/Fm, YII, qP, and NPQ were all higher in Top leaves than in Central and Bottom leaves. Correlation analysis showed that CAT and POD activities were negatively correlated with Fv/Fm, YII, and qP. This study demonstrates changes in leaf functional traits under shading treatments, and shows that 50% shading created the optimal growth conditions for A. elata. These results can contribute to improving the growth characteristics of this species.

Automated summary

This study found that 50% shading treatment can increase the growth height of Aralia elata and reduce the activity of antioxidant enzymes and relative conductivity. It also increases chlorophyll content and improves the maximum quantum efficiency of photosystem II, quantum efficiency of electron transfer, and photochemical quenching. Meanwhile, antioxidant enzyme activity, chlorophyll content, maximum quantum efficiency, quantum efficiency of electron transfer, photochemical quenching, and non-photochemical quenching are all higher in top leaves compared to central and bottom leaves.