Construction and evaluation of Polygonatum cyrtonema Hua intercropping based on the growth and physiological adaptability

Polygonatum cyrtonema Hua is typically cultivated under forest conditions that mimic its natural habitat. The understory environment of Actinidia chinensis Planch. orchards shares similar ecological characteristics with forests, suggesting the potential feasibility of intercropping P. cyrtonema within A. chinensis orchards. However, optimizing an appropriate planting model and creating a suitable growth environment for P. cyrtonema requires experimental validation. This study assessed the growth and physiological adaptability of P. cyrtonema under different intercropping conditions by varying A. chinensis cultivars (‘Hongyang’ and ‘Jinyan’), canopy densities (60%, 30%, and full sunlight), and planting densities (row spacing of 25 cm×25 cm, 25 cm×40 cm, and 35 cm×40 cm). Results demonstrated that P. cyrtonema exhibited greater plant height and basal diameter in orchards planted with A. chinensis cv. Jinyan. Under 60% canopy density, chlorophyll content was elevated, while malondialdehyde (MDA) content and ascorbate peroxidase (APX) activity were lower. A 30% canopy density promoted greater plant height. In full sunlight, leaves had reduced relative water content but exhibited increased soluble protein, proline, MDA, total phenol, and flavonoid concentrations, along with higher catalase (CAT) and APX activity. Lower planting densities resulted in reduced MDA and total phenol concentrations in leaves, whereas higher planting densities were associated with increased MDA content. These findings indicate that intercropping P. cyrtonema within A. chinensis orchards is feasible. Optimal planting conditions were a canopy density of 30%–60% and a row spacing of (25–35) cm×40 cm.