Growth and Physiological Characteristics of Polygonatum cyrtonema Under Different Shading Treatments

In this study, Polygonatum cyrtonema with two-year tubers growth was selected as the research materials. Moreover, the full light (control), light shading, medium shading, and heavy shading treatments were set up to study the changes in physiological and biochemical indicators of P. cyrtonema. The results showed that with the increase of shading intensity, resulting in the reduced light transmittance, the biomass of blocks, roots and leaves of P. cyrtonema exhibited a decreasing trend, but the stem bimoass displayed an increasing trend. Under the heavy shading treatment, the fresh weight of blocks, leaves, roots and stems of P. cyrtonema decreased by 42.90%, 44.67% and 81.82% and increased by 36.36%, respectively, compared with the control treatment. The chlorophyll a and chlorophyll b contents in the leaves of P. cyrtonema were significantly changed under different shading treatments, but the carotenoid content and the value of chlorophyll a/b in the leaves were not significant changed. In addition, the contents of soluble sugar and soluble protein in the leaves increased at first and then decreased, and the highest and the lowest contents were observed in medium shading treatment and heavy shading treatment, respectively. The maximum value was 1.63 and 1.21 times of the minimum value. The activities of free proline, malondialdehyde (MDA), relative conductivity, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in leaves showed a trend of decreasing first and then increased. Under the medium shading treatment, the activities were 24.13%, 57.00%, 6.69%, 32.94%, 44.94% and 47.49% lower than those of the control treatment, respectively. In summary, the results indicate that P. cyrtonema can grow adaptively under medium shading treatment by regulating MDA content, antioxidant enzyme activities and osmotic regulatory substances.