Growth and Physiological Responses of Picea asperata Seedlings to Long-term Abscisic Acid Application

The paper describes the effects of long-term application of abscisic acid (ABA) at different concentrations in Picea asperata at the Maoxian Ecological Experimental Station of Chinese Academy of Sciences during a 5-year pot experiment. Long-term exogenous ABA application significantly affected the height and biomass (root, stem, and leaf weight); chlorophyll, osmoprotectant (proline, soluble sugar, soluble protein), and malonic dialdehyde (MDA) content; and antioxidative enzyme activity. ABA treatments at 5 mg·L⁻¹, 10 mg·L⁻¹ and 15 mg·L⁻¹ significantly improved root weight, stem weight and total biomass; increased the soluble protein and proline content; and reduced MDA content in needles. However, the highest application of ABA (20 mg·L⁻¹) caused a significant reduction in accumulation of chlorophyll, free proline and soluble sugar and a significant increase in MDA content in needles. These results suggest that the effects of exogenous ABA application on Picea asperata is concentration dependent, and long-term high exogenous ABA (20 mg·L⁻¹) is unfavorable for plant growth. Moreover, the height, chlorophyll content, and activities of superoxide dismutase and ascorbate peroxidase were significantly reduced with application of exogenous ABA.