Abstract:

To address the lack of scientific basis for potassium fertilizer management of Lycium barbarum var. formosanum, in order to reveal the effects of potassium deficiency stress on seedling growth and antioxidant characteristics, and to analyze the physiological mechanism of potassium nutrition, 40-day-old Lycium barbarum var. formosanum seedlings were used as materials, and two treatments of normal potassium (CK) and potassium deficiency were set up. The agronomic traits, biomass, chlorophyll content, soluble sugar content, malondialdehyde (MDA) content and superoxide dismutase (SOD) activity of seedlings were measured after 28 days. The results showed that potassium deficiency caused leaf yellowing or browning at the edges and tips, significantly reduced plant height and leaf spread, but significantly increased root length (P<0.001). The root-shoot ratio increased from 0.058 to 0.169, and the dry and fresh weight of the aboveground and underground parts decreased significantly. The contents of chlorophyll a, chlorophyll b and total chlorophyll decreased slightly, but the difference was not significant (P>0.05). The content of soluble sugar in plants was significantly increased (potassium deficiency 14.307 mg/(g·FW), CK 12.184 mg/(g·FW), P<0.001), the content of MDA was significantly increased (potassium deficiency 276.039 nmol/(g·FW), CK 207.099 nmol/(g·FW), P<0.001), and the activity of superoxide dismutase SOD was significantly decreased (potassium deficiency 171.412 U/g, CK 211.718 U/g, P<0.001). Potassium deficiency affects cell membrane stability and inhibits secondary metabolic processes by aggravating the accumulation of reactive oxygen species. The results showed that potassium deficiency stress inhibited the shoot growth and reduced biomass accumulation of Lycium barbarum var. formosanum by inducing oxidative stress and weakening antioxidant defense. ‘Suppressing the ground and promoting the underground’ was its stress adaptation strategy. This study provides a theoretical basis for the scientific potassium fertilizer management of Lycium barbarum var. formosanum. In the future, potassium concentration gradient can be set, the test cycle can be extended, and the molecular mechanism of its response to potassium deficiency stress can be deeply analyzed.

Key words: Lycium barbarum, potassium deficiency, growth, agronomic traits, antioxidant, malondialdehyde (MDA), superoxide dismutase (SOD)