Effects of Foliar Application of Potassium Fertilizer on Anatomical and Physiological Changes of Neosinocalamus affinis Leaves

Foliar fertilization, an effective strategy for enhancing crop yields, is relatively uncommon in bamboo cultivation. To investigate the impact of potassium fertilizer applied directly to bamboo leaves, we applied K2CO3 on the fresh leaves of 1-year-old Neosinocalamus affinis culms. The results indicated that potassium fertilization significantly promoted leaf growth and development, evidenced by thicker leaf and epidermal and mesophyll cells and increased areas of bulliform and fusoid cells. Additionally, the chlorophyll content rose, while the moisture levels declined. Notably, the soluble sugar, starch, and non-structural carbohydrate (NSC) contents in the leaves also increased. Further analysis of the sugar metabolism revealed that the exogenous potassium application boosted the activities of key enzymes involved in sucrose metabolism, including soluble acid convertase (SAI), cell wall invertase (CWI), sucrose synthase (SuSy), and sucrose phosphate synthetase (SPS). The foliar application of K2CO3 also promoted starch synthesis in the leaves by elevating the activities of ADPG pyrophosphorylase (AGPase), soluble starch synthase (SSS), and granular-bound starch synthase (GBSS), while simultaneously diminishing the activities of starch phosphorylase (STP), alpha-amylase, and beta-amylase. Moreover, the targeted application of K2CO3 significantly reduced the contents of malondialdehyde (MDA) and hydrogen peroxide (H2O2) and significantly enhanced the activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), thereby improving the stress resistance of bamboo leaves. This study suggested that the foliar application of potassium fertilizer promoted leaf growth, enhanced bamboo's sugar metabolism and storage, and increased the stress resistance of bamboo leaves.