Fig. 7

Hypothetical K⁺-deficiency stress response model for sweetpotato cv. Xu32 and cv. NZ1. In response to K+-deficiency stress, a more stable photosystem, higher numbers of differentially expressed genes (DEGs) involved in glucose metabolism, higher transcript levels of K⁺ transporters (IbHAK5), higher stress-related hormone contents, and stronger antioxidation reactions were induced in Xu32 than in NZ1, resulting in different levels of K⁺-deficiency tolerance. Dark and light blue boxes denote strongly and weakly induced metabolisms or expression genes by K⁺-deficiency stress, respectively. Arrows denote overall upstream/downstream relationships in the K⁺-deficiency stress response pathway. Thick and thin red arrows in photosynthesis indicate strongly and weakly decreased photosynthetic efficiency, respectively. The upstream and downstream direction of red-line arrows indicate increased and decreased contents of stress-related hormones (abscisic acid (ABA), salicylic acid (SA), and jasmonic acid (JA)), respectively