Potassium deficiency inhibits leaf-growth and promotes leaf necrotic spots in Neolamarckia cadamba

Abstract

Abstract Leaves, being a key plant organ involved in photosynthesis, play an important role in plant growth and development. Although there have been few studies on the effects of potassium (K+) deficiency on the leaves of woody plants, however, knowledge about mechanism of necrotic spot formation on leaves during K+ deficiency is scares. We used hydroponics setup to understand effects of K+ deficiency on Neolamarckia cadamba. K+ deficiency resulted in smaller leaves and necrotic spots on the older leaves, while regulatory modules of the differentially expressed genes (DEGs) involved in cell proliferation, cell cycle and cell expansion were down-regulated. K+ deficiency increased the activity of reactive oxygen species (ROS) scavenging enzymes such as SOD, APX and MDA and expression of DEGs related to these was also upregulated. Strong diaminobenzidine (DAB) staining was observed on the older leaves showing accumulation of H2O2 during K+ deficiency treatment. Additionally, putrescine (Put) and ethylene synthesis genes were upregulated. Fifteen DEGs in response to ethylene signaling, including ETR1, ETR2, EBF1, ERF1 and ERF2, were upregulated at the 3rd week. The leaf-growth changes caused by K+ deficiency in N. cadamba were well demonstrated by our findings.