From hidden to visual K deficiency in plants: Integration of subcellular K+ distribution and photosynthetic performance

The earliest occurrence of chlorosis at the tips of the oldest leaves is widely recognized as a reliable indicator for diagnosing potassium (K) deficiency and determining the need for K fertilizer. However, hidden K deficiency, typically associated with a decrease in individual leaf photosynthetic area, precedes the onset of visible yellowing symptoms. These concealed symptoms pose challenges for the early diagnosis of K deprivation in plants. The two distinct stages of deficiency exhibit different photosynthetic performances, which are speculated to be closely linked to the subcellular K+ distribution. This minireview focuses on investigating K+ dynamics across subcellular compartments, along with the involvement of functional transporter proteins and ion channels during K deficiency. We propose potential mechanisms by which subcellular K+ regulates photosynthetic capacity under both hidden and visual K deficiency conditions, which sheds new light on the diagnosis of K deficiency. Additionally, future research prospects and areas deserving further investigation are also outlined.