Potassium nutrition recover impacts on stomatal, mesophyll and biochemical limitations to photosynthesis in Carya cathayensis and Hickory illinoensis

Abstract

Potassium (K) influences the photosynthesis process in a number of ways; However, the mechanism of photosynthetic response to the long-term supply of potassium is not yet clear. Concurrent measurements of gas exchange and chlorophyll fluorescence were made to investigate the effect of potassium nutrition on photosynthetic efficiency and stomatal conductance (gs), mesophyll conductance (gm) in Pecan (Carya illinoensis K.Kock) and Hickory (Carya cathayensis Sarg.) seedlings in a greenhouse. The results show that the photosynthetic capacity of Pecan and Hickory plants was not limited when the leaves had potassium concentrations >1.4% and 1.42% of dry weight. Most of limitation under potassium deficiency were dominated by MCL for Pecan and Hickory. Both cultivars showed remarkable improvement in SL, MCL, J and Vc,max with additional K supplies. However, effect from potassium deficiency on photosynthesis in plant leaves was irreversible. All of SL, MCL, and BL nearly half down with recovery K supply in both species. These results emphasize the important role of potassium on regulation of photosynthesis by three limitations.