Leaf physiological impedance and elasticity modulus in Orychophragmus violaceus seedlings subjected to repeated osmotic stress

Abstract Leaf water status is always influenced by plant growth and environment and dynamically changes over time. Rapid measurement of leaf physical characteristics helps to timely determine the plant water needs, in order to prevent inhibition of photosynthesis in plants and improve irrigation water-use efficiency (WUE) under water deficit conditions. The present study determined leaf electrophysiological and mechanical properties, water content (LWC), water potential (ΨL), carbonic anhydrase (CA) activity, net photosynthesis, and re-watering WUE (WUER) in relation to osmotic stress and following drought hardening in Orychophragmus violaceus seedlings. The study established a coupling model between gripping force and physiological impedance according to the Nernst equation, and the leaf water dissipation rate (LWDR) was defined and determined. Changes of cell stiffness and LWDR altered the intracellular water status, which affected the photosynthetic capacity and WUER. Photosynthesis was inhibited by the 40 g L−1 PEG (polyethylene glycol) treatment due to the reduction of intracellular water, and leaf cells were severely damaged at the higher, 80 g L‒1 PEG. Plants transferred from 20 to 10 g L‒1 PEG had the highest WUER. We have found that the physiological impedance provides more reliable information of plant water status compared with ΨL, which can help improve the irrigation WUE.