Potassium deficiency limits water deficit tolerance of rice by reducing leaf water potential and stomatal area

A pot experiment with two potassium (K) levels 0.15 (+K) and 0 (−K) g K2O kg−1 soil and two irrigation regimes well-watered (Ww) and water-deficit (Wd) imposed on two rice genotypes drought-sensitive (CR) and drought-resistant (WDR) was conducted to explore the effects of K deficiency on water use efficiency, leaf water status, osmotic adjustment, gas exchange traits and stomatal characteristics of rice under water deficit. The results showed that K deficiency broke water balance of plants under deficit irrigation by reducing relative water content and water potential of leaf, thereby limited water deficit tolerance of both rice genotypes. In addition, K deficiency resulted in a reduction in stomatal area and conductance, which aggravated the negative impact of water deficit on leaf gas exchange, thereby reduced grain yield and water use efficiency of rice. It should be noted that sufficient K is an important prerequisite for WDR to show water deficit tolerance. The decrease of leaf water potential and stomatal area was the main reason for the limited water deficit tolerance of WDR caused by K deficiency. Our results indicated that K plays an important role in maintaining water deficit tolerance of rice, which provides scientific basis for the breeding of drought-resistant genotypes and management of water and K in paddy fields.