Electric conductivity, Na⁺ content and photosynthetic activity in leaves of salt-stressed rice plants, and their cultivaral difference

The electric conductivity of a leaf (LEC) was determined with an insulation resistance tester, and discussed its relationship with Na⁺ content in a leaf (LNC) and the photosynthetic activity in salt-stressed rice cultivars. The measurements were carried out using three cultivars of O. sativa and O. glaberrima grown at the middle vegetative growth stage. The plants showed a clear response to the salt treatment within 24 hours after its application. Both LEC and LNC in these cultivars increased with an increase in NaCl concentration in culture solution from 0 to 0.1 μmol L^-1. LEC had a close linear relationship with LNC in each cultivar. A negative relationship was found between LEC and gross photosynthetic rate (Pg). The stomatal conductance (Gs) and mesophyll conductance (Gm) decreased with an increase in LNC. A clear cultivaral difference was recognized in responses to salt treatments. LEC was regarded as a useful indicator for the estimation or diagnosis of LNC and photosynthetic activity in salt-stressed rice cultivars.