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

The electric conductivity of a leaf (LEG) 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 LEG and LNG in these cultivars increased with an increase in NaCl concentration in culture solution from 0 to 0.1 mumol L-1. LEC had a close linear relationship with LNG in each cultivar. A negative relationship was found between LEG and gross photosynthetic rate (P-g). The stomatal conductance (G(s)) and mesophyll conductance (G(m)) decreased with an increase in LNC. A clear cultivaral difference was recognized in responses to salt treatments. LEG was regarded as a useful indicator for the estimation or diagnosis of LNG and photosynthetic activity in salt-stressed rice cultivars.