Image analysis as a tool to study deteriorated cabbage (Brassica oleracea L.) seed imbibition under salt stress conditions

Abstract

Cabbage seeds, aged at 15.8% moisture content and 35°C for 20d, were monitored for germination and swelling during imbibition by combining a standard germination and a salt stress integrated germination test with a computer-aided image analysis system. Exposure of seeds to -2MPa NaCl treatment from 16-24h, 8-24h and 0-24h during imbibition led to an increasing reduction in germination compared with that in a standard germination test. Both the reduction of final germination percentage and an increase of mean germination time were greater in seeds that had been aged for increasing period of time. Image analysis technique was applied to monitor both seed imbibition up to 36h, by measuring variations in seed area and the timing of germination onset under stress conditions. When seeds were transferred to NaCI at 16h or at 8h, the increase in area slowed down slightly up to 24h; upon stress removal, at 24h, a remarkable increase in seed area was detected during the first hour of water imbibition. This increase was less in deteriorated seeds, which also showed an increase in seed leachate conductivity during 24-25h imbibition. Highly significant correlations were established between germination parameters, leachate electrical conductivity and the change in seed area observed between 24 and 25h imbibition. These findings suggest that rapid image processing and recording of seed germination and size may represent an innovative technique for an accurate determination of any variation of seed hydration status. In addition, the measure of seed area may be taken as a good marker of seed vigour and tolerance to both advancing deterioration and salt stress.