A non destructive method to determine leaf chlorophyll content in grain sorghum

The performance of a portable leaf greenness meter (SPAD-502, Minolta Corp.) to provide a non-destructive measurement of total chlorophyll content in grain sorghum [Sorghum bicolor (L.) Moench] was evaluated. During the growing season measurements were carried out bi-weekly on three hybrids of grain sorghum grown with different nitrogen and water management. Linear regressions between SPAD readings and respective values of total chlorophyll content (TCHL), determined by spectrophotometric analysis, were calculated for each hybrid and treatment. Highly significant linear and positive relationships were found between SPAD readings and acetone-extractable leaf chlorophyll for all hybrids and treatments examined; there were no significant differences between the linear regressions calculated for each hybrid and treatment. A single regression, between SPAD readings and TCHL, accounted for 90% of the variability for all the data. The good performance of SPAD-502 was confirmed by analysis of TCHL values estimated by transforming SPAD values into TCHL using a calibration curve calculated at the beginning of the experiment: the standard error of estimate was 4.9 ?g cm-2. This work confirms that the portable chlorophyll meter can be a useful tool for non-destructive determination of TCHL in grain sorghum.