Non-destructive determination of leaf chlorophyll content in four crop species

A recent non-destructive technique allows estimation of leaf chlorophyll content using the portable SPAD-502 chlorophyll meter. Measurements were taken on four species (winter wheat, maize, soyabean and tobacco) subjected to different nitrogen regimes or senescence status and the non-destructive readings were compared with analytical results obtained by solvent extraction. In general, the relationship between the SPAD measurement and the analytical result was not linear and species was a factor in three out of four crops. Linear, quadratic and exponential curve fitting are presented; only the interpolation with a polynomial exponential function adequately describes the whole data set. The presence of statistically non-significant differences between the estimated values of wheat and maize on the one hand and significant points of difference between those of tobacco and soyabean on the other suggests distinct behaviour patterns for monocots and dicots. This type of response may be explained by differences in the optical properties of pigments with differing spatial distributions (sieve effect) and therefore by in vivo and in vitro different procedures and the structural diversity of leaves belonging to the two subclasses.