NONDESTRUCTIVE DETERMINATION OF LEAF CHLOROPHYLL CONTENT IN 4 CROP SPECIES

A recent non-destructive technique allows estimation of leaf chlorophy ll 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 obtain ed by solvent extraction. In general, the relationship between the SPA D measurement and the analytical result was not linear and species was a factor in three out of four crops. Linear, quadratic and exponentia l curve fitting are presented; only the interpolation with a polynomia l exponential function adequately describes the whole data set. The pr esence of statistically non-significant differences between the estima ted values of wheat and maize on the one hand and significant points o f difference between those of tobacco and soyabean on the other sugges ts distinct behaviour patterns for monocots and dicots. This type of r esponse may be explained by differences in the optical properties of p igments with differing spatial distributions (sieve effect) and theref ore by in vivo and in vitro different procedures and the structural di versity of leaves belonging to the two subclasses.