Influence of Diurnal Irradiance Variation on Chlorophyll Values in Wheat: A Comparative Study Using Different Chlorophyll Meters

The canopy greenness, a visible indicator of crop nitrogen content, photosynthetic efficiency and overall crop health status is directly influenced by chlorophyll content. A lot of ambiguity exists over use of available chlorophyll meters and proper time of measurement during the day. In order to find differences between chlorophyll meters and the effect of diurnal variation of irradiance on chlorophyll measurements, three different chlorophyll meters (atLEAF+, Opti-sciences CCM200 and SPAD-Minolta) were used to repeatedly measure chlorophyll content index (CCI) on a specific marked region of leaf at five different hours of the day for three consecutive days on six different wheat genotypes grown under field condition. The CCI values of a genotype measured at different hours of a day by a chlorophyll meter did not vary significantly. Although some variation were observed in CCI values by different chlorophyll meters, the relative trend of CCI values across chlorophyll meters remained same for a genotype. The results indicate that the CCI values measured were un-affected by both variation in diurnal irradiance and make of the instruments. Therefore all three chlorophyll meters tested can be efficiently used for chlorophyll measurements which can be done at any time of the day under field conditions in wheat.