Diurnal variation in the relationship between total solar radiation and photosynthetically active radiation

The total solar radiation (TSR) and photosynthetically active radiation (PAR) were measured daily Department starting from 630 h to 1630 h at a frequency of one hour with the help of LICOR 185B Photoradiometer (Pyranometer and quantum sensor), throughout the years for four years (2003 to 2006). Regression equations relating PAR and TSR were generated, Result revealed that at morning, noon and afternoon time respectively 82, 78 and 79 % variation of PAR could be explained by TSR value.