Abstract:The twenty-nine current rice cultivars in the Pearl River Delta(21°30′-23°10′N ),including early-crop and late-crop types,were subjected to 12daylength treatments,both natural and artificial,ranging from 10.0,10.5,11.0,11.5,12.0,12.5,13.0,13.5,14.0,15.0,24.0 hours.The resultsobtained were as fol