to measure level of vitamin D - spectrophotomeric method (Jan/23/2007 )

any body know protocol about determination of vitamin D in plant seed by spectophotometer

Has to be specy method, does it? VitD is usually done by immunoassay, HPLC or massSpec. I'm not sure you'll get good precision and accuracy with specy methods without the HPLC. Read at 256nm.
There might be a way of adapting a cholesterol assay. Chol assays use cholesterol oxidase to oxidise the 3 hydroxy position. This forms a ketone and H202. The H202 reacts with phenol and aminophenazone to form quinonamine dye in the presence of peroxidase. The dye colour is porportional to the concentration and is read between 480 and 520nm. I'm not sure if cholesterol oxidase would work on VitD or what other oxidisers you could try but if you got this going you wouldn't need the HPLC, Mass Spec or immunoassay set ups. You would need to control for cholesterol in the assay mix, though.