A study was conducted to study the effects of nitrogen deficiency on Castor cv. Hale leaf senescence, photosynthesis, pigments and leaf spectral reflectance properties. Plants were grown in out door pot culture conditions and pots of 12L capacity were used with sand as the growing media and initially treated with Hoagland's nutrient solution. Three treatments were imposed on plants (1) control (100% n) continued receiving the control solution; (2) reduced n to 20% of the control (20% n); and (3) withheld n from the solution (0% n). Photosynthetic rates, SPAD measurements, pigments and leaf reflectance have been collected from third, sixth and ninth leaves from the top at 24 day after treatment on plants in all the three treatments. Photosynthetic rates, chlorophyll and pigment concentrations decreased on 6th and 9th leaves when compared to 3rd leaf from top. Leaf reflectance increased in older leaves with decrease in nitrogen content. N deficiency increased reflectance at 555nm. Ratios of first derivatives at 765 and 455nm increased N prediction on area basis and at 1120 and 495nm increased for dry weight basis. First derivative of reflection at 2155 nm and at 1160nm increased prediction of chlorophyll on area basis and dry weight basis respectively. Analysis revealed the significance of effects of nitrogen nutrition and senescence on reflectance in 400-700 nm and 400-520nm regions and on photosynthetic pigments and leaf N content.