Reflectance, Transmittance, and Absorptance of Light by Subcellular Particles of Spinach (Spinacia oleracea L.) Leaves¹

This study considered the premise that subcellular particles in leaves contribute to the reflectance (R) and absorptance (A) of near‐infrared (IR) (light 750 to 350 nm). Subcellular particles of spinach ( Spinacia oleracea L.) leaves were differentially sedimented and resuspended in a buffered sucrose solution. A spectroreflectometer was used to measure R and transmittance (T) over the 500‐ to 2,500‐nm wavelength interval (WLI) on replicated aliquots of five preparations: buffered sucrose solution (control); chloroplast preparation; S1, sediment of chloroplast preparation supernatant; $2, sediment of S1 supernatant; and S3, sediment of S2 supernatant. Absorptance was calculated: A= 1 ‐ (R + T). All suspensions of particulates caused less R than the buffered sucrose solution over the 500‐ to 650‐nm WLI. The chloroplast preparation, compared with the buffered sucrose solution, increased R over the 750‐ to 950‐nm WLI. The chloroplast preparation, compared with the buffered sucrose solution, S2, and S3, decreased T over the 500‐ to 1,250‐nm WLI; SI decreased T over the 500‐ to 900‐ nm WLI. Compared with remaining treatments, the chloroplast preparation increased A over the 500‐ to 1,100‐nm WLI. Excluding the buffered sucrose solution, R and A increased and T decreased in the IR region as particle size increased. A conclusion was reached that subcellular particles in leaves contribute to the R and A of IR light.