PROBLEM TO BE SOLVED: To provide a photosynthesis promotion light source emitting light suitable for photosynthesis performed in organisms with a photosynthetic pigment, such as plants and algae.SOLUTION: A photosynthesis promotion light source 1 emits light having an emission spectrum that has a peak, where an optical intensity in the entire wavelength region is the maximum, in a wavelength region of 610-630 nm and satisfies relationships of λ1-70 [nm]≤λ2≤λ1-30 [nm] and λ1+30 [nm]≤λ3≤λ1+70 [nm], where λ1 [nm] is the peak wavelength, λ2 [nm] is a wavelength at which the optical intensity is 50% of the optical intensity at the peak wavelength λ1 and which is most closest to the peak wavelength λ1 on a shorter wavelength side than the peak wavelength λ1, and λ3 [nm] is a wavelength which is most closest to the peak wavelength λ1 on a longer wavelength side than the peak wavelength λ1.SELECTED DRAWING: Figure 3COPYRIGHT: (C)2016,JPO&INPIT【課題】 植物および藻類など光合成色素を有する生物において行われる光合成に好適な光を発する光合成促進光源を提供する。【解決手段】 光合成促進光源１は、６１０～６３０ｎｍの波長領域において、全波長領域における光強度が最大となるピークを有し、そのピーク波長をλ１［ｎｍ］とし、ピーク波長λ１における光強度の５０％の光強度となる、ピーク波長λ１よりも短波長側でピーク波長λ１に最も近い波長をλ２［ｎｍ］およびピーク波長λ１よりも長波長側でピーク波長λ１に最も近い波長をλ３［ｎｍ］とするとき、λ１－７０［ｎｍ］≦λ２≦λ１－３０［ｎｍ］、およびλ１＋３０［ｎｍ］≦λ３≦λ１＋７０［ｎｍ］の関係を満たす発光スペクトルの光を発する。【選択図】 図３
