Figure 2

Plants emit IR thermal radiation in proportion to temperature. In (a) and (b), spectral irradiance values were plotted against environmental temperatures at different physiological wavelengths using the data from Table 1. (a) Spectral irradiance of thermal radiation in the UV-B and visible wavelength ranges. (b) Spectral irradiance of thermal radiation at 10 mm in the IR range. (c) Total spectral irradiance of thermal radiation. Total spectral irradiance was calculated by integrating the spectral irradiance values with respect to the wavelength range at each temperature given in Fig. 1a. (d) IR thermal imaging of Arabidopsis seedlings at different temperatures. Six-day-old seedlings were subsequently incubated at the indicated temperatures for 1 h. IR images were recorded in the wavelength range of 7.5~13 mm by a forward-looking IR camera. Scale bars = 20 mm.