The heat output of the plant cells-Chlorella vulgaris has been determined using the LKB-2277 bloactivity monitor. The metabolic thermokinetic equation isdP/t = k0, k0 = 0The experimental results indicate that there is a linear relationship between the meatbolic power and the cell concentration and that the heat output produced by a single cell's metabolism depends oll the cell concentration and is inhibited by the increase of the cell density. It presents a special kind of space effect.