Abstract: There is a correlation between leaf thickness and stoma， which modulates water loss for plants. After optical design， a long-working-distance optical magnification system was adopted to build a microscopic observation platform， and CCD was used to realize in vivo image acquisition of leaf stomata. Peanut leaves grown in greenhouse were monitored by self-built living plant stomatal observation device， thus the real time information of stomatal aperture could be acquired directly. There was remarkable negative correlation between stomatal aperture and leaf thickness， and the coefficient was -0.82.

Key words: stomatal aperture, leaf thickness, CCD, microscope optical system