(1) Ripening of tomato fruit involves the differentiation of chloroplasts in young green fruit into chromoplasts in mature ripe red fruit.(2) As Zeiger et al. have recently emphasized, guard cell chloroplasts show remarkable functional plasticity.(3) Even in the late stages of leaf senescence, the chloroplasts of guard cells remain green and functional.(4) Fluorescence of guard cell chloroplasts was imaged when plants were at approximately the six-leaf stage.(5) The outer layer of the abaxial epidermis contains sunken stomata with strongly fluorescing chloroplasts in the guard cells.