In one embodiment, the present invention relates to a method for preventing sunburn, and other physiological disorders such as watercore, corking and bitterpit, without diminishing photosynthesis, comprising applying to at least a portion of a surface of a plant an effective amount of a finely divided particulate material to prevent sunburn, and other physiological disorders such as watercore, corking and bitterpit, in the plant, wherein the particulate material comprises a heat treated particulate material and the particulate material as applied permits an exchange of gases on the surface of the plant and the particulate material has a thickness from about 1 .mu.m to about 1,000 .mu.m.