A Modified Bradley's Squash Technique for Studying Embryo Sacs in Gramineae

Abstract

This procedure is especially suited for studying the embroyology of sexual and apomictic grasses. Material is fixed in a 2:2:1 alcohol-chloroform-propionic acid mixture for a minimum period of 2 days, soaked in 4% iron alum at 75 C for 7 min, and 2 min each in 2 changes of distilled water, also at 75 C. After 2–3 min in cold water, it is macerated in 50% HCI for 10 min at about 22–25 C, washed and mordanted for 12–16 hr in 50% alcohol saturated with ferric acetate. Ovules are then dissected out and squashed in 1% carmine in 45% propionic acid. Squashing should be firm enough to separate and flatten the embryo sacs but not to burst them. The slides are set aside for 12–24 hr for intensification of the stain.