Figure 1.

Screening strategy for CAM mutants of common ice plant. Mutagenized M₂ plants were irrigated with 0.3 m NaCl for 7 to 14 d to induce CAM. Duplicate leaf discs were collected at dawn or at dusk in a 48-well microtiter plate. Leaf discs were assayed using the pH indicator chlorophenol red; wild-type plants performing CAM show nocturnal acidification, whereas CAM-deficient mutants (marked as *) do not. As a secondary screen, leaf discs were screened for starch content at dawn and dusk using a mixture of iodine and potassium iodide. Wild-type plants that accumulate normal levels of starch show intense iodine staining, whereas mutants deficient in starch accumulation show weak iodine staining. Plants failing one or both tests were scored as putative CAM mutants.