Abstract
The influence of drought on the production of plant pigments was studied in sunflower seedlings. Excised cotyledons, when plasmolysed, produced no chlorophyll but only carotenoid pigments; when water-logged they produced all pigments, but the condition is unfavorable. Drought was induced by soaking the soil with sugar solns. of various concs. The optimum soil-moisture condition is not the same for all pigments. For the chlorophyll an equivalent resistance to water uptake of 7.5, and for the carotenoids 5.1 atmospheres may be taken as fair estimates of optimal conditions.