Response of Spirodela oligorrhiza to Phosphorus Deficiency.

The duckweed Spirodela oligorrhiza, growing in sterile defined nutrient media, was used to study some responses of plants to phosphorus deficiency. On a phosphate-deficient medium, growth of Spirodela soon slowed and eventually ceased. Older leaves became chlorotic, but newly formed leaves were dark green and contained much anthocyanin. The photosynthesis rate fell gradually, roots elongated, and chloroplasts became filled with starch.NITROGEN METABOLISM WAS NOT MARKEDLY AFFECTED: the total protein content changed only slightly, and, although levels of glutamine and asparagine increased, the concentrations of the other amino acids remained constant. The effects of phosphorus deficiency on Spirodela are discussed in relation to those found in other higher plants.