Proteoid root formation of Lupinus albus L. is triggered by high pH of theroot medium

In response to deficiency of nutrients, especially phosphate, Lupinus albus L. (white lupin) forms proteoid roots, bottle-brush-shaped root cluster, o n lateral roots. In the present study, induction and development of proteoi d roots by phosphate-sufficient L. albus were strongly altered by elevated pH of the nutrient solution (pH 7.7) and by the addition of organic (MES, T ES) or inorganic (HCO3.) buffers. High pH, buffered or unbuffered, induced cluster root formation. Additionally, length of clusters was strongly incre ased by buffered solution at high pH. In contrast, elongation of rootlets w as adversely affected by high pH and/or buffered solution. The results sugg est an interference of pH and buffer capacity in signaling pathways leading to proteoid root formation.