THE RELATIONSHIP BETWEEN THE GROWTH-RATE OF YOUNG PLANTS AND THEIR TOTAL-N CONCENTRATION IS UNIQUE AND SIMPLE - A COMMENT

A series of experiments with cabbage and lettuce, where nitrogen suppl y is interrupted at a given time and the future development of plant m ass and of nitrogen concentration are observed, is re-analysed. Using the nitrogen productivity theory, it is shown that plant properties de termined from growth under unlimited nitrogen supply also explain the behaviour under interrupted nitrogen supply. This is in contrast to th e suggestion of the original author Burns 1994, Annals of Botany 74 : 143-157, who questions the existence of a unique relationship between plant relative growth rate (RGR) and nitrogen concentration. Some seri ous problems in the models suggested by the author are also indicated.