Shoot: root interrelationships in leeks infected with the rust, Puccinia allii Rud.: Growth and nutrient relations

Growth and nutrient relations were examined in healthy leeks and in leeks inoculated with the rust, Puccinia allii, to give three different intensities of infection (i.e. 10, 20 and 30%). Experiments were conducted over an 8-week experimental period, although only data from 5 weeks after inoculation are shown. The dry weights of rust-infected plants were substantially reduced compared with controls over the entire experimental period. Although shoot: root (S: R) ratios were increased in rusted plants 2 weeks after inoculation, the trend was reversed thereafter and for the remainder of the experiment S:R ratio was reduced in comparison with healthy controls. The contents of nitrogen, phosphate, potassium and calcium were reduced in rusted plants compared to controls. On the other hand, with few exceptions, the concentrations and specific absorption rates of these minerals increased in rusted plants compared with healthy controls. The ability of infected plants to maintain a functional S:R equilibrium with respect to nutrient uptake was examined using an analysis based on comparing changes in incremental plant dry weight with incremental nutrient weight. Calculated values of functional equilibrium for control and rusted plants showed that rust infection altered functional equilibrium with respect to uptake of the four nutrients. The possible mechanisms underlying these changes in physiology and the analysis of such changes are discussed.