The Use of the 11 C Technique to Measure Plant Responses to Herbivorous Soil Nematodes

Abstract

An advantage of the short half-life (20_3 min) isotope method is the simultaneous measurement of several crucial plant processes without hindering or destroying whole-plant function. The technique was used to examine the effects of the herbivorous soil nematode, Meloidogyne javanica (Treub) Chitwood, on carbon assimilation and redistribution in tomato (Lycopersicum esculentum L.) and in two ecotypes [grazing adapted (GA) and non-grazing adapted (NGA)], of an African C4 grass, Panicum coloratum L. Preliminary tests, based on nematode eggs and galls, showed that M. javanica reproduced differentially on both P. coloratum ecotypes and suppressed GA shoot growth (weight), but had little effect on fresh root weight. In tomatoes, control plants had a higher pool of labile C in the roots than the nematode-infected plants. With P. coloratum, there were no differences in parameters between ecotypes. Plants with herbivorous nematodes had a lower stem sink activity, root activity and root transport speed than control plants. The technique proved valuable for measuring instantaneous changes in photosynthate accumulation and movement induced by herbivorous soil nematodes. Key-words: Carbon allocation, phytophages, root herbivory, soil nematodes