The Influence of Root Knot Nematode, Meloidog Yne Javanica, On Photosynthesis and On Nutrient Demand By Roots of Tomato Plants

With an inoculum of 250 larvae, photosynthetic rate was less than in uninfected control plants but as inoculum level increased there was a rise and then a marked fall in photosynthesis. It is suggested that the complex nature of this relationship is due to the influence of several factors on photosynthesis. 14C-glucose incorporation into the roots was initially constant and only fell at the highest inoculum level (2,000 nematodes/plant). There was a marked decrease in 14CO2 incorporation with an inoculum of 250 nematodes compared with uninfected controls and a further decrease with 1,000 nematodes. Inoculation with 2,000 nematodes did not reduce 14CO2 incorporation further. The results do not support the hypothesis that creation of metabolic sinks in the roots, caused by the formation of syncytia and galls, have a major influence on top growth. The photosynthesis data indicate that inhibition of upward translocation of water and nutrients may be more important.