EFFECTS OF AMMONIA AND ROOT-KNOT NEMATODE ON TOMATO

Tomato plants inoculated with 2000 juveniles (JJ2) of root-knot nematode (Meloidogyne incognita race 1) or intermittently exposed to 152 mu g NH3 m(-3) exhibited significant suppression in growth, yield and leaf pigments compared with uninoculated or unexposed plants. However, NH3 at 76 mu g m(-3) did not cause significant effects. The leaves of nematode-inoculated or uninoculated plants exposed to NH3 (152 mu g m(-3)) turned yellow in all treatments. Root galling and reproduction efficiency of M, incognita increased at 76 mu g NH3 m(-3) but was suppressed at 152 mu g m(-3) Fecundity, however, declined at both levels. The nematode and NH3 interacted synergistically at 76 mu g m(-3) and antagonistically at 152 mu g m(-3). Reductions in the plant growth, yield and photosynthetic pigments of the tomato were greatest in post- or concomitant-inoculation treatments at 152 mu g NH3 m(-3) and concomitant inoculation treatment at 76 mu g m(-3). Nitrogen content of foliage and roots increased significantly at both levels of the gas, being greater in post- and concomitant-inoculation treatments at 152 mu g and 76 mu g m(-3), respectively. Meloidogyne incognita or NH3 decreased the number and size of stomata but increased the width of stomatal pores. Length and number of trichomes increased in the exposed plants, but remained unaffected in plants inoculated with the nematode alone. A positive correlation mostly occurred between width of stomatal pore and percent reduction in the plant growth, yield and leaf pigments of tomato.