Does grafting provide tomato plants an advantage against H2O2 production under conditions of thermal shock?

Non-grafted tomato plants (Lycopersicon esculentum L. cv. Tmknvf(2)) and grafted tomato plants (L. esculentum L. cv. Tmknvf(2) x L. esculentum L. cv. RX-335) were grown for 30 days at three different temperatures (10degreesC, 25degreesC and 35degreesC). In the leaves of these plants, the enzymatic activities of SOD, GPX, CAT, APX, DHAR and GR were analysed, as were the concentrations of total H2O2, ascorbate and glutathione as well as foliar DW. Regardless of whether the plant was grafted or not, our results indicate that the thermal stress occurred mainly at 35degreesC, with the following effects: (1) high SOD activity; (2) H2O2 accumulation; (3) foliar-biomass reduction; (4) low GPX, CAT, APX, DHAR and GR activities; and (5) high concentrations of ascorbate and glutathione. In addition, our data show these effects to be much weaker in grafted than in non-grafted plants, directly reflected in greater biomass production. Therefore, the use of grafted plants under excessively high temperatures may offer an advantage over non-grafted plants in terms of resistance against thermal shock.