Effect of nighttime temperature on tomato plant defensive chemistry.

Given that the amplitude of diurnal temperature fluctuations has been decreasing, mainly via warmer night temperatures, we examined the effects of nighttime temperature on concentration of the catecholic phenolics chlorogenic acid and rutin in tomato plants. A two-factor design, with carbon dioxide (350 ppm and 700 ppm) and nighttime temperature (14, 15, 16, 17, and 18 degrees C, with a 26 degrees C daytime temperature) was used. Compared to the lower carbon dioxide level, for whole plants the concentration of phenolics was lower at the higher carbon dioxide level, but patterns for plant parts differed. Nighttime temperature did not affect concentration of phenolics for whole plants, but it did influence concentration of the phenolics for plant parts, although not in predictable ways. Furthermore, the pattern of concentration of chlorogenic acid was somewhat different from that of rutin. The amount of change in concentration of these allelochemicals is likely sufficient to have substantial effects on insect herbivores. We conclude that nighttime temperature affects concentration of allelochemicals in tomato plants in significant ways.