It is interesting because your question meets the research topic of an active grop of plasma physics researchers: it is called Plasma assisted ignition (PAI) and combustion (PAC).
The radicals mentionned by Alexander (when saying "plasmas are at such high energies...") are chemical species, created by the plasma (example: O atoms in an air - N2:02 - plasma, chops of organic compounds with very big reaction constants in air:hydrocarbon mixtures etc), which are very short lived (very short lifetime, because they react very fast with other species that can be found in the mixture under study), and normaly "could not exist in big relative concentrations" in the mixture without the action of the plasma, or of very high temperatures. These radicals, which need plasma to exist massively in the mixture at room temperature, react very fast, and with very low activation barriers. The activation barrier is for example what prevents coal to burn at room temperature: you have to heat it first, even locally with the flame of a match, so that reagents can consume their kinetic energy to start the reaction process, and the reaction chain that will lead to sustained combustion. With plasmas you no longer need an activation energy, or temperature: thus, while combustion starts after hundreds of microseconds and sometimes milliseconds in the case of successful car engine spark ignition, with a proper high voltage nanosecond discharge you can decrease this delay by one or two orders of magnitude, just because the activation factor is not only heat (like, mostly, in sparks), but the dissemination of radicals at a relatively high concentration, high enough to start the combustion at a much lower temperature, sometimes room temperature - or less.
The other application of plasmas, Plasma assisted combustion, shows up especially in unproper mixtures: lean or over-rich mixtures of gas and air, for example. Without plasma, gas can burn with air within some margin of their relative concentration: say 40-60% (don't remember the correct numbers). With the aid of a small, low-energy plasma you can extend this to much more, like 20-70, again because of all the radicals you create. You can stabilize the flame in the burner, although it would have vanished otherwise.
So, this to say, that indeed, in addition to any nuclear consideration, plasmas do "ignite" reactive mixtures in which they would be created, and not only with the heat produced by spark plugs!