Do plants give heat?

Answer

Best,
In general, plants themselves do not give heat.
However, there are species such as the arums (Araceae) where heat can be produced. Part of the inflorescence heats up, this helps the dispersion of fragrances that should attract the pollinators. You can find this nicely explained on the attached link.
The heat is produced by the cellular combustion (breakdown by controlled reaction with oxygen) of energy-rich substances such as sugars and fats, roughly comparable to what happens in our own cells.