They will not. 100 days is not enough time to evolve plants that can live without sunlight. Evolution requires many generations.
Now there might be some real-world examples: see this article:
Chemical analysis of effluent from the inaccessible subglacial pool suggests that its inhabitants have eked out a living by breathing iron leached from bedrock with the help of a sulfur catalyst. Lacking any light to support photosynthesis, the microbes have presumably survived by feeding on the organic matter trapped with them when the massive Taylor Glacier sealed off their habitat an estimated 1.5 to 2 million years ago.
I think you will favor survival of microbes that live deep underground already, not evolve new species in 100 days.
But in the short time span, you will see decay processes in action. The plants will die, and fungi will consume it. After that’s all been eaten, the fungus starves next (they eat each other until all the stored energy is used up).
For life to truely continue, it needs an energy source.