This is a slight continuation of my other post where I was trying to create realistic hollows with weather due to temperature changes due to bio minerals called Hearthstones. I was wondering if plant life would be possible in the hollows with the hearthstones as they currently are, which are crystalline organisms that can reach the size of a house and go through heating and cooling periods. The cool periods of the hearthstones is when the hearthstones adsorb ambient heat, light and radiation until temperatures in the hollows reach below a desired threshold of about 62 degrees Fahrenheit where they then will enter their heating faze.
Hearthstones become more and more inefficient the larger they grow, so hearthstones grow to a maximum size of ten meters tall and 3 meters across. Most hearthstones are about the size of a foot ball but vary in size. The hollows tunnels that the hearthstones inhabit are caverns and openings carved from underground rivers through limestone, underground lakes, lava-tubes,and ancient organisms. making the planet's crust riddled with caverns. Think the hollows from Gears of War.
The hearthstones will then release light and heat radiation that is predominately in the yellow and red spectrum but sometimes white depending on the species. The Hearthstones during this face with raise the temperature in the hollows to around 82 degrees Fahrenheit before entering a cooling period once again. So most of the time the light in the hollows is around that of a overcast day. With these conditions I was wondering if it would be possible to have plant life in the hollows.
So my question is: Is photosynthetic possible and if not what needs to change about the headstones to make it possible, or should it be mostly fungal and lichen based foliage?