This question only addresses the blueprint of the creation as described in the first chapter of Bereshit. It does not address the sequence of the actual creation, as described in Bereshit 2, or the empirical dependence of the plant life on photosynthesis as asked here.
Again, I ask about God's plan, God's idea of the Creation, not the implementation.
As I see it, on the end of the second day, the Earth is planned together with the upper and lower waters, divided by a firmament, and there's a notion of light. Now God says "what comes next logically? Aha, that would be the plant life, and only after that there will be planets, and after that, there will be animals".
In this blueprint, the plants are envisioned on the third day, before the planets, that are envisioned on the fourth, according to some Godly idea.
What is this idea (not implementation) of putting the plant life after the firmament and before the celestial bodies?
Does it mean the plants are more or less important? Do they correlate with certain Kabbalistic Sfiros? Is there any spirituality in them?