Trees that get energy from foliage vs roots

Question

I've heard the term that some trees get their energy and strength from roots while others get their energy from foliage. Something to do with deciduous vs conifers

But I've not been able to actually figure out which species of trees get it from where. Secondly, what exactly does that mean when a tree "gets strength" from foliage vs roots.

For example, all trees do photosynthesis from leaves and get nutrients from soil. The sugars are stored in the trunk and branches.

1. So what's the difference between trees that get strength from leaves and from those that get it from roots?
2. Do the two types of trees have different physiology?
3. Lastly, what is the implication on pruning and fertilizing? Does that mean that pruning should be more reserved for trees that get strength from foliage? Likewise, do trees that get strength from foliage require higher nitrogen fertilization?

p.s. There should be a tag for energy/development/etc. I don't have enough reps to add a tag.

Answer 1

I believe that the term you're referencing is incorrect; green plants get their energy from the leaves, not the roots. Here's an explanation from a certified arborist. As you noted, the roots act as both an anchor for the tree and as storage for the energy produced by photosynthesis. There's no energy production going on in the roots.

There is no one rule for pruning and fertilization—it's generally tree-species-specific. For example, some trees, like oaks, should be pruned only in the winter if oak wilt is present in the area (the wilt is spread by insects attracted to the sap leaking from the cut branches; the insects aren't present in the winter). Maples will leak copious amounts of sap if pruned during the spring, especially. On the other hand, plum trees are best pruned either in the spring (if in an area with humid summers) or during summer. This helps the tree to balance the amount of plums produced each year and avoid disease.

Answer 2

There are a number of ways of interpreting your question about energy in plants. The answer you are about to get from me will be a bit different from @Jurp excellent answer, this one through the lens of hibernation.

We know that some animals store fat and sleep during winter and rely on the energy stored in the fat to get them through winter and have reserves to use up during initial spring hunt for food. Trees need something similar, something to get them started in spring to expand buds and get the first leaves out to start the normal process of photosynthesis. So what is the energy that pushes out the first leaves and where is this stored? Mostly the storage is in carbohydrates which can be burned via respiration to produce the energy.

Clearly deciduous trees cannot store that energy in leaves since mostly the leaves are abandoned in fall together with all the carbs stored there. These trees must pull back sufficient stores into the superstructure and the root system. Conifers are a bit different in that while they still need to expand buds and produce new needles, they can store some carbs in the old needles as well as branches and roots.

This is why when we prune deciduous trees in winter and early spring we must be aware that we are removing some of the stored energy that the tree will rely on to resuscitate itself the following spring, and take action to ensure that any food taken away is given back in some way to be stored in what remains of the tree.