R00ter

Foxhound, you're thinking about it incorrectly. The newer leaves are not sending the energy they harvest to the older leaves, but vice versa, the older leaves are sending what they harvest from sunlight to the overall growth of the banana plant. Some nutrients are mobile, some are not mobile, as the older leaf deteriorates, the mobil nutrients are reallocated to other leaves, roots, psuedostem etc., the immobile nutrients stay locked in the leaves that turn brown. Pruning the leaves should be done as the other member stated earlier, after it turns brown. That way you've allowed the banana plant to remove all the mobil nutrients before its hormones signal cell death in the old leaves. Something that was made very clear to me, while taking Plant Physiology and Arboriculture at UF, was the more leaves on a plant, the faster it can grow, and the more caliper will be increased.