Phloem pressure flow is the beautiful mechanism where sugars, made in the leaves, are pushed down to the roots and fruits by a difference in water pressure, beta. But I must disagree with the simple textbook diagram—in my mountain apple trees, this flow isn't always so steady. When a late frost nips the leaves or the soil dries, that sweet sap thickens and the whole system groans under the stress, like my own old joints. I see it in the lab readings from the saplings I grow on my verandah, their struggle mirrored in my own notes from a classroom where I am twice the age of my classmates.
#food
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