Negative transport & resistance to water flow through plants

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Abstract
Experiments, conducted under conditions which eliminated the leaf-atmosphere interface and substituted a leaf-water interface, confirmed that water can move into and through plants equally well in both the normal and negative directions when the proper gradient is established. Water flows through the aerial parts of the plant more easily than through the root tissue and appears to escape through hydathodes of the leaves. This might explain the lower resistance observed in the leaf tissue, since the water needs to pass through only a few layers of loosely arrange cells in order to escape from the leaf. On entering the root, in comparison, the water probably encounters most of the resistance on traversing the epidermis, cortex, endodermis, and pericycle before reaching the xylem. The greatest resistance was found in the roots, followed by the leaves, with resistance to water flow very much lower in the stem.