Secret of water transport in highly branched broccoli xylem

Plants have evolved sophisticated transport networks that balance efficient water delivery with minimal energy expenditure. Many species exhibit vessel dimensions that align with Murray’s law, which minimizes hydraulic resistance by relating vessel radius to flow rate. Broccoli, with its highly branched morphology, maintains continuous water transport across its complex structure. This study presents a multiscale analysis of xylem architecture in broccoli, evaluating how its structure contributes to water transport in the context of Murray’s law. Internal vessel morphology was visualized using X-ray microimaging and systematically analyzed. Xylem forms a hierarchical network of progressively narrower vessels to facilitate uniform water distribution. However, vessel dimensions deviate from Murray’s prediction, resulting in lower conductance than theoretically expected. These findings suggest the additional transport mechanisms not accounted for in the original formulation. Based on observed radial transport within the stem, we developed an extension of Murray’s law that accounts for lateral water movement, providing an additional pathway beyond axial flow. This study offers new insight into plant hydraulic architecture and transport strategies based on xylem organization.