The mechanism of sugar export from long conifer needles

Summary The green leaves of plants are optimised for carbon fixation and the production sugars, which used as central units energy throughout plant. However, there physical limits to this optimisation that remain insufficiently understood. Here, quantitative anatomical analysis combined with mathematical modelling sugar transport rate measurements were determine how effectively sugars exported from needle‐shaped conifers in relation leaf length. Mathematical indicated phloem anatomy constrains export long needles. we identified two mechanisms by constraint is overcome, even needles longer than 20 cm: (1) grouping conduits, (2) a shift diurnal rhythm metabolism needle tips. efficiency can have significant influence on function. constraints described here conifer likely also be relevant other groups plants, such grasses angiosperm trees.