Universality of phloem transport in seed plants

摘要: Since Munch in the 1920s proposed that sugar transport phloem vascular system is driven by osmotic pressure gradients, his hypothesis has been strongly supported evidence from herbaceous angiosperms. Experimental constraints made it difficult to test this proposal large trees, where distance between source and sink might prove incompatible with hypothesis. Recently, theoretical optimization of mechanism was shown lead surprisingly simple predictions for dimensions sieve elements relation fast growing These results can be obtained a very transparent way using coupled resistor model. To universality mechanism, we compiled anatomical data 32 angiosperm 38 gymnosperm trees heights spanning 0.1-50 m. The species studied showed remarkable correlation scaling predictions. allowed calculating stem element conductivity predicting sap flow velocity. central finding work all plants seem have evolved efficient pumping units, despite their huge disparity size morphology. This contribution extends physical understanding transport, will facilitate detailed comparison theory field experiments.