80 to 90 %
||Kaare H. Jensen & Maciej A. Zwieniecki, Physical Limits to Leaf Size in Tall Trees, Physical review letters, PRL 110, 018104 (2013) DOI: 10.1103/PhysRevLett.110.018104 p.2 right column 3rd paragraphPubMed ID23383844
||J. Pate, in Transport and Transfer Processes in Plants, edited by I. F. Wardlaw and J. B. Passioura (Academic Press, New York, 1976), pp. 253–281.
||"Sugar transport in plants takes place in the phloem
vascular system...The total solute concentration is 25% wt/wt, and
sugars, of which sucrose is the most abundant type, constitute
80–90% of this (primary source)"