THE PHYSICS OF TREE LEAF SIZE
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Transcript of THE PHYSICS OF TREE LEAF SIZE
THE PHYSICS OF TREE LEAF SIZENick Curran, Morgan Irons, Ben WangOctober 8, 2013
“Physical Limits to Leaf Size in Tall Trees”. Kaare Jensen and Maciej Zwieniecki. Physical Review Letters.Vol 110. January 4, 2013
Introduction1. Why do trees grow where they grow?
2. The need to effectively transport sugar-rich fluid throughout the tree leads to restricted tree height. Xylem Vessel Phloem Vessel
Fluid Flow Rate Throughout A Tree
Fluid-Flow Theory
Leaf Size Versus Tree Height
Leaf Size (cm)
Tree Height (m)
Hypothesis Statement:“The near-uniform leaf size of the tallest trees is set
by the requirements of their vascular system.”
MethodsFlow Velocity
Energy
Max Leaf Length
Min Leaf Length
• Botanical Data set Mathematical model• Assumed an Ohmic analogy to describe plant
vasculature• The flow velocity u, is inversely proportional to tree
height h• Energy E, is proportional to flow velocity• The maximum leaf length Imax maximizes energy
gained per leaf. • The minimum leaf length Imin allows for a transport
mechanism that is barely faster than diffusion alone
RESULTS Data set of recorded tree height h, and
range of leaf length l, of 1925 species from 327 genera and 93 families
Noticeable drop in leaf length variability for taller tree species
Is there a relationship between the sugar export rate and its distribution network that sets a minimum and maximum for leaf size?
RESULTS
CONCLUSIONS Leaf size in trees are limited by the dimensions of their phloem
transport vasculature At a certain height, trunk resistance becomes sufficiently large that larger leaf
size is no longer practical from a metabolic investment perspective. If leaves are too small, the flow will be too slow to reach plant tissues at a
reasonable rate Patterns observed are not strictly phylogenetic but are caused by
intrinsic physical effects of transport systems