The effect of leaf shape on the interception of solar radiation , a5 h [5 B. H: `8 l* K( WC.B.S. Teh*" y* T5 Z5 f- L
Department of Land Management, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor,8 L" p4 }: u( h; a- Y
Malaysia f0 Z2 T0 C" Q: h3 c
5 Abstract - _1 ?6 ]5 @, p$ B1 i* z- T5 YOne of the properties of canopy architecture is leaf shape, and its effect on solar radiation + e8 j! {# O) {; i6 c7 y9 e. o2 ointerception by a plant is little understood and studied. Consequently, this study was to evaluate , C2 l- T. u( {$ K$ B7 Fthe effect of six leaf shapes on both direct and diffuse solar radiation interception using a9 C. [; L' j! R7 U
detailed 3-D solar radiation model. Six hypothetical plant prototypes were computer-generated- ~- m& ~3 X2 _/ U3 u* o+ ~7 o/ s
10 so that each prototype was equal to each other in all aspects; only the leaf shape for each , u; ]7 m8 F5 d( s% ]% [, q* yprototype was varied. The leaf shapes selected were round (RD), square (SQ), triangle (TR),2 w5 l" u) T; x N% l4 J3 k" m
inverted triangle (ITR), ellipse (EL) and lobe (LB). Computer simulations revealed that leaf / O9 E B6 m! ^: Y2 h! D: ~shape did have an effect on direct and diffuse solar radiation interception. However, its effect. Y% |0 ?1 T- s: y; E; q' s
was to a rather small extent of not more than 11% increase in solar radiation interception. The% a6 n, ]8 h- }) p- A
15 mean hourly interception of solar radiation by the prototypes decreased in the following & R6 T) E2 Y( C/ a6 {% w+ F% {manner: (ITR ≈ EL) > (RD ≈ SQ ≈ TR ≈ LB). Although leaf lobbing is often hypothesised to% G4 t3 z# _( m+ K+ h( h
produce deeper sunflecks within the canopy, this study however revealed that leaf lobbing per / R# |' A* H, ose had no effect on solar radiation interception. All properties being equal, solar radiation ' r9 }4 P2 A* W3 z9 T( n) Finterception could be increased by having leaf shapes that are: 1) long and narrow, 2) broader at& f" c1 X1 q1 j# P
20 the apex than at the basal, and 3) supported by leaf petioles. These three conditions increase 5 f5 Z- E0 z* W. wsolar radiation interception by causing the canopy to be spread out more uniformly in the aerial 0 o, G: a& g# u( E0 ?space; this, in turn, means less leaf clustering and self-shading. However, the effect of leaf% q" @$ K2 q7 {; ~% B( u5 D
shape on solar radiation interception decreases for near or full canopy cover because at this. R6 R# i7 [4 L4 B& P$ N
stage, the canopy is already intercepting solar radiation at near maximum capacity. Leaf shape7 U% E7 ^! N6 C) J$ F( P5 d8 ` {+ N
25 also did not affect the diurnal variation of direct and diffuse solar radiation interception. This# ]# v# d8 V- R
study may help to better select crop varieties having the “proper leaf form” for optimum plant ' y/ r+ a ~8 K+ v* Q5 mproduction, as well as to better understand plant adaptation mechanisms in response to) X# u" \) H( b9 E8 O& N V2 [
environmental stresses.3 m/ \* Z, q+ a4 L: q6 t
Keywords: leaf shape; solar radiation; Beer’s law; canopy architecture' h; O0 q1 P7 C; b" K( G1 H
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