The effect of leaf shape on the interception of solar radiation 7 |, r. }1 e' v6 m+ cC.B.S. Teh* & N5 [6 N7 N' i, d- ?0 E; yDepartment of Land Management, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor,$ k- v$ R( g2 R( [+ ]0 K
Malaysia . d V' R% Q, ~* y8 V: b5 Abstract5 n! w4 F! U o+ }; z; s& T: B' K
One of the properties of canopy architecture is leaf shape, and its effect on solar radiation8 \" o/ w/ o1 o# f
interception by a plant is little understood and studied. Consequently, this study was to evaluate$ V" N9 _$ E/ p# ]% @* d8 }
the effect of six leaf shapes on both direct and diffuse solar radiation interception using a* h/ c: E; g+ s" n
detailed 3-D solar radiation model. Six hypothetical plant prototypes were computer-generated $ ?( i$ [* P0 [& T F8 ?, y- H! \10 so that each prototype was equal to each other in all aspects; only the leaf shape for each , z) b- U1 V# L8 b' g3 yprototype was varied. The leaf shapes selected were round (RD), square (SQ), triangle (TR), / Y* n, L' e8 v0 t# j. |: q9 _# Ginverted triangle (ITR), ellipse (EL) and lobe (LB). Computer simulations revealed that leaf 1 j8 v4 `/ \& z* w- c# mshape did have an effect on direct and diffuse solar radiation interception. However, its effect8 C5 z: ]) j# B
was to a rather small extent of not more than 11% increase in solar radiation interception. The " p3 W8 v. [* M% E" @15 mean hourly interception of solar radiation by the prototypes decreased in the following 4 C* l& i; h. i7 a: Nmanner: (ITR ≈ EL) > (RD ≈ SQ ≈ TR ≈ LB). Although leaf lobbing is often hypothesised to) h: {# S; J. f
produce deeper sunflecks within the canopy, this study however revealed that leaf lobbing per / \4 Y2 @9 k) B: E" sse had no effect on solar radiation interception. All properties being equal, solar radiation . E( F( ~4 i( q: n! x% O9 tinterception could be increased by having leaf shapes that are: 1) long and narrow, 2) broader at* [" T, T! Z7 n! o
20 the apex than at the basal, and 3) supported by leaf petioles. These three conditions increase- `% }( E: L6 w. B
solar radiation interception by causing the canopy to be spread out more uniformly in the aerial * ?& S. M) j, L; h- Hspace; this, in turn, means less leaf clustering and self-shading. However, the effect of leaf 8 P. A; d4 q7 a2 Gshape on solar radiation interception decreases for near or full canopy cover because at this $ u1 l3 v: d% ?1 U# f: Xstage, the canopy is already intercepting solar radiation at near maximum capacity. Leaf shape 5 \) g5 H" A$ l& D4 D25 also did not affect the diurnal variation of direct and diffuse solar radiation interception. This* l4 T" y: C7 Z2 E
study may help to better select crop varieties having the “proper leaf form” for optimum plant 7 S6 z+ C j/ i ]( y3 c& j7 j; gproduction, as well as to better understand plant adaptation mechanisms in response to5 q8 s8 }+ j( T8 y
environmental stresses.0 k3 K% x" u6 j$ A( Q1 J- T
Keywords: leaf shape; solar radiation; Beer’s law; canopy architecture+ `' i0 m& O3 T3 Y