The effect of leaf shape on the interception of solar radiation 6 }4 F: @9 i7 r ~- b) L9 IC.B.S. Teh* ; U8 I9 G0 ~9 c% W8 NDepartment of Land Management, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor,! V) z( r* x4 n! O9 s9 E1 `% u1 o
Malaysia; n1 |5 U6 D( r" q( g, F( o* p
5 Abstract2 y9 d/ k4 O8 x8 N2 B0 a4 F
One of the properties of canopy architecture is leaf shape, and its effect on solar radiation / C: X* P4 ^! c6 n& C, N( ]interception by a plant is little understood and studied. Consequently, this study was to evaluate 1 F9 a' R, K" x/ N& T( s% v7 pthe effect of six leaf shapes on both direct and diffuse solar radiation interception using a ( z7 g5 M' b# m4 |; W3 ]detailed 3-D solar radiation model. Six hypothetical plant prototypes were computer-generated : H6 J9 a# w4 K R& v; Z8 H10 so that each prototype was equal to each other in all aspects; only the leaf shape for each' D- g) m3 N- z1 m) k9 s
prototype was varied. The leaf shapes selected were round (RD), square (SQ), triangle (TR), 4 C' k0 l0 W$ ] rinverted triangle (ITR), ellipse (EL) and lobe (LB). Computer simulations revealed that leaf& D W4 _; ^4 w
shape did have an effect on direct and diffuse solar radiation interception. However, its effect. I+ |9 D2 I& e; E
was to a rather small extent of not more than 11% increase in solar radiation interception. The' H% ?# L: I) k0 x2 }
15 mean hourly interception of solar radiation by the prototypes decreased in the following 5 i4 T) Q6 r: V+ I9 E0 imanner: (ITR ≈ EL) > (RD ≈ SQ ≈ TR ≈ LB). Although leaf lobbing is often hypothesised to" ]/ d, B( d% H( o" B! v
produce deeper sunflecks within the canopy, this study however revealed that leaf lobbing per % `, {7 |! ^3 G& U9 B) U/ ~* @se had no effect on solar radiation interception. All properties being equal, solar radiation: ]( k- z+ y8 h9 M( P
interception could be increased by having leaf shapes that are: 1) long and narrow, 2) broader at) z+ Y3 W" C0 J! k7 u7 V& ]
20 the apex than at the basal, and 3) supported by leaf petioles. These three conditions increase ! c/ {6 |8 l6 { k6 e" Asolar radiation interception by causing the canopy to be spread out more uniformly in the aerial9 t$ F" b. ~4 z( D+ b
space; this, in turn, means less leaf clustering and self-shading. However, the effect of leaf/ u: v0 O& Y9 d0 u/ ^! U# Y
shape on solar radiation interception decreases for near or full canopy cover because at this* B5 o6 s7 J( R- F1 ?" p
stage, the canopy is already intercepting solar radiation at near maximum capacity. Leaf shape8 R- A( G0 P! Y T
25 also did not affect the diurnal variation of direct and diffuse solar radiation interception. This* ?. o* V6 @/ j5 a6 C# A1 q
study may help to better select crop varieties having the “proper leaf form” for optimum plant) u2 x9 m! W2 j$ a2 O7 K
production, as well as to better understand plant adaptation mechanisms in response to- w+ b6 F G7 S7 p0 M- Q' R
environmental stresses. 7 v7 h: L! s9 U0 }% ?6 e6 ^Keywords: leaf shape; solar radiation; Beer’s law; canopy architecture; Z4 ]9 S9 K; E3 X" |