The effect of leaf shape on the interception of solar radiation ! v) Z% q" h9 H- DC.B.S. Teh*" o+ ]2 y8 m3 z V( M
Department of Land Management, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor,$ u+ l& e/ u5 L& s- A' E
Malaysia; M3 ?2 b% l( _& Z9 Z4 Y
5 Abstract/ ~/ X, u8 V( J5 y1 G
One of the properties of canopy architecture is leaf shape, and its effect on solar radiation $ M/ W( ~$ ?, V- R) c5 s9 B. Linterception by a plant is little understood and studied. Consequently, this study was to evaluate 5 `' Q1 W2 [4 w! |+ U! W! B$ M mthe effect of six leaf shapes on both direct and diffuse solar radiation interception using a " _1 K( ?( n. h: @* _( l$ Zdetailed 3-D solar radiation model. Six hypothetical plant prototypes were computer-generated 7 E: t0 F( B8 ^& s* P5 c10 so that each prototype was equal to each other in all aspects; only the leaf shape for each7 D& q$ i" m7 I6 _: \
prototype was varied. The leaf shapes selected were round (RD), square (SQ), triangle (TR),. g6 y( e9 m0 B9 }2 p0 Y
inverted triangle (ITR), ellipse (EL) and lobe (LB). Computer simulations revealed that leaf9 k% ~8 J7 f1 M+ g$ l( E; W" w
shape did have an effect on direct and diffuse solar radiation interception. However, its effect5 X- B Y5 u8 q% P5 w4 d
was to a rather small extent of not more than 11% increase in solar radiation interception. The' c L0 K) n* S- |5 t9 o; l |+ D
15 mean hourly interception of solar radiation by the prototypes decreased in the following% R8 u) j) i R. R" l) G
manner: (ITR ≈ EL) > (RD ≈ SQ ≈ TR ≈ LB). Although leaf lobbing is often hypothesised to3 ]4 O. v+ p7 o% h# ?
produce deeper sunflecks within the canopy, this study however revealed that leaf lobbing per$ s$ Z! Q: w5 x
se had no effect on solar radiation interception. All properties being equal, solar radiation/ b" H K$ M% S4 r$ ~& Q+ p
interception could be increased by having leaf shapes that are: 1) long and narrow, 2) broader at . q) G( W+ d+ `* u+ i20 the apex than at the basal, and 3) supported by leaf petioles. These three conditions increase " `6 Q, O" E, h/ ?2 A, D: v& _solar radiation interception by causing the canopy to be spread out more uniformly in the aerial % c, m6 }9 p3 [8 |space; this, in turn, means less leaf clustering and self-shading. However, the effect of leaf ! m X4 F, f' @; xshape on solar radiation interception decreases for near or full canopy cover because at this - b( y7 N$ K u, h& ~5 b+ Q/ dstage, the canopy is already intercepting solar radiation at near maximum capacity. Leaf shape $ w( T/ J7 @, `1 S$ i; Z E25 also did not affect the diurnal variation of direct and diffuse solar radiation interception. This * H" I6 S& k, u4 [study may help to better select crop varieties having the “proper leaf form” for optimum plant4 v- V1 m( A) {4 c; s
production, as well as to better understand plant adaptation mechanisms in response to * g7 \% G% L( |# _6 E, F4 T1 ]environmental stresses. 2 |& h5 L( Z* Z2 S" o7 |! @Keywords: leaf shape; solar radiation; Beer’s law; canopy architecture # \3 J* D" o1 d2 U& D8 } \ \3 ~ d! y+ S5 l% m9 I
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