The effect of leaf shape on the interception of solar radiation - c' |, v8 U7 b7 f VC.B.S. Teh* @( F7 X' A" O- o+ x, F$ n4 yDepartment of Land Management, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, * u- {; t; j7 g) I+ K2 EMalaysia # n2 ?0 d4 D( O' i) T. h5 Abstract% Q3 v. v% z5 t4 y# z( g8 O
One of the properties of canopy architecture is leaf shape, and its effect on solar radiation + C" t. p7 S( C: Uinterception by a plant is little understood and studied. Consequently, this study was to evaluate ( P/ V a1 ~# b% M( Uthe effect of six leaf shapes on both direct and diffuse solar radiation interception using a4 m& r) P& r* C& Q" l
detailed 3-D solar radiation model. Six hypothetical plant prototypes were computer-generated* ^4 c+ V' p0 u0 V# l" L' i. i
10 so that each prototype was equal to each other in all aspects; only the leaf shape for each : o: s6 ]8 p) @, Uprototype was varied. The leaf shapes selected were round (RD), square (SQ), triangle (TR), ( |! B" W8 S( D- _8 r3 u4 hinverted triangle (ITR), ellipse (EL) and lobe (LB). Computer simulations revealed that leaf $ D9 `! T8 x4 l3 p' R. Fshape did have an effect on direct and diffuse solar radiation interception. However, its effect , j& [- X/ e& q' Z! j7 `$ A# nwas to a rather small extent of not more than 11% increase in solar radiation interception. The# H1 Y: B$ w; Q# ` m* j
15 mean hourly interception of solar radiation by the prototypes decreased in the following* S5 G3 H Y! A( b
manner: (ITR ≈ EL) > (RD ≈ SQ ≈ TR ≈ LB). Although leaf lobbing is often hypothesised to 5 C }+ v* m% p- f, O1 _produce deeper sunflecks within the canopy, this study however revealed that leaf lobbing per 1 E1 M# ?1 e6 m% V; R+ C! @8 Tse had no effect on solar radiation interception. All properties being equal, solar radiation # R, D3 A- A X- A' B* Iinterception could be increased by having leaf shapes that are: 1) long and narrow, 2) broader at 4 j G5 ~( h; u' M20 the apex than at the basal, and 3) supported by leaf petioles. These three conditions increase+ m/ k* O8 g: D5 X# t
solar radiation interception by causing the canopy to be spread out more uniformly in the aerial 5 D" }" K! n% p# T3 Yspace; this, in turn, means less leaf clustering and self-shading. However, the effect of leaf 6 X3 ]/ |9 a; w. b7 P+ Vshape on solar radiation interception decreases for near or full canopy cover because at this 2 ~; @9 _: T/ ]8 K; s5 Wstage, the canopy is already intercepting solar radiation at near maximum capacity. Leaf shape/ G' g+ L5 i, \* u
25 also did not affect the diurnal variation of direct and diffuse solar radiation interception. This) D: S. Y$ z) F- K' {8 n9 N
study may help to better select crop varieties having the “proper leaf form” for optimum plant3 M& p" L& M: j7 B: F9 ?3 O
production, as well as to better understand plant adaptation mechanisms in response to / b- j3 N) C6 e5 n6 j2 f" l) Ienvironmental stresses. ) |/ h t- Z- ]' D1 h) bKeywords: leaf shape; solar radiation; Beer’s law; canopy architecture; q5 F" k( S: ]+ T- _
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