对太阳辐射的拦截叶形状的影响 The effect of leaf shape on the interception of sol

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The effect of leaf shape on the interception of solar radiation
C.B.S. Teh*
' z& h$ c2 M! ODepartment of Land Management, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor,
' C, _: g5 h, E" W" B# mMalaysia
' O! E. D) v6 N/ s; U* a# y5 Abstract
& X2 V9 t6 |  W& u( c, P. Z; Q1 yOne of the properties of canopy architecture is leaf shape, and its effect on solar radiation
- O0 G  m  {" _# tinterception by a plant is little understood and studied. Consequently, this study was to evaluate
the effect of six leaf shapes on both direct and diffuse solar radiation interception using a
: S& U' H+ o, y6 l0 a4 idetailed 3-D solar radiation model. Six hypothetical plant prototypes were computer-generated
10 so that each prototype was equal to each other in all aspects; only the leaf shape for each
" |6 X4 a: \' Z0 k9 kprototype was varied. The leaf shapes selected were round (RD), square (SQ), triangle (TR),
inverted triangle (ITR), ellipse (EL) and lobe (LB). Computer simulations revealed that leaf
shape did have an effect on direct and diffuse solar radiation interception. However, its effect
: n! J% c9 P2 M% E# }5 P7 A3 Awas to a rather small extent of not more than 11% increase in solar radiation interception. The
. e- {8 S: Y- s$ }3 y1 O15 mean hourly interception of solar radiation by the prototypes decreased in the following
manner: (ITR ≈ EL) > (RD ≈ SQ ≈ TR ≈ LB). Although leaf lobbing is often hypothesised to
produce deeper sunflecks within the canopy, this study however revealed that leaf lobbing per
se had no effect on solar radiation interception. All properties being equal, solar radiation
interception could be increased by having leaf shapes that are: 1) long and narrow, 2) broader at
20 the apex than at the basal, and 3) supported by leaf petioles. These three conditions increase
solar radiation interception by causing the canopy to be spread out more uniformly in the aerial
8 N" q( j2 M2 ~7 m) \# [  pspace; this, in turn, means less leaf clustering and self-shading. However, the effect of leaf
8 M% U% u" n1 g3 r4 Hshape on solar radiation interception decreases for near or full canopy cover because at this
/ I+ @6 O  k6 ?# [9 J! sstage, the canopy is already intercepting solar radiation at near maximum capacity. Leaf shape
25 also did not affect the diurnal variation of direct and diffuse solar radiation interception. This
5 m( g3 x! R- Ystudy may help to better select crop varieties having the “proper leaf form” for optimum plant
production, as well as to better understand plant adaptation mechanisms in response to
3 c. Q% W$ @* W" k% lenvironmental stresses.
Keywords: leaf shape; solar radiation; Beer’s law; canopy architecture
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