The effect of leaf shape on the interception of solar radiation + A& m2 t; p6 `, X2 D- v' p3 j1 {: e/ DC.B.S. Teh* 4 r2 s% ^9 {* K+ B/ v# wDepartment of Land Management, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, % [! a# R# P0 n8 C R4 zMalaysia / ^. e- y, H8 x( a# E/ ?8 s* Z5 Abstract 9 I6 b* Y) Q, u. t# [) F* OOne of the properties of canopy architecture is leaf shape, and its effect on solar radiation 0 W+ j9 e/ U- ainterception by a plant is little understood and studied. Consequently, this study was to evaluate$ E2 w* |% k2 ~& y3 ~
the effect of six leaf shapes on both direct and diffuse solar radiation interception using a ; _. \9 e3 r4 F8 t& X/ Vdetailed 3-D solar radiation model. Six hypothetical plant prototypes were computer-generated 7 a1 I7 ^% v. q5 }10 so that each prototype was equal to each other in all aspects; only the leaf shape for each - c' p/ ~4 a8 M% q2 Nprototype was varied. The leaf shapes selected were round (RD), square (SQ), triangle (TR),0 Q0 r1 z9 ?# ^
inverted triangle (ITR), ellipse (EL) and lobe (LB). Computer simulations revealed that leaf . p7 x9 s; j- v5 fshape did have an effect on direct and diffuse solar radiation interception. However, its effect ) K- f4 _: S0 Q" a3 f4 P# v: uwas to a rather small extent of not more than 11% increase in solar radiation interception. The & i1 s4 {( Y: \6 \% C15 mean hourly interception of solar radiation by the prototypes decreased in the following - Y! R3 U% d; G2 {manner: (ITR ≈ EL) > (RD ≈ SQ ≈ TR ≈ LB). Although leaf lobbing is often hypothesised to- F4 I8 C6 l! o5 ^9 p- t s
produce deeper sunflecks within the canopy, this study however revealed that leaf lobbing per, n6 }6 ^+ `9 _6 z% s
se had no effect on solar radiation interception. All properties being equal, solar radiation8 V) s! O; F$ H8 U8 n9 z
interception could be increased by having leaf shapes that are: 1) long and narrow, 2) broader at # `$ Y/ d& ]9 m# `20 the apex than at the basal, and 3) supported by leaf petioles. These three conditions increase 5 o/ ?3 E; p* u* V+ Wsolar radiation interception by causing the canopy to be spread out more uniformly in the aerial ]+ X1 D7 _6 @' R" K4 z
space; this, in turn, means less leaf clustering and self-shading. However, the effect of leaf* d* h! q \) e
shape on solar radiation interception decreases for near or full canopy cover because at this : k. L! ~. e% Q7 O# t+ A5 ~stage, the canopy is already intercepting solar radiation at near maximum capacity. Leaf shape 3 N4 a# c3 X7 @25 also did not affect the diurnal variation of direct and diffuse solar radiation interception. This ; e/ H4 p9 ^/ ^. c; nstudy may help to better select crop varieties having the “proper leaf form” for optimum plant8 d* C" A/ B5 P, ?" g
production, as well as to better understand plant adaptation mechanisms in response to % F$ P' |3 M S* j$ b! s9 ienvironmental stresses.6 t0 ^2 f0 B! F% z
Keywords: leaf shape; solar radiation; Beer’s law; canopy architecture( n }* `+ _- Z( F! G