Vergara - 1976 - Physiological and morphological adaptability of ri

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curt-ran; AND RICE
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2. A) Dependence CIfCKtlIICIlOH coefficient (In and k3) on
solar elevation (Lldagawa et 211.. 1974a}: B) Dependence
of albedo of rice crop on leaf area index (RGE. 1967a;
Kishida. 1973); C) Radiant energy partition of ricefield
as influenced by plant growth (Kishidzi. l973).
Penetration of direct sunlight
The penetration of direct sunlight into plant canopies plays an important role
in establishing tl1e eanopf; microcliinate as well
thesis rates The extinction of direct solar radiation flux with the increase of leaf
area index can be approximated by the expression
511D = $49) ¢XP(—R».L) (3)
where 8&0) is the direct solar-radiation flux at the top of the canopy and kl, is
the extinction coefficient for direct solar radiation. From the geometrical consideration
of lhc interaction between light bcalns and leaves. kb is given by
k, = coscc hoGthJ (4)
where h. is the solar elevation and (Rh) is the mean effective leaf-area-prtijection
function which depends on h“. Results obtained from Eq. (4) are reproduced