Vergara - 1976 - Physiological and morphological adaptability of ri

140 CLIMATE AND RICE
estimated by the energy-balance method was compared with pan evaporation obtained. Energybalance
measurements were made during the period of rice growth.
FISCHER: ls the albedo averaged over the da_v of an erect-leaf canopy different from that ofa
less-erect canopy‘!
Lichlflma: Yes, the albedo averaged over the day is somewhat larger for a horizontal-leaved
canopy than for an erect-leaved canopy But the difference in the albedo between the two canopies
is usually at a level of 0.05. under ordinary xveatlier conditions. Additionally; we have to
pay much attention to the dependence of albedo on the variation of radiation constituent
(direct and diffuse radiation).
LIURATA: “lhat is the relative importance to net photosynthesis of respiration increase due
to increased leaf temperature when it is calm as compared with when it is windy"?
Uchi/ima: As can be seen in Table l. our simulation results indicate that the influence of
(IQ-depression in daylight hours on daily net photosynthesis of a canopy is larger than that
of increment of respiration due to increased leaf temperature.
VENKATESWZARLLY: Is reflection of radiation more during a wet or dry season’?
Llchi/ima: Gencrallv speaking. reflectivity of canopy is larger in a dry season than in a wet
season, because the reflectivity increases with a decrease of water content in plant tissue and
soil.
VENKATESnIARIJJ: Is greater reflection advantageous under a high light-intensity situation’?
Uchijrma: Cireater reflectivity of leaves. particularly‘ PAR. is advantageous to maintain the
even distribution of radiation within the canopy and to prevent the excess increase in leaf temperature
undcr high light conditions.
VENKATESWARLU: ls there variability in reflection between dark-green and light-green
leaves?
Urhrjima: With change of leaf color from dark green to light green. the reflectivity of leaves
in the wave hand of PAR shows the small change in the value. Hove/ever. about half of reaching
radiation energy is in the wave band of infrared radiation. So. such a change of leaf color gives
no significant variation on the reflectivity in total short-nave radiation.
\r"ENIL-\TESVVARLLY: “lliat are the levels of reflection of radiation among the erect and horizontal
lcavwrs?
Uchijima." 'lhe reflectivity of a horizontal-leaved canopy shows no change with sun eleva—
tion. and is about 0.2. However. the reflectivity of a vertical-leaves! canopy decreases drastically
with increasing sun elevation from 0.3 at sun elevation of about 5'1‘ to 0.05 or less at sun elevation
ot" 90°.