In the production of plug seedlings, the air current speed around the seedlings is an important environmental factor affecting the rates of net photosynthesis (
P) and evapotranspiration (
E) . In the present experiment, a plug sheet consisting of tomato plug seedlings and soil mix was placed in a wind tunnel with artificial lights, and the
P and
E rates of the plug sheet were examined under different air current speeds, at an air temperature of 29-30°C, relative humidity of 60-70%, CO
2 concentration of 340-360 μmol mol
-1 and photosynthetic photon flux density of 270 μmol m
-2s
-1 At the inlet and outlet of the wind tunnel, absolute humidities (
yin and
yout, respectively) and CO
2 concentrations (
Cin and
Cout, respectively) were determined with a dew point analyzer and an infrared CO
2 analyzer, respectively. The weight of the plug sheet was measured with an electronic balance. The
E was estimated based on the change with time in the weight of plug sheet. The air flow rate in the wind tunnel,
F, was determined using an equation :
E =
F (
yout-
yin) /
A, where
A is the area of plug sheet. The
P was determined using the equation :
P=
F (
Cin -
Cout) /
A. The
P and
E increased as the air current speed and LA! (leaf area index of the seedlings) increased. However, the increase in
P with the increase in LAI was less than the increase in
E with the increase in LAI. Eleven days after seeding, when LAI=0.43, the
P and
E at an air current speed of 0.6 m s
-1 were 1.4 and 1.9 times those at an air current of 0.1 m s
-1, respectively.
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