PP Systems TARGAS-1, Operation Manuals

Page: 152 / 159

TARGAS-1 Operation Manual V. 1.02 152 support@ppsystems.com
𝑯𝑯 = 𝑸𝑸 × 𝑻𝑻𝑯𝑯𝒂𝒂𝒊𝒊𝒔𝒔
Where
𝑻𝑻𝑯𝑯𝒂𝒂𝒊𝒊𝒔𝒔
= 0.14 the ratio of infrared to visible radiation, and converting photon flux to energy units
To simply computation, the following approximation is made:
𝟒𝟒𝟒𝟒 × �
(
𝑻𝑻
𝒄𝒄
+ 𝟐𝟐𝟐𝟐𝟑𝟑 )
𝟑𝟑
� ≅ �𝟒𝟒 . 𝟔𝟔𝟑𝟑𝟗𝟗 + ( 𝟎𝟎 . 𝟓𝟓𝟓𝟓𝟑𝟑𝟒𝟒 × 𝑻𝑻
𝒄𝒄
)
�
(A.7) Then, the leaf temperature is:
𝑻𝑻
𝒎𝒎𝒆𝒆𝒂𝒂𝒍𝒍
= ( 𝑻𝑻
𝒄𝒄
+ ∆𝒐𝒐
)
Saturation Vapor Pressure
Derive saturation vapor pressure at leaf temperature (
𝒆𝒆
𝒎𝒎𝒆𝒆𝒂𝒂𝒍𝒍
) from
𝑻𝑻
𝒎𝒎𝒆𝒆𝒂𝒂𝒍𝒍
(A.8) From Buck, 1981 (using e
w1
and f
w1
) we calculate :
𝒆𝒆
𝒎𝒎𝒆𝒆𝒂𝒂𝒍𝒍
= 𝟔𝟔 . 𝟏𝟏𝟑𝟑𝟔𝟔𝟓𝟓 × 𝒆𝒆𝒆𝒆𝒑𝒑 �
𝑻𝑻
𝒎𝒎𝒆𝒆𝒂𝒂𝒍𝒍
× ( 𝟏𝟏𝟐𝟐 . 𝟓𝟓𝟎𝟎𝟐𝟐
)
𝑻𝑻
𝒎𝒎𝒆𝒆𝒂𝒂𝒍𝒍
+ 𝟐𝟐𝟒𝟒𝟎𝟎 . 𝟗𝟗𝟐𝟐 �
Where
𝒆𝒆
𝒎𝒎𝒆𝒆𝒂𝒂𝒍𝒍
= saturated water vapor pressure inside leaf at
𝑻𝑻
𝒎𝒎𝒆𝒆𝒂𝒂𝒍𝒍
Stomatal Conductance
Calculate stomatal conductance (g
s
)
(A.9) From von Caemmerer & Farquhar, 1981 (Eq B14), total leaf conductance to H
2
O transfer is
calculated as:
𝒈𝒈
𝒐𝒐𝒎𝒎𝒐𝒐𝒂𝒂𝒎𝒎
=
𝑬𝑬 × �𝑷𝑷 − ( 𝒆𝒆
𝒎𝒎𝒆𝒆𝒂𝒂𝒍𝒍
+ 𝒆𝒆
𝒎𝒎𝒐𝒐𝒐𝒐
)/ 𝟐𝟐�
�𝒆𝒆
𝒎𝒎𝒆𝒆𝒂𝒂𝒍𝒍
− 𝒆𝒆
𝒎𝒎𝒐𝒐𝒐𝒐
�
(A.10) Since
1/
𝒈𝒈
𝒐𝒐𝒎𝒎𝒐𝒐𝒂𝒂𝒎𝒎
= 𝑯𝑯
𝒔𝒔
+ 𝑯𝑯
𝒃𝒃
,
(A.11) stomatal resistance can be calculated as:
𝑯𝑯
𝒔𝒔
�𝒎𝒎
𝟐𝟐
𝒔𝒔 𝒎𝒎𝒎𝒎𝒎𝒎
−𝟏𝟏
� = �
�𝒆𝒆
𝒎𝒎𝒆𝒆𝒂𝒂𝒍𝒍
− 𝒆𝒆
𝒎𝒎𝒐𝒐𝒐𝒐
�
�𝑬𝑬 × ( 𝑷𝑷 − ( 𝒆𝒆
𝒎𝒎𝒆𝒆𝒂𝒂𝒍𝒍
+ 𝒆𝒆
𝒎𝒎𝒐𝒐𝒐𝒐
)/ 𝟐𝟐 ) �
� − 𝑯𝑯
𝒃𝒃
(A.12) Stomatal conductance is the inverse of stomatal resistance:
𝒈𝒈
𝒔𝒔
�𝒎𝒎𝒎𝒎𝒎𝒎𝒎𝒎
𝒎𝒎
−𝟐𝟐
𝒔𝒔
−𝟏𝟏
�
=
𝟏𝟏
𝑯𝑯
𝒔𝒔
× 𝟏𝟏𝟎𝟎
𝟑𝟑
�
𝒎𝒎𝒎𝒎𝒎𝒎𝒎𝒎
𝒎𝒎𝒎𝒎𝒎𝒎 �
Net Photosynthesis
Determine the rate of net photosynthesis (
𝑨𝑨
) from the difference between CO
2
concentrations entering
(C
in
) and exiting (C
out
) the cuvette