n
The net uptake and release of gases by a
plant depend on which process occurs at a faster rate:
|
(39) Respiration
|
(40) Photosynthesis
|
|
n produces (41) carbon
dioxide
and consume (42) oxygen
n takes place all the time at a rather constant
rate.
|
n produce (43) oxygen and
consume (44) carbon dioxide
n
its rate is
greatly affected by
(45) light intensity (光強度)
|
n
Therefore, the
net uptake or release of gases by a plant would be affected by light intensity.
|
At high light intensity
(e.g. in the daytime)
|
At low light intensity
(e.g. at night)
|
|
l
The rate of photosynthesis is
(46) higher /
l
As a
result, there is a net (47) uptake /
(48) release of
oxygen.
|
l
(49)
Photosynthesis stops and only
(50)
respiration occurs.
l
As a
result, there is a net (51) uptake
of oxygen and a net (52)
release
of
carbon dioxide.
|
n
The relationship between light intensity and carbon
dioxide exchange in a plant:
|
|
|
Description
|
|
A
|
 |
In
the dark:
Ÿ
Only (53) respiration takes place
Ÿ
The plant releases
carbon dioxide and takes in oxygen
|
|
B
|
|
Light
intensity slowly increases as the morning comes:
Ÿ
Photosynthesis takes place at an increasing rate
that is (54)
Ÿ
More and more carbon dioxide is used up
Ÿ
Carbon dioxide released in respiration remains (55)
constant
Ÿ
Net release of
carbon dioxide and net
uptake of oxygen decrease
|
|
C
|
|
At (45) compensation
point (補償點):
Ÿ
The rate of photosynthesis is (46) equal to the rate of
respiration
Ÿ
No net exchange
of gases
|
|
D
|
|
Light
intensity increases further:
Ÿ
Photosynthesis occurs at a (47) higher rate than
respiration
Ÿ
Net uptake of
carbon dioxide and net release of oxygen
|
|
E
|
|
Light
intensity increases even further after reaching a particular level:
Ÿ
Photosynthesis reaches maximum rate and does not
increase further
Ÿ
Net uptake of carbon dioxide does not increase
Ÿ
Another factor (e.g. carbon dioxide concentration)
limits the rate of
(48) photosynthesis (Limiting factors限制因素)
|
沒有留言:
張貼留言