Articles
DIURNAL CHANGES OF GAS EXCHANGE AND CHLOROPHYLL FLUORESCENCE IN MYRICA RUBRA PLANTS
Article number
769_31
Pages
221 – 229
Language
English
Abstract
Diurnal changes of photosynthesis in one-year-old Myrica rubra cv.
Dongkui young trees under natural conditions were studied by measuring gas exchange and chlorophyll fluorescence parameters.
On clear day, the diurnal changes of net photosynthetic rate (Pn), and stomatal conductance (Gs) and apparent quantum yield (AQY) showed two-peaked curve, the maximum value occurred at about 9:00, then declined, and reached the lowest values at about 13:00 then increased and reached the second peak at about 15:00. However, with the consistent decline of Pn and Gs in the afternoon, the ratio of values of intercellular CO2 concentration (Ci) to atmospheric CO2 concentration (Ca) increased.
The diurnal change of the maximum yield of fluorescence after dark adaptation Fm and the maximal photochemical efficiency of PS2 Fv/Fm exhibited an inverse bell shape.
In the morning, Fm and Fv/Fm decreased continuously until it reached its minimum at 13:00, while the reverse change occurred in the later afternoon.
The quantum yield of PS2ΦPS2 declined after 9:00, but the initial fluorescence Fo increased.
The decrease in rate of QA reduction, and increase in inactive PS2 reaction centers were observed during day time.
Non-photochemical quenching (qN) and its component slow (qS) increased at about midday, while fast (qF) declined.
These results suggest that stomatal limitation and photoinhibition are the main cause of the midday depression of Pn. The decreased rate of QA and increased inactive PS2 reaction centers may result declined photochemical efficiency.
Dongkui young trees under natural conditions were studied by measuring gas exchange and chlorophyll fluorescence parameters.
On clear day, the diurnal changes of net photosynthetic rate (Pn), and stomatal conductance (Gs) and apparent quantum yield (AQY) showed two-peaked curve, the maximum value occurred at about 9:00, then declined, and reached the lowest values at about 13:00 then increased and reached the second peak at about 15:00. However, with the consistent decline of Pn and Gs in the afternoon, the ratio of values of intercellular CO2 concentration (Ci) to atmospheric CO2 concentration (Ca) increased.
The diurnal change of the maximum yield of fluorescence after dark adaptation Fm and the maximal photochemical efficiency of PS2 Fv/Fm exhibited an inverse bell shape.
In the morning, Fm and Fv/Fm decreased continuously until it reached its minimum at 13:00, while the reverse change occurred in the later afternoon.
The quantum yield of PS2ΦPS2 declined after 9:00, but the initial fluorescence Fo increased.
The decrease in rate of QA reduction, and increase in inactive PS2 reaction centers were observed during day time.
Non-photochemical quenching (qN) and its component slow (qS) increased at about midday, while fast (qF) declined.
These results suggest that stomatal limitation and photoinhibition are the main cause of the midday depression of Pn. The decreased rate of QA and increased inactive PS2 reaction centers may result declined photochemical efficiency.
Authors
Yan-Ping Guo, Mei-Jun Hu, Guang-Hui Zeng, De-Ping Guo, Qiao-Mei Wang
Keywords
Myrica rubra, photoinhibition, photosynthesis, chlorophyll fluorescence
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