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DIURNAL CHANGES IN THE PHOTOSYNTHESIS OF FIELD-GROWN GRAPE VINES
W J S Downton1, W J R Grant1, B R Loveys1
1CISRO Division of Horticultural Research, GPO Box 350, Adelaide, 5001, Australia.
The New Phytologist
|April 20, 2021
Summary
Grape vine photosynthesis declines daily, especially without fruit. Non-stomatal factors, not water stress, cause this reduction, impacting sugar accumulation.
Area of Science:
- Plant Physiology
- Agricultural Science
- Viticulture
Background:
- Grape vines (Vitis vinifera L.) exhibit significant diurnal fluctuations in gas exchange.
- Understanding photosynthesis is crucial for optimizing grape yield and quality, particularly during fruit sugar accumulation.
Purpose of the Study:
- To investigate diurnal changes in net photosynthesis of Riesling grape vines.
- To identify factors contributing to the decline in photosynthesis during the day.
- To assess the role of stomatal conductance and non-stomatal factors in regulating photosynthesis.
Main Methods:
- Field studies measuring gas exchange (net photosynthesis, stomatal conductance, intercellular CO2 concentration) in Riesling and Colombard grape vines.
- Analysis of diurnal changes in photosynthetic parameters under varying irrigation regimes.
- Examination of CO2 compensation point, oxygen enhancement, and light/temperature responses.
Main Results:
- Riesling grape vines showed significant diurnal declines in net photosynthesis, linked to fruit presence.
- Decreases in photosynthesis correlated with stomatal conductance but were not solely explained by it (20-40%).
- Non-stomatal inhibition of photosynthesis was observed, unrelated to photorespiration or leaf water potential.
- Frequently watered Colombard vines maintained stable photosynthetic rates compared to those under a typical watering cycle.
Conclusions:
- Diurnal photosynthesis reduction in grape vines is influenced by non-stomatal factors, not just stomatal closure or water stress.
- Fruit presence affects the timing of photosynthetic decline.
- Water availability plays a role in mitigating diurnal photosynthetic reductions.
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