Journal
FUNCTIONAL PLANT BIOLOGY
Volume 43, Issue 8, Pages 797-805Publisher
CSIRO PUBLISHING
DOI: 10.1071/FP15235
Keywords
genotype; Helianthus annuus L; net CO2 assimilation rate; senescence; transpiration; water stress
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Funding
- French National Research Agency (Sunrise project) [2012-19]
- Association Nationale de la Recherche et de la Technologie (CIFRE) [2010/1467]
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Water deficit influences leaf transpiration rate and photosynthetic activity. The genotype-dependent response of the latter has not been assessed in sunflower (Helianthus annuus L.), particularly during the reproductive period when grain filling and lipogenesis depend greatly on photosynthate availability. To evaluate genotypic responses to water deficit before and after flowering, two greenhouse experiments were performed. Four genotypes-two inbred lines (PSC8, XRQ) and two cultivars (Inedi, Melody)-were subjected to progressive water deficit. Non-linear regression was used to calculate the soil water deficit threshold (FTSWt) at which processes (transpiration and photosynthetic activity) were affected by water deficit. In the vegetative growth stage, photosynthetic activity was affected at a lower mean value of FTSWt (0.39) than transpiration (0.55). However, in the reproductive stage, photosynthetic activity was more sensitive to soil water deficit (FTSWt=0.45). We found a significant (P=0.02) effect of plant growth stage on the difference between photosynthesis and transpiration rate thresholds and, a significant (P=0.03) effect of leaf age on transpiration. Such results will improve phenotyping methods and provide paths for integrating genotypic variability into crop models.
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