Abstract
Aim: Nitrogen is a major element conditioning grapevine growth, yield and aromatic profiles of berries and wines. Different tools can be used in order to detect differences in N status of the plant, including direct measurements of soil, plant nitrogen status (eg. petiole; must), or indirect observations of plant nutritional status such as leaf transmittance or reflectance (eg. SPAD; NDVI). However, the relationships between these indicators of nitrogen status and the overall plant functioning over vintages remain poorly known. The present study aimed at quantifying key vegetative and reproductive responses to plant nitrogen status over two successive seasons under different nitrogen supply levels.Methods and results: Potted plants of Sauvignon Blanc grafted onto SO4 were grown outdoors in 2017 and 2018 with no water limitation. Four mineral nitrogen fertilization levels (equivalent to 0 kg of N ha-1 or 0U, 20U, 40U, 80U) and one organic nitrogen fertilization level (40U) were imposed in 2017. These treatments were doubled in 2018 to increase the degree of nitrogen supply and consequently, the range of observed effects on plant growth and yield. Plant nitrogen status (SPAD) was monitored weekly during both growing cycles. Yield components were determined over the two seasons. Lastly, plant carbon status was addressed through dynamic measurement of plant development and photosynthesis, and destructive measurement of dry matter accumulation and carbon storage in annual and perennial organs at flowering, veraison and harvest.The SPAD values progressively decreased under lower N supply (0N) during the first year (from 31 to 16) and they were more than halved between the maximum and the minimum N treatments straight after budburst in year two (40 for 160N and 19 for 0N). Then, the differences in SPAD values among treatments were maintained up to harvest (2018). The gradient of N status resulted in a gradient of berry numbers per inflorescence (from 180 to 34 berries/inflorescence for 80N and 0N, respectively in 2018) and of individual berry dry matter at harvest (from 0.13 to 0.41 g for 160N and 0N, respectively in 2018). Quantitative relationships between N status and the relative reductions (% of reduction per %SPAD decrease) in terms of C gain (leaf area, photosynthesis), C growth (shoot, berry, trunk and root dry matter) and C storage (trunk and root) were fitted at flowering, veraison and harvest. The reduction in C gain under lower N supply was mainly related to the decrease in total leaf area before flowering (-1.64%). Although the photosynthesis rate tended to decrease under N deficiency over the season, it only poorly contributed to the reduction in C gain. The whole plant C growth was inhibited when N status decreased (-1.13% at harvest), due to the inhibition of shoot dry matter before veraison (-1.81%) and to a lower extent, to the lower dry matter in berries (-0.80%), trunks (-0.42%) and roots (-0.84%) at harvest. Part of the reduction in root dry matter was related to the lower starch reserves (-0.31%) at harvest. Interestingly, starch reserves tended to be higher under organic N supply than mineral N supply.Conclusion: The present results provided a general framework of carbon gain and use over time (within and between seasons) as impacted by N supply levels and form. Such a framework will be useful when building a model of the pluri-annual dynamics of carbon balance related to yield elaboration in grapevines.
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Claims 14
Claim · model-written summary
Under low nitrogen, SPAD declined from 31 to 16 in the first year.
VitisNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The SPAD values progressively decreased under lower N supply (0N) during the first year (from 31 to 16)”
t0“grapevine”
Claim · model-written summary
In year two, SPAD was 40 at 160N and 19 at 0N after budburst.
- Treatment
- 0Ne0
- Outcome
- more than halvede0
- Direction
- more than halvede0
- Value
- 19 for 0Ne0
- Qualifier
- 40 for 160Ne0
- Comparator
- 160Ne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“they were more than halved between the maximum and the minimum N treatments straight after budburst in year two (40 for 160N and 19 for 0N)”
t0“grapevine”
Claim · model-written summary
SPAD differences among nitrogen treatments persisted through 2018 harvest.
- Outcome
- differences in SPAD values among treatments were maintained up to harveste0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the differences in SPAD values among treatments were maintained up to harvest (2018)”
t0“grapevine”
Claim · model-written summary
Berry number per inflorescence ranged from 180 at 80N to 34 at 0N.
- Treatment
- 0Ne0
- Outcome
- berry numbers per inflorescencee0
- Value
- 180 to 34 berries/inflorescencee0
- Comparator
- 80Ne0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“berry numbers per inflorescence (from 180 to 34 berries/inflorescence for 80N and 0N, respectively in 2018)”
t0“grapevine”
Claim · model-written summary
Individual berry dry matter increased from 0.13 at 160N to 0.41 g at 0N.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“individual berry dry matter at harvest (from 0.13 to 0.41 g for 160N and 0N, respectively in 2018)”
t0“grapevine”
Claim · model-written summary
Lower N reduced carbon gain mainly through leaf area reduction before flowering.
- Treatment
- lower N supplye0
- Outcome
- total leaf areae0
- Direction
- decreasee0
- Value
- -1.64%e0
- Qualifier
- before floweringe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The reduction in C gain under lower N supply was mainly related to the decrease in total leaf area before flowering (-1.64%)”
t0“grapevine”
Claim · model-written summary
Photosynthesis tended to decrease under N deficiency but contributed little to reduced carbon gain.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photosynthesis rate tended to decrease under N deficiency over the season, it only poorly contributed to the reduction in C gain”
t0“grapevine”
Claim · model-written summary
Whole-plant carbon growth fell with declining nitrogen status by -1.13% at harvest.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The whole plant C growth was inhibited when N status decreased (-1.13% at harvest)”
t0“grapevine”
Claim · model-written summary
Shoot dry matter was inhibited before veraison by -1.81%.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“inhibition of shoot dry matter before veraison (-1.81%)”
t0“grapevine”
Claim · model-written summary
Berry dry matter was lower by -0.80% at harvest.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“lower dry matter in berries (-0.80%), trunks (-0.42%) and roots (-0.84%) at harvest”
t0“grapevine”
Claim · model-written summary
Trunk dry matter was lower by -0.42% at harvest.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“lower dry matter in berries (-0.80%), trunks (-0.42%) and roots (-0.84%) at harvest”
t0“grapevine”
Claim · model-written summary
Root dry matter was lower by -0.84% at harvest.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“lower dry matter in berries (-0.80%), trunks (-0.42%) and roots (-0.84%) at harvest”
t0“grapevine”
Claim · model-written summary
Lower root starch reserves were associated with root dry matter reduction at harvest.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Part of the reduction in root dry matter was related to the lower starch reserves (-0.31%) at harvest”
t0“grapevine”
Claim · model-written summary
Starch reserves tended to be higher under organic than mineral nitrogen supply.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“starch reserves tended to be higher under organic N supply than mineral N supply”
t0“grapevine”
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