Abstract
• Identified a critical pure nitrogen threshold of 3–4 g plant −1 for regulating summer shoot growth and maintaining physiological health in potted 'Newhall' navel orange seedlings. • Elucidated the complex regulatory mechanism of summer shoot growth, demonstrating joint mediation by root-zone nitrogen availability, root system architectural plasticity, and the intricate ABA-Pro-Chl metabolic balance. • Developed a robust multiple regression predictive model integrating soil available nitrogen (NO 3 − -N and NH 4 + -N) and root morphological parameters to effectively forecast summer shoot growth dynamics (R 2 = 0.53–0.72). Nitrogen (N) is the primary nutrient that initiates the summer-flush (SF) in citrus trees. However, the integrated "soil-root-shoot" feedback mechanism regulating SF intensity remains poorly understood in fertigation-based systems. To quantify dose-dependent effects on SF morphogenesis, nutrient allocation, root-tissue, and soil N concentrations, we conducted a greenhouse pot experiment with two-year-old 'Newhall' navel orange grafted onto Poncirus trifoliata rootstocks. The plants were subjected to six summer N rates (pure N 1, 2, 3, 4, 5, and 7 g plant −1 ). The results showed that: (1) Reducing N supply progressively delayed SF emergence and advanced maturation, thereby shortening the flush period; (2) Compared to high N treatment (5–7 g plant −1 ), moderate N (3–4 g plant −1 ) application treatment significantly suppressed SF growth, reducing shoot number, length, basal diameter, leaf number, emergence rate and biomass by 42.86 %, 8.99 %, 9.76 %, 16.74 %, 29.37 %, and 47.59 %, respectively. Conversely, this optimal N range maximized the net increments in plant height (1.96 cm) and main stem diameter (1.52 cm); (3) Within this range, the summer shoots maintained medium-to-high levels of nutrient content (N, phosphorus, potassium) and physiologically active substances (abscisic acid, chlorophyll, proline), while root growth was moderated to a medium-low level. Meanwhile, the nutrient status of the root zone soil and roots remained in the medium-to-high range; (4) Root zone soil ammonium nitrogen and nitrate nitrogen concentrations and root length density were strongly correlated with SF architectural traits. Multiple regression models incorporating these variables explained >50 % of the variance in SF phenotype. This regulation was attributed to an N-driven "soil-root-shoot" feedback mechanism, where the root zone inorganic N pool, root morphology, and the balance of key shoot physiologically active substances collectively defined summer-flush growth patterns. Therefore, it is advisable to apply 3–4 g N plant −1 as the ideal summer rate for potted citrus seedlings in controlled environments. This effectively maintains a balance between vegetative growth and nutrient homeostasis through the identified "soil-root-shoot" feedback loop. However, these conclusions need to be verified in orchard-grown, fruit-bearing trees to substantiate their relevance in commercial cultivation systems before broader implementation.
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Claims 18
Claim · model-written summary
Reducing nitrogen supply progressively delayed summer flush emergence in citrus.
CitrusNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“citrus”
e1“Reducing N supply progressively delayed SF emergence and advanced maturation, thereby shortening the flush period”
Claim · model-written summary
Reducing nitrogen supply advanced maturation of the summer flush, shortening the flush period.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“citrus”
e1“Reducing N supply progressively delayed SF emergence and advanced maturation, thereby shortening the flush period”
Claim · model-written summary
Moderate N (3–4 g per plant) significantly suppressed summer flush growth relative to high N (5–7 g per plant), reducing shoot number by 42.86 %.
- Treatment
- moderate N (3–4 g plant −1 ) application treatmente1
- Outcome
- shoot numbere1
- Direction
- reducinge1
- Value
- 42.86 %e1
- Comparator
- high N treatment (5–7 g plant −1 )e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“citrus”
e1“Compared to high N treatment (5–7 g plant −1 ), moderate N (3–4 g plant −1 ) application treatment significantly suppressed SF growth, reducing shoot number, length, basal diameter, leaf number, emergence rate and biomass by 42.86 %, 8.99 %, 9.76 %, 16.74 %, 29.37 %, and 47.59 %, respectively”
Claim · model-written summary
Moderate N (3–4 g per plant) significantly suppressed summer flush growth relative to high N (5–7 g per plant), reducing length by 8.99 %.
- Treatment
- moderate N (3–4 g plant −1 ) application treatmente1
- Outcome
- lengthe1
- Direction
- reducinge1
- Value
- 8.99 %e1
- Comparator
- high N treatment (5–7 g plant −1 )e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“citrus”
e1“Compared to high N treatment (5–7 g plant −1 ), moderate N (3–4 g plant −1 ) application treatment significantly suppressed SF growth, reducing shoot number, length, basal diameter, leaf number, emergence rate and biomass by 42.86 %, 8.99 %, 9.76 %, 16.74 %, 29.37 %, and 47.59 %, respectively”
Claim · model-written summary
Moderate N (3–4 g per plant) significantly suppressed summer flush growth relative to high N (5–7 g per plant), reducing basal diameter by 9.76 %.
- Treatment
- moderate N (3–4 g plant −1 ) application treatmente1
- Outcome
- basal diametere1
- Direction
- reducinge1
- Value
- 9.76 %e1
- Comparator
- high N treatment (5–7 g plant −1 )e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“citrus”
e1“Compared to high N treatment (5–7 g plant −1 ), moderate N (3–4 g plant −1 ) application treatment significantly suppressed SF growth, reducing shoot number, length, basal diameter, leaf number, emergence rate and biomass by 42.86 %, 8.99 %, 9.76 %, 16.74 %, 29.37 %, and 47.59 %, respectively”
Claim · model-written summary
Moderate N (3–4 g per plant) significantly suppressed summer flush growth relative to high N (5–7 g per plant), reducing leaf number by 16.74 %.
- Treatment
- moderate N (3–4 g plant −1 ) application treatmente1
- Outcome
- leaf numbere1
- Direction
- reducinge1
- Value
- 16.74 %e1
- Comparator
- high N treatment (5–7 g plant −1 )e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“citrus”
e1“Compared to high N treatment (5–7 g plant −1 ), moderate N (3–4 g plant −1 ) application treatment significantly suppressed SF growth, reducing shoot number, length, basal diameter, leaf number, emergence rate and biomass by 42.86 %, 8.99 %, 9.76 %, 16.74 %, 29.37 %, and 47.59 %, respectively”
Claim · model-written summary
Moderate N (3–4 g per plant) significantly suppressed summer flush growth relative to high N (5–7 g per plant), reducing emergence rate by 29.37 %.
- Treatment
- moderate N (3–4 g plant −1 ) application treatmente1
- Outcome
- emergence ratee1
- Direction
- reducinge1
- Value
- 29.37 %e1
- Comparator
- high N treatment (5–7 g plant −1 )e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“citrus”
e1“Compared to high N treatment (5–7 g plant −1 ), moderate N (3–4 g plant −1 ) application treatment significantly suppressed SF growth, reducing shoot number, length, basal diameter, leaf number, emergence rate and biomass by 42.86 %, 8.99 %, 9.76 %, 16.74 %, 29.37 %, and 47.59 %, respectively”
Claim · model-written summary
Moderate N (3–4 g per plant) significantly suppressed summer flush growth relative to high N (5–7 g per plant), reducing biomass by 47.59 %.
- Treatment
- moderate N (3–4 g plant −1 ) application treatmente1
- Outcome
- biomasse1
- Direction
- reducinge1
- Value
- 47.59 %e1
- Comparator
- high N treatment (5–7 g plant −1 )e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“citrus”
e1“Compared to high N treatment (5–7 g plant −1 ), moderate N (3–4 g plant −1 ) application treatment significantly suppressed SF growth, reducing shoot number, length, basal diameter, leaf number, emergence rate and biomass by 42.86 %, 8.99 %, 9.76 %, 16.74 %, 29.37 %, and 47.59 %, respectively”
Claim · model-written summary
The optimal N range maximized the net increment in plant height (1.96 cm).
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“citrus”
e1“this optimal N range maximized the net increments in plant height (1.96 cm) and main stem diameter (1.52 cm)”
Claim · model-written summary
The optimal N range maximized the net increment in main stem diameter (1.52 cm).
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“citrus”
e1“this optimal N range maximized the net increments in plant height (1.96 cm) and main stem diameter (1.52 cm)”
Claim · model-written summary
Within the optimal N range, summer shoots maintained medium-to-high levels of nutrient content (N, phosphorus, potassium).
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“citrus”
e1“the summer shoots maintained medium-to-high levels of nutrient content (N, phosphorus, potassium) and physiologically active substances (abscisic acid, chlorophyll, proline)”
Claim · model-written summary
Within the optimal N range, summer shoots maintained medium-to-high levels of physiologically active substances (abscisic acid, chlorophyll, proline).
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“citrus”
e1“the summer shoots maintained medium-to-high levels of nutrient content (N, phosphorus, potassium) and physiologically active substances (abscisic acid, chlorophyll, proline)”
Claim · model-written summary
Within the optimal N range, root growth was moderated to a medium-low level.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“citrus”
e1“root growth was moderated to a medium-low level”
Claim · model-written summary
The nutrient status of the root zone soil and roots remained in the medium-to-high range.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“citrus”
e1“the nutrient status of the root zone soil and roots remained in the medium-to-high range”
Claim · model-written summary
Root zone soil ammonium and nitrate nitrogen concentrations and root length density were strongly correlated with summer flush architectural traits.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“citrus”
e1“Root zone soil ammonium nitrogen and nitrate nitrogen concentrations and root length density were strongly correlated with SF architectural traits”
Claim · model-written summary
Multiple regression models incorporating soil nitrogen and root variables explained more than 50% of the variance in summer flush phenotype.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“citrus”
e1“Multiple regression models incorporating these variables explained >50 % of the variance in SF phenotype”
Claim · model-written summary
The regulation of summer flush growth is attributed to an N-driven soil-root-shoot feedback in which the root zone inorganic N pool, root morphology and the balance of shoot active substances jointly define growth patterns.
- Outcome
- summer-flush growth patternse1
- Qualifier
- root zone inorganic N pool, root morphology, and the balance of key shoot physiologically active substancese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“citrus”
e1“where the root zone inorganic N pool, root morphology, and the balance of key shoot physiologically active substances collectively defined summer-flush growth patterns”
Claim · model-written summary
Applying 3–4 g N per plant is advisable as the ideal summer rate for potted citrus seedlings in controlled environments.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“citrus”
e1“it is advisable to apply 3–4 g N plant −1 as the ideal summer rate for potted citrus seedlings in controlled environments”
The same questions in other papers
nitrogen · growth · CitrusPositive and negative results
14 papers in the same direction as this paper · 2 in the opposite direction
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