Abstract
Rapeseed (Brassica napus L.) is a major oil crop in China, with the world’s largest planted area and total yield. Rapeseed has a high demand for nitrogen (N), and nitrogen deficiency in soil is an important limiting factor for rapeseed production. However, rapeseed responds to N deprivation by regulating its own morphology, structure, and physiology. We carried out the current experiment by utilizing low N (LN: 0.3 mM NO3−) and normal N (CK: 6.0 mM NO3−) treatments using Brassica napus as the experimental material. The study results showed that low N induced root elongation in rapeseed, and the root length of LN treatment was 2.37 times that of HN treatment. The dry matter of roots also significantly increased due to low N treatment. Meanwhile, low N treatment decreased photosynthetic pigment (including chlorophyll a, chlorophyll b, and carotenoids) contents and dry mass accumulation of leaves. A higher root/shoot ratio and N physiological efficiency were observed under low N treatment. The changes in cell wall components (pectin, cellulose, hemicellulose, and lignin), related enzymes, and genes’ transcription levels in roots were determined and the results suggested that low N promoted the demethylation of ion-bound pectin (ISP) and covalently bound pectin (CSP), the content of CSP and cellulose. The promoted pectin methylesterase (PME) activity, inhibited pectin and cellulose degradation enzymes, and up/downregulation of related genes also confirming the results of cell wall components. The low N-increased demethylation degree of pectin and content of pectin and cellulose in cell walls was conducive to cell wall loosening and cell wall synthesis during cell division and elongation, ultimately promoting root-adaptive elongation. The study revealed a possible mechanism in which the alteration of cell wall component content and structure participates in cell elongation and expansion, which directly induces root elongation under N deficiency. The successful implementation of this research may be conducive to facilitating the development of rapeseed cultivars with high N use efficiency through root-based genetic improvements and improving plant adaptability to low N.
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Claims 14
Claim · model-written summary
Low nitrogen increased root length to 2.37 times the HN treatment.
Verbatim
e0“low N induced root elongation in rapeseed, and the root length of LN treatment was 2.37 times that of HN treatment”
Claim · model-written summary
Low nitrogen significantly increased root dry matter.
Not reportedComparator
Verbatim
e0“The dry matter of roots also significantly increased due to low N treatment”
t0“Rapeseed Roots”
Claim · model-written summary
Low nitrogen decreased leaf photosynthetic pigments.
- Taxon
- Rapeseedt0
- Treatment
- low N treatmente0
- Outcome
- photosynthetic pigment (including chlorophyll a, chlorophyll b, and carotenoids) contentse0
- Direction
- decreasede0
Not reportedComparator
Verbatim
e0“low N treatment decreased photosynthetic pigment (including chlorophyll a, chlorophyll b, and carotenoids) contents”
t0“Rapeseed Roots”
Claim · model-written summary
Low nitrogen decreased leaf dry mass accumulation.
- Taxon
- Rapeseedt0
- Treatment
- low N treatmente0
- Outcome
- dry mass accumulation of leavese0
- Direction
- decreasede0
Not reportedComparator
Verbatim
e0“low N treatment decreased photosynthetic pigment (including chlorophyll a, chlorophyll b, and carotenoids) contents and dry mass accumulation of leaves”
t0“Rapeseed Roots”
Claim · model-written summary
Root to shoot ratio was higher under low nitrogen.
Not reportedComparator
Verbatim
e0“A higher root/shoot ratio and N physiological efficiency were observed under low N treatment”
t0“Rapeseed Roots”
Claim · model-written summary
Nitrogen physiological efficiency was higher under low nitrogen.
Not reportedComparator
Verbatim
e0“A higher root/shoot ratio and N physiological efficiency were observed under low N treatment”
t0“Rapeseed Roots”
Claim · model-written summary
Low nitrogen promoted demethylation of ion-bound pectin.
Not reportedComparator
Verbatim
e0“low N promoted the demethylation of ion-bound pectin (ISP) and covalently bound pectin (CSP)”
t0“Rapeseed Roots”
Claim · model-written summary
Low nitrogen promoted demethylation of covalently bound pectin.
Not reportedComparator
Verbatim
e0“low N promoted the demethylation of ion-bound pectin (ISP) and covalently bound pectin (CSP)”
t0“Rapeseed Roots”
Claim · model-written summary
Low nitrogen promoted CSP content.
Not reportedComparator
Verbatim
e0“low N promoted the demethylation of ion-bound pectin (ISP) and covalently bound pectin (CSP), the content of CSP and cellulose”
t0“Rapeseed Roots”
Claim · model-written summary
Low nitrogen promoted cellulose content.
Not reportedComparator
Verbatim
e0“low N promoted the demethylation of ion-bound pectin (ISP) and covalently bound pectin (CSP), the content of CSP and cellulose”
t0“Rapeseed Roots”
Claim · model-written summary
Pectin methylesterase activity increased under low nitrogen.
- Taxon
- Rapeseedt0
- Treatment
- low Ne1
- Gene
- pectin methylesterase (PME)e0
- Outcome
- pectin methylesterase (PME) activitye0
- Direction
- promotede0
Not reportedComparator
Verbatim
e0“The promoted pectin methylesterase (PME) activity”
e1“low N promoted”
t0“Rapeseed Roots”
Claim · model-written summary
Pectin and cellulose degradation enzymes were inhibited.
- Taxon
- Rapeseedt0
- Treatment
- low Ne1
- Outcome
- pectin and cellulose degradation enzymese0
- Direction
- inhibitede0
Not reportedComparator
Verbatim
e0“inhibited pectin and cellulose degradation enzymes”
e1“low N promoted”
t0“Rapeseed Roots”
Claim · model-written summary
Related genes were regulated up or down under low nitrogen.
Verbatim
e0“up/downregulation of related genes”
t0“Rapeseed Roots”
Claim · model-written summary
Authors infer that cell wall changes promote root elongation under nitrogen deficiency.
Verbatim
e0“alteration of cell wall component content and structure participates in cell elongation and expansion, which directly induces root elongation under N deficiency”
t0“Rapeseed Roots”
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