Abstract
The increasing frequency of drought and flooding events due to climate change exposes rice to intensified alternating drought and flooding stress during different growth stages. To elucidate the impacts of alternating drought and flooding stress on rice growth and carbon (C) and nitrogen (N) metabolism, five irrigation regimes were established: alternating cycle of light drought-flooding-light drought during the tillering stage (T-LD), heavy drought-flooding-heavy drought during the tillering stage (T-HD), light drought-flooding-light drought during the jointing stage (J-LD), heavy drought-flooding-heavy drought during the jointing stage (J-HD), and frequent irrigation with shallow water depth (0–5 cm) for growth stages except for the maturation stage (CK). The results indicated that the tiller numbers, K + concentrations in leaves, and above-ground biomass subjected to T-HD and T-LD treatments were significantly lower than in CK, J-HD and J-LD. Compared to CK, T-LD enhanced chlorophyll content and nitrate reductase activity (NRA) in rice leaves, leading to elevated photosynthetic rates (P n ) and improved δ 13 C values. The δ 15 N values under the CK, T-HD, and T-LD treatments were significantly greater than those under the J-HD and J-LD treatments ( p <0.05). Additionally, NRA showed a significant positive correlation with leaf N concentration during the jointing stage. Path analysis indicates that δ 13 C, leaf water content, tiller number, leaf area, K⁺ concentration, and N concentration were directly related to above-ground biomass, whereas photosynthetic parameters indirectly affected biomass through N-metabolism related indicators. This result offers a theoretical support for the scheduling of irrigation and drainage practices in the field. • Above-ground biomass had negative correlations with leaf nitrate reductase activity (NRA), δ 13 C, and δ 15 N. • Higher chlorophyll content in T-LD led to improved photosynthetic rate and δ 13 C compared to CK. • NRA was positively related to δ 13 C under alternating drought and flooding stress.
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Claims 9
Claim · model-written summary
Tillering-stage drought and flooding treatments lowered tiller number, leaf K + and above-ground biomass relative to the other regimes.
- Taxon
- rice
Oryza sativat0 - Treatment
- T-HD and T-LD treatmentse0
- Outcome
- tiller numbers, K + concentrations in leaves, and above-ground biomasse0
- Direction
- lowere0
- Comparator
- CK, J-HD and J-LDe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The results indicated that the tiller numbers, K + concentrations in leaves, and above-ground biomass subjected to T-HD and T-LD treatments were significantly lower than in CK, J-HD and J-LD”
t0“rice”
Claim · model-written summary
T-LD enhanced chlorophyll content and nitrate reductase activity in rice leaves compared with CK.
- Taxon
- riceOryza sativae0
- Organ / stage
- leavese0
- Treatment
- T-LDe0
- Outcome
- chlorophyll content and nitrate reductase activity (NRA)e0
- Direction
- enhancede0
- Comparator
- CKe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared to CK, T-LD enhanced chlorophyll content and nitrate reductase activity (NRA) in rice leaves”
Claim · model-written summary
T-LD elevated photosynthetic rates and improved δ 13 C values compared with CK.
- Taxon
- riceOryza sativat0
- Treatment
- T-LDe0
- Outcome
- photosynthetic rates (P n ) and improved δ 13 C valuese0
- Direction
- elevatede0
- Comparator
- CKe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared to CK, T-LD enhanced chlorophyll content and nitrate reductase activity (NRA) in rice leaves, leading to elevated photosynthetic rates (P n ) and improved δ 13 C values”
t0“rice”
Claim · model-written summary
CK, T-HD and T-LD had greater δ 15 N values than J-HD and J-LD.
- Taxon
- riceOryza sativat0
- Treatment
- CK, T-HD, and T-LD treatmentse0
- Outcome
- δ 15 N valuese0
- Direction
- greatere0
- Value
- p <0.05e0
- Comparator
- J-HD and J-LD treatmentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The δ 15 N values under the CK, T-HD, and T-LD treatments were significantly greater than those under the J-HD and J-LD treatments ( p <0.05)”
t0“rice”
Claim · model-written summary
NRA positively correlated with leaf N concentration during jointing.
- Taxon
- riceOryza sativat0
- Organ / stage
- jointing stagee0
- Compound
- N concentratione0
- Outcome
- NRAe0
- Direction
- positive correlatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NRA showed a significant positive correlation with leaf N concentration during the jointing stage”
t0“rice”
Claim · model-written summary
Water, tiller, leaf area, K⁺, N and δ 13 C indicators were directly related to biomass.
- Taxon
- riceOryza sativat0
- Organ / stage
- leafe0
- Outcome
- above-ground biomasse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“δ 13 C, leaf water content, tiller number, leaf area, K⁺ concentration, and N concentration were directly related to above-ground biomass”
t0“rice”
Claim · model-written summary
Photosynthetic parameters indirectly affected biomass through N-metabolism indicators in path analysis.
- Taxon
- riceOryza sativat0
- Outcome
- biomasse0
- Qualifier
- through N-metabolism related indicatorse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photosynthetic parameters indirectly affected biomass through N-metabolism related indicators”
t0“rice”
Claim · model-written summary
Above-ground biomass negatively correlated with NRA, δ 13 C and δ 15 N.
- Taxon
- riceOryza sativat0
- Organ / stage
- leafe0
- Outcome
- Above-ground biomasse0
- Direction
- negative correlationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Above-ground biomass had negative correlations with leaf nitrate reductase activity (NRA), δ 13 C, and δ 15 N”
t0“rice”
Claim · model-written summary
NRA was positively related to δ 13 C under alternating drought and flooding.
- Taxon
- riceOryza sativat0
- Treatment
- alternating drought and flooding stresse0
- Outcome
- NRAe0
- Direction
- positively relatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NRA was positively related to δ 13 C under alternating drought and flooding stress”
t0“rice”