Abstract
ABSTRACT High temperature during early grain‐filling stage is one of the serious abiotic stresses limiting maize yield in the North China Plain. Nitrogen (N) fertiliser has an important role in promoting crop growth, especially under abiotic stresses. However, its contribution to alleviating heat stress (HS) inhibition on maize photosynthesis during early grain‐filling stage is still unclear. Experiments with three N rates (LN, low nitrogen; MN, medium nitrogen; HN, high nitrogen) and two temperature (HS, heat stress; CK, ambient temperature as control) regimes were conducted to examine the effects of increasing N supply on photosynthesis, N assimilation, antioxidant system, and hormones homeostasis of maize during early grain‐filling stage using two maize hybrids Xianyu335 (XY335, heat‐sensitive) and Zhengdan (ZD958, heat‐tolerant). HS negatively affected photosynthesis of both two hybrids, exhibited lower net photosynthetic rate, chlorophyll content and activities of Rubisco and phosphoenolpyruvate carboxylase (PEPC) compared with CK, and then decreased dry matter accumulation of maize, with a lesser extent for ZD958 than XY335. However, increasing N supply alleviated the adverse effects of HS on maize photosynthesis due to improved N assimilation capacity. Under HS condition, greater N content and higher activities of glutamine synthetase and glutamate synthase in maize ear leaf were found in treatment of HN compared with LN and MN. HN with higher N assimilation capacity directly increased the net photosynthetic rate due to improved chlorophyll content, activities of Rubisco and PEPC and antioxidant capacity. HS‐induced abscisic acid (ABA) accumulation was also repressed by HN, and then enhanced the stomatal conductance and transpiration rate to maintain higher photosynthetic capacity compared with LN and MN. Moreover, the positive effects of increasing N supply on maize photosynthesis under HS condition exhibited a larger extent for XY335 than ZD958. As a result of improved photosynthesis and N assimilation capacity by adequate N supply, maize accumulated more biomass under HS, especially for heat‐sensitive hybrid.
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Claims 12
Claim · model-written summary
Heat stress lowered net photosynthetic rate and chlorophyll content of both maize hybrids compared with ambient temperature control.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e1“HS negatively affected photosynthesis of both two hybrids, exhibited lower net photosynthetic rate, chlorophyll content and activities of Rubisco and phosphoenolpyruvate carboxylase (PEPC) compared with CK”
Claim · model-written summary
Heat stress lowered the activities of Rubisco and phosphoenolpyruvate carboxylase (PEPC) in both maize hybrids compared with the control.
- Treatment
- HSe1
- Outcome
- activities of Rubisco and phosphoenolpyruvate carboxylase (PEPC)e1
- Direction
- lowere1
- Comparator
- CKe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e1“HS negatively affected photosynthesis of both two hybrids, exhibited lower net photosynthetic rate, chlorophyll content and activities of Rubisco and phosphoenolpyruvate carboxylase (PEPC) compared with CK”
Claim · model-written summary
Heat stress decreased dry matter accumulation of maize.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e1“HS negatively affected photosynthesis”
e2“and then decreased dry matter accumulation of maize, with a lesser extent for ZD958 than XY335”
Claim · model-written summary
The heat-stress decrease in dry matter accumulation was smaller for ZD958 than for XY335.
- Material
- ZD958e2
- Treatment
- HSe1
- Outcome
- dry matter accumulatione2
- Direction
- lesser extente2
- Comparator
- XY335e2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e1“HS negatively affected photosynthesis”
e2“and then decreased dry matter accumulation of maize, with a lesser extent for ZD958 than XY335”
Claim · model-written summary
Increasing nitrogen supply alleviated the adverse effects of heat stress on maize photosynthesis, due to improved nitrogen assimilation capacity.
- Treatment
- increasing N supplye1
- Outcome
- adverse effects of HS on maize photosynthesise1
- Direction
- alleviatede1
- Qualifier
- improved N assimilation capacitye1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e1“increasing N supply alleviated the adverse effects of HS on maize photosynthesis due to improved N assimilation capacity”
Claim · model-written summary
Under heat stress, high nitrogen treatment gave greater N content in maize ear leaf than low and medium nitrogen.
- Organ / stage
- ear leafe1
- Treatment
- HNe1
- Outcome
- N contente1
- Direction
- greatere1
- Qualifier
- Under HS conditione1
- Comparator
- LN and MNe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e1“Under HS condition, greater N content and higher activities of glutamine synthetase and glutamate synthase in maize ear leaf were found in treatment of HN compared with LN and MN”
Claim · model-written summary
Under heat stress, high nitrogen treatment gave higher activities of glutamine synthetase and glutamate synthase in maize ear leaf than low and medium nitrogen.
- Organ / stage
- ear leafe1
- Treatment
- HNe1
- Outcome
- activities of glutamine synthetase and glutamate synthasee1
- Direction
- highere1
- Qualifier
- Under HS conditione1
- Comparator
- LN and MNe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e1“Under HS condition, greater N content and higher activities of glutamine synthetase and glutamate synthase in maize ear leaf were found in treatment of HN compared with LN and MN”
Claim · model-written summary
High nitrogen with higher N assimilation capacity directly increased net photosynthetic rate, due to improved chlorophyll content, Rubisco and PEPC activities and antioxidant capacity.
- Treatment
- HNe1
- Outcome
- net photosynthetic ratee1
- Direction
- increasede1
- Qualifier
- improved chlorophyll content, activities of Rubisco and PEPC and antioxidant capacitye1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e1“HN with higher N assimilation capacity directly increased the net photosynthetic rate due to improved chlorophyll content, activities of Rubisco and PEPC and antioxidant capacity”
Claim · model-written summary
Heat-stress-induced abscisic acid accumulation was repressed by high nitrogen.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e1“HS‐induced abscisic acid (ABA) accumulation was also repressed by HN, and then enhanced the stomatal conductance and transpiration rate to maintain higher photosynthetic capacity compared with LN and MN”
Claim · model-written summary
High nitrogen enhanced stomatal conductance and transpiration rate under heat stress to maintain higher photosynthetic capacity compared with low and medium nitrogen.
- Treatment
- HNe1
- Outcome
- stomatal conductance and transpiration ratee1
- Direction
- enhancede1
- Comparator
- LN and MNe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e1“HS‐induced abscisic acid (ABA) accumulation was also repressed by HN, and then enhanced the stomatal conductance and transpiration rate to maintain higher photosynthetic capacity compared with LN and MN”
Claim · model-written summary
Under heat stress the positive effects of increasing N supply on maize photosynthesis were larger for XY335 than for ZD958.
- Material
- XY335e1
- Treatment
- increasing N supplye1
- Outcome
- maize photosynthesise1
- Direction
- larger extente1
- Qualifier
- under HS conditione1
- Comparator
- ZD958e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e1“the positive effects of increasing N supply on maize photosynthesis under HS condition exhibited a larger extent for XY335 than ZD958”
Claim · model-written summary
Through improved photosynthesis and N assimilation capacity from adequate N supply, maize accumulated more biomass under heat stress, especially the heat-sensitive hybrid.
- Treatment
- adequate N supplye1
- Outcome
- biomasse1
- Direction
- moree1
- Qualifier
- under HS, especially for heat‐sensitive hybride1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e1“As a result of improved photosynthesis and N assimilation capacity by adequate N supply, maize accumulated more biomass under HS, especially for heat‐sensitive hybrid”
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