Abstract
The objective of this study is to understand how nitrogen (N) application rates affected on grain yield and N use efficiency (NUE) of japonica-indica hybrid rice cultivar Yongyou-1540 and its physiological bases. In the present study, a japonica-indica hybrid rice cultivar Yongyou 1540, which was widely planted in Zhejiang province was field grown in 2020 and 2021, and four N application rates [0 kg hm-2 (N0), 80 kg hm-2 (N1), 160 kg hm-2 (N2), and 240 kg hm-2 (N3)] were applied during rice growing season. The results indicated that, (1) N application rate had significant effects on grain yield and NUE of rice. Grain yield was significantly increased with the increase of N application rate from 0 kg hm-2 to 160 kg hm-2, and the increase in grain yield was mainly attributed to the increase in total spikelets per unit area. However, there were no significantly difference in grain yield between N2 and N3 treatments, which was mainly due to the reduce in grain filling percentage in N3 treatment. When compared with N2 treatment, N3 treatment significantly reduced N harvest index and NUE, including agronomic N use efficiency (AEN), N recovery efficiency (REN), N partial factor productivity (PFPN), and internal N use efficiency (IEN). (2) N application rate had significant effects on shoot growth and development. Shoot dry weight was significantly increased at jointing, heading, and maturity stages and harvest index was significantly decreased with the increase of N application rate from 0 kg hm-2 to 240 kg hm-2. The net photosynthetic rate of flag leaf, the concentration of zeatin plus zeatin riboside (Z+ZR) in flag leaves, and the activities of key enzymes involved in sucrose-to-starch conversion in grains were significantly increased with the increase of N application rate from 0 kg hm-2 to 160 kg hm-2, however, N3 treatment could not increase or even reduce the above indicators compared with N2 treatment. (3) N application rate had significant effects on rice root morphological and physiological traits. Root dry weight, root dry weight in both 0-10 cm and 10-20 cm soil layers, total root length, root length density, specific root length at jointing, heading, and maturity stages, and root oxidation activity (ROA) and concentration of Z+ZR in both roots and root-bleeding sap at mid- and late grain filling stages were significantly increased with the increase of N application rate from 0 kg hm-2 to 160 kg hm-2. However, when compared with N2 treatment, N3 treatment significantly increased root dry weight, and root dry weight in 0-10 cm soil layer, total root length and root length density. (4) The results of the correlation analysis showed that ROA, and concentration of Z+ZR in roots or in root-bleeding sap, were significantly positively correlated with net photosynthetic rate of flag leaves, the concentration of Z+ZR in flag leaves, and activities of key enzymes involved in sucrose-to-starch conversion in grains. Generally, the appropriate N application rate could improve rice root morphological and physiological traits and promote shoot growth and development, and then improved plant physiological performances during the mid- and late grain filling stages, and finally achieved the due goal of increase both grain yield and NUE.
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Claims 12
Claim · model-written summary
Grain yield increased significantly from 0 to 160 kg hm-2 nitrogen.
- Taxon
- rice
Oryza sativat0 - Material
- Yongyou 1540t0
- Treatment
- N application ratee0
- Outcome
- Grain yielde0
- Direction
- increasede0
- Comparator
- 0 kg hm-2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Grain yield was significantly increased with the increase of N application rate from 0 kg hm-2 to 160 kg hm-2”
t0“rice cultivar Yongyou 1540”
Claim · model-written summary
Total spikelets per area increased and accounted for the yield increase.
- Taxon
- riceOryza sativat0
- Outcome
- total spikelets per unit areae0
- Direction
- increasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the increase in grain yield was mainly attributed to the increase in total spikelets per unit area”
t0“rice cultivar Yongyou 1540”
Claim · model-written summary
Yield did not differ significantly between N2 and N3.
- Taxon
- riceOryza sativat0
- Treatment
- N3e0
- Outcome
- grain yielde0
- Direction
- no significantly differencee0
- Comparator
- N2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there were no significantly difference in grain yield between N2 and N3 treatments”
t0“rice cultivar Yongyou 1540”
Claim · model-written summary
N3 reduced grain filling percentage.
- Taxon
- riceOryza sativat0
- Treatment
- N3e0
- Outcome
- grain filling percentagee0
- Direction
- reducee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the reduce in grain filling percentage in N3 treatment”
t0“rice cultivar Yongyou 1540”
Claim · model-written summary
N3 significantly reduced N harvest index and four nitrogen efficiency measures relative to N2.
- Taxon
- riceOryza sativat0
- Treatment
- N3 treatmente0
- Outcome
- N harvest index and NUEe0
- Direction
- reducede0
- Comparator
- N2 treatmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When compared with N2 treatment, N3 treatment significantly reduced N harvest index and NUE, including agronomic N use efficiency (AEN), N recovery efficiency (REN), N partial factor productivity (PFPN), and internal N use efficiency (IEN)”
t0“rice cultivar Yongyou 1540”
Claim · model-written summary
Shoot dry weight increased across nitrogen rates.
- Taxon
- riceOryza sativat0
- Treatment
- N application ratee0
- Outcome
- Shoot dry weighte0
- Direction
- increasede0
- Comparator
- 0 kg hm-2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Shoot dry weight was significantly increased at jointing, heading, and maturity stages and harvest index was significantly decreased with the increase of N application rate from 0 kg hm-2 to 240 kg hm-2”
t0“rice cultivar Yongyou 1540”
Claim · model-written summary
Harvest index decreased as nitrogen increased to 240 kg hm-2.
- Taxon
- riceOryza sativat0
- Treatment
- N application ratee0
- Outcome
- harvest indexe0
- Direction
- decreasede0
- Comparator
- 0 kg hm-2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“harvest index was significantly decreased with the increase of N application rate from 0 kg hm-2 to 240 kg hm-2”
t0“rice cultivar Yongyou 1540”
Claim · model-written summary
Flag leaf photosynthesis, zeatin compounds, and grain sucrose to starch enzymes increased up to N2.
- Taxon
- riceOryza sativat0
- Treatment
- N application ratee0
- Outcome
- net photosynthetic rate of flag leaf, the concentration of zeatin plus zeatin riboside (Z+ZR) in flag leaves, and the activities of key enzymes involved in sucrose-to-starch conversion in grainse0
- Direction
- increasede0
- Comparator
- 0 kg hm-2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The net photosynthetic rate of flag leaf, the concentration of zeatin plus zeatin riboside (Z+ZR) in flag leaves, and the activities of key enzymes involved in sucrose-to-starch conversion in grains were significantly increased with the increase of N application rate from 0 kg hm-2 to 160 kg hm-2”
t0“rice cultivar Yongyou 1540”
Claim · model-written summary
N3 did not improve those leaf and grain physiological measures versus N2.
- Taxon
- riceOryza sativat0
- Treatment
- N3 treatmente0
- Outcome
- above indicatorse0
- Direction
- could not increase or even reducee0
- Comparator
- N2 treatmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N3 treatment could not increase or even reduce the above indicators compared with N2 treatment”
t0“rice cultivar Yongyou 1540”
Claim · model-written summary
Root mass, architecture, oxidation activity and root zeatin compounds increased through N2.
- Taxon
- riceOryza sativat0
- Treatment
- N application ratee0
- Outcome
- Root dry weight, root dry weight in both 0-10 cm and 10-20 cm soil layers, total root length, root length density, specific root lengthe0
- Direction
- increasede0
- Comparator
- 0 kg hm-2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Root dry weight, root dry weight in both 0-10 cm and 10-20 cm soil layers, total root length, root length density, specific root length at jointing, heading, and maturity stages, and root oxidation activity (ROA) and concentration of Z+ZR in both roots and root-bleeding sap at mid- and late grain filling stages were significantly increased with the increase of N application rate from 0 kg hm-2 to 160 kg hm-2”
t0“rice cultivar Yongyou 1540”
Claim · model-written summary
N3 further increased root mass and length measures relative to N2.
- Taxon
- riceOryza sativat0
- Treatment
- N3 treatmente0
- Outcome
- root dry weight, and root dry weight in 0-10 cm soil layer, total root length and root length densitye0
- Direction
- increasede0
- Comparator
- N2 treatmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“when compared with N2 treatment, N3 treatment significantly increased root dry weight, and root dry weight in 0-10 cm soil layer, total root length and root length density”
t0“rice cultivar Yongyou 1540”
Claim · model-written summary
Root oxidation and zeatin levels correlated positively with leaf photosynthesis, zeatin and grain enzyme activities.
- Taxon
- riceOryza sativat0
- Organ / stage
- rootse0
- Outcome
- net photosynthetic rate of flag leaves, the concentration of Z+ZR in flag leaves, and activities of key enzymes involved in sucrose-to-starch conversion in grainse0
- Direction
- positively correlatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ROA, and concentration of Z+ZR in roots or in root-bleeding sap, were significantly positively correlated with net photosynthetic rate of flag leaves, the concentration of Z+ZR in flag leaves, and activities of key enzymes involved in sucrose-to-starch conversion in grains”
t0“rice cultivar Yongyou 1540”
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