The authors have declared that no competing interests exist.
Lodging is one of the constraints that limit wheat yields and quality due to the unexpected bending or breaking stems on wheat (
Wheat is one of the most important agricultural crops in the world. Achieving high wheat yields in both irrigated and rain-fed environments has been limited by the disorders known as lodging [
Lodging occurs due to the interactions between plant, wind, rain and soil. Wind and rain exert a force which bends or breaks the stem base (stem lodging), or displaces the roots within the soil (root lodging) [
Plant breeders have reduced lodging risk by introducing dwarfing genes to decrease plant height which is negatively correlating with lodging resistance [
Plant breeders and farmers have to keep improving lodging resistance to counter the escalating lodging risk arising from continued yield increases. Plant breeders have reduced lodging risk by introducing dwarfing genes to produce shorter varieties [
Yangmai 20, a high-yielding winter wheat variety, is widely planted in the middle and lower reaches of the Yangtze River. This variety is a medium-gluten type which is used for dumplings and noodles. Yangmai 20 has high yield potential, while the performance of lodging resistance is unstable in different years, which is the key factor influencing wheat yield.
The influence of nitrogen rates to the lodging resistance of wheat have been reported by several studies. However, it is not clear how far the effects of nitrogen ratios could be additive, or the degree to which the combined effects of nitrogen rates and nitrogen ratios would make the plant be resistant to lodging. Additionlly, little information was about the optimal combination of nitrogen rate and ratio, which could improve lodging resistance without reducing yield potential. Accordingly, the trial was conducted to study the effects of different nitrogen levels and nitrogen application ratios on lodging resistance and investigate the relationship between plant morphology, stem anatomical structures, chemical components and other indicators with lodging resistance and to explore the nitrogen application techniques for anti-lodging and high-yielding.
A field trial was designed at the Agricultural Experiment Station (32°39’E, 119°42’N) of Agricultural College of Yangzhou University in China during the growing seasons of 2012–2013 (2012) and 2013–2014 (2013). The experiments were performed in the field with winter wheat–rice rotation, where the soil was a light loam with mean contents of 72.16 mg kg–1 available N, 52.20 mg kg–1 available P, and 157.24 mg kg-1 available K at 0 to 20 cm upper soil layer. The experiments were carried out in a zone of humid subtropical climate with an annual average temperature of 13.2°C–16.0°C, total precipitation of 800 mm–1200 mm, total sunshine of 2000 h–2600 h, and a frost-free season of 220 d–240 d. Weather conditions during the wheat growing season (
A high-yielding winter wheat cultivar currently used in local production, Yangmai 20, was chosen in the experiment. This cultivar was obtained from the Agricultural Science Institute of the Lixiahe District. The experiments were laid out in a split-plot design with three replicates. Main plots were total nitrogen (N) levels, including 180, 225, and 270 kg ha-1. Subplots were nitrogen ratios, including 70%:10%:20%:0% (labeled as 7:1:2:0), 50%:10%:20%:20% (labeled as 5:1:2:2) and 30%:10%:30%:30% (labeled as 3:1:3:3) applied at four stages. The 1st, 2nd, 3rd and 4th nitrogen application was applied pre-sowing, the four-leaf stage (DC 14) [
Lodging was assessed by measuring the lodging rates and the angle of inclination of the stem base from the vertical with a score calculated following the method of Fischer and Stapper [
Five culms from a single row in each plot were used to measure pushing resistance from the center of gravity at milk stage (DC 73) with a prostrate tester (FG-5005, SATO SHOUJI INC., Japan). Pushing resistance of the lower stem part at right angles to the row direction was measured when plants were forced to 45° relative to the ground [
Ten standing plants were selected randomly from each plot at milk stage (DC 73), avoiding the outer two rows, to measure the height at center of gravity (HCG) and culm breaking strength of the 2nd internode (CBS). The CBS of basal second internodes was measured with a plant lodging tester (YYD-1A, Zhejiang TOP Instrument Co., Ltd, China). Put the sampled basal second internode with removed stem sheath on the groove of support pillars with a distance of 5 cm. The tester was set perpendicular to the stem at the middle, loading gradually, and CBS was measured when culm internode was pushed to break [
Twenty representative stalks per plot without stem damage were collected to measure the length, diameter, wall thickness, filling degree of the basal second internode and the plant height at DC 73 according to the methods in Wei et al. [
Twenty culms of similar height were selected and uprooted from the middle rows of each plot at DC73. For each sample, the lower internodes were placed in a fan-driven dehydrator (Memmert UF750) and dried at 80°C for 48 h. The dried samples were ground to pass through a 1 mm sieve in a pulverizer and then used to extract water-solute carbohydrates (WSC) using boiling deionized water. WSC concentrations were quantified by colorimetry using anthrone reagent [
Plant samples were treated similarly in both two years. The twenty randomly culms were selected from each plot at milk stage (DC73). The basal internodes were oven dried at 80°C and then ground to pass through a 1 mm sieve. Tissues from the basal internodes from three replications were analyzed for cellulose content, lignin content [
At maturity (DC93), an area of 1.2 m × 1 m per plot of the center four rows was manually harvested for each experiment, avoiding edge rows on the each plot end. Then the grain weight was determined after 1–2 weeks of sun drying at the standard 130 g kg-1 moisture content, which is used for grain yield designation throughout. At the time of harvest, number of spikes was counted manually for three rows within 1 m. Fifty spikes from each plot was taken in succession and its number of kernels per spike was recorded. For 1000-kernels weight, 1000 kernels were randomly counted and weighed.
Analysis of variance (ANOVA) was performed using Statistical Product and Service Solution 15.0 for Windows (SPSS Inc., Chicago, IL, USA) for all traits. The significance of each source was determined by F-test. Least significant difference (LSD) tests were performed to determine significant differences between individual means. Simple correlation coefficients between the characters examined were calculated using correlation analysis. The relationships between culm traits and culm lodging resistance index (CLRI) were revealed by grey relational analysis described in the SPSS.
As shown
Year | N level (kg ha -1) | N ratio | Lodging stage |
Lodging angle (°) | Lodging rate (%) | Lodging score | Spikes (104 per ha-1) | Kernels per spike | 1000-kernels weight (g) | Grain yield (kg ha -1) |
---|---|---|---|---|---|---|---|---|---|---|
2012–2013 | 180 | 7:1:2:0 | NL | 0 | 0 | 0 | 447.08d |
44.02ab | 38.88bc | 7072.22d |
5:1:2:2 | DC83 | 15 | 10 | 1.67 | 494.72abc | 41.19bc | 40.72a | 7708.33abc | ||
3:1:3:3 | NL | 1 | 0 | 0 | 462.50cd | 42.92abc | 40.18ab | 7391.67bcd | ||
225 | 7:1:2:0 | DC83 | 70 | 40 | 32.22 | 506.67ab | 44.58a | 35.28de | 7233.33cd | |
5:1:2:2 | DC87 | 20 | 17.5 | 3.89 | 533.33a | 45.34a | 36.03d | 8075.00a | ||
3:1:3:3 | NL | 0 | 0 | 0 | 477.50bcd | 45.73a | 38.67c | 7916.67ab | ||
270 | 7:1:2:0 | DC75 | 72.5 | 80 | 71.11 | 509.72ab | 40.34c | 34.10e | 6950.00d | |
5:1:2:2 | NL | 0 | 0 | 0 | 507.50ab | 43.03abc | 35.99d | 7775.00ab | ||
3:1:3:3 | NL | 0 | 0 | 0 | 497.22abc | 40.78c | 36.65d | 7400.00bcd | ||
2013–2014 | 180 | 7:1:2:0 | DC65 | 50 | 32.5 | 18.06 | 452.24d | 41.95b | 37.75ab | 7091.67cd |
5:1:2:2 | DC65 | 45 | 15 | 7.5 | 478.36bc | 42.68ab | 37.58b | 7650.00abc | ||
3:1:3:3 | DC73 | 20 | 15 | 3.33 | 451.69d | 43.86ab | 39.01a | 7633.33abc | ||
225 | 7:1:2:0 | DC65 | 72.5 | 55 | 44.31 | 484.47bc | 43.75ab | 36.51b | 7216.67bcd | |
5:1:2:2 | DC65 | 65 | 22.5 | 16.25 | 508.91a | 43.40ab | 36.81b | 7833.33a | ||
3:1:3:3 | DC65 | 40 | 12.5 | 5.56 | 500.03ab | 44.52ab | 37.05b | 7933.33a | ||
270 | 7:1:2:0 | DC65 | 85 | 65 | 57.78 | 469.20cd | 43.57ab | 36.92b | 6991.67d | |
5:1:2:2 | DC65 | 77.5 | 55 | 44.31 | 474.19cd | 44.73a | 37.48b | 7791.67ab | ||
3:1:3:3 | DC65 | 70 | 55 | 41.25 | 464.47cd | 44.66ab | 37.73ab | 7519.44abcd |
α NL: No lodging; DC65: Anthesis; DC73: Early milk stage; DC75: Medium milk stage; DC83: Early dough stage; DC87: Hard dough stage
β Values in a column followed by the same letter are not significantly different at P < 0.05 as determined by the LSD test. The test was conducted separately between the two years.
In this experimental condition, nitrogen level and ratio had a significant effect on grain yield and its components of Yangmai 20 (
The culm breaking strength and culm lodging resistant index (CLRI) decreased with the increase of nitrogen application rate during 2012–2013, under the same nitrogen application rate, both of the two traits increased with the increase of topdressing fertilizer ratio (
N level (kg ha -1) | N ratio | 2012–2013 | 2013–2014 | ||||
---|---|---|---|---|---|---|---|
Lodging score | Culm breaking strength(Newtons) | Culm lodging resistance index | Lodging score | Culm breaking strength(Newtons) | Culm lodging resistance index | ||
180 | 7:1:2:0 | 0 | 13.57abc |
25.81ab | 18.06 | 13.84ab | 26.00ab |
5:1:2:2 | 1.67 | 16.36a | 32.02a | 7.5 | 15.52a | 29.43a | |
3:1:3:3 | 0 | 16.74a | 33.01a | 3.33 | 15.49a | 29.83a | |
225 | 7:1:2:0 | 32.22 | 12.10bc | 23.24b | 44.31 | 12.77ab | 24.06ab |
5:1:2:2 | 3.89 | 15.32abc | 29.72ab | 16.25 | 14.39ab | 27.12ab | |
3:1:3:3 | 0 | 15.78ab | 30.84ab | 5.56 | 15.21a | 28.91ab | |
270 | 7:1:2:0 | 71.11 | 11.81c | 22.43b | 57.78 | 11.19b | 20.83b |
5:1:2:2 | 0 | 12.99abc | 25.28ab | 44.31 | 12.60ab | 23.48ab | |
3:1:3:3 | 0 | 13.15abc | 25.63ab | 41.25 | 13.16ab | 24.40ab | |
F | |||||||
Nitrogen levels(NL) | 9.85 |
8.46 |
7.34 |
8.84 |
|||
Nitrogen ratio(NR) | 10.16 |
10.40 |
0.99 | 4.99 |
|||
NL×NR | 0.69 | 0.56 | 1.96 | 0.07 |
α Values in a column followed by the same letter are not significantly different at P < 0.05 as determined by the LSD test. The test was conducted separately between the two years.
* F-test significant at 5% level.
** F-test significant at 1% level.
Data of the two-years showed that the nitrogen fertilizer had a significant effect on the culm breaking strength and CLRI. The increase of nitrogen level could lead to the decrease of the lodging resistance. Therefore, reducing the application amount of nitrogen fertilizer moderately, with postponing nitrogen application could relief the lodging stress.
It can be seen from
Different letters on the culm mean significant difference among the treatments at P < 0.05 as determined by the LSD test. The test was conducted separately between the two years.
The correlation analysis showed that there was a significant negative correlation between the pushing resistance of wheat stem and CLRI, and the equation was y = 0.2211x + 10.383(r = -0.68**), indicating that it is feasible of using pushing resistance as an indicator to measure the lodging resistance of wheat.
As shown in
N level (kg ha-1) | N ratio | 2012–2013 | 2013–2014 | ||||||
---|---|---|---|---|---|---|---|---|---|
Length of basal internodes (cm) | Plant height (cm) | Length of basal internodes/Plant height (%) | Length of basal internodes (cm) | Plant height (cm) | Length of basal internodes/Plant height (%) | ||||
I | II | I | II | ||||||
180 | 7:1:2:0 | 6.71abc |
10.63ab | 90.54a | 18.06ab | 5.72abc | 9.53b | 92.34a | 18.11ab |
5:1:2:2 | 6.44bc | 10.48ab | 90.93a | 17.56ab | 5.49bc | 9.48b | 92.79a | 17.66ab | |
3:1:3:3 | 5.99c | 10.46b | 91.27a | 17.11b | 5.16c | 9.45b | 93.47a | 17.18b | |
225 | 7:1:2:0 | 7.02ab | 10.84ab | 91.54a | 18.32a | 5.92ab | 10.13ab | 93.63a | 18.86ab |
5:1:2:2 | 6.57bc | 10.61ab | 91.68a | 17.69ab | 5.61abc | 9.78b | 94.64a | 17.77ab | |
3:1:3:3 | 6.08c | 10.48b | 92.02a | 17.36ab | 5.49bc | 9.71b | 94.25a | 17.20b | |
270 | 7:1:2:0 | 7.50a | 10.93a | 92.09a | 18.45a | 6.06a | 10.71a | 95.25a | 19.69a |
5:1:2:2 | 7.33ab | 10.65ab | 92.06a | 17.96ab | 5.88ab | 9.79b | 95.70a | 18.45ab | |
3:1:3:3 | 6.70abc | 10.48b | 93.04a | 17.18b | 5.51abc | 9.92ab | 96.30a | 17.76ab | |
F | |||||||||
Nitrogen levels(NL) | 14.44 |
2.87 | 5.30 |
1.28 | 6.94 |
8.15 |
4.85 |
4.40 |
|
Nitrogen ratio(NR) | 14.26 |
11.11 |
1.35 | 16.39 |
14.08 |
5.31 |
0.55 | 10.01 |
|
NL×NR | 0.19 | 0.70 | 0.16 | 0.30 | 0.31 | 2.26 | 0.03 | 0.44 |
α Values in a column followed by the same letter are not significantly different at P < 0.05 as determined by the LSD test. The test was conducted separately between the two years.
* F-test significant at 5% level.
** F-test significant at 1% level.
The effect of nitrogen fertilizer on the basal internodes length of Yangmai 20 was significant (
The above results indicated that excessive application of nitrogen fertilizer and superfluous basal fertilizer can easily cause excessive elongation of the basal internodes and even lodging.
It can be seen from
N level (kg ha -1) | N ratio | 2012–2013 | 2013–2014 | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Diameter (mm) | Wall thickness (mm) | Filling degree (mg DW cm-2) | Diameter (mm) | Wall thickness (mm) | Filling degree (mg DW cm-2) | ||||||||
I | II | I | II | I | II | I | II | I | II | I | II | ||
180 | 7:1:2:0 | 4.20ab |
4.56a | 0.62ab | 0.55ab | 23.34ab | 22.91abc | 4.51ab | 4.96a | 0.60abc | 0.53b | 22.10abc | 21.20ab |
5:1:2:2 | 4.49ab | 4.86a | 0.65ab | 0.63a | 28.80ab | 30.28abc | 4.58ab | 5.06a | 0.63abc | 0.55ab | 26.07ab | 25.75a | |
3:1:3:3 | 4.60a | 4.89a | 0.66a | 0.63a | 34.45a | 33.69a | 4.83a | 5.17a | 0.69a | 0.61a | 26.49a | 25.37ab | |
225 | 7:1:2:0 | 4.15ab | 4.55a | 0.58ab | 0.53b | 22.00b | 20.71bc | 4.46ab | 4.94a | 0.58bc | 0.55ab | 20.58bc | 20.86ab |
5:1:2:2 | 4.57a | 4.80a | 0.64ab | 0.63a | 28.13ab | 28.52abc | 4.57ab | 4.96a | 0.61abc | 0.57ab | 24.65ab | 24.07ab | |
3:1:3:3 | 4.60a | 4.85a | 0.66a | 0.63a | 32.01ab | 32.09ab | 4.54ab | 4.97a | 0.64ab | 0.58ab | 24.05abc | 23.38ab | |
270 | 7:1:2:0 | 4.03b | 4.48a | 0.56b | 0.53b | 20.40b | 20.08c | 4.44b | 4.86a | 0.54c | 0.53b | 18.69c | 19.67b |
5:1:2:2 | 4.47ab | 4.80a | 0.61ab | 0.61ab | 26.85ab | 25.66abc | 4.56ab | 4.92a | 0.58bc | 0.53b | 21.41abc | 20.22ab | |
3:1:3:3 | 4.52a | 4.77a | 0.62ab | 0.61ab | 29.32ab | 28.68abc | 4.68ab | 4.95a | 0.56bc | 0.53b | 22.13abc | 22.55ab | |
F | |||||||||||||
Nitrogen levels(NL) | 1.37 | 0.59 | 5.33 |
0.76 | 1.82 | 2.89 | 2.36 | 4.10 | 7.60 |
6.53 |
12.50 |
7.07 |
|
Nitrogen ratio(NR) | 24.89 |
9.18 |
11.10 |
29.05 |
16.46 |
18.22 |
7.12 |
2.02 | 16.27 |
6.24 |
13.08 |
7.73 |
|
NL×NR | 0.27 | 0.06 | 0.61 | 0.08 | 0.14 | 0.13 | 1.26 | 0.47 | 1.46 | 2.18 | 0.22 | 1.10 |
α Values in a column followed by the same letter are not significantly different at P < 0.05 as determined by the LSD test. The test was conducted separately between the two years.
* F-test significant at 5% level.
** F-test significant at 1% level.
The effect of nitrogen fertilizer on the wall thickness of the stem was as follows: the wall thickness of stem decreased with the increase of nitrogen level generally (
With the increase of nitrogen level, the nitrogen content of the stem was significantly increased and showed a downtrend with the decrease of basal fertilizer at low nitrogen level (180kg ha-1). When the amount of nitrogen application was 225 kg ha-1 and 270 kg ha-1, the excessive proportion of basal fertilizer should result in high nitrogen content in the stem, and the appropriate postponing of basal fertilizer could decrease the nitrogen content. However, if the ratio of nitrogen at the booting stage (DC 41) was too high, it also could lead to the increase of nitrogen content. Therefore, the nitrogen content of the stem in the treatment of 5: 1: 2: 2 was lower than the other two nitrogen ratio treatments. Variance analysis showed that nitrogen application rate had a significant effect on the nitrogen content of stem, but the effect of nitrogen ratio and the interaction among them was not significant (
N level (kg ha -1) | N ratio | 2012–2013 | 2013–2014 | ||||
---|---|---|---|---|---|---|---|
Nitrogen content (%) | Water-solute carbohydrates (%) | WSC/N | Nitrogen content (%) | Water-solute carbohydrates (%) | WSC/N | ||
180 | 7:1:2:0 | 0.680bc |
15.93ab | 23.43ab | 0.703cd | 15.45a | 21.98ab |
5:1:2:2 | 0.643c | 17.08a | 26.57a | 0.688d | 16.87a | 24.52a | |
3:1:3:3 | 0.634c | 16.62a | 26.21a | 0.672d | 16.32a | 24.29a | |
225 | 7:1:2:0 | 0.705abc | 14.30abc | 20.29bc | 0.740abcd | 13.87ab | 18.74bc |
5:1:2:2 | 0.678bc | 15.08ab | 22.25ab | 0.712cd | 14.63ab | 20.55ab | |
3:1:3:3 | 0.688abc | 16.03ab | 23.30ab | 0.722bcd | 15.55a | 21.52ab | |
270 | 7:1:2:0 | 0.789a | 11.35c | 14.38d | 0.797ab | 11.99b | 15.04c |
5:1:2:2 | 0.764ab | 13.01bc | 17.03cd | 0.781abc | 13.67ab | 17.51bc | |
3:1:3:3 | 0.777ab | 14.59abc | 18.77bcd | 0.809a | 14.15ab | 17.49bc | |
F | |||||||
Nitrogen levels(NL) | 26.61 |
21.76 |
54.52 |
34.53 |
15.07 |
38.78 |
|
Nitrogen ratio(NR) | 1.67 | 6.15 |
8.98 |
1.14 | 4.85 |
6.22 |
|
NL×NR | 0.19 | 1.10 | 0.36 | 0.66 | 0.42 | 0.11 |
α WSC/N: the ratio of water-solute carbohydrates to nitrogen
β Values in a column followed by the same letter are not significantly different at P < 0.05 as determined by the LSD test. The test was conducted separately between the two years.
* F-test significant at 5% level.
** F-test significant at 1% level.
The laws of water-solute carbohydrates and WSC/N ratio were the same basically (
The lignin content increased first and then decreased with the increase of total nitrogen level (
Different letters on the culm mean significant difference among the treatments at P < 0.05 as determined by the LSD test. The test was conducted separately between the two years.
Silicon mainly exists in the cell wall of epidermal cells and abundant silicon can enhance the hardness, toughness and elasticity of the stem. The content of silicon increased first and then decreased with the increase of total nitrogen application. Reducing the proportion of basal nitrogen (the treatments of 5: 1: 2: 2 and 3: 1: 3: 3) could increase the silicon content of the basal internodes compared with the treatment of 7: 1: 2: 0. The results of variance analysis showed that the effect of nitrogen ratio on the silicon content was significant, while the nitrogen level only significantly affected the silicon content in 2013–2014 (
It was suggested that the moderate increase of nitrogen level was beneficial to improve the content of lignin, cellulose and silicon in basal internodes, but the proportion of basal fertilizer should be reduced, which could enhance the lodging resistance of wheat.
Correlation analysis demonstrated that stem wall thickness and filling degree of first and second basal internodes, lignin, cellulose and WSC/N ratio positively correlated with culm lodging resistance index (CLRI) significantly. Remarkable negatively correlations were also found between the length of first internode and CLRI. Stem wall thickness were significantly positively associated with filling degree, lignin, cellulose and WSC/N ratio of the basal internodes. Stem wall thickness and filling degree of first and second basal internodes were also significantly (P < 0.05) negatively correlated with plant height. Interestingly, the diameter of basal internodes did not correlate with the length of first basal internode, while, negatively and significantly (P < 0.01) correlated with the length of second basal internode (
CLRI | LS | PH | L-I | L-II | D-I | D-II | WT-I | WT-II | F-I | F-II | LC | CC | SC | WSC/N | |
CLRI | 1.00 | ||||||||||||||
LS | -0.79 |
1.00 | |||||||||||||
PH | -0.44 | 0.54 |
1.00 | ||||||||||||
L-I | -0.67 |
0.74 |
0.77 |
1.00 | |||||||||||
L-II | -0.23 | 0.13 | -0.49 |
-0.40 | 1.00 | ||||||||||
D-I | 0.52 |
-0.39 | 0.41 | 0.05 | -0.65 |
1.00 | |||||||||
D-II | 0.40 | -0.22 | 0.49 |
0.30 | -0.83 |
0.91 |
1.00 | ||||||||
WT-I | 0.90 |
-0.87 |
-0.46 |
-0.69 |
-0.22 | 0.51 |
0.38 | 1.00 | |||||||
WT-II | 0.78 |
-0.77 |
-0.47 |
-0.76 |
0.18 | 0.44 | 0.18 | 0.81 |
1.00 | ||||||
F-I | 0.85 |
-0.80 |
-0.49 |
-0.81 |
0.09 | 0.42 | 0.17 | 0.80 |
0.90 |
1.00 | |||||
F-II | 0.86 |
-0.75 |
-0.47 |
-0.78 |
0.13 | 0.43 | 0.17 | 0.77 |
0.90 |
0.98 |
1.00 | ||||
LC | 0.59 |
-0.54 |
0.15 | -0.26 | -0.46 |
0.62 |
0.53 |
0.58 |
0.52 |
0.54 |
0.51 |
1.00 | |||
CC | 0.66 |
-0.68 |
-0.13 | -0.52 |
-0.20 | 0.43 | 0.28 | 0.66 |
0.68 |
0.65 |
0.62 |
0.92 |
1.00 | ||
SC | 0.34 | -0.25 | 0.48 |
0.01 | -0.52 |
0.70 |
0.64 |
0.28 | 0.35 | 0.35 | 0.33 | 0.75 |
0.62 |
1.00 | |
WSC/N | 0.89 |
-0.77 |
-0.53 |
-0.57 |
-0.27 | 0.37 | 0.33 | 0.82 |
0.55 |
0.67 |
0.67 |
0.34 | 0.43 | 0.10 | 1.00 |
α CLRI: culm lodging resistance index; LS: lodging score; PH: plant height; L-I: length of first basal internode; L-II: Length of second basal internode; D-I: diameter of first basal internode; D-II: diameter of second basal internode; WT-I: wall thickness of first basal internode; WT-II: wall thickness of second basal internode; F-I: filling degree of first basal internode; F-II: filling degree of second basal internode; LC: lignin content; CC: cellulose content; SC: silicon content; WSC/N: the ratio of water-solute carbohydrates to nitrogen.
* F-test significant at 5% level.
** F-test significant at 1% level.
In order to study the influence degree of different culm traits on lodging resistance, grey relational analysis for culm lodging resistance index (CLRI) and stem characters were carried out (
Culm characters | Grey correlation degree (p = 0.5) | Ranking |
---|---|---|
Plant height | 0.345 | 11 |
Length of first basal internode | 0.299 | 13 |
Length of second basal internode | 0.343 | 12 |
Diameter of first basal internode | 0.362 | 9 |
Diameter of second basal internode | 0.360 | 10 |
Wall thickness of first basal internode | 0.634 | 1 |
Wall thickness of second basal internode | 0.550 | 4 |
Filling degree of first basal internode | 0.550 | 5 |
Filling degree of second basal internode | 0.562 | 3 |
Lignin content | 0.485 | 6 |
Cellulose content | 0.448 | 7 |
Silicon content | 0.388 | 8 |
The ratio of water-solute carbohydrates to nitrogen | 0.567 | 2 |
Lodging is one of detrimental constraints limiting wheat yields and quality by bending or breaking stems on wheat production worldwide [
In the present study, culm lodging resistance index (CLRI) is an important parameter to measure the lodging resistant ability of crops and to evaluate the lodging risk in the agricultural production. Correlation analysis demonstrated that stem wall thickness and filling degree of basal internodes, lignin, cellulose and WSC/N ratio were positively and significantly correlated with CLRI. Remarkable negatively correlations were also found between the length of first internode and CLRI. While, plant height, the length and diameter of second internode and silicon of basal internode had no significantly correlation with CLRI, which is different from several previous studies [
The application of nitrogen could effected lodging risk and grain yield significantly. The increase in the nitrogen rates promoted higher lodging, affected the grain and flour quality and had no effect on yield [
Recent work has shown that the morphological and anatomical traits of culm with beneficial effects on lodging may be changed by reducing and delaying applications of fertilizer, such as wide stem bases with thick walls, high lignin and cellulose content and efficient canopy structure which can increase light interception at the base of plant [
The present field experiment was conducted to study the effects of different nitrogen management on lodging resistance and yield potential and to determine whether nitrogen management can reduce lodging risk without reducing yield potential finally. The result shown that grain yield response to nitrogen doses was quadratic and grain yield reached the highest at 225 kg ha-1 nitrogen level. The treatment of 5:1:2:2 increased by 10.05% and 2.27% compared with the treatments of 7:1:2:0 and 3:1:3:3, respectively. As the increase of nitrogen level and basal nitrogen ratio, the basal internodes became slender and fragile, and the stem wall thickness, filling degree and the strength of the stem were decreased gradually, which increased the lodging risk significantly. The results were similar to previous studies. In a word, choosing the moderate nitrogen level and reducing the basal fertilizer ratio could increase the stem strength and toughness and the culm lodging resistance effectively and got the higher grain yield simultaneously.
In conclusion, for Yangmai 20, the planting density of 180×104 ha-1, nitrogen level of 225 kg ha-1, and the proportion of 5: 1: 2: 2 (the ratio of nitrogen amount applied before sowing, at tillering, jointing and booting stage) effectively reduced plant height and the length of basal internodes, increased the wall thickness, filling degree, the WSC/N ratio and the contents of lignin and cellulose in basal internodes. Moreover, this combination of planting density and nitrogen level and ratio also increased the lodging resistance and grain yield.
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