Effects of La3+ on yield and quality traits of wheat with different gluten types

JOURNAL OF RARE EARTHS, Vol. 32, No. 7, July 2014, P. 672

Effects of La3+ on yield and quality traits of wheat with different gluten types OU Hongmei (欧红梅)1, ZHANG Zili (张自立)1, YAO Danian (姚大年)2,* (1. College of Resources and Environment, Anhui Agricultural University, Hefei 230036, China; 2. College of Agronomy, Anhui Agricultural University, Hefei 230036, China) Received 15 November 2013; revised 17 January 2014

Abstract: To test the roles of La3+ on yield and quality of wheat for different end uses, experiments were conducted using split-plot design for different La3+ treatments as main plot and different gluten types of wheat as subplot, by foliar spraying La3+ at jointing stage and filling stage. The results showed that spraying 0.5–1.5 mmol/L La3+ increased the yield and 1000-kernel weight of wheat of different gluten types. The protein content of strong-gluten wheat Wanmai 33 increased after spraying 0.5–1.5 mmol/L La3+ , which made it achieve the good quality standard of strong-gluten wheat, whereas its LOX and PPO activity reduced, the carotenoid content increased. These La3+ treatments prolonged the storage period of grain, improved flour nutritional value and the food processing quality. Spraying 0.5–1.5 mmol/L La3+ also increased flour peak viscosity of medium-gluten wheat Yangmai 158, as improving its starch properties. Spraying La3+ significantly decreased flour water absorption rate of weak gluten type variety Wanmai 48 to meet the weak-gluten flour standard. The total pentosan content reduced at 1–1.5 mmol/L La3+, which would be good for making biscuit. Results suggested that spraying appropriate concentration of La3+ increased wheat yield and benefited wheat quality for different end uses. Keywords: lanthanum ion; gluten type; yield; quality trait; wheat for different end uses; rare earths

Rare earth elements (REEs) which enter farmland systems continue to mount up with the rare earth mining, smelting and REEs micronutrient fertilizers popularizing in agriculture. Moreover, even with the exclusion of special application of REEs into farmland, a certain amount of REEs still enter the field with use of trace element fertilizer[1] and phosphate fertilizer of slag forms[2]; and adding the influence of soil background value[3,4], REEs will still enter the food chain in a certain dosage. REEs in the environment affect human health through the food chain. Long-term exposure to or low-dose uptake REEs may have adverse consequences for health and metabolism in human[5–7]. But poisonous side-effects of REEs correlate with its dosage, and proper amount of REEs’ organic matter obtained through the consumption of animals and plants is safe and beneficial. REEs are also used in diagnosis and treatment in many clinical cases[8–10]. Wheat is one of the main cereal crops in China, many studies have been carried out for the application of REEs in wheat since 1970s. Liu et al. studied the effect of spraying REE ions on the growth and development of wheat, and showed that REE ions increased plant height, root weight, panicle length, grain number per panicle, 1000-kernel weight and yield[11]. Shi et al. studied the effect of spraying rare earth in different growth period on the wheat, and found that spraying 0.1% rare earth solu-

tion at the jointing stage increased approximately 15% yield[12]. With the improvement of people's living standard, the demand for high-quality wheat for end uses is growing consistently; however, its quality is still unsatisfactory for lack of high quality of varieties and restriction of cultivation systems. Now in China, most varieties contain medium-gluten which are suitable for making noodles and steamed stuffed bun. However, few varieties contain high quality strong-gluten wheat flour suitable for making bread and high quality weak-gluten wheat flour for biscuit. The researches showed that quality traits of wheat are quantitative traits, which are influenced by the genetic characteristics, environment and their interaction[13–15]. The nutritional quality and processing quality of wheat could be improved by spraying molybdenum, zinc and other trace elements[16]. Therefore, by improving the cultivation condition, or spraying trace element fertilizer, it is possible to improve wheat quality. The effects of REEs on processing quality and nutritional quality of wheat have not been reported. Here, we studied the effect of spraying the rare earths lanthanum (La) to wheat with different gluten types at the jointing and filling stage on the yield and quality of wheat. The goal of this experiment was to elucidate the role of La on wheat quality for different end uses and provide reference for the application of REEs in agriculture.

Foundation item: Project supported by National Natural Science Foundation of China (31371615, 31071404) * Corresponding author: YAO Danian (E-mail: [email protected]; Te1.: +86-551-65786213) DOI: 10.1016/S1002-0721(14)60124-1

OU Hongmei et al., Effects of La3+ on yield and quality traits of wheat with different gluten types

1 Materials and methods 1.1 Materials The field experiments were carried out in the experimental farm of Anhui Agricultural University from 2011 to 2012. The soil was yellow cinnamon soil, its basic characters are listed in Table 1. Three cultivars of wheat were used, which were Wanmai 33 (strong gluten wheat), Yangmai 158 (medium gluten wheat) and Wanmai 48 (weak gluten wheat). The stock solution of La3+ (20 mmol/L) was prepared by dissolving lanthanum oxide (99.99% purity) with concentrated hydrochloric acid and fixing the volume with distilled water. Table 1 Chemical properties of tested soil pH Organic matter/ Total N/ Alkaline hydrolytic Available Available K/ (H2O)

(g/kg)

(g/kg)

N/(mg/kg)

P/(mg/kg)

(mg/kg)

6.3

19.0

0.34

54.1

43.9

335.2

1.2 Field trials A split-plot design was used in this experiment, in which 5 different concentrations of La3+ (0, 0.5, 1, 1.5, 2 mmol/L) were used as the main plot, 3 wheat varieties as subplot. The experiment was repeated 4 times, each replicate included 15 plots, randomly distributed in the field. Each plot was planted in five rows, with 2 m each row and 25 cm between rows, and 100 seeds were sown per row. Routine field management was conducted during growing periods. Different concentrations of La3+ were respectively sprayed on wheat at the jointing and filling stage. The pH of solution was adjusted to 5.5 before spraying, and spraying dosage was 150 mL/m2, and the control groups (0 mmol/L) were sprayed with the same dose of distilled water (pH=5.5). 1.3 Determination of yield, 1000-kernel weight and grain quality traits At maturity, all the spikes in each plot were collected, dried and threshed. Whole grains were cleaned, weighed for production, and stored in a dry room. 1000-kernel in each plot was counted in duplicate and weighed, respectively, to calculate the average value. Grain quality traits were determined using near infrared grain analyzer (InfratecTM1241, Foss, Denmark) for grain protein, moisture content, total starch content, wet gluten content, sedimentation value and hardness. 1.4 Preparation of wheat flour 1.4.1 Whole wheat flour preparation The dry grains (moisture≤13%) were milled by cyclone mill with 0.5 mm flour sifter (Cyclotec 1093, Foss Tecator, Denmark). The whole wheat flour was used for determining lipoxygenase (LOX) activity, polyphenol oxidase (PPO) activity and carotenoid content. 1.4.2 Wheat flour preparation

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After grain samples were conditioned to 14% moisture content by dampening wheat for 24 h, they were milled through 100 mesh sieve by experimental grinding powder (880110, Brabender, Germany), and flour extraction was about 60%. Wheat flour was sealed and preserved in a refrigerator, and used for the determination of La content, pentosan content, rapid viscosity parameters and farinograph parameters. 1.5 Determination of La3+ and carotenoid content, LOX and PPO activities Concentration of La3+ in wheat flour was determined by ICP (ICP-MS 6300, Thermo Electron, USA) after the samples were digested with a mixture of 5 mL HNO3 and 0.5 mL HClO4. Detailed procedure was conducted according to the methods described by Liu et al.[17]. LOX extract was prepared by 30 min blend from whole wheat flour with phosphate buffer (0.1 mol/L, pH 7.5), then centrifuged at 4 ºC at 8000 g for 10 min, and the supernatant was as the enzyme extract. LOX activity was determined by an ultraviolet spectrophotometer (UV-1100, Mapada, Shanghai) as described by Larisa et al.[18]. PPO activity was determined according to the method of Anderson and Morris[19,20], with 10 mmol/L levo-3,4dihydroxyphenylalanine (L-DOPA) as substrate in 50 mmol/L morpholinopropane sulfonic acid (MOPS) (pH 6.5). The carotenoid content was measured according to AACC14-50 with slight changes. The whole wheat flour was extracted with water-saturated n-butanol, shocked repeatedly for 1 h, let stand for 10 min, then the supernatant was centrifuged at 4000 g for 10 min, and determined at 436 nm with water-saturated n-butanol as control. 1.6 Determination of starch gelatinization properties, pentosan content and dough rheological property parameters Starch gelatinization properties were determined by rapid visco analyzer (RVA) (Super3, Newport Scientific, Australia) using 3 g wheat flour with 25 mL distilled water, the sample of each plot was measured 3 times and averaged. Water-soluble pentosan and total pentosan content were determined using the orcinol hydrochloric acid method[21], and then water insoluble pentosan content was converted subsequently. The dough rheological property parameters were determined according to the AACC54-21 method (AACC, 1995) with farinograph (Farinograph 810104, Brabender, Germany). The statistical software SPSS 11.5 was used to calculate means, standard errors (S.E.), ANOVA and LSD multiple comparison (a=0.05).

2 Results and discussion 2.1 Effect of La3+ on 1000-kernel weight, yield and La3+ concentration of the wheat flour

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Table 2 shows that La3+ had the tendency to increase 1000-kernel weight of wheat. The 0.5, 1, 1.5 mmol/L La3+ increased yield of different gluten types of wheat, in which yield increased remarkably for Wanmai 33 sprayed with 1, 1.5 mmol/L La3+, and Yangmai 158 and Wanmai 48 sprayed with 0.5, 1, 1.5 mmol/L La3+, while spraying 2.0 mmol/L La3+ had no significant effect on the yield of wheat. REE show dosage-dependent effect on plant growth. The previous studies[11,12,22,23] showed that the jointing and flowering stage are the best spraying stage, when concentration of mixed rare earth oxides in REE fertilizer was from 160 to 250 mg/kg, REEs gave the best effect on increase of yield, while its concentration was more than 300 mg/kg REE has no obvious effect or has inhibitory effect. Spraying was applied in the jointing and filling stage in this study, concentration of La3+ was set to be 0 (control), 0.5 mmol/L (La2O3, 81 mg/kg), 1.0 mmol/L (La2O3, 163 mg/kg), 1.5 mmol/L (La2O3, 244 mg/kg) and 2.0 mmol/L (La2O3, 326 mg/kg), which covered from stimulation concentration to inhibition concentration in order to fully analyze the effect of La on wheat quality. Our results showed that suitable concentration range was consistent with the previous reports. The effect of La3+ on physiological indexes confirmed that spraying La3+ increased chlorophyll content and nitrate reductase activity[24], thereby accelerated the nitrogen metabolism. The REE could promote the absorption of nitrogen, phosphorus and potassium by roots, and transport of nutrition to grains[11,25]. Therefore, it enhanced dry matter accumulation in grain and increased 1000-kernel weight. Studies showed that spraying suitable concentration of REE was able to enhance the grain number per panicle, and had good effect on the net photosynthesis rate and respiration inten-

sity in crop[26,27], resulting in increase of yield. The main feeding part of wheat is flour, so the accumulation of La3+ in the flour deserved attention. As shown in Table 2, La3+ concentration in flour gradually increased with the increase of La3+ concentration compared with the control. This could be influenced by several factors: first, single La replaced the mixed rare earth in this experiment; second, the second spraying time was the filling stage that is the late growth stage of wheat, the grain maturity had been in the effective time of extraneous La treatment. Moreover, there was no effective precipitation after second spraying. It has been shown that the sprayed light rare earth concentrated easily in plants[28,29], and extraneous REEs had significant effects on the content and distribution of REEs at its “effective time”[30]. But our data were close to background concentration in wheat grain reported by Liang et al.[31], especially, when spraying the suitable concentration (0.5–1.5 mmol/L), La3+ concentration in flour is in a secure level. This experiment was conducted to found out that a suitable concentration that could not only improve the quality of wheat but also control the amount of rare earth in edible parts was in secure level. From the transfer coefficient which was ratio of total amount of La3+ in the flour after deductions for background value to total amount of spraying La3+, the transfer coefficient was higher at low concentration, and decreased gradually as La3+ concentration increased. Different gluten types of wheat had the same change trend. The results showed that La3+ concentration in flour was not proportional to the La3+amount sprayed due to plant uptake and transport capacity constraints, which agree with study of accumulation and migration of 226Ra in soil-crops system[32].

Table 2 Effect of La3+ on yield, 1000-kernel weight and La3+ concentration in wheat flour * Cultivar

Wanmai 33

La3+ concentration/

1000-kernel

Yield/

La3+ concentration in

Transfer coefficient of

(mmol/L)

weight/g

(kg/hm2)

wheat flour/(ng/g)

La3+/(10-4)

d

0

37.3±0.19

5054.0±98.0

40.0±10.1

–

38.5±0.25 a

5432.0±182.6ab

78.3±14.5cd

9.51±3.54a

1.0

38.2±0.05 ab

5882.6±236.0a

102.5±9.6bc

4.75±0.34ab

1.5

38.3±0.17

ab

a

37.6±0.60

ab

5226.7±242.5

37.5±0.30 a

5048.0±90.3c

5845.3±252.7

ab

ab

3.89±0.57b

a

3.82±0.75b

121.9±11.2

158.9±16.8 33.1±6.2b

–

0.5

38.1±0.71

a

a

5809.3±126.7

105.8±30.9a

11.13±3.45a

1.0

37.9±0.56 a

5581.0±83.0ab

122.5±28.7a

7.16±2.25ab

1.5

38.3±0.36

a

b

a

5.85±0.81ab

2.0

37.6±0.37

a

a

4.28±0.91b

0

38.2±0.64 a

0

Wanmai 48

b

0.5

2.0

Yangmai 158

b

a

5379.0±97.5

146.3±15.0

c

151.9±22.7

4666.7±76.9d

45.0±5.2b

–

5315.4±172.7

74.0±7.3b

8.45±0.13a

5026.0±34.0

bc

0.5

38.6±1.23

1.0

39.8±0.91 a

5722.0±216.0a

102.5±1.4a

6.68±2.28a

1.5

39.8±0.67

a

ab

a

3.78±1.85ab

38.7±0.47

a

2.0

5530.0±30.0

cd

5057.0±63.0

113.1±9.6

a

143.3±39.3

1.83±0.49b

* Values shown are means ±S.E. (n=4) (In the same column of the same cultivar, different letters mean significant difference between any two treatments respectively at p<0.05)

OU Hongmei et al., Effects of La3+ on yield and quality traits of wheat with different gluten types

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mining quality[34,35]. In this experiment, the key period of the wheat yield and quality formation was under effective time of lanthanum treatment by spraying twice. The effective use of nitrogen can achieve simultaneous increase of grain yield and protein content, the yield and quality of protein could affect content of wet gluten, sedimentation value, flour water absorption, stable period and other quality traits. In order to fulfill requirements of good quality wheat for different end uses, researchers optimized the cultivation management to improve the quality of wheat, which has become an important way to meet the demand of wheat flour for different end uses in China[36]. Ma et al.[37] showed that grain yield of wheat had negative correlation to protein content, sedimentation value and hardness, and improving the yield of durum wheat with high protein content and strong gluten was not very easy, but was easier for soft wheat with low protein content and weak gluten. From Table 2 and 3, it could be seen that spraying La3+ increased not only wheat yield, but also protein content of durum wheat with strong gluten (Wanmai 33) and wet gluten content of soft wheat with weak gluten (Wanmai 48), which showed that spraying La3+ had a certain advantage in increasing crop yield of wheat with good end use qualities compared with other conventional cultivation measures.

2.2 Effect of La3+ on grain quality traits of the wheat The grain protein content of Wanmai 33 significantly increased at the 1.0 mmol/L of La3+ (Table 3), but decreased slightly when the La3+ concentration increased to 2.0 mmol/L. Nevertheless, protein content of Yangmai 158 and Wanmai 48 at different La3+ concentrations slightly increased compared with the controls. Total starch content of Wanmai 48 decreased significantly at 1.0 mmol/L La3+, and that of the other treatments did not obviously change. However, the change trend of wet gluten content was different. At 1.5, 2 mmol/L La3+, wet gluten content of Wanmai 33 significantly decreased, while that of Wanmai 48 increased at different La3+ concentrations. Sedimentation value of Wanmai 33 under La3+ treatments decreased, and that of Yangmai 158 and Wanmai 48 had no obvious change compared with the controls. Hardness of Wanmai 33 and Wanmai 48 decreased at 0.5 mmol/L La3+, then increased with the increasing of the La3+ concentration, and increase extent dropped when the concentration of La3+ reached up to 2 mmol/L, and that of Wanmai 48 significantly increased at 1.5 mmol/L La3+, while hardness of Yangmai 158 was lower than that of the control but not significant. Therefore, La3+ had influence on the protein content, wet gluten content and Zeleny sedimentation value of strong-gluten and weak-gluten wheat, but had no obvious influence on grain quality traits of medium-gluten wheat. The suitable concentration of REE can promote the absorption and use of nutrients of crops, and the most significant effect is the absorption of nitrogen[27,33]. It is generally believed that the jointing stage is the yield efficient period of applying nitrogen fertilizer, while booting to flowering period is the high efficient stage for deter-

2.3 Effect of La3+ on starch gelatinization properties of the wheat Starch gelatinization properties are an important index to reflect the starch quality in wheat, and have an important influence on the edible quality of wheat noodles. According to Table 4, breakdown, peak time and pasting temperature of wheat with different gluten types were not

Table 3 Effect of La3+ on grain quality traits of the wheat* Cultivar

La3+ concentration/

Protein content

Starch

Wet gluten

Zeleny sedimentation

(mmol/L)

(dry basis)/%

content/%

(14% wet basis)/%

value/mL

0

14.8±0.1bc

68.3±0.4ab

32.3±0.6a

34.5±2.3a

78.1±1.6ab

b

ab

ab

ab

76.8±2.9b

32.7±1.1

ab

30.7±2.1

82.0±1.6ab

0.5 Wanmai 33

68.7±0.4

ab

31.4±0.7

a

31.1±0.3

16.2±0.2

68.6±0.2

1.5

15.4±0.6b

68.2±0.3b

30.1±0.5b

28.9±0.9b

85.1±2.9a

2.0

c

14.1±0.5

a

69.1±0.2

b

30.9±1.0

b

78.9±1.7ab

0

14.5±0.5a

68.2±0.2ab

31.3±0.9a

38.6±4.9a

89.7±1.8a

a

a

a

a

86.1±1.6a

a

14.8±0.2

a

68.3±0.4

30.6±0.6

67.4±0.2

30.5±1.0

38.4±1.9

88.6±1.9a

1.5

14.7±0.1a

68.4±0.4a

30.7±0.9a

38.5±0.4a

86.8±1.8a

2.0

a

15.0±0.1

ab

67.7±0.1

a

30.8±0.8

a

38.1±2.4

86.1±1.7a

0

13.7±0.1a

68.6±0.2a

27.8±0.5c

33.4±0.4ab

36.6±1.1bc

a

ab

ab

b

34.3±0.2c

29.3±0.7

ab

36.1±2.4

39.3±1.0b

a

68.2±0.1

b

a

36.9±2.0

15.4±0.3

13.9±0.3

b

28.7±2.0

1.0

0.5 Wanmai 48

a

1.0

0.5 Yangmai 158

15.1±0.1

Hardness

29.3±0.9

ab

31.7±1.3

1.0

13.9±0.3

67.6±0.3

1.5

14.3±0.1a

67.9±0.3ab

30.3±0.3a

37.2±0.1a

44.0±0.8a

2.0

a

a

bc

ab

39.6±1.4b

13.9±0.2

68.6±0.3

28.6±0.7

34.9±1.4

* Values shown are means±S.E. (n=4) (In the same column of the same cultivar, different letters mean significant difference between any two treatments respectively at p<0.05)

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Table 4 Effect of La3+ on starch gelatinization properties of the wheat* Cultivar

Wanmai 33

Yangmai 158

Wanmai 48

La concentration/

Peak

Trough

(mmol/L)

viscosity/cp

0

2560±19b

0.5

2364±179bc c

Breakdown/

Final

viscosity/cp

cp

viscosity/cp

1623±17b

1016±17a

2685±32b

1446±45c

1035±12a

2574±11b

1138±22a

d

a

Setback/

c

Peak

Pasting

cp

Time/min

temperature/ºC

1128±3ab

6.17±0.05a

69.0±0.1a

6.07±0.06a

69.4±0.1a

a

d

1.0

2172±18

1219±32

1023±9

2174±16

961±29

6.03±0.05

69.1±0.3a

1.5

2495±40b

1612±49b

1068±21a

2530±28b

1064±10bc

6.13±0.03a

69.0±0.2a

2.0

2804±51a

1749±15a

1042±18a

2969±56a

1043±11c

6.09±0.06a

69.4±0.2a

b

ab

a

a

bc

a

1854±20

1040±21

3023±42

1167±11

6.22±0.03

68.7±0.3a

2958±65a

1890±63ab

1069±15a

3139±82a

1249±19a

6.21±0.04a

68.8±0.1a

a

ab

a

a

ab

a

6.21±0.04

68.7±0.4a

6.17±0.04a

68.9±0.2a

1157±9

a

6.20±0.02

68.9±0.2a

3371±19a

1353±20a

6.12±0.02a

70.4±0.2a

1124±13a

3414±32a

1379±13a

6.06±0.03a

70.6±0.2a

a

c

a

1351±16

a

6.05±0.03

70.0±0.1a

3182±47b

1394±32a

6.06±0.03a

71.1±0.8a

b

a

a

70.4±0.5a

0

2738±25

0.5 1.0

2958±47

1824±10

1.5

3045±76a

2.0

b

2792±29

1763±49

1036±29

3058±12

0

3001±61b

2024±23a

1114±16a

0.5

3125±18a

2001±17a

1.0

b

2890±27

c

1746±22

1138±23

3031±69

1.5

2903±33b

1870±39b

1102±23a

2.0

b

bc

a

2952±24

1088±25

3109±68

1222±9

1892±21a

1078±21a

3138±56a

1166±26c

b

a

a

1827±29

1108±14

3163±15

c

1360±17

6.09±0.03

* Values shown are means±S.E. (n=4) (In the same column of the same cultivar, different letters mean significant difference between any two treatments respectively at p<0.05)

significantly different between wheat treated with La3+ and the control. Peak viscosity, trough viscosity and final viscosity of starch in Wanmai 33 declined as concentration of La3+ increased, then began to ascend at 1.5 mmol/L La3+. Both viscosity decreasing at 1.0 mmol/L La3+ and increasing at 2.0 mmol/L La3+ were significant compared with the control. Peak viscosity of Yangmai 158 increased significantly at 0.5–1.5 mmol/L La3+, its setback increased at lower concentration of La3+, and increased significantly at 0.5 mmol/L La3+, then decreased as the La3+ concentration increased. The peak viscosity of Wanmai 48 increased significantly at 0.5 mmol/L La3+, while the trough viscosity and final viscosity decreased significantly over the range of 1–2 mmol/L La3+. In general, the higher the peak viscosity of the flour, the better its noodle quality[38]. The starch quality of Wanmai 33 with strong gluten was improved at 2.0 mmol/L La3+, which would help improve noodles taste. Yangmai 158 with medium gluten at 0.5–1.5 mmol/L La3+ and Wanmai 48 with weak gluten at 0.5 mmol/L La3+ improved the flour starch quality. Starch content is major component in wheat grain, and transformative capacity of material is one of the main factors determining starch accumulation[39,40]. The suitable concentration of REE can promote the transport of nutrition elements in plant, and N and K supply could increase the activity of enzymes for starch formation[41], so the suitable concentration of REE might promote starch formation in grain and change composition of starch. Research had shown that the RVA gelatinization viscosity value was relatively high when gluten content was low and starch content was high[42]. Spraying 2.0 mmol/L

La3+, wet gluten content of Wanmai 33 decreased and starch content increased, then viscosity increased, which was consistent with previous research. Through spraying 0.5–1.5 mmol/L La3+, peak viscosity of Yangmai 158 with medium gluten increased and exceeded 2900 cp, which greatly improved noodle-making quality. Although part of the starch gelatinization characteristic had fluctuations, wet gluten contents of the strong gluten and medium gluten wheat were over 30% and the peak viscosity was over 2000 cp, which could meet the index requirements of high-quality noodle. 2.4 Effect of La3+ on LOX, PPO activities and carotenoid content of wheat with different gluten types The change trends of the LOX, PPO activity and carotenoid content of wheat with different gluten types were different (Fig. 1). The LOX activity of Wanmai 33 remarkably reduced except with the treatment of 1 mmol/L La3+; that of Yangmai 158 increased with the increase of La3+ concentration, but significantly decreased when the concentration of La3+ reached 2 mmol/L; that of Wanmai 48 decreased significantly at 0.5 mmol/L La3+, and then increased as La3+ concentration increased. The variation trend of PPO activity of Wanmai 33 was consistent with that of LOX. PPO activity of Yangmai 158 and Wanmai 48 increased significantly at 1.0 mmol/L La3+, and that of other concentrations of La3+ did not significantly change compared with the control. Carotenoid content of Wanmai 33 increased at different La3+ concentrations, while that of Yangmai 158 reduced, and significantly decreased at 1.0 and 1.5 mmol/L La3+, which was opposite to the trend of Wanmai 33. Carotenoid content of Wanmai 48

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tary, but excessive LOX activity would make the wheat flour too white and lose a lot of nutrients[46]. Chemical reaction catalyzed by PPO in wheat was the main reason of the enzymatic browning, and it had been proved that PPO activity and browning of bread, steamed buns, Chinese noodles had close connection[47,48]. Therefore, 0.5–1.5 mmol/L La3+ increased the protein content and carotenoid content of Wanmai 33, decreased its LOX and PPO activity, thus improved nutritional value of flour, prolonged the storage period of wheat grain, and maintained stable resistance of grain and the whiteness of flour. Spraying 1.0–1.5 mmol/L La3+ increased LOX activity and carotenoid content of Yangmai 158, and decreased PPO activity, which made flour white, but shortened its safe storage period. The nutritional value of Wanmai 48 was improved at low concentration of La3+, but the flour was a bit yellowish, and disease resistance of grain decreased at high concentration of La3+. 2.5 Effect of La3+ on pentosan content of wheat

Fig. 1 Effect of La3+ on LOX, PPO activities and carotenoid content of wheat with different gluten types (Values designated over the bars in different letters are significantly different at p<0.05. The concentrations of La3+ treatment were 0, 0.5, 1.0, 1.5 and 2.0 mmol/L)

increased at low concentration (0.5, 1.0 mmol/L), then decreased gradually with increasing La3+ concentrations, and significantly decreased when the concentration of La3+ reached 2 mmol/L. The suitable concentration of REE can improve the activity of enzyme in plants, accelerate the process of physiological metabolism, and improve adversity resistance of plants[27,43,44], which may indirectly affect enzyme activity of the grain and related quality. The LOX activity is one of the main factors affecting wheat grain and flour storage characteristics. Low LOX activity can reduce the oxidation of grain, thus prolong the storage period[45]. LOX could couple the oxidation over the carotenoids in wheat, replace chemical bleach and whiten wheat flour, thus improve its commodity. Carotenoids could improve the nutritional components of human die-

As shown in Fig. 2, the total pentosan of Wanmai 33 had no obvious change, but water soluble pentosan increased at 1.5 mmol/L, while significantly decreased as the concentration of La3+ was 2 mmol/L, and water insoluble pentosan significantly increased at low concentration (0.5 mmol/L La3+), then decreased with the increase of La3+ concentration, but increased when concentration of La3+ rose up to 2 mmol/L content, which showed the double-peak feature. For Yangmai 158, total pentosan and water insoluble pentosan increased at different La3+ concentrations, and water soluble pentosan did not significantly change compared with the control. The total pentosan and water insoluble pentosan of Wanmai 48 gradually reduced at low concentration, but increase when concentration of La3+ was 2 mmol/L. For dough baking property, water soluble pentosan could increase the size, structure and surface color of bread, and extend its shelf life[49,50]. Water-soluble pentosan and total pentosan content were negatively correlated with the cookie diameter[51]. Spraying 1.5 mmol/L La3+ on Wanmai 33 (strong gluten wheat) increased its water soluble pentosan, and significantly reduced its water insoluble pentosan, which improved the bread quality. For Wanmai 48 (weak gluten wheat), because it is suitable for making cake and biscuits, spraying 1–1.5 mmol/L La3+ significantly reduced its total pentosan, which could improve biscuit processing quality. 2.6

Effect of La3+ on farinograph parameter of wheat flour

Water absorption and stable period are the important index to measure the quality of flour and protein. The flour water absorption of Wanmai 33, although significantly reduced in the La3+ treatments (Table 5), could still stay over 60% at 0.5–1.5 mmol/L La3+ and meet the re-

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JOURNAL OF RARE EARTHS, Vol. 32, No. 7, July 2014 Table 5 Effect of La3+ on farinograph parameter of wheat flour* La3+

Water

Development

Cultivar concentration/ absorp-

Wanmai 33

Yangmai 158

48

Softness/

period/

FU

(mmol/L)

tion/%

0

61.4±0.3a

3.2±0.2a

10.6±0.2c 69.5±4.5a

0.5

60.6±0.1b

3.4±0.1a

8.8±0.4d

1.0

b

a

60.2±0.0

b

3.7±0.3

a

min

76.0±7.0a

a

66.5±2.5a

bc

68.5±3.5a

13.8±0.4

1.5

60.2±0.1

3.2±0.2

11.3±0.6

2.0

59.3±0.1c

3.7±0.3a

12.4±0.4ab 68.5±7.5a

b

a

2.8±0.1

7.0±0.8a

50.0±6.0a

0

60.5±0.2

0.5

60.7±0.1b

2.3±0.1b

5.5±1.1a

57.0±2.0a

1.0

a

ab

a

55.5±0.5a

a

5.7±0.5

60.0±5.0a 60.0±5.0a

61.2±0.1

a

2.5±0.1

ab

6.5±0.4

1.5

61.3±0.0

2.7±0.3

2.0

61.2±0.1a

3.0±0.5a

5.9±0.6a

a

a

a

131.5±6.5a

a

123.0±10.0a

0 Wanmai

time/min

Stable

57.0±0.8

b

1.6±0.2

a

3.4±0.4

0.5

55.5±0.1

1.5±0.1

2.7±0.6

1.0

55.8±0.1b

1.8±0.3a

2.9±0.5a 119.5±5.5a

1.5

b

55.6±0.1

a

1.7±0.0

2.6±0.4a 119.0±5.0a

2.0

55.6±0.1b

1.4±0.0a

2.6±0.2a 116.0±6.0a

* Values shown are means±S.E. (n=4) (In the same column of the same cultivar, different letters mean significant difference between any two treatments respectively at p<0.05)

3 Conclusions

Fig. 2 Effect of La3+ on pentosan content of wheat with different gluten types (Values designated over the bars in different letters are significantly different at P<0.05. The concentrations of La3+ treatment were 0, 0.5, 1.0, 1.5 and 2.0 mmol/L)

quirement of strong gluten flour. The stable period significantly decreased at low concentration (0.5 mmol/L), then extended with increasing concentration of La3+, and significantly increased at 1.0 and 2.0 mmol/L La3+. For Yangmai 158 (medium gluten wheat), flour water absorption significantly increased at 1–2 mmol/L La3+, stable period significantly reduced at 0.5 mmol/L La3+. Stable period of strong and medium gluten wheat was 5.5–13.8 min, and appropriate to the wet gluten content and peak viscosity index, which achieved the requirements of high quality noodle. For the treatments with different concentrations of La3+, flour water absorption of Wanmai 48 (weak gluten wheat) significantly reduced and met the requirement of weak gluten flour (<56%), and stable period had a tendency to decrease.

Spraying 0.5–1.5 mmol/L La3+ increased the yield of wheat and improved its quality for different end uses. La3+ concentration of the flour was in a safe level. Moreover, the effects of La3+ on the quality traits of wheat with different gluten types were different. For strong gluten type variety Wanmai 33, spraying 0.5–1.5 mmol/L La3+ increased protein content and carotenoid content, decreased LOX and PPO activity, thus increased the nutritional value of flour and prolonged storage period. Different La3+ concentration treatments significantly reduced flour water absorption, but it still met the requirement of high-gluten flour. Spraying 1.5 mmol/L La3+ increased water-soluble pentosan, and had a certain effect on improving the quality. For medium gluten type variety Yangmai 158, spraying 0.5–1.5 mmol/L La3+ increased starch pasting peak viscosity, thus improved the flour processing quality. LOX and PPO activity increased, and carotenoid content reduced, which whitened the flour and improved commodity values, but the security storage period was shortened. For weak gluten type variety Wanmai 48, spraying 0.5–1.5 mmol/L La3+ significantly increased wet gluten content. Peak viscosity significantly increased and LOX activity decreased obviously at 0.5 mmol/L La3+, and PPO activity and carotenoid content significantly increased at 1.0 mmol/L La3+. The nutritional value increased at low La3+ concentration but the flour color was yellowish. Flour water absorption of all treatments of La3+ significantly reduced, stable pe-

OU Hongmei et al., Effects of La3+ on yield and quality traits of wheat with different gluten types

riod decreased, and total pentosan reduced at 1–1.5 mmol/L La3+, thus improved the biscuit processing quality.

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