Potassium induces positive changes in nitrogen metabolism and antioxidant system of oat (Avena sativa L cultivar Kent)

Figures & data

Table 1. Characteristics of soil used for present study.

Soil type	Sandy clay loam
Sand	60.10%
Silt	17.90%
Clay	22%
pH	7.5
Electrical conductivity (EC)	0.1366 Milli Siemens
Carbon (C)	0.39%
Sodium (Na)	0.016%
Potassium (K)	0.134%
Calcium (Ca)	0.029%
Nitrogen (N)	1.877%

Table 2. Shoot/root length and fresh/dry weight of oat (A. sativa L. cultivar KENT) seedlings raised under different potassium treatments (7 DAS).

Treatments	Shoot length (cm)	Root length (cm)	Shoot fresh weight (mg)	Shoot dry weight (mg)	Root fresh weight (mg)	Root dry weight (mg)
Control	7.34 ± 0.51^c	5.65 ± 0.44^d	203.2 ± 1.9^e	19.1 ± 0.035^c	103.4 ± 1.5^d	7.2 ± 0.21^b
0.1 M KNO3	3.77 ± 0.67^d	4.07 ± 0.60^e	224.9 ± 2.4^cd	13.9 ± 0.21^d	116.7 ± 1.2^c	8.6 ± 0.17^b
0.01 M KNO3	7.98 ± 0.35^b	6.21 ± 0.43^bc	301.5 ± 3.4^b	27.2 ± 0.04^a	116.0 ± 1.5^c	8.9 ± 0.31^b
0.001 M KNO3	8.71 ± 0.66^a	7.17 ± 0.57^a	346.0 ± 4.0^a	22.4 ± 0.042^b	149.8 ± 2.5^b	7.5 ± 0.23^b
0.1 M K2O	2.42 ± 0.26^d	2.97 ± 0.21^f	96.3 ± 1.3^f	10.5 ± 0.12^d	69.4 ± 1.0^e	6.7 ± 0.22^b
0.01 M K2O	8.18 ± 0.66^a	6.65 ± 0.25^b	316.7 ± 4.3^b	27.9 ± 0.05^a	159.6 ± 2.9^b	10.9 ± 0.09^a
0.001 M K2O	7.73 ± 0.16^b	6.38 ± 0.34^b	246.8 ± 3.6^c	21.1 ± 0.32^b	100.6 ± 1.9^d	8.7 ± 0.21^b
0.1 M KCl	3.03 ± 0.58^d	3.20 ± 0.68^f	137.0 ± 1.8^f	22.7 ± 0.21^b	133.4 ± 2.5^c	9.3 ± 0.14^ab
0.01 M KCl	8.41 ± 0.71^a	5.84 ± 0.23^b	318.8 ± 2.3^ab	24.3 ± 0.26^ab	236.2 ± 2.3^a	10.4 ± 0.21^a
0.001 M KCl	7.20 ± 0.27^b	6.11 ± 0.11^bc	229.4 ± 3.0^cd	28.1 ± 0.07^a	109.4 ± 3.7^c	10.8 ± 0.25^a

Note: Data followed by same letter are not significantly different at p < .05.

Table 3. Shoot/root length and fresh/dry weight of oat (A. sativa L. cultivar KENT) seedlings raised under different potassium treatments and PEG-induced water stress (7 DAS).

Treatments	Shoot length (cm)	Root length (cm)	Shoot fresh weight (mg)	Shoot dry weight (mg)	Root fresh weight (mg)	Root dry weight (mg)
Control	11.7 ± 0.96^a	9.9 ± 0.63^a	231.1 ± 2.2^a	18.3 ± 0.29^a	126.4 ± 2.1^a	9.1 ± 0.13^a
−2.7 bars	7.2 ± 0.85^bc	7.5 ± 1.02^bc	153.1 ± 3.1^d	9.2 ± 0.037^d	78.1 ± 1.9^d	5.3 ± 0.34^d
−2.7 bars + 0.1 M KNO3	3.4 ± 0.36^d	3.7 ± 0.53^d	–	–	–	–
−2.7 bars + 0.01 M KNO3	11.6 ± 1.16^a	8.6 ± 0.28^b	201.1 ± 2.1^b	14.5 ± 0.12^b	94.6 ± 0.96^b	6.9 ± 0.03^bc
−2.7 bars + 0.001 M KNO3	10.1 ± 1.03^ab	9.5 ± 1.11^a	199.4 ± 1.9^c	12.1 ± 0.03^c	89.1 ± 0.71^b	5.7 ± 0.01^c
−2.7 bars + 0.1 M K2O	–	1.9 ± 0.10^e	–	–	–	–
−2.7 bars + 0.01 M K2O	8.9 ± 0.89^b	10.1 ± 0.27^a	190.1 ± 3.7^c	13.9 ± 0.04^b	88.3 ± 0.74^b	7.3 ± 0.05^b
−2.7 bars + 0.001 M K2O	7.8 ± 1.25^c	8.4 ± 0.51^b	173.1 ± 2.3^c	11.6 ± 0.31^c	86.7 ± 0.93^b	7.6 ± 0.63^b
−2.7 bars + 0.1 M KCl	2.9 ± 0.00^d	2.5 ± 0.40^d	–	–	–	–
−2.7 bars + 0.01 M KCl	9.8 ± 0.44^b	9.4 ± 0.27^a	184.9 ± 2.4^c	12.9 ± 0.25^c	74.6 ± 0.86^c	6.1 ± 0.41^c
−2.7 bars + 0.001 M KCl	8.4 ± 0.59^bc	8.2 ± 0.40^b	169.5 ± 2.1^d	12.3 ± 0.21^c	79.1 ± 1.01b^c	5.7 ± 0.07^c

Note: Data followed by same letter are not significantly different at p < .05.

Table 4. Plant height, Number of tillers and RWC in A. sativa L. cultivar KENT supplied with different salts of potassium (55 DAS).

Treatments	Plant height (cm)	Number of tillers (per pot)	RWC
Control	64.04 ± 1.17^d	10.00 ± 0.577^d	78.92 ± 0.241^d
K2O 20 kg ha^−1	65.76 ± 1.62^c	10.66 ± 0.881^d	81.69 ± 0.141^b
K2O 40 kg ha^−1	67.92 ± 1.15^c	12.66 ± 0.333^bc	80.40 ± 0.463^c
K2O 60 kg ha^−1	72.52 ± 1.07^b	12.66 ± 0.881^bc	82.05 ± 0.161^b
KNO3 20 kg ha^−1	67.02 ± 1.95^c	10.66 ± 0.881^d	80.87 ± 0.832^c
KNO3 40 kg ha^−1	72.00 ± 0.27^b	13.33 ± 0.333^b	87.57 ± 0.083^a
KNO3 60 kg ha^−1	74.32 ± 1.78^a	15.33 ± 0.333^a	83.51 ± 0.67^ab

Note: Data followed by same letter are not significantly different at p < .05.

Table 5. Chlorophyll and Carotenoid (mg g⁻¹ fresh wt) contents in oat (A. sativa L. cultivar KENT) seedlings raised under different potassium treatments (7 DAS).

Treatments	Chlorophyll a	Chlorophyll b	Total Chlorophylls	Carotenoids
Control	0.102 ± 0.007^c	0.046 ± 0.003^c	0.149 ± 0.010^d	0.101 ± 0.006^d
0.1 M KNO3	0.081 ± 0.002^d	0.039 ± 0.001^d	0.120 ± 0.003^e	0.083 ± 0.003^e
0.01 M KNO3	0.139 ± 0.009^a	0.064 ± 0.011^a	0.204 ± 0.019^a	0.124 ± 0.001^a
0.001 M KNO3	0.119 ± 0.003^b	0.058 ± 0.004^ab	0.160 ± 0.024^c	0.117 ± 0.003^b
0.1 M K2O	0.041 ± 0.002^e	0.007 ± 0.001^e	0.034 ± 0.003^g	0.021 ± 0.001^g
0.01 M K2O	0.121 ± 0.001^ab	0.051 ± 0.003^b	0.172 ± 0.003b^c	0.127 ± 0.003^a
0.001 M K2O	0.114 ± 0.001^b	0.048 ± 0.002^bc	0.159 ± 0.014^c	0.116 ± 0.005^b
0.1 M KCl	0.086 ± 0.004^d	0.011 ± 0.002^e	0.051 ± 0.001^f	0.050 ± 0.002^f
0.01 M KCl	0.136 ± 0.012^a	0.058 ± 0.004^ab	0.185 ± 0.006^b	0.112 ± 0.002^b
0.001 M KCl	0.110 ± 0.002^b	0.049 ± 0.005^b	0.159 ± 0.017^c	0.109 ± 0.003^c

Note: Data followed by same letter are not significantly different at p < .05.

Table 6. Chlorophyll and Carotenoid (mg g⁻¹ fresh wt.) contents in oat (A. sativa L. cultivar KENT) seedlings raised under different potassium treatments and PEG-induced water stress (7 DAS).

Treatments	Chlorophyll a	Chlorophyll b	Total Chlorophylls	Carotenoids
Control	0.227 ± 0.004^a	0.094 ± 0.013^a	0.321 ± 0.007^a	0.251 ± 0.009^a
−2.7 bars	0.124 ± 0.007^e	0.054 ± 0.014^e	0.178 ± 0.006^e	0.138 ± 0.011^f
−2.7 bars + 0.1 M KNO3	–	–	–	–
−2.7 bars + 0.01 M KNO3	0.213 ± 0.015^b	0.075 ± 0.019^c	0.278 ± 0.021^c	0.241 ± 0.010^b
−2.7 bars + 0.001 M KNO3	0.217 ± 0.005^b	0.082 ± 0.007^b	0.291 ± 0.015^b	0.236 ± 0.016^bc
−2.7 bars + 0.1 M K2O	–	–	–	–
−2.7 bars + 0.01 M K2O	0.205 ± 0.013^c	0.074 ± 0.011^c	0.281 ± 0.019^bc	0.186 ± 0.007^e
−2.7 bars + 0.001 M K2O	0.195 ± 0.013^d	0.071 ± 0.004^c	0.166 ± 0.015^f	0.235 ± 0.011^c
−2.7 bars + 0.1 M KCl	–	–	–	–
−2.7 bars + 0.01 M KCl	0.210 ± 0.010^bc	0.084 ± 0.018^b	0.295 ± 0.005^b	0.225 ± 0.020^c
−2.7 bars + 0.001 M KCl	0.193 ± 0.012^d	0.069 ± 0.012^d	0.223 ± 0.001^d	0.203 ± 0.010^d

Note: Data followed by same letter are not significantly different at p < .05.

Table 7. Chlorophyll a, b, Total Chlorophylls and Carotenoid (mg g⁻¹ fr wt.) contents in flag leaf of A. sativa L. cultivar KENT supplied with different salts of potassium (55 DAS).

Treatments	Chlorophyll a	Chlorophyll b	Total Chlorophylls	Carotenoids
Control	0.4538 ± 0.022^d	0.3633 ± 0.030^d	0.8175 ± 0.052^c	0.7734 ± 0.055^c
K2O 20 kg ha^−1	0.5365 ± 0.014^c	0.7315 ± 0.059^a	1.0653 ± 0.186^b	0.9586 ± 0.041^b
K2O 40 kg ha^−1	0.5927 ± 0.015^ab	0.5603 ± 0.017^b	1.1540 ± 0.023^a	1.1143 ± 0.027^a
K2O 60 kg ha^−1	0.5766 ± 0.047^b	0.5183 ± 0.052^bc	1.1258 ± 0.097^a	1.1129 ± 0.093^a
KNO3 20 kg ha^−1	0.5816 ± 0.008^b	0.5841 ± 0.098^b	1.1306 ± 0.121^a	0.9527 ± 0.037^b
KNO3 40 kg ha^−1	0.5700 ± 0.012^b	0.5153 ± 0.024^bc	1.0001 ± 0.091^b	1.1229 ± 0.014^a
KNO3 60 kg ha^−1	0.6300 ± 0.007^a	0.5540 ± 0.008^b	1.1865 ± 0.008^a	1.1627 ± 0.034^a

Note: Data followed by same letter are not significantly different at p < .05.

Figure 1. Nitrate reductase activity (µ mole NO₂ produced hr⁻¹ g⁻¹ fr wt) in oat (A. sativa L. cultivar KENT) seedlings raised under different potassium treatments (A) and PEG (B) induced water stress (7 DAS).

Note: Data followed by same letter are not significantly different at p < .05.

Figure 2. Nitrate reductase activity (µ mole NO₂ produced hr⁻¹ g⁻¹ fr wt) in flag leaf of A. sativa L. cultivar KENT supplied with different salts of potassium (55 DAS).

Note: Data followed by same letter are not significantly different at p < .05.

Figure 3. Alanine (A) and Aspartate (B) aminotransferase activity (µ mol keto acid released mg⁻¹ protein min⁻¹) in oat (A. sativa L. cultivar KENT) seedlings raised under different potassium treatments (7 DAS).

Note: Data followed by same letter are not significantly different at p < .05.

Figure 4. Alanine (A) and Aspartate (B) aminotransferase activity (µ mol keto acid released mg⁻¹ protein min⁻¹) in oat (A. sativa L. cultivar KENT) seedlings raised under different potassium treatments and PEG-induced water stress (7 DAS).

Note: Data followed by same letter are not significantly different at p < .05.

Figure 5. Alanine (A) and Aspartate Aminotransferase (B) (µ mol keto acid released mg⁻¹ protein min⁻¹) in flag leaf of A. sativa L. cultivar KENT supplied with different salts of potassium (55 DAS).

Note: Data followed by same letter are not significantly different at p < .05.

Table 8. Phenols and Tannins (mg g⁻¹ dry wt.) contents in A. sativa L. cultivar KENT supplied with different salts of potassium (55 DAS).

	Phenols			Tannins
Treatments	Flag leaf	Stem	Root	Flag leaf	Stem	Root
Control	3.93 ± 0.077^d	3.72 ± 0.110^c	1.07 ± 0.047^c	77.00 ± 1.22^c	22.52 ± 0.27^d	21.22 ± 0.72^d
K2O 20 kg ha^−1	4.18 ± 0.031^c	3.40 ± 0.212^d	1.16 ± 0.019^c	79.02 ± 1.73^b	24.75 ± 0.75^d	22.37 ± 0.25^cd
K2O 40 kg ha^−1	4.64 ± 0.050^bc	4.80 ± 0.070^b	1.44 ± 0.021^b	82.32 ± 1.28^b	34.77 ± 0.29^c	25.52 ± 0.84^c
K2O 60 kg ha^−1	5.78 ± 0.031^ab	5.92 ± 0.047^a	1.87 ± 0.025^a	88.95 ± 1.47^a	36.25 ± 0.47^b	28.25 ± 0.85^b
KNO3 20 kg ha^−1	4.19 ± 0.052^c	4.07 ± 0.085^c	1.42 ± 0.026^b	75.27 ± 1.33^b	37.65 ± 1.11^b	25.65 ± 0.96^c
KNO3 40 kg ha^−1	5.02 ± 0.026^b	4.95 ± 0.210^b	1.49 ± 0.013^b	87.30 ± 0.47^a	39.22 ± 0.44^b	30.62 ± 0.23^b
KNO3 60 kg ha^−1	6.39 ± 0.020^a	5.97 ± 0.062^a	2.15 ± 0.050^a	94.20 ± 1.79^a	47.27 ± 0.93^a	33.75 ± 0.62^a

Note: Data followed by same letter are not significantly different at p < .05.

Figure 6. Superoxide dismutase (A), Catalase (B) and Ascorbate peroxidase (C) (EU mg⁻¹ protein) activity in flag leaf of A. sativa L. cultivar KENT supplied with different salts of potassium (55 DAS).

Note: Data followed by same letter are not significantly different at p < .05.

Table 9. Free amino acids (mg g⁻¹ dry wt.) Proline (µ mole proline g⁻¹ dry wt.) and Free sugars (mg g⁻¹ dry wt.) contents in A. sativa L. cultivar KENT supplied with different salts of potassium (55 DAS).

	Free amino acids			Proline			Free Sugars
Treatments	Flag leaf	Stem	Root	Flag leaf	Stem	Root	Flag leaf	Stem	Root
Control	70.32 ± 0.86^c	3.72 ± 0.23^d	2.97 ± 0.06^e	36.27 ± 0.34^e	24.49 ± 0.29^d	20.93 ± 0.30^c	63.5 ± 3.18^d	56.75 ± 2.5^e	52.75 ± 2.78^d
K2O 20 kg ha^−1	72.25 ± 1.1^c	4.07 ± 0.24^c	4.35 ± 0.34^d	36.97 ± 1.09^e	27.75 ± 0.35^c	21.15 ± 0.32^c	82.8 ± 2.5^c	62.00 ± 2.0^d	64.00 ± 1.87^c
K2O 40 kg ha^−1	92.77 ± 2.2^b	4.90 ± 0.28^c	6.05 ± 0.44^c	50.25 ± 0.99^d	31.32 ± 0.76^c	23.27 ± 0.16^b	88.3 ± 2.4^b	72.00 ± 1.5^c	65.25 ± 1.65^b
K2O 60 kg ha^−1	138.12 ± 1.8^a	7.50 ± 0.46^b	8.72 ± 0.69^a	58.61 ± 0.68^c	34.58 ± 0.69^b	24.68 ± 0.16^ab	120.5 ± 6.1^a	85.75 ± 2.0^ab	67.50 ± 2.72^b
KNO3 20 kg ha^−1	73.15 ± 0.35^c	5.52 ± 0.34^c	7.80 ± 0.33^ab	54.07 ± 2.00^d	33.48 ± 0.53^b	22.48 ± 0.38^b	99.7 ± 4.5^b	64.12 ± 0.91	57.01 ± 1.77^c
KNO3 40 kg ha^−1	137.27 ± 3.3^a	8.55 ± 0.46^b	7.07 ± 0.26^b	68.55 ± 1.3^ab	36.73 ± 0.35^b	25.48 ± 0.34^a	114.7 ± 3.0^a	80.50 ± 2.2^b	67.75 ± 1.70^b
KNO3 60 kg ha^−1	101.42 ± 1.4^b	11.32 ± 0.31^a	7.57 ± 0.31^ab	77.73 ± 1.21^a	45.36 ± 0.48^a	27.26 ± 0.38^a	122.5 ± 3.7^a	93.25 ± 1.7^a	83.00 ± 2.48^a

Note: Data followed by same letter are not significantly different at p < .05.

Table 10. Malondialdehyde content (µ mol g⁻¹ fr wt.) in flag leaf of A. sativa L. cultivar KENT supplied with different salts of potassium (55 DAS).

Treatments	MDA content
Control	1.0760 ± 0.054^a
K2O 20 kg ha^−1	0.8590 ± 0.035^b
K2O 40 kg ha^−1	0.8236 ± 0.025^bc
K2O 60 kg ha^−1	0.7173 ± 0.010^c
KNO3 20 kg ha^−1	0.8813 ± 0.008^b
KNO3 40 kg ha^−1	0.8613 ± 0.082^b
KNO3 60 kg ha^−1	0.7236 ± 0.036^c

Note: Data followed by same letter are not significantly different at p < .05.

Table 11. Sodium, potassium and Calcium (mg g⁻¹ dry wt.) contents in A. sativa L. cultivar KENT supplied with different salts of potassium (55 DAS).

	Sodium			Potassium			calcium
Treatments	Flag leaf	Root	Stem	Flag leaf	Root	Stem	Flag leaf	Root	Stem
Control	0.977 ± 0.02^a	3.37 ± 1.08^a	8.01 ± 0.08^a	11.86 ± 1.57^d	1.77 ± 0.32^e	9.47 ± 0.48^c	3.94 ± 0.4^d	2.82 ± 0.64^e	4.33 ± 0.07^e
K2O 20 kg ha^−1	0.670 ± 0.17^c	2.40 ± 0.59^b	6.91 ± 0.97^b	14.47 ± 0.70^b	2.46 ± 0.60^b	9.61 ± 0.16^c	4.91 ± 0.8^c	3.22 ± 0.49^d	4.93 ± 0.17^d
K2O 40 kg ha^−1	0.391 ± 0.02^f	1.69 ± 0.35^d	4.51 ± 1.13^d	14.16 ± 0.58^b	2.43 ± 0.54^b	10.81 ± 0.67^b	4.53 ± 0.4^c	4.23 ± 1.15^a	4.92 ± 0.19^d
K2O 60 kg ha^−1	0.419 ± 0.08^e	1.92 ± 0.14^c	3.51 ± 0.36^e	15.56 ± 1.55^a	2.53 ± 0.41^b	10.41 ± 0.43^b	6.81 ± 2.0^a	2.88 ± 0.40^e	5.57 ± 0.07^b
KNO3 20 kg ha^−1	0.877 ± 0.02^b	1.86 ± 0.08^c	4.60 ± 1.18^d	13.26 ± 1.43^c	2.25 ± 0.50^c	8.85 ± 0.36^d	6.25 ± 1.7^b	4.01 ± 0.68^ab	6.87 ± 0.47^a
KNO3 40 kg ha^−1	0.671 ± 0.06^c	1.81 ± 0.25^c	5.15 ± 0.20^c	12.90 ± 0.85^c	2.03 ± 0.23^d	10.87 ± 0.44^b	4.54 ± 1.3^a	3.68 ± 0.60^c	5.44 ± 0.78^b
KNO3 60 kg ha^−1	0.647 ± 0.05^d	1.95 ± 0.18^c	3.22 ± 0.98^e	14.51 ± 1.18^b	3.29 ± 0.49^a	11.04 ± 0.89^a	6.49 ± 0.6^ab	3.72 ± 0.69^c	5.42 ± 0.34^bc

Note: Data followed by same letter are not significantly different at p < .05.