Chin Bull Bot ›› 2020, Vol. 55 ›› Issue (1): 49-61.doi: 10.11983/CBB19047

• EXPERIMENTAL COMMUNICATIONS • Previous Articles     Next Articles

Regulatory Mechanism of Salicylic Acid on Seed Germination Under Salt Stress in Kale

Cao Dongdong1,3,Chen Shanyu1,Qin Yebo2,Wu Huaping3,Ruan Guanhai1,Huang Yutao1,*()   

  1. 1Institute of Crop and Nuclear Technology Utilization, Zhejiang Academy of Agricultural Science, Hangzhou 310021, China
    2Crop Management Bureau of Zhejiang Province, Hangzhou 310020, China
    3Huzhou Keao Seed Co. Ltd, Huzhou 313000, China
  • Received:2019-03-14 Accepted:2019-07-26 Online:2019-12-20 Published:2020-01-01
  • Contact: Huang Yutao E-mail:hytcsy@zju.edu.cn

Abstract:

Salinity is a major abiotic constraint affecting seed germination and plant growth. The effects of salt stress and salicylic acid (SA) and 2-aminoindan-2-phosphonic acid (SA synthesis inhibitor, AIP) on seed germination were investigated using kale (Brassica oleracea var. acephala) variety ‘Nagoya’. The results showed that the seed vigor of kale was significant decreased under 150 or 200 mmol·L -1 NaCl treatment by significantly reducing seed water uptake rate, seed vigor, and seedling quality, inhibited phenylalanine ammonia and lyase activity, decreasing endogenous SA content, and increasing hydrogen peroxide (H2O2) and superoxide anion (O2 -.) contents. SA treatment effectively alleviated the inhibition of salt stress on seed germination, promoted endogenous SA anabolism, increased seed water absorption rate and seed vigor, promoted K + and Mg 2+ absorption, and reduced the Na + content. Furthermore, SA treatment significantly increased superoxide dismutase and peroxidase activities and inhibited H2O2 and O2 -.accumulation. By contrast, AIP treatment significantly inhibited the germination process under salt stress, likely due to the reduced level of endogenous SA. This study demonstrates that exogenous SA enhances salt tolerance in kale seeds primarily through increasing the protective enzyme activities, reducing reactive oxygen species accumulation, and maintaining ion homeostasis during seed germination.

Key words: kale, seed germination, salt stress, salicylic acid, physiological characteristics

Table 1

Primers used for qRT-PCR"

Gene name No. of accession Primer sequence (5°-3°)
18srRNA NC_016118.1 F: GGAAGGACTTGTACGGTAACATTG
R: TGGACCTGCCTCATCATACTCA
BoPAL1 XM_013781025.1 F: TCGATCTTCCACAAGATTGGT
R: TCCACTTCGTCAGGAAGCA
BoPAL2 XM_013749252.1 F: AATCAGCTGAGCAACATAACCA
R: GACGTTTTGCGAGACGAGA
BoCAT1 XM_013742034.1 F: ATCCTCGTGGTTTTGCTGTC
R: TGCCAACAAGATCAAAGTTCC
BoCAT2 XM_013774413.1 F: ATGGAAGGCTCAGGTGTCAA
R: CGTAGTGAGCTTTTCCGGATT
BoSOD1 XM_013783393.1 F: ACATCATTGTTGGAGATGATGG
R: GAGGGATCTGGCAGTCAGTG
BoSOD3 XM_013750980.1 F: TGGTGATCCTGATGACCTTG
R: CCTGCGTTTCCTGTTGATTT
BoPOD2 XM_013729485.1 F: GGTGGTTTCTTGCGCTGA
R: CCATGGTCCGTTGATCACTA
BoPOD3 XM_013728218.1 F: CGTCAGGAAACACGGAGAA
R: CCTCAATGAAGCCAAATCCT

Figure 1

Effects of salt stress on seed germination of kale (A) Time course of seed germination under salt stress; (B) Seed germination after 96 hours of NaCl treatments with different concentration "

Table 2

Effects of salicylic acid (SA) and SA synthesis inhibitor (2-aminoindano-2-phosphonic acid, AIP) on water uptake rate during seed germination of kale under salt stress "

Treatments Water uptake rate (%)
0-4 h 4-8 h 8-16 h 16-24 h 24-36 h 36-48 h
Control-1 47.18±3.52 a 42.56±2.19 a 19.14±0.81 a 18.33±2.04 a 18.21±1.33 a 27.26±2.67 a
Control-2 37.11±4.31 b 31.67±3.15 c 14.62±1.09 b 12.62±0.09 c 10.21±1.02 b 17.64±0.08 b
SA 42.27±2.89 a 37.75±3.09 b 14.31±1.59 b 14.24±0.15 b 16.77±1.44 a 25.81±1.77 a
AIP 32.12±2.71 c 30.41±4.93 c 13.41±1.07 c 12.78±0.21 c 8.21±0.06 c 7.55±1.23 c

Table 3

Effects of salicylic acid (SA) and SA synthesis inhibitor (2-aminoindano-2-phosphonic acid, AIP) on seed germination of kale under salt stress"

Treatments Germination
energy (%)
Germination
percentage (%)
Germination
index
Vigor index Seedling length (cm) Seedling dry weight (g)
Control-1 85.333±3.270 a 85.333±3.272 a 15.742±0.742 a 1.610±0.892 a 8.241±0.711 a 0.083±0.010 a
Control-2 53.667±3.208 c 56.333±4.044 c 8.231±0.810 c 0.908±0.071 c 7.822±0.635 b 0.076±0.008 b
SA 62.333±4.615 b 68.667±4.730 b 10.558±0.556 b 1.167±0.064 b 7.837±0.706 b 0.079±0.009 b
AIP 41.000±3.331 d 46.667±2.516 d 7.267±0.597 d 0.762±0.079 d 7.156±0.523 c 0.064±0.004 c

Figure 2

Effects of salicylic acid (SA) and SA synthesis inhibitor (2-aminoindano-2-phosphonic acid, AIP) on kale seedling growth at 5 days post-germination under salt stress Control-1, Control-2, SA and AIP are the same as Table 2."

Figure 3

Effects of salicylic acid (SA) and SA synthesis inhibitor (2-aminoindano-2-phosphonic acid, AIP) on SA content (A), PAL activity (B) and BoPAL1-2 expression (C, D) in kale seeds during germination under salt stress PAL: Phenylalanine ammonia-lyase. Control-1, Control-2, SA and AIP are the same as Table 2. Different lowercase letters above the bars indicate significant differences (P<0.05) among treatments at the same sown time."

Table 4

Effects of salicylic acid (SA) and SA synthesis inhibitor (2-aminoindano-2-phosphonic acid, AIP) on ions contents during seed germination of kale under salt stress"

Germination time (h) Treatments Ion content (mg·g-1 FW)
Na+ K+ Ca2+ Mg2+
12 Control-1 2.553±0.219 c 1.471±0.134 a 0.221±0.018 a 0.431±0.026 a
Control-2 3.711±0.431 a 1.227±0.203 b 0.192±0.012 b 0.313±0.033 c
SA 3.292±0.331 b 1.435±0.053 a 0.183±0.009 b 0.372±0.042 b
AIP 3.809±0.504 a 1.170±0.077 c 0.211±0.018 a 0.211±0.018 d
24 Control-1 3.951±0.412 c 1.682±0.117 a 0.148±0.017 a 0.477±0.033 a
Control-2 5.587±0.581 a 1.427±0.109 b 0.123±0.017 b 0.385±0.049 b
SA 5.108±0.432 b 1.623±0.152 a 0.112±0.006 b 0.462±0.053 a
AIP 5.717±0.367 a 1.301±0.083 c 0.118±0.008 b 0.321±0.019 c
36 Control-1 3.762±0.319 c 1.677±0.092 a 0.176±0.074 a 0.597±0.055 a
Control-2 6.193±0.419 a 1.486±0.106 c 0.093±0.012 b 0.511±0.022 b
SA 5.654±0.384 b 1.583±0.201 b 0.101±0.004 b 0.590±0.044 a
AIP 6.202±0.609 a 1.472±0.013 c 0.095±0.011 b 0.367±0.048 c
48 Control-1 4.188±0.381 b 1.769±0.208 a 0.132±0.008 a 0.646±0.054 a
Control-2 5.772±0.720 a 1.311±0.011 c 0.073±0.003 c 0.491±0.060 c
SA 5.790±0.364 a 1.422±0.015 b 0.072±0.009 c 0.582±0.015 b
AIP 5.831±0.519 a 1.226±0.064 d 0.094±0.014 b 0.401±0.008 d

Table 5

Effects of salicylic acid (SA) and SA synthesis inhibitor (2-aminoindano-2-phosphonic acid, AIP) on osmotic adjustment substances during seed germination of kale under salt stress"

Germination time (h) Treatments Osmotic adjustment substance
Soluble sugar (mg·g-1 FW) Soluble protein (mg·g-1 FW) Free proline (μg·g-1 FW)
12 Control-1 13.56±0.81 d 3.57±0.40 d 108.19±1.23 c
Control-2 23.19±1.73 b 8.11±0.71 b 143.77±1.35 b
SA 29.28±2.00 a 12.17±1.03 a 156.53±1.17 a
AIP 19.13±1.23 c 6.59±0.33 c 157.11±0.90 a
24 Control-1 17.11±0.92 c 6.17±0.55 c 115.64±0.87 c
Control-2 26.35±1.74 b 9.27±0.49 b 167.59±2.11 a
SA 33.27±4.02 a 13.56±0.84 a 142.13±1.33 b
AIP 25.77±3.19 b 6.59±0.30 c 122.64±2.16 c
36 Control-1 23.85±1.39 d 6.12±0.41 c 117.26±1.55 c
Control-2 37.50±2.47 b 11.73±1.23 a 141.33±1.46 b
SA 43.59±4.33 a 12.19±1.19 a 172.57±1.15 a
AIP 30.66±2.20 c 9.13±0.52 b 109.33±0.82 c
48 Control-1 22.74±3.10 c 5.80±0.37 b 133.52±0.81 c
Control-2 34.19±2.79 a 8.62±0.79 a 167.29±1.31 b
SA 36.82±2.12 a 8.93±0.64 a 128.19±1.55 c
AIP 26.70±2.34 b 6.18±0.56 b 186.53±2.08 a

Figure 4

Effects of salicylic acid (SA) and SA synthesis inhibitor (2-aminoindano-2-phosphonic acid, AIP) on H2O2 (A) and O2-. (B) contents of kale seed during germination under salt stress Control-1, Control-2, SA and AIP are the same as Table 2. Different lowercase letters above the bars indicate significant differences (P<0.05) among treatments at the same sown time."

Figure 5

Effects of salicylic acid (SA) and SA synthesis inhibitor (2-aminoindano-2-phosphonic acid, AIP) on the activities of catalase (CAT) (A), superoxide dismutase (SOD) (B), and peroxidase (POD) (C) in kale seeds during germination under salt stress Control-1, Control-2, SA and AIP are the same as Table 2."

Figure 6

Effects of salicylic acid (SA) and SA synthesis inhibitor (2-aminoindano-2-phosphonic acid, AIP) on gene expression of BoCAT1 (A), BoCAT2 (B), BoSOD1 (C), BoSOD3 (D), BoPOD2 (E), and BoPOD3 (F) during seed germination of kale under salt stress Control-1, Control-2, SA and AIP are the same as Table 2. Different lowercase letters above the bars indicate significant differences (P<0.05) among treatments at the same sown time."

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