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Selenium enhances the vase life of Lilium longiflorum cut flower by regulating postharvest physiological characteristics
Scientia Horticulturae 264 (2020) 109172
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Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti
Short communication
Selenium enhances the vase life of Lilium longiflorum cut flower by regulating postharvest physiological characteristics
T
Ninghai Lu*, Limin Wu, Mingwang Shi Henan Institute of Science and Technology, Xinxiang 453003, China
A R T I C LE I N FO
A B S T R A C T
Keywords: Lilium longiflorum Sodium selenite Vase life Antioxidant system Osmotic adjustment
In this paper, we studied the role of sodium selenite (Na2SeO3) in improving cut flower’s vase life of Lilium longiflorum. Experimental findings displayed that Na2SeO3 remarkably enhanced the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR), improved relative water content (RWC) and the levels of soluble sugar, proline and soluble protein in cut flower’s petals of Lilium longiflorum, compared with control. Meanwhile, Na2SeO3 remarkably decreased the production of malondialdehyde (MDA) and hydrogen peroxide (H2O2), compared with control. Furthermore, Na2SeO3 remarkably improved the vase life of L. longiflorum cut flower, compared with control. These findings suggested that Na2SeO3 improved the vase life by regulating the antioxidant system and osmotic adjustment ability of L. longiflorum cut flower.
1. Introduction Fresh cut flowers are often used in our life. For example, cut flowers can be used as gifts for relatives and friends. Lilium longiflorum is one important cut flower for its ornamental uses. However, the short vase life of L. longiflorum cut flower limits its uses. Many studies showed that exogenous chemicals improved the vase life of cut flowers (Shan and Zhao, 2015; Tognon et al., 2016; Zheng and Guo, 2018). Shan and Zhao (2015) showed that one rare earth element named lanthanum improved the vase life of L. longiflorum cut flower. Zheng and Guo (2018) reported that another rare earth element named cerium improved the vase life of Dianthus caryophyllus cut flower. Selenium (Se) is an important trace element, which plays important roles in regulating the growth and stress tolerance of plants (Sattar et al., 2019). However, whether and how Se regulates the vase life of L. longiflorum cut flower is still unclear. Thus, it is interesting to study the roles of Se in regulating the vase life of L. longiflorum cut flower. Excessive production of reactive oxygen species (ROS) often leads to oxidative damage to cut flowers, which further resulted in their aging and death. Previous studies showed that the vase life of cut flowers had close relationship with their ability to scavenge ROS (Hou et al., 2018; Zheng and Guo, 2019). Plants have a complicated antioxidant defense system to scavenge ROS. The antioxidant defense system includs enzymatic system and non-enzymatic system. Enzymatic system includes
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various antioxidant enzymes, such as superoxide dismutase (SOD) and catalase (CAT), etc.. Recent studies showed that Se improved the ability of many plants to scavenge ROS through enzymatic system (Chi et al., 2017; Pereira et al., 2018). Wu et al. (2017) reported that Se enhanced the activities of SOD and CAT in the roots and leaves of Chinese cabbage exposed to cadmium stress. It has also been reported that Se enhanced the activities of peroxidase (POD), CAT and SOD in cucumber roots exposed to water stress (Jozwiak and Politycka, 2019). Ascorbateglutathione (AsA-GSH) cycle is also an important component of the enzymatic system. Plants can scavenge one type of ROS named hydrogen peroxide (H2O2) through AsA-GSH cycle. Wu et al. (2017) reported that Se enhanced the activity of AsA-GSH cycle through ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR) in the roots and leaves of Chinese cabbage exposed to cadmium stress. For cut flowers, Tognon et al. (2016) reported that Se could alleviate oxidative damage during postharvest aging process of cut snapdragon flower, which improved its post-harvest performance. However, whether and how Se regulates the enzymatic system of L. longiflorum cut flower is still unclear. Therefore, it is interesting to study the effects of Se on the antioxidant enzyme system and AsA-GSH cycle in the petals of L. longiflorum cut flower, which will provide fundamental basis for its application in enhancing the vase life of cut flower. After harvest, the water balance of fresh cut flowers plays an
Corresponding author. E-mail address: [email protected] (N. Lu).
https://doi.org/10.1016/j.scienta.2019.109172 Received 8 November 2019; Received in revised form 30 December 2019; Accepted 31 December 2019 0304-4238/ © 2020 Elsevier B.V. All rights reserved.
Scientia Horticulturae 264 (2020) 109172
N. Lu, et al.
important role in improving the vase life of cut flowers (Shan and Zhao, 2015; Zheng and Guo, 2019). During postharvest aging process, Shan and Zhao (2015) showed that the water balance ability of cut flowers was determined by the osmotic adjustment ability. The osmotic adjustment ability has close relationship with the levels of osmolytes, including soluble protein, soluble sugar and proline. Zheng and Guo (2019) showed that neodymium also improved the water balance ability of Lilium Casa Blanca by enhancing the levels of above osmolytes, which further improved the water content of petals. For Se, Dadnia et al. (2010) reported that Se played an important role in maintaining the turgor of wheat subjected to water deficit. Stattar et al. (2019) showed that Se had an important role in regulating osmotic potential and turgor pressure of bread wheat subjected to water deficit. Handa et al. (2018) reported that Se improved the levels of proline, glycine betaine and trehalose, which further increased the osmolality and the water balance ability of Brassica juncea seedlings exposed to chromium stress. These previous findings indicated that Se could regulate the water balance of plants through osmotic adjustment. However, whether and how Se regulates the osmotic adjustment ability of L. longiflorum petals is still unclear. Thus, it is interesting to investigate the roles of Se in regulating the water balance ability of L. longiflorum petals, which can further provide more fundamental basis for its application in enhancing the vase life of L. Longiflorum cut flower. In current study, we investigated the effects of sodium selenite (Na2SeO3) on the vase life, the relative water content (RWC), the activities of SOD, POD, CAT, APX, glutathione reductase (GR), DHAR and MDHAR, as well as the contents of soluble protein, soluble sugar and proline, malondialdehyde (MDA) and H2O2 in the petals of L. longiflorum cut flower. The purpose of current study was to clarify the roles of Na2SeO3 in improving the vase life of L. Longiflorum cut flower.
Table 1 Effects of Na2SeO3 on the vase life and the contents of MDA and H2O2. Values represent mean ± standard deviations (SD) (n = 3). Duncan’s multiple range test was used to determine statistical significance, different letters indicate statistical difference at P < 0.05. Treatment
MDA (nmol g−1 FW)
H2O2 (μmol g−1 FW)
Vase life (d)
Control 1 mg·L−1 Se 3 mg·L−1 Se 6 mg L−1 Se 12 mg L−1 Se
8.2 ± 0.81a 6.9 ± 0.74c 6.7 ± 0.56c 5.4 ± 0.49d 7.0 ± 0.73b
14.52 ± 1.11a 12.44 ± 1.30c 12.30 ± 1.35c 8.15 ± 0.76d 13.02 ± 1.58b
7.2 ± 0.67d 8.6 ± 0.93c 9.8 ± 1.10b 11.7 ± 1.29a 8.3 ± 0.95c
2.3. Assays of MDA, H2O2, RWC and the vase life MDA content was assayed according to Hodges et al. (1999). H2O2 content was measured according to Brennan and Frenkel (1977). Soluble sugar, proline and soluble protein were measured according to Shan and Zhao (2015). RWC was measured according to Hou et al. (2018) by using the equation: RWC = [(FW - DW)/(TW - DW)] × 100. The vase life was recorded according to Zheng and Guo (2019). 2.4. Statistical analysis The data in Tables 1–4 of Results were the mean of three replications. Means were compared by one-way analysis of variance and Duncan’s multiple range test at the 5 % level of significance. 3. Results 3.1. Effects of Na2SeO3 on MDA, H2O2 and vase life
2. Materials and methods Compared with control, Na2SeO3 markedly decreased the contents of MDA and H2O2 in petals (Table 1). Compared with control, 1, 3, 6 and 12 mg L−1 Na2SeO3 improved MDA content by 15.9 %, 18.3 %, 34.1 % and 14.6 %, respectively. 1, 3, 6 and 12 mg L−1 Na2SeO3 increased H2O2 content by 14.3 %, 15.3 %, 43.9 % and 10.3 %, respectively. Compared with control, Na2SeO3 markedly improved the vase life (Table 1). Compared with control, 1, 3, 6 and 12 mg L−1 Na2SeO3 improved the vase life by 19.4 %, 36.1 %, 62.5 % and 15.3 %, respectively. Among all the concentrations, 6 mg L−1 Na2SeO3 had the better positive effects in alleviating oxidative damage than other concentrations, which further improved the vase life of L. longiflorum cut flower.
2.1. Plant material and treatments L. longiflorum cut flowers were used as materials for current study. Cut flowers were bought from the local flower market. The flowers with two buds and similar sizes were selected for our experiments. The stems of all cut flowers were cut into the same length by the sharp scalpel. Cut flowers were treated by distilled water (Control), 1, 3, 6 and 12 mg L−1 Na2SeO3, respectively. Then above cut flowers were all placed in an artificial climate box. In artificial climate box, the day/night temperature, the relative humidity (RH), the photosynthetic active radiation and photoperiod were set as (25 ± 2) °C/(16 ± 2) °C, (60 ± 5) %, 300 μmol m–2 s–1 and 10 h, respectively. Each treatment had three replicates with 2 cut flowers for each replicate. The solutions used for different treatment were changed every two days. After 4 days of treatments, the petals of the first opened flowers under each treatment were selected and used to measure physiological indicators. After the loss of ornamental value, the vase life of cut flowers under each treatment was determined.
3.2. Effects of Na2SeO3 on the activities of SOD, POD and CAT Compared with control, Na2SeO3 markedly increased the activities of SOD, POD and CAT in petals (Table 2). Compared with control, 1, 3, 6 and 12 mg L−1 Na2SeO3 enhanced SOD activity by 21.2 %, 53.2 %, 95.9 % and 67.7 %, respectively. 1, 3, 6 and 12 mg L−1 Na2SeO3 enhanced POD activity by 44.7 %, 73.7 %, 136.8 % and 84.2 %,
2.2. Assays of antioxidant enzymes
Table 2 Effects of Na2SeO3 on the activities of SOD, POD and CAT. Values represent mean ± standard deviations (SD) (n = 3). Duncan’s multiple range test was used to determine statistical significance, different letters indicate statistical difference at P < 0.05.
The activities of SOD, POD and CAT were measured according to Shan and Zhao (2015). One unit of SOD activity was defined as the amount of enzyme required to cause a 50 % inhibition of NBT reduction. One unit of POD activity was defined as an increase of 0.01 per minute in absorbance at 470 nm. One unit of CAT activity was defined as a decrease of 0.001 per minute in absorbance at 240 nm. The activities of APX, GR, MDHAR and DHAR were measured according to Zheng and Guo (2018). One unit of APX activity was defined as a decrease of 0.01 per minute in absorbance. One unit of other enzymes in AsA-GSH cycle, including GR, DHAR and MDHAR, was defined as a decrease of 0.001 per minute in absorbance.
Treatment
Control 1 mg·L−1 Se 3 mg·L−1 Se 6 mg L−1 Se 12 mg L−1 Se
2
SOD (U·g−1 FW)
POD(U·g FW)
CAT(U·g−1 FW)
−1
115.8 ± 12.5d 140.3 ± 12.0c 177.4 ± 20.7b 226.9 ± 24.4a 194.2 ± 21.7b
3.8 ± 0.44d 5.5 ± 0.70c 6.6 ± 0.79b 9.0 ± 1.10a 7.0 ± 0.60b
2.72 ± 0.25e 4.35 ± 0.50b 3.22 ± 0.24d 5.21 ± 0.28a 3.53 ± 0.26c
Scientia Horticulturae 264 (2020) 109172
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4. Discussion
Table 3 Effects of Na2SeO3 on the activities of enzymes in AsA-GSH cycle. Values represent mean ± standard deviations (SD) (n = 3). Duncan’s multiple range test was used to determine statistical significance, different letters indicate statistical difference at P < 0.05. Treatment
Control 1 mg·L−1 Se 3 mg·L−1 Se 6 mg L−1 Se 12 mg L−1 Se
APX (U·g−1 FW)
GR(U·g FW)
DHAR(U·g FW)
MDHAR(U·g−1 FW)
−1
−1
0.77 ± 0.10c 1.07 ± 0.11b 1.29 ± 0.16a 1.29 ± 0.13a 1.05 ± 0.14b
5.2 ± 0.63d 6.6 ± 0.57c 8.7 ± 0.72b 9.9 ± 0.87a 7.0 ± 0.81c
2.5 ± 0.28d 3.7 ± 0.42c 5.9 ± 0.70b 7.6 ± 0.83a 5.3 ± 0.59b
7.2 ± 0.63d 9.6 ± 1.11c 12.5 ± 1.40b 15.7 ± 1.33a 10.0 ± 0.94c
More and more studies showed that exogenous chemicals improved the vase life of cut flowers by delaying their senescence (Zheng and Guo, 2018, 2019). In this study, we found that Na2SeO3 also improved the vase life of L. longiflorum cut flower. The senescence of cut flowers has close relationship with the lipid peroxidation of the petals. Increasing evidences showed that Se could alleviate the lipid peroxidation by enhancing the activities of antioxidant enzymes in plants under stresses. For example, Jozwiak and Politycka (2019) showed that Se enhanced the activities of SOD, POD and CAT in cucumber roots under water deficit. For cut flowers, Tognon et al. (2016) reported that Se improved the post-harvest performance and vase life of snapdragon cut flower by alleviating oxidative damage. However, how Se alleviates oxidative damage during postharvest aging process of cut flower is still unclear. In this study, we found that Na2SeO3 improved the activities of SOD, POD and CAT in the petals of L. longiflorum cut flower, which was consistent with the results of other studies on cucumber, wheat and eggplant (Jozwiak and Politycka, 2019; Liu et al., 2019; Lan et al., 2018). Many studies showed that AsA-GSH cycle is also an important part of the antioxidant system. During postharvest aging process, some studies showed that AsA-GSH cycle played important roles in alleviating oxidative damage of cut flowers (Hou et al., 2018; Zheng and Guo, 2018). It has been reported that Se enhanced AsA-GSH cycle by improving the activities of APX, GR and DHAR in cabbage subjected to cadmium stress (Wu et al., 2017). However, whether and how Se regulates AsA-GSH cycle in the petals of cut flowers is still unclear. In the present study, we also found that Na2SeO3 improved the activity of AsA-GSH cycle by enhancing APX, GR and DHAR in the petals of L. longiflorum cut flower, which was consistent with the results of Wu et al. (2017) for cabbage. Besides, we found that Se also enhanced the activity of MDHAR in the petals of L. longiflorum cut flower. Our current results clearly indicated that Na2SeO3 could alleviate oxidative damage of L. longiflorum cut flower during postharvest aging process by improving the activity of AsA-GSH cycle through APX, GR, DHAR and MDHAR, which further prolonged the vase life of L. longiflorum cut flower. Water balance of petals plays important roles in improving the vase life of cut flowers. Many studies showed that water balance had close relationship with the osmotic adjustment ability of cut flowers (Hou et al., 2018; Shan and Zhao, 2015; Zheng and Guo, 2019). In plants, the osmotic adjustment ability had close relationship with the levels of osmolytes, including soluble protein, soluble sugar and proline, etc.. Increasing evidences showed exogenous chemicals could enhance water balance by regulating the levels of osmolytes, including soluble protein, soluble sugar and proline (Shan and Zhao, 2015; Zheng and Miao, 2019). For L. longiflorum cut flower, Shan and Zhao (2015) showed that lanthanum enhanced water balance by increasing the levels of soluble protein, soluble sugar and proline, which further improved RWC of the petals and prolonged the vase life. For Se, more and more studies showed that Se could regulate water balance of plants through osmotic adjustment (Handa et al., 2018; Sattar et al., 2019). Handa et al. (2018) showed that Se regulated the osmolality of Brassica juncea seedlings
respectively. 1, 3, 6 and 12 mg L−1 Na2SeO3 increased CAT activity by 59.9 %, 18.4 %, 91.5 % and 81.0 %, respectively. Among different concentrations, 6 mg L−1 Na2SeO3 had the better positive effects on above antioxidant enzymes than other concentrations. Above findings implied that Na2SeO3 enhanced the ability of the petals to scavenge reactive oxygen species through SOD, POD and CAT.
3.3. Effects of Na2SeO3 on the activity of AsA-GSH cycle Compared with control, Na2SeO3 significantly improved the activity of AsA-GSH cycle in petals through APX, GR, DHAR and MDHAR (Table 3). Compared with control, 1, 3, 6 and 12 mg L−1 Na2SeO3 enhanced APX activity by 38.9 %, 67.5 %, 67.5 % and 36.4 %, respectively. 1, 3, 6 and 12 mg L−1 Na2SeO3 increased GR activity by 26.9 %, 67.3 %, 90.4 % and 34.6 %, respectively. 1, 3, 6 and 12 mg L−1 Na2SeO3 increased DHAR activity by 48.0 %, 136.0 %, 204.0 % and 112.0 %, respectively. 1, 3, 6 and 12 mg L−1 Na2SeO3 increased MDHAR activity by 33.3 %, 73.6 %, 118.0 % and 111.1 %, respectively. Among different concentrations, 6 mg L−1 Na2SeO3 had the better positive effects on above enzymes in AsA-GSH cycle than other concentrations. Above findings implied that Na2SeO3 enhanced the ability of the petals to scavenge H2O2 through AsA-GSH cycle.
3.4. Effects of Na2SeO3 on RWC and the levels of osmolytes Compared with control, Na2SeO3 markedly increased RWC and the levels of osmolytes soluble protein, soluble sugar and proline in the petals (Table 4). Compared with control, 1, 3, 6 and 12 mg L−1 Na2SeO3 improved the level of soluble protein by 26.7 %, 63.4 %, 76.2 % and 60.4 %, respectively. 1, 3, 6 and 12 mg L−1 Na2SeO3 improved the level of soluble sugar by 13.0 %, 36.4 %, 72.2 % and 41.0 %, respectively. 1, 3, 6 and 12 mg L−1 Na2SeO3 improved the level of proline by 26.8 %, 67.7 %, 221.0 % and 88.8 %, respectively. 1, 3, 6 and 12 mg L−1 Na2SeO3 increased RWC of the petals by 6.3 %, 10.6 %, 14.6 % and 9.0 %, respectively. Among different concentrations, 6 mg L−1 Na2SeO3 had the better positive effects on osmotic adjustment substances than other concentrations, which further improved RWC of the petals.
Table 4 Effects of Na2SeO3 on RWC and the contents of osmotic adjustment substances. Values represent mean ± standard deviations (SD) (n = 3). Duncan’s multiple range test was used to determine statistical significance, different letters indicate statistical difference at P < 0.05. Treatment
Soluble protein (μg·g−1 FW)
Soluble sugar (μg·g−1 FW)
Proline(μg·g−1 FW)
RWC (%)
Control 1 mg·L−1 Se 3 mg·L−1 Se 6 mg L−1 Se 12 mg L−1 Se
101 ± 12.3d 128 ± 16.0c 165 ± 10.7a 178 ± 18.4a 162 ± 12.9b
379.3 ± 33.7d 428.6 ± 46.3c 517.5 ± 63.6b 653.0 ± 72.3a 534.8 ± 60.0b
2.76 ± 0.31e 3.50 ± 0.28d 4.63 ± 0.52c 8.86 ± 0.70a 5.21 ± 0.57b
80.0 ± 7.8c 85.0 ± 8.5b 88.5 ± 9.4ab 91.7 ± 11.0a 87.2 ± 9.0ab
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Scientia Horticulturae 264 (2020) 109172
N. Lu, et al.
Acknowledgement
under chromium stress by increasing the levels of proline, glycine betaine and trehalose, which further improved the water balance. However, there is still no report for the roles of Se in regulating the levels of osmolytes in the petals of L. longiflorum cut flower. In this study, we found that Se also increased the level of proline in the petals, which was consistent with the results of Handa et al. (2018) for Brassica juncea seedlings. Besides, we found that Se also increased the levels of osmolytes soluble protein and soluble sugar in the petals. Above current findings indicated that Se could enhance the osmotic adjustment by increasing the levels of above osmolytes, which further improved RWC of the petals and prolonged the vase life of L. longiflorum cut flower. Whereas, how Se regulates the levels of above osmolytes is still unclear. Thus, it will be interesting to clarify the physiological and molecular mechanisms of Se in regulating the levels of above osmolytes, which will further provide more basis for the use of Se in improving the vase life of L. longiflorum cut flower. In this study, we found that low concentrations of Na2SeO3 had positive dose effects on antioxidant enzymes (SOD, POD, CAT, APX, GR, DHAR and MDHAR), RWC and the contents of soluble protein, soluble sugar and proline in the petals, which further reduced the production of MDA and H2O2 and improved the vase life of L. longiflorum cut flower. However, the highest concentration of Na2SeO3 had negative effects on above indicators, compared with moderate concentrations of Na2SeO3. It has been reported that excess Se caused toxicity to plants by enhancing the production of ROS, which further aggravated the oxidative damage to plants (Silva et al., 2018). In current study, we also found that the highest concentration of Na2SeO3 aggravated the oxidative damage to L. longiflorum cut flower by enhancing the production of MDA and H2O2, compared with the moderate concentrations of Na2SeO3. For this reason, the highest Se level had a lower effect on the vase life of L. longiflorum cut flower than the moderate levels. This phenomenon suggested that the selection of a proper Se concentration was important for its application in prolonging the vase life of L. longiflorum cut flower.
Thanks for Dr. Zhou for his help in editing English. References Brennan, T., Frenkel, C., 1977. Involvement of hydrogen peroxide in the regulation of senescence in pear. Plant Physiol. 59, 411–416. Chi, S.L., Xu, W.H., Liu, J., Wang, W.Z., Xiong, Z.T., 2017. Effect of exogenous selenium on activities of antioxidant enzymes, cadmium accumulation and chemical forms of cadmium in tomatoes. Int. J. Agric. Biol. 19, 1615–1622. Dadnia, M.R., Lack, S., Kayshams, B., 2010. Osmotic adjustment in wheat in relation to foliar application of selenium timing under water deficit stress. Res. Crop. 11, 640–643. Handa, N., Kohli, S.K., Sharma, A., Thukral, A.K., Bhardwaj, R., Alyemeni, M.N., Wijaya, L., Ahmad, P., 2018. Selenium ameliorates chromium toxicity through modifications in pigment system, antioxidative capacity, osmotic system, and metal chelators in Brassica juncea seedlings. S. Afr. J. Bot. 119, 1–10. Hodges, M.D., DeLong, J.M., Forney, C.F., Prange, R.K., 1999. Improving the thiobarbituric acid-reactive-substances assay for estimating lipid peroxidation in plant tissues containing anthocyanin and other interfering compounds. Planta 207, 604–611. Hou, K., Bao, D., Shan, C., 2018. Cerium improves the vase life of Lilium longiflorum cut flowers through ascorbate-glutathione cycle and osmoregulation in the petals. Sci. Hortic. 227, 142–145. Jozwiak, W., Politycka, B., 2019. Effect of selenium on alleviating oxidative stress caused by a water deficit in cucumber roots. Plants-Basel 8, 217. Lan, M., Yin, M., Lu, W., Wen, Y., Sun, M., Gao, Z., Hao, X., 2018. Effects of exogenous selenium on drought resistance of wheat seedlings under drought stress. Soils 50, 1182–1189. Liu, X., Cheng, B., Zhao, R., Hua, X., Wang, S., Wang, Z., Ren, Z., 2019. Effects of selenium on the physiological characteristics and chromium uptake of eggplant under chromium stress. J. Soil Water Conserv. 33, 357–363. Pereira, A.S., Dorneles, A.O.S., Bernardy, K., Sasso, V.M., Bernardy, D., Possebom, G., Rossato, L.V., Dressler, V.L., Tabaldi, L.A., 2018. Selenium and silicon reduce cadmium uptake and mitigate cadmium toxicity in Pfaffia glomerata (Spreng.) Pedersen plants by activation antioxidant enzyme system. Environ. Sci. Pollut. Res. 25, 18548–18558. Sattar, A., Cheema, M.A., Sher, A., Ijaz, M., Ul-Allah, S., Nawaz, A., Abbas, T., 2019. Physiological and biochemical attributes of bread wheat (Triticum aestivum L.) seedlings are influenced by foliar application of silicon and selenium under water deficit. Acta Physiol. Plant. 41, 146. Shan, C., Zhao, X., 2015. Lanthanum delays the senescence of Lilium longiflorum cut flowers by improving antioxidant defense system and water retaining capacity. Sci. Hortic. 197, 516–520. Silva, V.M., Boleta, E.H.M., Bereta Lanza, M.G.D., Lavres, J., Martins, J.T., Santos, E.F., dos Santos, F.L.M., Putti, F.F., Junior, E.F., White, P.J., Broadley, M.R., de Carvalho, H.W.P., dos Reis, A.R., 2018. Physiological, biochemical, and ultrastructural characterization of selenium toxicity in cowpea plants. Environ. Exp. Bot. 150, 172–182. Tognon, G.B., Sanmartín, C., Alcolea, V., Cuquel, F.L., Goicoechea, N., 2016. Mycorrhizal inoculation and/or selenium application affect post-harvest performance of snapdragon flowers. Plant Growth Regul. 78, 389–400. Wu, Z.C., Liu, S., Zhao, J., Wang, F.H., Du, Y.Q., Zou, S.M., Li, H.M., Wen, D., Huang, Y.D., 2017. Comparative responses to silicon and selenium in relation to antioxidant enzyme system and the glutathione-ascorbate cycle in flowering Chinese cabbage (Brassica campestrisL. ssp chinensis var. utilis) under cadmium stress. Environ. Exp. Bot. 133, 1–11. Zheng, M., Guo, Y., 2018. Cerium improves the vase life of Dianthus caryophyllus cut flower by regulating the ascorbate and glutathione metabolism. Sci. Hortic. 240, 492–495. Zheng, M., Guo, Y., 2019. Effects of neodymium on the vase life and physiological characteristics of Lilium casa Blanca petals. Sci. Hortic. 256, 108553.
Credit author state The contribution of Ninghai Lu is to design the whole experiment and measure the vase life and the contents of MDA and H2O2. Ninghai Lu has also important roles in writing and revising this article. The contribution of Limin Wu is to measure the activities of antioxidant enzymes SOD, POD, CAT, APX, GR, DHAR and MDHAR. The contribution of Mingwang Shi is to measure RWC and the contents of soluble sugar, soluble protein and proline and analyze data. Declaration of Competing Interest There is no conflict interest between authors.
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Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti
Short communication
Selenium enhances the vase life of Lilium longiflorum cut flower by regulating postharvest physiological characteristics
T
Ninghai Lu*, Limin Wu, Mingwang Shi Henan Institute of Science and Technology, Xinxiang 453003, China
A R T I C LE I N FO
A B S T R A C T
Keywords: Lilium longiflorum Sodium selenite Vase life Antioxidant system Osmotic adjustment
In this paper, we studied the role of sodium selenite (Na2SeO3) in improving cut flower’s vase life of Lilium longiflorum. Experimental findings displayed that Na2SeO3 remarkably enhanced the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR), improved relative water content (RWC) and the levels of soluble sugar, proline and soluble protein in cut flower’s petals of Lilium longiflorum, compared with control. Meanwhile, Na2SeO3 remarkably decreased the production of malondialdehyde (MDA) and hydrogen peroxide (H2O2), compared with control. Furthermore, Na2SeO3 remarkably improved the vase life of L. longiflorum cut flower, compared with control. These findings suggested that Na2SeO3 improved the vase life by regulating the antioxidant system and osmotic adjustment ability of L. longiflorum cut flower.
1. Introduction Fresh cut flowers are often used in our life. For example, cut flowers can be used as gifts for relatives and friends. Lilium longiflorum is one important cut flower for its ornamental uses. However, the short vase life of L. longiflorum cut flower limits its uses. Many studies showed that exogenous chemicals improved the vase life of cut flowers (Shan and Zhao, 2015; Tognon et al., 2016; Zheng and Guo, 2018). Shan and Zhao (2015) showed that one rare earth element named lanthanum improved the vase life of L. longiflorum cut flower. Zheng and Guo (2018) reported that another rare earth element named cerium improved the vase life of Dianthus caryophyllus cut flower. Selenium (Se) is an important trace element, which plays important roles in regulating the growth and stress tolerance of plants (Sattar et al., 2019). However, whether and how Se regulates the vase life of L. longiflorum cut flower is still unclear. Thus, it is interesting to study the roles of Se in regulating the vase life of L. longiflorum cut flower. Excessive production of reactive oxygen species (ROS) often leads to oxidative damage to cut flowers, which further resulted in their aging and death. Previous studies showed that the vase life of cut flowers had close relationship with their ability to scavenge ROS (Hou et al., 2018; Zheng and Guo, 2019). Plants have a complicated antioxidant defense system to scavenge ROS. The antioxidant defense system includs enzymatic system and non-enzymatic system. Enzymatic system includes
⁎
various antioxidant enzymes, such as superoxide dismutase (SOD) and catalase (CAT), etc.. Recent studies showed that Se improved the ability of many plants to scavenge ROS through enzymatic system (Chi et al., 2017; Pereira et al., 2018). Wu et al. (2017) reported that Se enhanced the activities of SOD and CAT in the roots and leaves of Chinese cabbage exposed to cadmium stress. It has also been reported that Se enhanced the activities of peroxidase (POD), CAT and SOD in cucumber roots exposed to water stress (Jozwiak and Politycka, 2019). Ascorbateglutathione (AsA-GSH) cycle is also an important component of the enzymatic system. Plants can scavenge one type of ROS named hydrogen peroxide (H2O2) through AsA-GSH cycle. Wu et al. (2017) reported that Se enhanced the activity of AsA-GSH cycle through ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR) in the roots and leaves of Chinese cabbage exposed to cadmium stress. For cut flowers, Tognon et al. (2016) reported that Se could alleviate oxidative damage during postharvest aging process of cut snapdragon flower, which improved its post-harvest performance. However, whether and how Se regulates the enzymatic system of L. longiflorum cut flower is still unclear. Therefore, it is interesting to study the effects of Se on the antioxidant enzyme system and AsA-GSH cycle in the petals of L. longiflorum cut flower, which will provide fundamental basis for its application in enhancing the vase life of cut flower. After harvest, the water balance of fresh cut flowers plays an
Corresponding author. E-mail address: [email protected] (N. Lu).
https://doi.org/10.1016/j.scienta.2019.109172 Received 8 November 2019; Received in revised form 30 December 2019; Accepted 31 December 2019 0304-4238/ © 2020 Elsevier B.V. All rights reserved.
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important role in improving the vase life of cut flowers (Shan and Zhao, 2015; Zheng and Guo, 2019). During postharvest aging process, Shan and Zhao (2015) showed that the water balance ability of cut flowers was determined by the osmotic adjustment ability. The osmotic adjustment ability has close relationship with the levels of osmolytes, including soluble protein, soluble sugar and proline. Zheng and Guo (2019) showed that neodymium also improved the water balance ability of Lilium Casa Blanca by enhancing the levels of above osmolytes, which further improved the water content of petals. For Se, Dadnia et al. (2010) reported that Se played an important role in maintaining the turgor of wheat subjected to water deficit. Stattar et al. (2019) showed that Se had an important role in regulating osmotic potential and turgor pressure of bread wheat subjected to water deficit. Handa et al. (2018) reported that Se improved the levels of proline, glycine betaine and trehalose, which further increased the osmolality and the water balance ability of Brassica juncea seedlings exposed to chromium stress. These previous findings indicated that Se could regulate the water balance of plants through osmotic adjustment. However, whether and how Se regulates the osmotic adjustment ability of L. longiflorum petals is still unclear. Thus, it is interesting to investigate the roles of Se in regulating the water balance ability of L. longiflorum petals, which can further provide more fundamental basis for its application in enhancing the vase life of L. Longiflorum cut flower. In current study, we investigated the effects of sodium selenite (Na2SeO3) on the vase life, the relative water content (RWC), the activities of SOD, POD, CAT, APX, glutathione reductase (GR), DHAR and MDHAR, as well as the contents of soluble protein, soluble sugar and proline, malondialdehyde (MDA) and H2O2 in the petals of L. longiflorum cut flower. The purpose of current study was to clarify the roles of Na2SeO3 in improving the vase life of L. Longiflorum cut flower.
Table 1 Effects of Na2SeO3 on the vase life and the contents of MDA and H2O2. Values represent mean ± standard deviations (SD) (n = 3). Duncan’s multiple range test was used to determine statistical significance, different letters indicate statistical difference at P < 0.05. Treatment
MDA (nmol g−1 FW)
H2O2 (μmol g−1 FW)
Vase life (d)
Control 1 mg·L−1 Se 3 mg·L−1 Se 6 mg L−1 Se 12 mg L−1 Se
8.2 ± 0.81a 6.9 ± 0.74c 6.7 ± 0.56c 5.4 ± 0.49d 7.0 ± 0.73b
14.52 ± 1.11a 12.44 ± 1.30c 12.30 ± 1.35c 8.15 ± 0.76d 13.02 ± 1.58b
7.2 ± 0.67d 8.6 ± 0.93c 9.8 ± 1.10b 11.7 ± 1.29a 8.3 ± 0.95c
2.3. Assays of MDA, H2O2, RWC and the vase life MDA content was assayed according to Hodges et al. (1999). H2O2 content was measured according to Brennan and Frenkel (1977). Soluble sugar, proline and soluble protein were measured according to Shan and Zhao (2015). RWC was measured according to Hou et al. (2018) by using the equation: RWC = [(FW - DW)/(TW - DW)] × 100. The vase life was recorded according to Zheng and Guo (2019). 2.4. Statistical analysis The data in Tables 1–4 of Results were the mean of three replications. Means were compared by one-way analysis of variance and Duncan’s multiple range test at the 5 % level of significance. 3. Results 3.1. Effects of Na2SeO3 on MDA, H2O2 and vase life
2. Materials and methods Compared with control, Na2SeO3 markedly decreased the contents of MDA and H2O2 in petals (Table 1). Compared with control, 1, 3, 6 and 12 mg L−1 Na2SeO3 improved MDA content by 15.9 %, 18.3 %, 34.1 % and 14.6 %, respectively. 1, 3, 6 and 12 mg L−1 Na2SeO3 increased H2O2 content by 14.3 %, 15.3 %, 43.9 % and 10.3 %, respectively. Compared with control, Na2SeO3 markedly improved the vase life (Table 1). Compared with control, 1, 3, 6 and 12 mg L−1 Na2SeO3 improved the vase life by 19.4 %, 36.1 %, 62.5 % and 15.3 %, respectively. Among all the concentrations, 6 mg L−1 Na2SeO3 had the better positive effects in alleviating oxidative damage than other concentrations, which further improved the vase life of L. longiflorum cut flower.
2.1. Plant material and treatments L. longiflorum cut flowers were used as materials for current study. Cut flowers were bought from the local flower market. The flowers with two buds and similar sizes were selected for our experiments. The stems of all cut flowers were cut into the same length by the sharp scalpel. Cut flowers were treated by distilled water (Control), 1, 3, 6 and 12 mg L−1 Na2SeO3, respectively. Then above cut flowers were all placed in an artificial climate box. In artificial climate box, the day/night temperature, the relative humidity (RH), the photosynthetic active radiation and photoperiod were set as (25 ± 2) °C/(16 ± 2) °C, (60 ± 5) %, 300 μmol m–2 s–1 and 10 h, respectively. Each treatment had three replicates with 2 cut flowers for each replicate. The solutions used for different treatment were changed every two days. After 4 days of treatments, the petals of the first opened flowers under each treatment were selected and used to measure physiological indicators. After the loss of ornamental value, the vase life of cut flowers under each treatment was determined.
3.2. Effects of Na2SeO3 on the activities of SOD, POD and CAT Compared with control, Na2SeO3 markedly increased the activities of SOD, POD and CAT in petals (Table 2). Compared with control, 1, 3, 6 and 12 mg L−1 Na2SeO3 enhanced SOD activity by 21.2 %, 53.2 %, 95.9 % and 67.7 %, respectively. 1, 3, 6 and 12 mg L−1 Na2SeO3 enhanced POD activity by 44.7 %, 73.7 %, 136.8 % and 84.2 %,
2.2. Assays of antioxidant enzymes
Table 2 Effects of Na2SeO3 on the activities of SOD, POD and CAT. Values represent mean ± standard deviations (SD) (n = 3). Duncan’s multiple range test was used to determine statistical significance, different letters indicate statistical difference at P < 0.05.
The activities of SOD, POD and CAT were measured according to Shan and Zhao (2015). One unit of SOD activity was defined as the amount of enzyme required to cause a 50 % inhibition of NBT reduction. One unit of POD activity was defined as an increase of 0.01 per minute in absorbance at 470 nm. One unit of CAT activity was defined as a decrease of 0.001 per minute in absorbance at 240 nm. The activities of APX, GR, MDHAR and DHAR were measured according to Zheng and Guo (2018). One unit of APX activity was defined as a decrease of 0.01 per minute in absorbance. One unit of other enzymes in AsA-GSH cycle, including GR, DHAR and MDHAR, was defined as a decrease of 0.001 per minute in absorbance.
Treatment
Control 1 mg·L−1 Se 3 mg·L−1 Se 6 mg L−1 Se 12 mg L−1 Se
2
SOD (U·g−1 FW)
POD(U·g FW)
CAT(U·g−1 FW)
−1
115.8 ± 12.5d 140.3 ± 12.0c 177.4 ± 20.7b 226.9 ± 24.4a 194.2 ± 21.7b
3.8 ± 0.44d 5.5 ± 0.70c 6.6 ± 0.79b 9.0 ± 1.10a 7.0 ± 0.60b
2.72 ± 0.25e 4.35 ± 0.50b 3.22 ± 0.24d 5.21 ± 0.28a 3.53 ± 0.26c
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4. Discussion
Table 3 Effects of Na2SeO3 on the activities of enzymes in AsA-GSH cycle. Values represent mean ± standard deviations (SD) (n = 3). Duncan’s multiple range test was used to determine statistical significance, different letters indicate statistical difference at P < 0.05. Treatment
Control 1 mg·L−1 Se 3 mg·L−1 Se 6 mg L−1 Se 12 mg L−1 Se
APX (U·g−1 FW)
GR(U·g FW)
DHAR(U·g FW)
MDHAR(U·g−1 FW)
−1
−1
0.77 ± 0.10c 1.07 ± 0.11b 1.29 ± 0.16a 1.29 ± 0.13a 1.05 ± 0.14b
5.2 ± 0.63d 6.6 ± 0.57c 8.7 ± 0.72b 9.9 ± 0.87a 7.0 ± 0.81c
2.5 ± 0.28d 3.7 ± 0.42c 5.9 ± 0.70b 7.6 ± 0.83a 5.3 ± 0.59b
7.2 ± 0.63d 9.6 ± 1.11c 12.5 ± 1.40b 15.7 ± 1.33a 10.0 ± 0.94c
More and more studies showed that exogenous chemicals improved the vase life of cut flowers by delaying their senescence (Zheng and Guo, 2018, 2019). In this study, we found that Na2SeO3 also improved the vase life of L. longiflorum cut flower. The senescence of cut flowers has close relationship with the lipid peroxidation of the petals. Increasing evidences showed that Se could alleviate the lipid peroxidation by enhancing the activities of antioxidant enzymes in plants under stresses. For example, Jozwiak and Politycka (2019) showed that Se enhanced the activities of SOD, POD and CAT in cucumber roots under water deficit. For cut flowers, Tognon et al. (2016) reported that Se improved the post-harvest performance and vase life of snapdragon cut flower by alleviating oxidative damage. However, how Se alleviates oxidative damage during postharvest aging process of cut flower is still unclear. In this study, we found that Na2SeO3 improved the activities of SOD, POD and CAT in the petals of L. longiflorum cut flower, which was consistent with the results of other studies on cucumber, wheat and eggplant (Jozwiak and Politycka, 2019; Liu et al., 2019; Lan et al., 2018). Many studies showed that AsA-GSH cycle is also an important part of the antioxidant system. During postharvest aging process, some studies showed that AsA-GSH cycle played important roles in alleviating oxidative damage of cut flowers (Hou et al., 2018; Zheng and Guo, 2018). It has been reported that Se enhanced AsA-GSH cycle by improving the activities of APX, GR and DHAR in cabbage subjected to cadmium stress (Wu et al., 2017). However, whether and how Se regulates AsA-GSH cycle in the petals of cut flowers is still unclear. In the present study, we also found that Na2SeO3 improved the activity of AsA-GSH cycle by enhancing APX, GR and DHAR in the petals of L. longiflorum cut flower, which was consistent with the results of Wu et al. (2017) for cabbage. Besides, we found that Se also enhanced the activity of MDHAR in the petals of L. longiflorum cut flower. Our current results clearly indicated that Na2SeO3 could alleviate oxidative damage of L. longiflorum cut flower during postharvest aging process by improving the activity of AsA-GSH cycle through APX, GR, DHAR and MDHAR, which further prolonged the vase life of L. longiflorum cut flower. Water balance of petals plays important roles in improving the vase life of cut flowers. Many studies showed that water balance had close relationship with the osmotic adjustment ability of cut flowers (Hou et al., 2018; Shan and Zhao, 2015; Zheng and Guo, 2019). In plants, the osmotic adjustment ability had close relationship with the levels of osmolytes, including soluble protein, soluble sugar and proline, etc.. Increasing evidences showed exogenous chemicals could enhance water balance by regulating the levels of osmolytes, including soluble protein, soluble sugar and proline (Shan and Zhao, 2015; Zheng and Miao, 2019). For L. longiflorum cut flower, Shan and Zhao (2015) showed that lanthanum enhanced water balance by increasing the levels of soluble protein, soluble sugar and proline, which further improved RWC of the petals and prolonged the vase life. For Se, more and more studies showed that Se could regulate water balance of plants through osmotic adjustment (Handa et al., 2018; Sattar et al., 2019). Handa et al. (2018) showed that Se regulated the osmolality of Brassica juncea seedlings
respectively. 1, 3, 6 and 12 mg L−1 Na2SeO3 increased CAT activity by 59.9 %, 18.4 %, 91.5 % and 81.0 %, respectively. Among different concentrations, 6 mg L−1 Na2SeO3 had the better positive effects on above antioxidant enzymes than other concentrations. Above findings implied that Na2SeO3 enhanced the ability of the petals to scavenge reactive oxygen species through SOD, POD and CAT.
3.3. Effects of Na2SeO3 on the activity of AsA-GSH cycle Compared with control, Na2SeO3 significantly improved the activity of AsA-GSH cycle in petals through APX, GR, DHAR and MDHAR (Table 3). Compared with control, 1, 3, 6 and 12 mg L−1 Na2SeO3 enhanced APX activity by 38.9 %, 67.5 %, 67.5 % and 36.4 %, respectively. 1, 3, 6 and 12 mg L−1 Na2SeO3 increased GR activity by 26.9 %, 67.3 %, 90.4 % and 34.6 %, respectively. 1, 3, 6 and 12 mg L−1 Na2SeO3 increased DHAR activity by 48.0 %, 136.0 %, 204.0 % and 112.0 %, respectively. 1, 3, 6 and 12 mg L−1 Na2SeO3 increased MDHAR activity by 33.3 %, 73.6 %, 118.0 % and 111.1 %, respectively. Among different concentrations, 6 mg L−1 Na2SeO3 had the better positive effects on above enzymes in AsA-GSH cycle than other concentrations. Above findings implied that Na2SeO3 enhanced the ability of the petals to scavenge H2O2 through AsA-GSH cycle.
3.4. Effects of Na2SeO3 on RWC and the levels of osmolytes Compared with control, Na2SeO3 markedly increased RWC and the levels of osmolytes soluble protein, soluble sugar and proline in the petals (Table 4). Compared with control, 1, 3, 6 and 12 mg L−1 Na2SeO3 improved the level of soluble protein by 26.7 %, 63.4 %, 76.2 % and 60.4 %, respectively. 1, 3, 6 and 12 mg L−1 Na2SeO3 improved the level of soluble sugar by 13.0 %, 36.4 %, 72.2 % and 41.0 %, respectively. 1, 3, 6 and 12 mg L−1 Na2SeO3 improved the level of proline by 26.8 %, 67.7 %, 221.0 % and 88.8 %, respectively. 1, 3, 6 and 12 mg L−1 Na2SeO3 increased RWC of the petals by 6.3 %, 10.6 %, 14.6 % and 9.0 %, respectively. Among different concentrations, 6 mg L−1 Na2SeO3 had the better positive effects on osmotic adjustment substances than other concentrations, which further improved RWC of the petals.
Table 4 Effects of Na2SeO3 on RWC and the contents of osmotic adjustment substances. Values represent mean ± standard deviations (SD) (n = 3). Duncan’s multiple range test was used to determine statistical significance, different letters indicate statistical difference at P < 0.05. Treatment
Soluble protein (μg·g−1 FW)
Soluble sugar (μg·g−1 FW)
Proline(μg·g−1 FW)
RWC (%)
Control 1 mg·L−1 Se 3 mg·L−1 Se 6 mg L−1 Se 12 mg L−1 Se
101 ± 12.3d 128 ± 16.0c 165 ± 10.7a 178 ± 18.4a 162 ± 12.9b
379.3 ± 33.7d 428.6 ± 46.3c 517.5 ± 63.6b 653.0 ± 72.3a 534.8 ± 60.0b
2.76 ± 0.31e 3.50 ± 0.28d 4.63 ± 0.52c 8.86 ± 0.70a 5.21 ± 0.57b
80.0 ± 7.8c 85.0 ± 8.5b 88.5 ± 9.4ab 91.7 ± 11.0a 87.2 ± 9.0ab
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Acknowledgement
under chromium stress by increasing the levels of proline, glycine betaine and trehalose, which further improved the water balance. However, there is still no report for the roles of Se in regulating the levels of osmolytes in the petals of L. longiflorum cut flower. In this study, we found that Se also increased the level of proline in the petals, which was consistent with the results of Handa et al. (2018) for Brassica juncea seedlings. Besides, we found that Se also increased the levels of osmolytes soluble protein and soluble sugar in the petals. Above current findings indicated that Se could enhance the osmotic adjustment by increasing the levels of above osmolytes, which further improved RWC of the petals and prolonged the vase life of L. longiflorum cut flower. Whereas, how Se regulates the levels of above osmolytes is still unclear. Thus, it will be interesting to clarify the physiological and molecular mechanisms of Se in regulating the levels of above osmolytes, which will further provide more basis for the use of Se in improving the vase life of L. longiflorum cut flower. In this study, we found that low concentrations of Na2SeO3 had positive dose effects on antioxidant enzymes (SOD, POD, CAT, APX, GR, DHAR and MDHAR), RWC and the contents of soluble protein, soluble sugar and proline in the petals, which further reduced the production of MDA and H2O2 and improved the vase life of L. longiflorum cut flower. However, the highest concentration of Na2SeO3 had negative effects on above indicators, compared with moderate concentrations of Na2SeO3. It has been reported that excess Se caused toxicity to plants by enhancing the production of ROS, which further aggravated the oxidative damage to plants (Silva et al., 2018). In current study, we also found that the highest concentration of Na2SeO3 aggravated the oxidative damage to L. longiflorum cut flower by enhancing the production of MDA and H2O2, compared with the moderate concentrations of Na2SeO3. For this reason, the highest Se level had a lower effect on the vase life of L. longiflorum cut flower than the moderate levels. This phenomenon suggested that the selection of a proper Se concentration was important for its application in prolonging the vase life of L. longiflorum cut flower.
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Credit author state The contribution of Ninghai Lu is to design the whole experiment and measure the vase life and the contents of MDA and H2O2. Ninghai Lu has also important roles in writing and revising this article. The contribution of Limin Wu is to measure the activities of antioxidant enzymes SOD, POD, CAT, APX, GR, DHAR and MDHAR. The contribution of Mingwang Shi is to measure RWC and the contents of soluble sugar, soluble protein and proline and analyze data. Declaration of Competing Interest There is no conflict interest between authors.
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