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Cerium improves the vase life of Lilium longiflorum cut flowers through ascorbate-glutathione cycle and osmoregulation in the petals
Scientia Horticulturae 227 (2018) 142–145
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Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti
Short Communication
Cerium improves the vase life of Lilium longiflorum cut flowers through ascorbate-glutathione cycle and osmoregulation in the petals Kun Houa, Donge Baoa, Changjuan Shana,b, a b
MARK
⁎
Henan Institute of Science and Technology, Xinxiang 453003 China Collaborative Innovation Center of Modern Biological Breeding, Henan Province, Xinxiang 453003 China
A R T I C L E I N F O
A B S T R A C T
Keywords: Cerium nitrate Ascorbate-glutathione cycle Redox status Lilium longiflorum
The present study investigated the role of cerium nitrate (Ce(NO3)3) in regulating the ascorbate-glutathione (AsA-GSH) cycle, the relative water content (RWC), and the contents of malondialdehyde (MDA), hydrogen peroxide (H2O2), soluble sugar and proline in the petals, and the contents of chlorophyll a (Chl a), chlorophyll b (Chl b) and carotenoids (Car) in the leaves of Lilium longiflorum cut flowers. The findings showed that Ce(NO3)3 markedly improved the activities of ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR), the ratios of AsA/DHA and GSH/GSSG, RWC, and the contents of proline and soluble sugar in the petals, and markedly reduced the contents of MDA and H2O2 in the petals, compared with the control. Meanwhile, Ce(NO3)3 markedly improved the contents of Chl a, Chl b and Car in the leaves. Among different concentrations of Ce(NO3)3, 40 μM Ce(NO3)3 is the most effective treatment for the improvement of the vase life of Lilium longiflorum cut flowers. Above results indicated that Ce (NO3)3 improves the vase life of Lilium longiflorum cut flowers by enhancing the AsA-GSH cycle and water retaining capacity.
1. Introduction Lilium longiflorum cut flower is an important type of cut flowers. However, the vase life of L. longiflorum cut flower is short, which limits its efficient marketing. The vase life of cut flower is closely related with the disruption of plasma membrane integrity, which was induced by the lipid peroxidation of the plasma membranes indicated by the contents of malondialdehyde (MDA), hydrogen peroxide (H2O2) (Rubinstein, 2000; Zhang et al., 2011). While, the contents of MDA and H2O2 in cut flowers are closely related with the imbalance of reactive oxygen metabolism. It has been reported that ascorbate-glutathione (AsA-GSH) cycle had important role in balancing the reactive oxygen metabolism (Ahmad et al., 2017). In this cycle, ascorbate peroxidase (APX) utilizes reduced ascorbate (AsA) as electron donor for reduction of H2O2, monodehydroascorbate is reduced to AsA by monodehydroascorbate reductase (MDHAR) and dehydroascorbate is reduced to AsA by dehydroascorbate reductase (DHAR). Oxidized glutathione (GSSG) produced in this cycle is reduced to reduced glutathione GSH by glutathione reductase (GR) (Ahmad et al., 2017). By this way, AsA and GSH are regenerated and H2O2 is scavenged. Thus, AsA-GSH cycle plays an important role in balancing the reactive oxygen metabolism and maintaining the redox states of ascorbate and glutathione. So, AsA-GSH
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cycle has an important role in improving the vase life of cut flowers. Meanwhile, studies showed that the water retaining capacity was also very important for the increase in the vase life of cut flowers (Shan and Zhao, 2015). In the preservation of cut flowers, people usually use some exogenous regulators, such as hydrogen sulfide (H2S) and salicylic acid (SA), to improve their vase life (Zhang et al., 2011; Alaey et al., 2011). Therefore, it is very important to study the effects of exogenous regulators on the AsA-GSH cycle and the water retaining capacity, in order to provide the theoretical basis for their application in improving the vase life of cut flowers. Our previous studies showed that the rare earth element lanthanum (La) can regulate the reactive oxygen metabolism and the water retaining capacity, which, in turn, delay the flower senescence of L. longiflorum cut flowers (Shan and Zhao, 2015). Cerium (Ce) is another important rare earth element. It has been reported that Ce could enhance antioxidant defense system in rape seedlings under ultraviolet-B radiation (Liang et al., 2006). Liu et al. (2016) reported that Ce could enhance the activity of AsA-GSH cycle through APX, GR, DHAR and MDHAR in turf grass Poa pratensis seedlings. Wang et al. (2017) showed that Ce improved the vase life of Rosa chinensis Jacq. cut flowers by incresing the activity of AsA-GSH cycle through APX and GR. Xu et al. (2016) also suggested that Ce could enhance the activity of AsA-GSH
Corresponding author at: Henan Institute of Science and Technology, Xinxiang 453003 China. E-mail address: [email protected] (C. Shan).
http://dx.doi.org/10.1016/j.scienta.2017.09.040 Received 14 July 2017; Received in revised form 8 September 2017; Accepted 25 September 2017 0304-4238/ © 2017 Elsevier B.V. All rights reserved.
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enzymes, the decrease in the absorption was all followed for 3 min. The absorption value decreased by 0.001 per min was defined as one unit of APX, GR and MDHAR. The absorption value decreased by 0.01 per min was defined as one unit of DHAR. The specific enzyme activity for all the above enzymes was expressed as Units g−1 FW.
cycle through APX. However, whether Ce regulates the AsA-GSH cycle of L. longiflorum cut flowers is still unknown. In addition, whether Ce regulates the water retaining capacity of L. longiflorum cut flowers is also still unknown. Thus, it is very interesting to elucidate the role of Ce in regulating the AsA-GSH cycle and the water retaining capacity of L. longiflorum cut flowers. As the balance of reactive oxygen metabolism is important for the vase life of L. longiflorum cut flowers, the measurement of the activities of enzymes in AsA-GSH cycle and the contents of MDA and H2O2 in the petals is critical to the vase life of L. longiflorum cut flowers. As the imbalance of reactive oxygen metabolism will accelerate the degradation of chloroplast pigments, the measurement of the contents of chlorophyll a (Chl a), chlorophyll b (Chl b) and carotenoids (Car) in the leaves is also critical to the vase life. As the water retaining capacity is important for the increase in the vase life of cut flowers, the measurement of RWC and the contents of proline and soluble sugar in the petals is also critical to the vase life. In the present study, the role of Ce(NO3)3 in regulating the activities of enzymes in AsA-GSH cycle, RWC and the contents of MDA, H2O2, proline and soluble sugar in the petals, and the contents of Chl a, Chl b and Car in the leaves of L. longiflorum cut flowers were investigated. The objective of the present study was to provide theoretical basis for the application of Ce(NO3)3 in improving the vase life of L. longiflorum cut flowers.
2.3. Analysis of the ratios of AsA/DHA and GSH/GSSG AsA and DHA was measured according to Hodges et al. (1996). GSH and GSSG was measured according to Griffith (1980). AsA/DHA was expressed as the ratio between the content of AsA and the content of DHA. GSH/GSSG was expressed as the ratio between the content of GSH and the content of GSSG. 2.4. Measurement of the contents of MDA and H2O2 The content of MDA was measured by thiobarbituric acid (TBA) reaction as described by Hodges et al. (1999). The content of H2O2 was measured according to Patterson et al. (1984). 2.5. Measurement of the contents of praline and soluble sugar The content of proline was determined according to the method of Bates et al. (1973). The content of soluble sugar was determined according to the method of Wei (2009).
2. Materials and methods 2.6. Measurement of the relative water content (RWC) 2.1. Plant material and treatments RWC were determined by the method of Barrs and Weatherley (1962). Twenty discs of 1 cm diameter were cut by using a punch and weighed to determine fresh weight (FW). Then discs were immersed in distilled water for 6 h and the turgid weight (TW) were determined. Dry weight (DW) was determined after oven drying at 80 °C for 48 h. RWC was calculated according below equation: RWC = [(FW-DW)/(TWDW)] × 100
L. longiflorum was supplied by the Flower Market of Xinxiang City. Cut flowers were excised uniformly with a sharp scalpel to prevent blockage of water uptake and cultured in distilled water (Control), 20, 40, 60 and 120 μM Ce(NO3)3 under the same conditions as our previous study (Shan and Zhao, 2015). Treatment solutions were changed daily. The petals of the first fully opened flowers were used to determine the activities of enzymes in AsA-GSH cycle, the ratios of AsA/DHA and GSH/GSSG, and the contents of MDA, H2O2, proline and soluble sugar. The first fully expanded leaves of the upper stem were used to determine the contents of Chl a, Chl b and Car at 4 d after treatment.
2.7. Measurement of the contents of Chl a, Chl b and Car The contents of Chl a, Chl b and Car were measured according to the method of Lichtenthaler and Wellburn (1983).
2.2. Analysis of APX, GR, DHAR and MDHAR 2.8. Statistical analysis Each frozen sample (0.5 g) was ground into a fine powder in liquid N2 with a mortar and pestle. Fine powder was homogenized in 6 ml 50 mM KH2PO4 (pH 7.5) containing 0.1 mM ethylenediaminetetraacetic acid, 0.3% (v/v) Triton X-100, and 1% (w/v) soluble polyvinylpolypyrrolidone, with the addition of 1 mM AsA in the case of the APX assay. The extract was immediately centrifuged at 13000×g for 15 min at 2 °C. The supernatant was then used immediately for measuring the following enzymes. The activities of ascorbate peroxidase (APX, EC 1.11.1.11), glutathione reductase (GR, EC 1.6.4.2), monodehydroascorbate reductase (MDHAR, EC 1.6.5.4) and dehydroascorbate reductase (DHAR, EC 1.8.5.1) were measured according to Nakano and Asada (1981), Grace and Logan (1996), Miyake and Asada (1992) and Dalton et al. (1986), respectively. For above four
The whole experiment was repeated 5 times with 3 replicates each time. The results presented were the mean of 5 times. 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 Ce(NO3)3 on the length of vase life of L. longiflorum cut flowers Different concentrations of Ce(NO3)3 all improved the vase life of L. longiflorum cut flower, compared with the control (Table 1). Compared
Table 1 Effects of different concentrations of Ce(NO3)3 on the length of vase life and the activities of enzymes in AsA-GSH cycle in the petals of L. longiflorum cut flowers. Values represent mean ± standard deviations (SD) (n = 15), different letters indicate statistical difference at P < 0.05. Treatments
Length of vase life (d)
APX (Units g−1 FW)
GR (Units g−1 FW)
DHAR (Units g−1 FW)
MDHAR (Units g−1 FW)
Control 20 μM Ce(NO3)3 40 μM Ce(NO3)3 80 μM Ce(NO3)3 120 μM Ce(NO3)3
7.0 ± 0.80d 8.4 ± 0.95c 10.6 ± 1.22a 9.3 ± 1.01b 8.1 ± 0.86c
1.6 2.3 4.7 3.0 2.1
5.5 ± 0.67d 7.9 ± 0.83c 12.6 ± 1.30a 10.2 ± 1.11b 7.3 ± 0.80c
3.0 4.0 6.7 5.3 3.8
9.5 ± 1.03d 12.6 ± 1.15c 18.9 ± 1.95a 15.6 ± 1.38b 11.7 ± 1.30c
± ± ± ± ±
0.19d 0.22c 0.53a 0.34b 0.25c
143
± ± ± ± ±
0.27d 0.35c 0.73a 0.44b 0.41c
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with the control, 20, 40, 80 and 120 μM Ce(NO3)3 all significantly increased the vase life of L. longiflorum cut flower by 20%, 51.4%, 32.8% and 15.7%, respectively. Compared with other concentrations, 40 μM Ce(NO3)3 significantly improved the vase life of L. longiflorum cut flowers.
Table 3 Effects of different concentrations of Ce(NO3)3 on the relative water content and the contents of proline and soluble sugar in petals of L. longiflorum cut flowers. These indicators were determined on day 4. Values represent mean ± standard deviations (SD) (n = 15), different letters indicate statistical difference at P < 0.05.
3.2. Effects of Ce(NO3)3 on the activities of APX, GR, DHAR and MDHAR Different concentrations of Ce(NO3)3 all significantly increased the activities of enzymes in the AsA-GSH cycle, including APX, GR, DHAR and MDHAR, compared with the control (Table 1). Compared with the control, 20, 40, 80 and 120 μM Ce(NO3)3 increased the activity of APX by 43.7%, 193.7%, 87.5% and 31.2%, respectively. 20, 40, 80 and 120 μM Ce(NO3)3 increased the activity of GR by 43.6%, 129.1%, 85.5% and 32.7%, respectively. 20, 40, 80 and 120 μM Ce(NO3)3 increased the activity of DHAR by 33.3%, 123.3%, 76.7% and 26.7%, respectively. 20, 40, 80 and 120 μM Ce(NO3)3 increased the activity of MDHAR by 32.6%, 98.9%, 64.2% and 23.2%, respectively. Among different concentrations of Ce(NO3)3, the activities of above enzymes in the AsA-GSH cycle in the petals treated by 40 μM Ce(NO3)3 were higher than those in the petals treated by other concentrations of Ce(NO3)3.
Control 20 μM Ce (NO3)3 40 μM Ce (NO3)3 80 μM Ce (NO3)3 120 μM Ce (NO3)3
18.0 ± 2.11c 20.3 ± 2.30b
18.6 ± 1.74c 22.0 ± 2.16b
8.6 ± 0.85a 7.0 ± 0.77b
6.2 ± 0.66a 5.1 ± 0.53b
23.7 ± 2.56a
25.9 ± 2.73a
5.0 ± 0.47d
3.5 ± 0.44d
21.0 ± 2.23b
23.0 ± 2.30b
6.1 ± 0.54c
4.2 ± 0.41c
19.6 ± 2.11b
21.5 ± 2.15b
7.4 ± 0.84b
5.3 ± 0.61b
11.6 ± 1.30d 16.3 ± 1.54c
517.7 ± 43.38d 724.0 ± 87.11c
78.0 ± 7.22d 85.3 ± 9.14c
23.7 ± 2.16a
1180.0 ± 121.5a
92.6 ± 8.83a
19.5 ± 2.00b
950.9 ± 105.3b
88.8 ± 7.38b
15.4 ± 1.71c
686.3 ± 76.19c
84.5 ± 8.88c
4. Discussion As MDA is one important product of the lipid peroxidation induced by imbalance of reactive oxygen metabolism, the vase life of cut flower is closely related with the content of MDA. In this study, different concentrations of exogenous Ce(NO3)3 significantly reduced MDA
Table 2 Effects of different concentrations of Ce(NO3)3 on the ratios of AsA/DHA and GSH/GSSG and the contents of AsA, GSH, MDA and H2O2 in the petals of L. longiflorum cut flowers. These indicators were determined on day 4. Values represent mean ± standard deviations (SD) (n = 15), different letters indicate statistical difference at P < 0.05. H2O2 (μmol g−1 FW)
Control 20 μM Ce (NO3)3 40 μM Ce (NO3)3 80 μM Ce (NO3)3 120 μM Ce (NO3)3
Different concentrations of Ce(NO3)3 all markedly increased the contents of Chl a, Chl b and Car, compared with the control (Table 4). Compared with the control, 20, 40, 80 and 120 μM Ce(NO3)3 increased the content of Chl a by 23.4%, 66.2%, 44.2% and 14.9%, respectively. 20, 40, 80 and 120 μM Ce(NO3)3 increased the content of Chl b by 28.6%, 62.8%, 38.6% and 27.1%, respectively. 20, 40, 80 and 120 μM Ce(NO3)3 increased the content of Car by 32.7%, 63.5%, 34.6% and 25%, respectively. Among different concentrations of Ce(NO3)3, the contents of above indicators in the leaves treated by 40 μM Ce(NO3)3 were significantly higher than those treated by other concentrations of Ce(NO3)3.
Different concentrations of Ce(NO3)3 all significantly decreased the contents of MDA and H2O2, compared with the control (Table 2). Compared with control, 20, 40, 80 and 120 μM Ce(NO3)3 decreased the content of MDA by 18.6%, 41.9%, 29.1% and 13.9%, respectively. 20, 40, 80 and 120 μM Ce(NO3)3 decreased the content of H2O2 by 17.7%, 43.5%, 32.3% and 14.5%, respectively. Among different concentrations of Ce(NO3)3, the contents of MDA and H2O2 in the petals treated by 40 μM Ce(NO3)3 was significantly lower than those treated by other concentrations of Ce(NO3)3.
MDA (nmol g−1 FW)
Relative water content (%)
3.6. Effects of Ce(NO3)3 on the contents of Chl a, Chl b and Car
3.4. Effects of Ce(NO3)3 on the contents of MDA and H2O2
GSH/GSSG
Soluble sugar (μg g−1 FW)
Different concentrations of Ce(NO3)3 all markedly increased the relative water content and the contents of proline and soluble sugar, compared with the control (Table 3). Compared with the control, 20, 40, 80 and 120 μM Ce(NO3)3 increased the relative water content by 9.4%, 18.7%, 13.8% and 8.3%, respectively. 20, 40, 80 and 120 μM Ce (NO3)3 increased the content of proline by 40.5%, 104.3%, 68.1% and 32.8%, respectively. 20, 40, 80 and 120 μM Ce(NO3)3 increased the content of soluble sugar by 39.8%, 127.9%, 83.7% and 32.6%, respectively. Among different concentrations of Ce(NO3)3, the contents of above indicators in the petals treated by 40 μM Ce(NO3)3 were significantly higher than those treated by other concentrations of Ce (NO3)3.
Different concentrations of Ce(NO3)3 all significantly increased the ratios of AsA/DHA and GSH/GSSG, compared with the control (Table 2). Compared with control, 20, 40, 80 and 120 μM Ce(NO3)3 increased the ratio of AsA/DHA by 12.8%, 31.7%, 16.7% and 8.9%, respectively. 20, 40, 80 and 120 μM Ce(NO3)3 increased the ratio of GSH/GSSG by 18.3%, 39.2%, 23.7% and 15.6%, respectively. Among different concentrations, the ratios of AsA/DHA and GSH/GSSG in the petals treated by 40 μM Ce(NO3)3 was significantly higher than that treated by other concentrations of Ce(NO3)3. There was no significant difference between 20, 80 and 120 μM Ce(NO3)3.
AsA/DHA
Proline (μg g−1 FW)
3.5. Effects of Ce(NO3)3 on the relative water content and the contents of proline and soluble sugar
3.3. Effects of Ce(NO3)3 on the ratios of AsA/DHA and GSH/GSSG
Treatments
Treatments
Table 4 Effects of different concentrations of Ce(NO3)3 on the contents of Chl a, Chl b and Car in the leaves of L. longiflorum cut flowers. These indicators were determined on day 4. Values represent mean ± standard deviations (SD) (n = 15), different letters indicate statistical difference at P < 0.05.
144
Treatments
Chl a (mg g−1 FW)
Chl b (mg g−1 FW)
Car (mg g−1 FW)
Control 20 μM Ce(NO3)3 40 μM Ce(NO3)3 80 μM Ce(NO3)3 120 μM Ce(NO3)3
1.54 1.90 2.56 2.22 1.77
0.70 0.90 1.14 0.97 0.89
0.52 0.69 0.85 0.70 0.65
± ± ± ± ±
0.17d 0.23c 0.37a 0.29b 0.21c
± ± ± ± ±
0.10c 0.11b 0.20a 0.14b 0.11b
± ± ± ± ±
0.08c 0.09b 0.11a 0.08b 0.10b
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content in the petals of L. longiflorum cut flowers, compared with the control. Meanwhile, we observed that different concentrations of Ce (NO3)3 significantly improved the vase life of L. longiflorum cut flowers, which was probably due to the reduction in the content of MDA induced by Ce(NO3)3, especially for 40 μM Ce(NO3)3. The extended vase life observed in Ce(NO3)3-treated cut flowers is prolonged maintenance of the integrity of the plasma membrane indicated by the lower MDA content, especially for 40 μM Ce(NO3)3. As an important ROS, H2O2 is a reliable indicator used to measure the extent of the imbalance of reactive oxygen metabolism. In the present study, the content of H2O2 in petals of controls was markedly higher than those treated by different concentrations of Ce(NO3)3, which indicated that Ce(NO3)3 may balance the reactive oxygen metabolism, especially for 40 μM Ce(NO3)3. Besides, our findings showed that different concentrations of Ce(NO3)3 markedly increased the activities of enzymes in the AsA-GSH cycle, including APX, GR, DHAR and MDHAR, and the ratios of AsA/DHA and GSH/GSSG, especially for 40 μM Ce(NO3)3. These increases in the activities of enzymes in the AsA-GSH cycle and the ratios of AsA/DHA and GSH/GSSG were helpful in scavenging excess H2O2, which, in turn, improved the vase life of L. longiflorum cut flowers, especially for 40 μM Ce(NO3)3. The vase life of cut flowers is also closely related with RWC of petals. Whereas, RWC is closely related with the contents of osmoregulation substances. In the present study, different concentrations of Ce(NO3)3 markedly increased the contents of osmoregulation substances soluble sugar and proline, which increased the RWC of petals. These increases improved the water retaining capacity, which, in turn, improved the vase life of L. longiflorum cut flowers, especially for 40 μM Ce(NO3)3. There is close relationship between the contents of photosynthetic pigments and the vase life of cut flowers because aging can lead to the degradation of photosynthetic pigments, especially for chlorophyll a and b. Besides, carotenoids are one important type of antioxidants in balancing the reactive oxygen metabolism. Thus, higher contents of photosynthetic pigments mean longer vase life. In our study, different concentrations of Ce(NO3)3 significantly increased the contents of chlorophyll a, chlorophyll b and carotenoids in the leaves of L. longiflorum cut flowers after 4 d of treatment, especially for 40 μM Ce (NO3)3. These increases were helpful in preventing senescence, which resulted in the increase in the vase life of cut flowers. More studies showed that signal molecules such as Ca2+, NO, abscisic acid (ABA) and jasmonic acid (JA) can regulate the vase life of cut flowers (Rubinstein, 2000; Rogers, 2006). However, there is still no study about the effects of Ce(NO3)3 on signal molecules Ca2+, NO, ABA and JA in the regulation of the vase life of L. longiflorum cut flowers. So, it will be very interesting to study the effects of Ce(NO3)3 on signal molecules Ca2+, NO, ABA and JA, etc. This part work will provide valuable knowledge for the elucidation of the mechanism of the vase life of L. longiflorum cut flowers regulated by Ce(NO3)3. In conclusion, our results clearly suggest that Ce(NO3)3 improves the vase life of Lilium longiflorum cut flowers through ascorbate-glutathione cycle and osmoregulation in the petals, especially for 40 μM Ce (NO3)3.
Acknowledgement This study was supported by the Important Scientific Research Project of Henan Institute of Science and Technology (2011010). References Ahmad, P., Ahanger, M.A., Alyemeni, M.N., Wijaya, L., Alam, P., 2017. Exogenous application of nitric oxide modulates osmolyte metabolism, antioxidants, enzymes of ascorbate-glutathione cycle and promotes growth under cadmium stress in tomato. Protoplasma. http://dx.doi.org/10.1007/s00709-017-1132-x. Alaey, M., Babalar, M., Naderi, R., Kafi, M., 2011. Effect of pre- and postharvest salicylic acid treatment on physio-chemical attributes in relation to vase-life of rose cut flowers. Postharvest Biol. Technol. 61, 91–94. Barrs, H.D., Weatherley, P.E., 1962. A re-examination of the relative turgidity technique for estimating water deficits in leaves. Aust. J. Biol. Sci. 24, 519–570. Bates, L.E., Waldren, R.P., Teare, I.D., 1973. Rapid determination of free proline for water-stress studies. Plant Soil 39, 205–207. Dalton, D.A., Russell, S.A., Hanus, F.J., Pascoe, G.A., Evans, H.J., 1986. Enzymatic reactions of ascorbate and glutathione that prevent peroxide damage in soybean root nodules. Proc. Natl. Acad. Sci. U. S. A. 83, 3811–3815. Grace, S.C., Logan, B.A., 1996. Acclimation of foliar antioxidant systems to growth irradiance in three broad-leaved evergreen species. Plant Physiol. 112, 1631–1640. Griffith, O.W., 1980. Determination of glutathione and glutathione disulfide using glutathione reductase and 2-vinylpyridine. Anal. Biochem. 106, 207–212. Hodges, D.M., Andrews, C.J., Johnson, D.A., Hamilton, R.I., 1996. Antioxidant compound responses to chilling stress in differentially sensitive inbred maize lines. Plant Physiol. 98, 685–692. 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. Liang, C., Huang, X., Tao, W., Zhou, Q., 2006. Effect of rare earths on plants under supplementary ultraviolet-B radiation: II. Effect of cerium on antioxidant defense system in rape seedlings under supplementary ultraviolet-B radiation. J. Rare Earths 24, 364–368. Lichtenthaler, H.K., Wellburn, A.L., 1983. Determination of total carotenoids and chlorophylls a and b of leaf exacts in different solvents. Biochem. Soc. Trans. 11, 591–593. Liu, R., Shan, C., Gao, Y., Wang, J., Xu, Z., Zhang, L., Ma, W., Tan, R., 2016. Cerium improves the copper tolerance of turf grass Poa pratensis by affecting the regeneration and biosynthesis of ascorbate and glutathione in leaves. Braz. J. Bot. 39, 779–785. Miyake, C., Asada, K., 1992. Thylakoid-bound ascorbate peroxidase in spinach chloroplasts and photoreduction of its primary oxidation product monodehydroascorbate radicals in thylakoids. Plant Cell Physiol. 33, 541–553. Nakano, Y., Asada, K., 1981. Hydrogen peroxide is scavenged by ascorbate specific peroxidase in spinach chloroplasts. Plant Cell Physiol. 22, 867–880. Patterson, B.D., Mackae, E.A., Ferguson, I.B., 1984. Estimation of hydrogen peroxide in plant extracts using titanium (IV). Anal. Biochem. 139, 487–492. Rogers, H.J., 2006. Programmed cell death in floral organs: how and why do flowers die? Ann. Bot. 97, 309–315. Rubinstein, B., 2000. Regulation of cell death in flower petals. Plant Mol. Biol. 44, 303–318. 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. Wang, Q., Mu, J., Shan, C., Wang, W., Fu, S., 2017. Effects of cerium on the antioxidant defence system in the petals and the contents of pigments in the calyces of Rosa chinensis Jacq. cut flower. J. Hortic. Sci. Biotechnol. http://dx.doi.org/10.1080/ 14620316.2017.1338924. Wei, Q., 2009. The Experiment of Basic Biochemistry. Higher Education Press, Beijing, pp. 84–86. Xu, Q., Wang, Y., Liu, H., Cheng, J., 2016. Physiological responses and chromosomal aberration in root tip cells of Allium sativum L. to cerium treatments. Plant Soil 409, 447–458. Zhang, H., Hu, S., Zhang, Z., Hu, L., Jiang, C., Wei, Z., Liu, J., Wang, H., Jiang, S., 2011. Hydrogen sulfide acts as a regulator of flower senescence in plants. Postharvest Biol. Technol. 60, 251–257.
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Short Communication
Cerium improves the vase life of Lilium longiflorum cut flowers through ascorbate-glutathione cycle and osmoregulation in the petals Kun Houa, Donge Baoa, Changjuan Shana,b, a b
MARK
⁎
Henan Institute of Science and Technology, Xinxiang 453003 China Collaborative Innovation Center of Modern Biological Breeding, Henan Province, Xinxiang 453003 China
A R T I C L E I N F O
A B S T R A C T
Keywords: Cerium nitrate Ascorbate-glutathione cycle Redox status Lilium longiflorum
The present study investigated the role of cerium nitrate (Ce(NO3)3) in regulating the ascorbate-glutathione (AsA-GSH) cycle, the relative water content (RWC), and the contents of malondialdehyde (MDA), hydrogen peroxide (H2O2), soluble sugar and proline in the petals, and the contents of chlorophyll a (Chl a), chlorophyll b (Chl b) and carotenoids (Car) in the leaves of Lilium longiflorum cut flowers. The findings showed that Ce(NO3)3 markedly improved the activities of ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR), the ratios of AsA/DHA and GSH/GSSG, RWC, and the contents of proline and soluble sugar in the petals, and markedly reduced the contents of MDA and H2O2 in the petals, compared with the control. Meanwhile, Ce(NO3)3 markedly improved the contents of Chl a, Chl b and Car in the leaves. Among different concentrations of Ce(NO3)3, 40 μM Ce(NO3)3 is the most effective treatment for the improvement of the vase life of Lilium longiflorum cut flowers. Above results indicated that Ce (NO3)3 improves the vase life of Lilium longiflorum cut flowers by enhancing the AsA-GSH cycle and water retaining capacity.
1. Introduction Lilium longiflorum cut flower is an important type of cut flowers. However, the vase life of L. longiflorum cut flower is short, which limits its efficient marketing. The vase life of cut flower is closely related with the disruption of plasma membrane integrity, which was induced by the lipid peroxidation of the plasma membranes indicated by the contents of malondialdehyde (MDA), hydrogen peroxide (H2O2) (Rubinstein, 2000; Zhang et al., 2011). While, the contents of MDA and H2O2 in cut flowers are closely related with the imbalance of reactive oxygen metabolism. It has been reported that ascorbate-glutathione (AsA-GSH) cycle had important role in balancing the reactive oxygen metabolism (Ahmad et al., 2017). In this cycle, ascorbate peroxidase (APX) utilizes reduced ascorbate (AsA) as electron donor for reduction of H2O2, monodehydroascorbate is reduced to AsA by monodehydroascorbate reductase (MDHAR) and dehydroascorbate is reduced to AsA by dehydroascorbate reductase (DHAR). Oxidized glutathione (GSSG) produced in this cycle is reduced to reduced glutathione GSH by glutathione reductase (GR) (Ahmad et al., 2017). By this way, AsA and GSH are regenerated and H2O2 is scavenged. Thus, AsA-GSH cycle plays an important role in balancing the reactive oxygen metabolism and maintaining the redox states of ascorbate and glutathione. So, AsA-GSH
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cycle has an important role in improving the vase life of cut flowers. Meanwhile, studies showed that the water retaining capacity was also very important for the increase in the vase life of cut flowers (Shan and Zhao, 2015). In the preservation of cut flowers, people usually use some exogenous regulators, such as hydrogen sulfide (H2S) and salicylic acid (SA), to improve their vase life (Zhang et al., 2011; Alaey et al., 2011). Therefore, it is very important to study the effects of exogenous regulators on the AsA-GSH cycle and the water retaining capacity, in order to provide the theoretical basis for their application in improving the vase life of cut flowers. Our previous studies showed that the rare earth element lanthanum (La) can regulate the reactive oxygen metabolism and the water retaining capacity, which, in turn, delay the flower senescence of L. longiflorum cut flowers (Shan and Zhao, 2015). Cerium (Ce) is another important rare earth element. It has been reported that Ce could enhance antioxidant defense system in rape seedlings under ultraviolet-B radiation (Liang et al., 2006). Liu et al. (2016) reported that Ce could enhance the activity of AsA-GSH cycle through APX, GR, DHAR and MDHAR in turf grass Poa pratensis seedlings. Wang et al. (2017) showed that Ce improved the vase life of Rosa chinensis Jacq. cut flowers by incresing the activity of AsA-GSH cycle through APX and GR. Xu et al. (2016) also suggested that Ce could enhance the activity of AsA-GSH
Corresponding author at: Henan Institute of Science and Technology, Xinxiang 453003 China. E-mail address: [email protected] (C. Shan).
http://dx.doi.org/10.1016/j.scienta.2017.09.040 Received 14 July 2017; Received in revised form 8 September 2017; Accepted 25 September 2017 0304-4238/ © 2017 Elsevier B.V. All rights reserved.
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enzymes, the decrease in the absorption was all followed for 3 min. The absorption value decreased by 0.001 per min was defined as one unit of APX, GR and MDHAR. The absorption value decreased by 0.01 per min was defined as one unit of DHAR. The specific enzyme activity for all the above enzymes was expressed as Units g−1 FW.
cycle through APX. However, whether Ce regulates the AsA-GSH cycle of L. longiflorum cut flowers is still unknown. In addition, whether Ce regulates the water retaining capacity of L. longiflorum cut flowers is also still unknown. Thus, it is very interesting to elucidate the role of Ce in regulating the AsA-GSH cycle and the water retaining capacity of L. longiflorum cut flowers. As the balance of reactive oxygen metabolism is important for the vase life of L. longiflorum cut flowers, the measurement of the activities of enzymes in AsA-GSH cycle and the contents of MDA and H2O2 in the petals is critical to the vase life of L. longiflorum cut flowers. As the imbalance of reactive oxygen metabolism will accelerate the degradation of chloroplast pigments, the measurement of the contents of chlorophyll a (Chl a), chlorophyll b (Chl b) and carotenoids (Car) in the leaves is also critical to the vase life. As the water retaining capacity is important for the increase in the vase life of cut flowers, the measurement of RWC and the contents of proline and soluble sugar in the petals is also critical to the vase life. In the present study, the role of Ce(NO3)3 in regulating the activities of enzymes in AsA-GSH cycle, RWC and the contents of MDA, H2O2, proline and soluble sugar in the petals, and the contents of Chl a, Chl b and Car in the leaves of L. longiflorum cut flowers were investigated. The objective of the present study was to provide theoretical basis for the application of Ce(NO3)3 in improving the vase life of L. longiflorum cut flowers.
2.3. Analysis of the ratios of AsA/DHA and GSH/GSSG AsA and DHA was measured according to Hodges et al. (1996). GSH and GSSG was measured according to Griffith (1980). AsA/DHA was expressed as the ratio between the content of AsA and the content of DHA. GSH/GSSG was expressed as the ratio between the content of GSH and the content of GSSG. 2.4. Measurement of the contents of MDA and H2O2 The content of MDA was measured by thiobarbituric acid (TBA) reaction as described by Hodges et al. (1999). The content of H2O2 was measured according to Patterson et al. (1984). 2.5. Measurement of the contents of praline and soluble sugar The content of proline was determined according to the method of Bates et al. (1973). The content of soluble sugar was determined according to the method of Wei (2009).
2. Materials and methods 2.6. Measurement of the relative water content (RWC) 2.1. Plant material and treatments RWC were determined by the method of Barrs and Weatherley (1962). Twenty discs of 1 cm diameter were cut by using a punch and weighed to determine fresh weight (FW). Then discs were immersed in distilled water for 6 h and the turgid weight (TW) were determined. Dry weight (DW) was determined after oven drying at 80 °C for 48 h. RWC was calculated according below equation: RWC = [(FW-DW)/(TWDW)] × 100
L. longiflorum was supplied by the Flower Market of Xinxiang City. Cut flowers were excised uniformly with a sharp scalpel to prevent blockage of water uptake and cultured in distilled water (Control), 20, 40, 60 and 120 μM Ce(NO3)3 under the same conditions as our previous study (Shan and Zhao, 2015). Treatment solutions were changed daily. The petals of the first fully opened flowers were used to determine the activities of enzymes in AsA-GSH cycle, the ratios of AsA/DHA and GSH/GSSG, and the contents of MDA, H2O2, proline and soluble sugar. The first fully expanded leaves of the upper stem were used to determine the contents of Chl a, Chl b and Car at 4 d after treatment.
2.7. Measurement of the contents of Chl a, Chl b and Car The contents of Chl a, Chl b and Car were measured according to the method of Lichtenthaler and Wellburn (1983).
2.2. Analysis of APX, GR, DHAR and MDHAR 2.8. Statistical analysis Each frozen sample (0.5 g) was ground into a fine powder in liquid N2 with a mortar and pestle. Fine powder was homogenized in 6 ml 50 mM KH2PO4 (pH 7.5) containing 0.1 mM ethylenediaminetetraacetic acid, 0.3% (v/v) Triton X-100, and 1% (w/v) soluble polyvinylpolypyrrolidone, with the addition of 1 mM AsA in the case of the APX assay. The extract was immediately centrifuged at 13000×g for 15 min at 2 °C. The supernatant was then used immediately for measuring the following enzymes. The activities of ascorbate peroxidase (APX, EC 1.11.1.11), glutathione reductase (GR, EC 1.6.4.2), monodehydroascorbate reductase (MDHAR, EC 1.6.5.4) and dehydroascorbate reductase (DHAR, EC 1.8.5.1) were measured according to Nakano and Asada (1981), Grace and Logan (1996), Miyake and Asada (1992) and Dalton et al. (1986), respectively. For above four
The whole experiment was repeated 5 times with 3 replicates each time. The results presented were the mean of 5 times. 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 Ce(NO3)3 on the length of vase life of L. longiflorum cut flowers Different concentrations of Ce(NO3)3 all improved the vase life of L. longiflorum cut flower, compared with the control (Table 1). Compared
Table 1 Effects of different concentrations of Ce(NO3)3 on the length of vase life and the activities of enzymes in AsA-GSH cycle in the petals of L. longiflorum cut flowers. Values represent mean ± standard deviations (SD) (n = 15), different letters indicate statistical difference at P < 0.05. Treatments
Length of vase life (d)
APX (Units g−1 FW)
GR (Units g−1 FW)
DHAR (Units g−1 FW)
MDHAR (Units g−1 FW)
Control 20 μM Ce(NO3)3 40 μM Ce(NO3)3 80 μM Ce(NO3)3 120 μM Ce(NO3)3
7.0 ± 0.80d 8.4 ± 0.95c 10.6 ± 1.22a 9.3 ± 1.01b 8.1 ± 0.86c
1.6 2.3 4.7 3.0 2.1
5.5 ± 0.67d 7.9 ± 0.83c 12.6 ± 1.30a 10.2 ± 1.11b 7.3 ± 0.80c
3.0 4.0 6.7 5.3 3.8
9.5 ± 1.03d 12.6 ± 1.15c 18.9 ± 1.95a 15.6 ± 1.38b 11.7 ± 1.30c
± ± ± ± ±
0.19d 0.22c 0.53a 0.34b 0.25c
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± ± ± ± ±
0.27d 0.35c 0.73a 0.44b 0.41c
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with the control, 20, 40, 80 and 120 μM Ce(NO3)3 all significantly increased the vase life of L. longiflorum cut flower by 20%, 51.4%, 32.8% and 15.7%, respectively. Compared with other concentrations, 40 μM Ce(NO3)3 significantly improved the vase life of L. longiflorum cut flowers.
Table 3 Effects of different concentrations of Ce(NO3)3 on the relative water content and the contents of proline and soluble sugar in petals of L. longiflorum cut flowers. These indicators were determined on day 4. Values represent mean ± standard deviations (SD) (n = 15), different letters indicate statistical difference at P < 0.05.
3.2. Effects of Ce(NO3)3 on the activities of APX, GR, DHAR and MDHAR Different concentrations of Ce(NO3)3 all significantly increased the activities of enzymes in the AsA-GSH cycle, including APX, GR, DHAR and MDHAR, compared with the control (Table 1). Compared with the control, 20, 40, 80 and 120 μM Ce(NO3)3 increased the activity of APX by 43.7%, 193.7%, 87.5% and 31.2%, respectively. 20, 40, 80 and 120 μM Ce(NO3)3 increased the activity of GR by 43.6%, 129.1%, 85.5% and 32.7%, respectively. 20, 40, 80 and 120 μM Ce(NO3)3 increased the activity of DHAR by 33.3%, 123.3%, 76.7% and 26.7%, respectively. 20, 40, 80 and 120 μM Ce(NO3)3 increased the activity of MDHAR by 32.6%, 98.9%, 64.2% and 23.2%, respectively. Among different concentrations of Ce(NO3)3, the activities of above enzymes in the AsA-GSH cycle in the petals treated by 40 μM Ce(NO3)3 were higher than those in the petals treated by other concentrations of Ce(NO3)3.
Control 20 μM Ce (NO3)3 40 μM Ce (NO3)3 80 μM Ce (NO3)3 120 μM Ce (NO3)3
18.0 ± 2.11c 20.3 ± 2.30b
18.6 ± 1.74c 22.0 ± 2.16b
8.6 ± 0.85a 7.0 ± 0.77b
6.2 ± 0.66a 5.1 ± 0.53b
23.7 ± 2.56a
25.9 ± 2.73a
5.0 ± 0.47d
3.5 ± 0.44d
21.0 ± 2.23b
23.0 ± 2.30b
6.1 ± 0.54c
4.2 ± 0.41c
19.6 ± 2.11b
21.5 ± 2.15b
7.4 ± 0.84b
5.3 ± 0.61b
11.6 ± 1.30d 16.3 ± 1.54c
517.7 ± 43.38d 724.0 ± 87.11c
78.0 ± 7.22d 85.3 ± 9.14c
23.7 ± 2.16a
1180.0 ± 121.5a
92.6 ± 8.83a
19.5 ± 2.00b
950.9 ± 105.3b
88.8 ± 7.38b
15.4 ± 1.71c
686.3 ± 76.19c
84.5 ± 8.88c
4. Discussion As MDA is one important product of the lipid peroxidation induced by imbalance of reactive oxygen metabolism, the vase life of cut flower is closely related with the content of MDA. In this study, different concentrations of exogenous Ce(NO3)3 significantly reduced MDA
Table 2 Effects of different concentrations of Ce(NO3)3 on the ratios of AsA/DHA and GSH/GSSG and the contents of AsA, GSH, MDA and H2O2 in the petals of L. longiflorum cut flowers. These indicators were determined on day 4. Values represent mean ± standard deviations (SD) (n = 15), different letters indicate statistical difference at P < 0.05. H2O2 (μmol g−1 FW)
Control 20 μM Ce (NO3)3 40 μM Ce (NO3)3 80 μM Ce (NO3)3 120 μM Ce (NO3)3
Different concentrations of Ce(NO3)3 all markedly increased the contents of Chl a, Chl b and Car, compared with the control (Table 4). Compared with the control, 20, 40, 80 and 120 μM Ce(NO3)3 increased the content of Chl a by 23.4%, 66.2%, 44.2% and 14.9%, respectively. 20, 40, 80 and 120 μM Ce(NO3)3 increased the content of Chl b by 28.6%, 62.8%, 38.6% and 27.1%, respectively. 20, 40, 80 and 120 μM Ce(NO3)3 increased the content of Car by 32.7%, 63.5%, 34.6% and 25%, respectively. Among different concentrations of Ce(NO3)3, the contents of above indicators in the leaves treated by 40 μM Ce(NO3)3 were significantly higher than those treated by other concentrations of Ce(NO3)3.
Different concentrations of Ce(NO3)3 all significantly decreased the contents of MDA and H2O2, compared with the control (Table 2). Compared with control, 20, 40, 80 and 120 μM Ce(NO3)3 decreased the content of MDA by 18.6%, 41.9%, 29.1% and 13.9%, respectively. 20, 40, 80 and 120 μM Ce(NO3)3 decreased the content of H2O2 by 17.7%, 43.5%, 32.3% and 14.5%, respectively. Among different concentrations of Ce(NO3)3, the contents of MDA and H2O2 in the petals treated by 40 μM Ce(NO3)3 was significantly lower than those treated by other concentrations of Ce(NO3)3.
MDA (nmol g−1 FW)
Relative water content (%)
3.6. Effects of Ce(NO3)3 on the contents of Chl a, Chl b and Car
3.4. Effects of Ce(NO3)3 on the contents of MDA and H2O2
GSH/GSSG
Soluble sugar (μg g−1 FW)
Different concentrations of Ce(NO3)3 all markedly increased the relative water content and the contents of proline and soluble sugar, compared with the control (Table 3). Compared with the control, 20, 40, 80 and 120 μM Ce(NO3)3 increased the relative water content by 9.4%, 18.7%, 13.8% and 8.3%, respectively. 20, 40, 80 and 120 μM Ce (NO3)3 increased the content of proline by 40.5%, 104.3%, 68.1% and 32.8%, respectively. 20, 40, 80 and 120 μM Ce(NO3)3 increased the content of soluble sugar by 39.8%, 127.9%, 83.7% and 32.6%, respectively. Among different concentrations of Ce(NO3)3, the contents of above indicators in the petals treated by 40 μM Ce(NO3)3 were significantly higher than those treated by other concentrations of Ce (NO3)3.
Different concentrations of Ce(NO3)3 all significantly increased the ratios of AsA/DHA and GSH/GSSG, compared with the control (Table 2). Compared with control, 20, 40, 80 and 120 μM Ce(NO3)3 increased the ratio of AsA/DHA by 12.8%, 31.7%, 16.7% and 8.9%, respectively. 20, 40, 80 and 120 μM Ce(NO3)3 increased the ratio of GSH/GSSG by 18.3%, 39.2%, 23.7% and 15.6%, respectively. Among different concentrations, the ratios of AsA/DHA and GSH/GSSG in the petals treated by 40 μM Ce(NO3)3 was significantly higher than that treated by other concentrations of Ce(NO3)3. There was no significant difference between 20, 80 and 120 μM Ce(NO3)3.
AsA/DHA
Proline (μg g−1 FW)
3.5. Effects of Ce(NO3)3 on the relative water content and the contents of proline and soluble sugar
3.3. Effects of Ce(NO3)3 on the ratios of AsA/DHA and GSH/GSSG
Treatments
Treatments
Table 4 Effects of different concentrations of Ce(NO3)3 on the contents of Chl a, Chl b and Car in the leaves of L. longiflorum cut flowers. These indicators were determined on day 4. Values represent mean ± standard deviations (SD) (n = 15), different letters indicate statistical difference at P < 0.05.
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Treatments
Chl a (mg g−1 FW)
Chl b (mg g−1 FW)
Car (mg g−1 FW)
Control 20 μM Ce(NO3)3 40 μM Ce(NO3)3 80 μM Ce(NO3)3 120 μM Ce(NO3)3
1.54 1.90 2.56 2.22 1.77
0.70 0.90 1.14 0.97 0.89
0.52 0.69 0.85 0.70 0.65
± ± ± ± ±
0.17d 0.23c 0.37a 0.29b 0.21c
± ± ± ± ±
0.10c 0.11b 0.20a 0.14b 0.11b
± ± ± ± ±
0.08c 0.09b 0.11a 0.08b 0.10b
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content in the petals of L. longiflorum cut flowers, compared with the control. Meanwhile, we observed that different concentrations of Ce (NO3)3 significantly improved the vase life of L. longiflorum cut flowers, which was probably due to the reduction in the content of MDA induced by Ce(NO3)3, especially for 40 μM Ce(NO3)3. The extended vase life observed in Ce(NO3)3-treated cut flowers is prolonged maintenance of the integrity of the plasma membrane indicated by the lower MDA content, especially for 40 μM Ce(NO3)3. As an important ROS, H2O2 is a reliable indicator used to measure the extent of the imbalance of reactive oxygen metabolism. In the present study, the content of H2O2 in petals of controls was markedly higher than those treated by different concentrations of Ce(NO3)3, which indicated that Ce(NO3)3 may balance the reactive oxygen metabolism, especially for 40 μM Ce(NO3)3. Besides, our findings showed that different concentrations of Ce(NO3)3 markedly increased the activities of enzymes in the AsA-GSH cycle, including APX, GR, DHAR and MDHAR, and the ratios of AsA/DHA and GSH/GSSG, especially for 40 μM Ce(NO3)3. These increases in the activities of enzymes in the AsA-GSH cycle and the ratios of AsA/DHA and GSH/GSSG were helpful in scavenging excess H2O2, which, in turn, improved the vase life of L. longiflorum cut flowers, especially for 40 μM Ce(NO3)3. The vase life of cut flowers is also closely related with RWC of petals. Whereas, RWC is closely related with the contents of osmoregulation substances. In the present study, different concentrations of Ce(NO3)3 markedly increased the contents of osmoregulation substances soluble sugar and proline, which increased the RWC of petals. These increases improved the water retaining capacity, which, in turn, improved the vase life of L. longiflorum cut flowers, especially for 40 μM Ce(NO3)3. There is close relationship between the contents of photosynthetic pigments and the vase life of cut flowers because aging can lead to the degradation of photosynthetic pigments, especially for chlorophyll a and b. Besides, carotenoids are one important type of antioxidants in balancing the reactive oxygen metabolism. Thus, higher contents of photosynthetic pigments mean longer vase life. In our study, different concentrations of Ce(NO3)3 significantly increased the contents of chlorophyll a, chlorophyll b and carotenoids in the leaves of L. longiflorum cut flowers after 4 d of treatment, especially for 40 μM Ce (NO3)3. These increases were helpful in preventing senescence, which resulted in the increase in the vase life of cut flowers. More studies showed that signal molecules such as Ca2+, NO, abscisic acid (ABA) and jasmonic acid (JA) can regulate the vase life of cut flowers (Rubinstein, 2000; Rogers, 2006). However, there is still no study about the effects of Ce(NO3)3 on signal molecules Ca2+, NO, ABA and JA in the regulation of the vase life of L. longiflorum cut flowers. So, it will be very interesting to study the effects of Ce(NO3)3 on signal molecules Ca2+, NO, ABA and JA, etc. This part work will provide valuable knowledge for the elucidation of the mechanism of the vase life of L. longiflorum cut flowers regulated by Ce(NO3)3. In conclusion, our results clearly suggest that Ce(NO3)3 improves the vase life of Lilium longiflorum cut flowers through ascorbate-glutathione cycle and osmoregulation in the petals, especially for 40 μM Ce (NO3)3.
Acknowledgement This study was supported by the Important Scientific Research Project of Henan Institute of Science and Technology (2011010). References Ahmad, P., Ahanger, M.A., Alyemeni, M.N., Wijaya, L., Alam, P., 2017. Exogenous application of nitric oxide modulates osmolyte metabolism, antioxidants, enzymes of ascorbate-glutathione cycle and promotes growth under cadmium stress in tomato. Protoplasma. http://dx.doi.org/10.1007/s00709-017-1132-x. Alaey, M., Babalar, M., Naderi, R., Kafi, M., 2011. Effect of pre- and postharvest salicylic acid treatment on physio-chemical attributes in relation to vase-life of rose cut flowers. Postharvest Biol. Technol. 61, 91–94. Barrs, H.D., Weatherley, P.E., 1962. A re-examination of the relative turgidity technique for estimating water deficits in leaves. Aust. J. Biol. Sci. 24, 519–570. Bates, L.E., Waldren, R.P., Teare, I.D., 1973. Rapid determination of free proline for water-stress studies. Plant Soil 39, 205–207. Dalton, D.A., Russell, S.A., Hanus, F.J., Pascoe, G.A., Evans, H.J., 1986. Enzymatic reactions of ascorbate and glutathione that prevent peroxide damage in soybean root nodules. Proc. Natl. Acad. Sci. U. S. A. 83, 3811–3815. Grace, S.C., Logan, B.A., 1996. Acclimation of foliar antioxidant systems to growth irradiance in three broad-leaved evergreen species. Plant Physiol. 112, 1631–1640. Griffith, O.W., 1980. Determination of glutathione and glutathione disulfide using glutathione reductase and 2-vinylpyridine. Anal. Biochem. 106, 207–212. Hodges, D.M., Andrews, C.J., Johnson, D.A., Hamilton, R.I., 1996. Antioxidant compound responses to chilling stress in differentially sensitive inbred maize lines. Plant Physiol. 98, 685–692. 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. Liang, C., Huang, X., Tao, W., Zhou, Q., 2006. Effect of rare earths on plants under supplementary ultraviolet-B radiation: II. Effect of cerium on antioxidant defense system in rape seedlings under supplementary ultraviolet-B radiation. J. Rare Earths 24, 364–368. Lichtenthaler, H.K., Wellburn, A.L., 1983. Determination of total carotenoids and chlorophylls a and b of leaf exacts in different solvents. Biochem. Soc. Trans. 11, 591–593. Liu, R., Shan, C., Gao, Y., Wang, J., Xu, Z., Zhang, L., Ma, W., Tan, R., 2016. Cerium improves the copper tolerance of turf grass Poa pratensis by affecting the regeneration and biosynthesis of ascorbate and glutathione in leaves. Braz. J. Bot. 39, 779–785. Miyake, C., Asada, K., 1992. Thylakoid-bound ascorbate peroxidase in spinach chloroplasts and photoreduction of its primary oxidation product monodehydroascorbate radicals in thylakoids. Plant Cell Physiol. 33, 541–553. Nakano, Y., Asada, K., 1981. Hydrogen peroxide is scavenged by ascorbate specific peroxidase in spinach chloroplasts. Plant Cell Physiol. 22, 867–880. Patterson, B.D., Mackae, E.A., Ferguson, I.B., 1984. Estimation of hydrogen peroxide in plant extracts using titanium (IV). Anal. Biochem. 139, 487–492. Rogers, H.J., 2006. Programmed cell death in floral organs: how and why do flowers die? Ann. Bot. 97, 309–315. Rubinstein, B., 2000. Regulation of cell death in flower petals. Plant Mol. Biol. 44, 303–318. 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. Wang, Q., Mu, J., Shan, C., Wang, W., Fu, S., 2017. Effects of cerium on the antioxidant defence system in the petals and the contents of pigments in the calyces of Rosa chinensis Jacq. cut flower. J. Hortic. Sci. Biotechnol. http://dx.doi.org/10.1080/ 14620316.2017.1338924. Wei, Q., 2009. The Experiment of Basic Biochemistry. Higher Education Press, Beijing, pp. 84–86. Xu, Q., Wang, Y., Liu, H., Cheng, J., 2016. Physiological responses and chromosomal aberration in root tip cells of Allium sativum L. to cerium treatments. Plant Soil 409, 447–458. Zhang, H., Hu, S., Zhang, Z., Hu, L., Jiang, C., Wei, Z., Liu, J., Wang, H., Jiang, S., 2011. Hydrogen sulfide acts as a regulator of flower senescence in plants. Postharvest Biol. Technol. 60, 251–257.
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