Herbaceous peony (
Herbaceous peony (
Plant growth regulators are extracts from microorganisms or artificially synthesized whose physiological functions are similar to those of the plant hormones. They may be classified into growth promoters, growth inhibitors, and growth retardants depending upon their effects on plant growth [
To clarify the effect of applying PBZ on the plant growth, physiological activity, and flower quality in
The plant height and plant crown width were measured using a meter stick, and the stem diameter was measured using a micrometer scale. The leaf area was determined according to a paper weighing method, and the leaf thickness was determined under an optical microscope (OLYMPUS CX31, Japan).
The chlorophyll (Chl) a, Chl b, and Chl a+b, relative water content (RWC), relative electrical conductivity (REC), soluble protein, and soluble sugar contents were all determined according to the method reported by Zou [
Firstly, the extracts which was from 0.5 g leaf powders extracting by ice-cold 50 mM phosphate buffer (pH 7.8) were centrifuged at 4°C and 10,000 × g for 15 min, this isolated supernatants called crude extracts could be used for enzyme activities assay. Thereafter, superoxide dismutase (SOD, EC 1.15.1.1), peroxidase (POD, EC 1.11.1.7) and catalase (CAT, EC 1.11.1.6) activities were evaluated using the method reported by Zou [
Firstly, fifteen-minute wash were performed 3 times for fixed leaves using 0.1 mol·L-1 phosphate buffer, and post-fixed with 1% osmium tetroxide for 4 h at room temperature. After 3 times fifteen-minute wash again, the leaves were dehydrated using 50%, 70%, 85%, 95% and 100% gradient ethanol for 15 min each. Moreover, they were treated with 100% acetone solution (15 min) and acetone solution containing anhydrous sodium sulfate (15 min), infiltrated in Spurr resin and then hardened at 70°C for 24 h. seventy-nm-thick sections were cut using a Leica EM UC6 ultramicrotome (Leica Co., Austria) with a diamond knife and stained using 1% uranyl acetate in 70% methanol, and 1% lead citrate before examination. After these, the samples were observed and imaged with a Tecnai 12 transmission electron microscope (Philips Co., Holland).
The diameter and fresh weight of the flowers were measured using a micrometer scale and balance, respectively. The flower color indices were measured on a TC-P2A chroma meter (Beijing Optical Instrument Factory, China) using three color parameters including
Before sampling, the solid-phase microextraction fiber (75 μm CAR/PDMS, SUPELCO, USA) was aged for 20 min in the injection port of gas phase chromatography (Trace GC, Thermo, USA), the aged temperature was 250°C. The whole flower was put in the sample bottle under the condition of 40°C water bath, after 40 min adsorption, the aged microextraction fiber was inserted the injection port of gas chromatography/mass spectrometry (Trace DSQ II, Thermo, USA) and desorbed 2 min under 250°C, and then started the instrument to collect data. The flow rate of the helium carrier gas on Supelcowax 10 capillary chromatographic column with 30 m length, 0.25 mm inner diameter and 0.25 μm film was 0.8 mL·min-1. The injector temperature was 250°C, the column temperature was programmed as follows: the initial temperature was maintained at 40°C for 4 min, and then increased from 40°C to 90°C at 5 °C·min-1, and finally increased to 230°C at a rate of 8 °C·min-1, which was maintained for 4 min. The mass spectral ionization temperature was set to 200°C. The electron energy was 70 eV. Mass spectra were obtained by automatic scanning at m/z 33–450 amu. And the data were analyzed using the Xcalibur software.
Qualitative analysis was performed as follows: spectrometric data were compared with those obtained from the NIST library and Wiley library, combined with the manual resolution of mass spectra. Quantitative analysis was done with caprylic aldehyde as the internal standard with 0.082 g·L-1 concentration. The selected ion monitoring (SIM) technique was used for quantitative analysis of aromatic compounds, and the calculation formula was referenced to the method of Tian et al. [
Content of each compound (μg·g-1) = [Peak area of each compound/Peak area of internal standard × Concentration of internal standard (μg·μL-1) × Volume of internal standard (μL)] / Sample weight (g).
All data were means of three replicates at least with standard deviations. The results were analyzed for variance using the SAS/STAT statistical analysis package (version 6.12, SAS Institute, Cary, NC, USA). And the figures were completed by SigmaPlot 10.0 (SPSS Inc., USA).
PBZ application significantly affected the morphological indices of
Morphological indices | Control | PBZ | |
---|---|---|---|
Plant height (cm) | 109.11 ± 5.01a | 100.33 ± 5.52b | |
Plant crown width (cm) | 104.11 ± 8.67a | 88.78 ± 8.11b | |
Leaf area (cm2) | 26.89 ± 5.08a | 23.96 ± 4.56a | |
Leaf thickness (µm) | 0.33 ± 0.04b | 0.39 ± 0.03a | |
Stem diameter (cm) | Top | 0.56 ± 0.05a | 0.57 ± 0.07a |
Middle | 0.73 ± 0.07b | 0.83 ± 0.10a | |
Bottom | 0.94 ± 0.20b | 1.05 ± 0.10a |
Note: The values represent the mean ± standard deviation (n = 3), and different letters indicate significant differences (
The physiological indices were found to be a direct reflection of the current physiological state of the plant. Upon applying PBZ, the leaves of
Physiological indices | Control | PBZ |
---|---|---|
Chl a (ug·cm-2) | 0.27 ± 0.01b | 0.35 ± 0.02a |
Chl b (ug·cm-2) | 0.09 ± 0.00b | 0.12 ± 0.01b |
Chl a/b | 2.95 ± 0.04a | 2.98 ± 0.02a |
Chl a+b (ug·cm-2) | 0.36 ± 0.01b | 0.47 ± 0.02a |
SPAD | 57.14 ± 2.27b | 72.75 ± 1.23a |
RWC (%) | 32.04 ± 3.54a | 32.19 ± 1.14a |
REC (%) | 0.27 ± 0.01a | 0.22 ± 0.01b |
Soluble sugar (mg·g-1) | 26.71 ± 1.85b | 28.07 ± 3.42a |
Note: Chl a, Chlorophyll a; Chl b, Chlorophyll b; Chl a/b, Chlorophyll a/b; Chl a+b, Chlorophyll a+b; RWC, Relative water content; REC, Relative electrical conductivity. The values represent the mean ± standard deviation (n = 3), and different letters indicate the significant differences (
The activities of three protection enzymes including SOD, CAT and POD in
Observing the cell walls, vacuoles, and chloroplasts in the mesophyll cells during the bloom stage of
The development of
The differences in the flower color were observed upon applying PBZ as well as in the control group and evaluated by the
The shade of the violet series petals in
The GC/MS total ionic chromatogram of the aromatic compounds of
A total of 9 aromatic compounds was identified in S1, which included 4 and 8 components under the control conditions as well as upon PBZ application, respectively. In the control, the alcohols were found to have the highest content, and their relative content was found to reach 46.98%, the most abundant components being 1-octanol (1.05 μg·g-1). Meanwhile, the PBZ application was found to increase the levels of alkanes the most, with a relative content of 42.16%, and 1-octanol (3.37 μg·g-1) together with α- caryophyllene (2.54 μg·g-1) was found to constitute the maximum content. Additionally, 1-hexadecanol, octyl acetate, cis-3-hexenyl acetate, 1-dodecane, and α-caryophyllene were the unique components identified after applying PBZ.
A total of 36 aromatic compounds were identified in S2, which included 30 components in the control and 27 components upon the PBZ application, respectively. In the control, the alcohols were the most abundant with a relative content of 59.68%, and the major components comprised D-citronellol (58.89 μg·g-1), caryophyllene (26.28 μg·g-1) as well as 1-octanol (11.34 μg·g-1). Nevertheless, the alcohols were the most abundant with a relative content of 56.85% under the PBZ application, and D-citronellol (29.49 μg·g-1), caryophyllene (16.43 μg·g-1) as well as 1-octanol (10.93 μg·g-1) were found to have the maximum contents. Moreover, the application of PBZ was found to detect leaf alcohol, (E)-2-hexenal, ethyl octanoate, 1-dodecane, 2-ethenyl-1,1-dimethyl-3-methylene-cyclohexane and tricyclo[4,2,2,0(1,5)]dec-7-ene.
In S3, a total of 31 aromatic compounds was identified which included 28 components for the control group and 27 components for the PBZ-treated group. The alkanes were found to be the highest in the control group relative content reaching to about 67.45%, the most abundant components were (Z)-3,7-dimethyl-1,3,6-octatriene (127.49 μg·g-1), D-citronellol (38.32 μg·g-1), (E,Z)-2,6-Dimethyl-2,4,6-octatriene (26.54 μg·g-1), 1-octanol (16.90 μg·g-1), (2E,4E,6E)-3,4-dimethyl-2,4,6-octatriene (15.59 μg·g-1), myrcene (14.63 μg·g-1). Meanwhile, upon treatment with PBZ, the alcohols levels were found to be the highest with a relative content of 63.34%, and (Z)-3,7-dimethyl-1,3,6-octatriene (46.21 μg·g-1), D-citronellol (29.49 μg·g-1) together with D-citronellol (23.00 μg·g-1) were found to have the maximum contents. Additionally, 2-octen-1-ol, rhodinal and1-hexadecanol were the unique components found upon PBZ application.
In S4, a total of 15 aromatic compounds were identified which included 14 components for the control group and 12 components for the PBZ-treated group. In the control group, the alcohols were found to be the most abundant at a relative content of 40.75%, and the major components were 1-octanol (4.68 μg·g-1), octyl acetate (3.42 μg·g-1), (Z)-3,7-dimethyl-1,3,6-octatriene (2.99 μg·g-1), D-citronellol (2.02 μg·g-1), ethylbenzene (1.88 μg·g-1). Nevertheless, the application of PBZ, the alcohols were found to show the most abundant relative content of 45.68%, and 1-octanol (2.07 μg·g-1), D-citronellol (1.22 μg·g-1), octyl acetate (1.10 μg·g-1) as well as (Z)-3,7-dimethyl-1,3,6-octatriene (1.43 μg·g-1) was found to have the maximal contents. Moreover, PBZ application was found to detect 2-ethenyl-1,1-dimethyl-3-methylene-cyclohexane.
The assorted statistics of the main aromatic compounds have been listed in
The plant growth retardant, PBZ is a member of the triazole family, affecting the plant metabolism by interfering with the ent-kaurene oxidation pathway and finally inhibiting the biosynthesis of gibberellins (GAs) [
REC was the important metric under conditions of external environmental stress of the plants and is found to increase significantly under adverse conditions. In this study, PBZ application was found to significantly reduce the REC of
Plant growth retardants greatly affect the flowering quality. In flower diameter, the study by Newton et al. [
In conclusion, the present study demonstrated that applying PBZ can regulate the
Type | Aromatic compounds | S1 | S2 | S3 | S4 | ||||
---|---|---|---|---|---|---|---|---|---|
Control | PBZ | Control | PBZ | Control | PBZ | Control | PBZ | ||
Alcohols | Eucalyptol | - | - | 5.41 | 2.69 | - | - | 0.16 | - |
1-Octanol | 1.05 | 3.37 | 11.34 | 10.93 | 16.90 | 5.85 | 4.68 | 2.07 | |
Leaf alcohol | - | - | - | 1.74 | - | - | - | - | |
1-Hexadecanol | - | 0.12 | - | - | - | 1.95 | - | - | |
Carveol | - | - | 0.67 | 0.43 | 6.94 | - | - | - | |
Linalool | - | - | 0.31 | 0.24 | 2.84 | 1.04 | 0.13 | - | |
α-Terpineol | - | - | 1.26 | 0.25 | 0.13 | 0.23 | - | - | |
(S)-3,7-Dimethyl-7-octen-1-ol | - | - | 0.54 | 0.29 | - | - | - | - | |
D-Citronellol | - | - | 58.89 | 29.49 | 38.32 | 23.00 | 2.02 | 1.22 | |
3,7-Dimethyl-2,6-octadien-1-ol | - | - | 2.07 | 3.63 | 9.65 | 7.27 | 0.68 | 0.44 | |
trans-Shisool | - | - | - | - | 0.16 | - | - | - | |
1-Tridecanol | - | - | 0.27 | - | - | - | - | - | |
2-Octen-1-ol | - | - | - | - | - | 0.19 | - | - | |
Aldehydes | (E)-2-Hexenal | - | - | - | 0.15 | 0.68 | 2.19 | - | - |
(+)-Rhodinal | 0.27 | 1.74 | - | - | - | - | - | - | |
(E)-Citral | - | - | 0.33 | 0.33 | 1.18 | 0.65 | - | - | |
Rhodinal | - | - | 0.33 | 0.20 | - | 0.22 | - | - | |
Esters | Ethyl octanoate | - | - | - | 0.23 | 2.31 | 0.69 | - | - |
Octyl acetate | - | 0.13 | - | - | 2.99 | 0.22 | 3.42 | 1.10 | |
Ethyl benzoate | 0.41 | - | - | - | - | - | - | - | |
Methyl hexadecanoate | - | - | 0.11 | - | - | - | - | - | |
cis-3-Hexenyl acetate | - | 0.14 | 0.96 | 0.50 | 6.59 | 1.07 | 0.14 | - | |
Methyl cinnamate | - | - | 2.03 | 0.61 | 0.11 | 0.15 | - | - | |
Ethyl cinnamate | - | - | 0.20 | - | - | - | - | - | |
Citronellol acetate | - | - | - | - | 0.81 | 0.16 | - | - | |
5-Methyl-2-(1-methylethenyl)-4-hexen-1-ol acetate | - | - | - | - | 5.68 | 0.44 | 0.81 | 0.36 | |
Alkanes | 1-Dodecene | - | 0.21 | - | 0.52 | 0.33 | - | - | - |
Caryophyllene | 0.30 | 1.36 | 26.28 | 16.43 | 2.07 | 3.82 | - | - | |
α-Caryophyllene | - | 2.54 | 3.32 | 1.55 | 6.06 | 0.45 | 0.95 | 0.14 | |
Azulene | - | - | 0.10 | - | - | - | - | - | |
Phellandrene | - | - | 0.97 | 2.79 | 4.14 | 1.51 | - | - | |
Myrcene | - | - | 9.42 | 4.56 | 14.63 | 6.50 | 0.21 | 0.14 | |
D-Limonene | - | - | 0.61 | 0.27 | 0.86 | 0.45 | - | - | |
(Z)-3,7-Dimethyl-1,3,6-octatriene | - | - | 5.89 | 6.26 | 127.49 | 46.21 | 2.99 | 1.43 | |
m-Cymene | - | - | 1.09 | 1.20 | 5.04 | 1.44 | - | - | |
Cyclopentadiene,1,2,3,4,5-pentamethyl- | - | - | 0.28 | 0.14 | - | - | - | - | |
1-Cyclopropyl-propane | - | 0.14 | - | - | - | - | - | ||
(2E,4E,6E)-3,4-Dimethyl-2,4,6-octatriene | - | - | 0.77 | 1.00 | 15.59 | 4.97 | 0.17 | 0.11 | |
(E,Z)-2,6-Dimethyl-2,4,6-octatriene | - | - | 1.27 | - | 26.54 | 8.21 | 0.15 | 0.11 | |
1-Puenyl-1-butene | - | - | 0.29 | - | - | - | - | - | |
2-Ethenyl-1,1-dimethyl-3-methylene-cyclohexane | - | - | - | 0.37 | 6.01 | 4.49 | - | 0.13 | |
Tricyclo[4,2,2,0(1,5)]dec-7-ene | - | - | - | 0.26 | 2.01 | 0.68 | - | - | |
Ethylbenzene | - | - | - | - | - | - | 1.88 | 0.82 | |
Ketones | 3-Methyl-2-pent-2-enyl-cyclopent-2-enone | - | - | 0.17 | - | - | - | - | - |
4-(2,2-Dimethyl-6-methylenecyclohexylidene)-3-methylbutan-2-one | - | - | 0.12 | - | - | - | - | - | |
Perhydrofarnesyl acetone | - | - | - | - | 0.11 | - | - | - |
Note: “-” Not detected or not existed.
Developmental |
Treatment | Total content |
Contents of aromatic compounds (μg·g-1) | ||||
---|---|---|---|---|---|---|---|
Alcohols | Aldehydes | Esters | Alkanes | Ketones | |||
S1 | Control | 2.32 | 1.09 | 0.28 | 0.55 | 0.38 | - |
PBZ | 10.01 | 3.60 | 1.84 | 0.32 | 4.22 | - | |
S2 | Control | 135.59 | 80.92 | 0.66 | 3.30 | 50.41 | 0.29 |
PBZ | 87.64 | 49.82 | 0.72 | 1.47 | 35.54 | - | |
S3 | Control | 312.54 | 75.02 | 8.04 | 18.51 | 210.80 | 0.17 |
PBZ | 124.38 | 39.67 | 3.08 | 2.78 | 78.78 | - | |
S4 | Control | 18.65 | 7.60 | - | 4.47 | 6.49 | - |
PBZ | 8.45 | 3.86 | - | 1.61 | 2.92 | - |
Note: “-” Not detected or not existed.