Edited by: Jayakumar Bose, University of Adelaide, Australia
Reviewed by: Sudisha Jogaiah, Karnatak University, India; Parvaiz Ahmad, Sri Pratap College Srinagar, India
This article was submitted to Plant Abiotic Stress, a section of the journal Frontiers in Plant Science
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Soil salinization and alkalization greatly restrict crop growth and yield. In this study, NaCl (8 g kg−1) and Na2CO3 (8 g kg−1) were used to create saline stress and alkaline stress on cotton in pot cultivation in the field, and organic polymer compound material (OPCM) and stem girdling were applied before cotton sowing and at flowering and boll-forming stage, respectively, aiming to determine the effects of OPCM on K+ and Na+ absorption and transport and physiological characteristics of cotton leaf and root. The results showed that after applying the OPCM, the Na+ content in leaf of cotton under saline stress and alkaline stress were decreased by 7.72 and 6.49%, respectively, the K+/Na+ ratio in leaf were increased by 5.65 and 19.10%, respectively, the Na+ content in root were decreased by 9.57 and 0.53%, respectively, the K+/Na+ ratio in root were increased by 65.77 and 55.84%, respectively, and the transport coefficients of K+ and Na+ from leaf to root were increased by 39.59 and 21.38%, respectively. The activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), and the relative electrical conductivity (REC) in cotton leaf were significantly increased, while the content of malondialdehyde (MDA) was decreased; but the changes in those in root were not significant. The boll weights were increased by 11.40 and 13.37%, respectively, compared with those for the control. After stem girdling, the application of OPCM still promoted the ion transport of cotton organs; moreover, the CAT activity in root was increased by 25.09% under saline stress, and the SOD activity in leaf and CAT in root were increased by 42.22 and 6.91%, respectively under alkaline stress. Therefore, OPCM can significantly change the transport of K+ and Na+ to maintain the K+ and Na+ homeostasis in leaf and root, and regulate physiological and biochemical indicators to alleviate the stress-induced damage. Besides, the regulation effect of OPCM on saline stress was better than that on alkaline stress.
Soil salinization causes abiotic stress to crops and greatly limits crop growth. It has become one of the global environmental problems for agriculture production (
Cotton is one of the important economic crops in the world. However, saline and alkaline stresses have caused low emergence rate and low boll set rate in cotton cultivation in many regions (
This study used cotton in the flowering and boll-forming stage as the study material, combined with stem girdling, to explore the effects of organic polymer compound material (OPCM) on K+ and Na+ transport and accumulation as well as oxidative damage in cotton organs under saline and alkaline stresses. We hypothesized: (1) the K+ and Na+ transport and physiological regulation in cotton organs might be different under saline and alkaline stresses; (2) OPCM might regulate the transport of K+ and Na+ in cotton organs; and (3) OPCM might maintain the ion homeostasis through regulating catalase (CAT) activity in cotton leaf and root to reduce saline and alkaline stresses on cotton. This study helps us understand how OPCM regulates ion transport and physiological characteristics of crops under saline and alkaline stresses, and provides a good method for reducing the saline and alkaline stresses on cotton cultivated in arid areas.
The experiment was conducted in Shihezi Grape Research Institute (44°20' N, 86°03' E) in 2018 and 2019. The climate is temperate continental. The test soil is gray desert soil, with soil pH of 7.72, soil cation exchange capacity of 17.32 cmol kg−1, soil organic matter of 12.5 g kg−1, alkali-hydrolyzed nitrogen of 54 mg kg−1, available phosphorus of 11.7 mg kg−1, and available potassium of 218 mg kg−1. The cotton variety is Xinluzao 62.
On April 25, 2018, salinization and alkalization of soils were carried out in the way of applying NaCl and Na2CO3, respectively, making the soil salt content reach 8 g kg−1. The pH value of salinized soil was 8.24, and soil electric conductivity (1:5) was 4.24 ds m−1; the pH value of alkalized soil was 9.78, and soil electric conductivity (1:5) was 2.78 ds m−1. On April 20, 2019, salinization and alkalization of soils were carried out in the same way, making the soil salt content reach 8 g kg−1. The pH value of salinized soil was 8.11, and soil electric conductivity (1:5) was 4.83 ds m−1; the pH value of alkalized soil was 9.62, and soil electric conductivity (1:5) was 2.57 ds m−1. There were eight treatments in total, S: salinized soil; A: alkalized soil (
Test design.
Group | Phloem girdling | Compound material application |
---|---|---|
S | No girdling | No added |
A | No girdling | No added |
S1 | No girdling | Organic polymer compound material |
A1 | No girdling | Organic polymer compound material |
S-J | Stem girdling | No added |
A-J | Stem girdling | No added |
S1-J | Stem girdling | Organic polymer compound material |
A1-J | Stem girdling | Organic polymer compound material |
Salinized soil and alkalized soil were separately put into barrels (50 cm in diameter and 60 cm in height), and barrels were buried in the field on April 2018 and 2019. Urea of 360 kg hm−2 and compound fertilizer (N: P2O5: K2O = 20: 9: 9) of 795 kg hm−2 were applied on April, 2018 and 2019. Cotton was sown in barrels on May 4. OPCM (300 kg hm−2) was dissolved in water and irrigated before seedling emergence on June 25. After emergence, six plants were retained per barrel. During the whole growth period, the total irrigation volume was 4,500 m3 hm−2, and the irrigated cycle was 10 days. Nine times of irrigation totally were conducted. No fertilizers and OPCM were applied in the later. On July 25 (in the flowering and boll-forming stage), girdling (width: 1 cm) on cotton main stem was performed. Five plant samples were collected from each treatment for the determination of physiological and biochemical indicators on August 10, 2018, and three cotton plants were randomly collected from different plots to determine the ion content. On August 5, 2019, three cotton plants were collected from the barrels to determine the growth indexes.
Samples were collected in the flowering and boll-forming stage in 2018 and 2019, and three plants from each treatment were collected and taken back to the lab. Plants were washed, and root, stem (including leaf sheath), and leaf were isolated. After that, organs were dried in an oven at 105°C for 30 min, and then dried at 75°C to the constant weight. Meanwhile, the boll weight of six cotton plants from each treatment was determined.
The content of thiobarbituric acid reactants (TBARS) was measured according to the method of
Preparation of enzyme extract: Potassium phosphate buffer (5 ml, 50 mM, pH: 7.8) was added to 0.5 g sample of each organ and ground to homogenate after an ice bath (
The soluble sugar content was measured according to the method of
The soluble protein content was measured according to the method of
Dried organ samples were pulverized. After that, 0.1 g pulverized sample was weighed, and 5 ml 98% H2SO4 and 300 g·l−1 H2O2 were added. The solution was heated until the liquid become transparent, and then distilled water was added to make the volume to 100 ml. After that, 5 ml of test solution was pipetted, and distilled water was added to make the volume to 50 ml. Finally, the solution was measured with flame photometer (FP6410 flame photometer, Shanghai Yidian Scientific Instrument Co., Ltd., China;
Selective transport of K+ and Na+ (STK-Na) in different cotton organs was measured according to the method proposed by
The higher the
Excel 2010 and Origin 8.5 software were used to process data and draw charts, respectively. One-way ANOVA and Duncan multiple-range tests in SPSS 23.0 software were used to test the significance of differences at
The plant height, root length, and total dry matter of cotton for the S1 and S treatments were higher than those for the A1 and A treatments; and the plant height, root length, and total dry matter for the S1 and A1 treatments were higher than those for the S and A treatments (
Effects of compound material on the growth indexes of cotton under saline and alkaline stresses.
Year | Treat | Plant height (cm) | Root length (cm) | Total dry matter (g) | Boll weight (g barrel−1) |
---|---|---|---|---|---|
2018 | S | 74.25 ± 1.77ab | 23.00 ± 2.83ab | 54.04 ± 1.01bc | 216.70 ± 10.49b |
S1 | 77.00 ± 1.41a | 26.50 ± 2.12a | 60.60 ± 3.97a | 250.14 ± 7.36a | |
A | 71.50 ± 2.12b | 19.00 ± 2.83b | 50.41 ± 1.12c | 218.22 ± 9.06b | |
A1 | 74.75 ± 3.89ab | 23.75 ± 2.47ab | 57.86 ± 0.53ab | 246.29 ± 12.08a | |
2019 | S | 59.40 ± 1.42a | 19.09 ± 2.35a | 45.93 ± 0.86ab | 175.52 ± 8.50b |
S1 | 63.14 ± 1.16a | 21.47 ± 1.72a | 49.69 ± 2.78a | 210.12 ± 6.18a | |
A | 57.92 ± 1.72a | 16.15 ± 2.41ab | 42.34 ± 0.95b | 185.49 ± 7.70b | |
A1 | 62.79 ± 2.72a | 19.71 ± 2.05a | 48.60 ± 0.45a | 201.96 ± 9.43ab |
S, S1 indicate no compound material was applied in salinized soil, organic polymer was applied in salinized soil, respectively; A, A1 indicate no compound material was applied in alkalized soil, organic polymer was applied in alkalized soil, respectively. Values are means ± SD of three independent replications (
For non-girdling cottons, the MDA content in root for the A treatment was significantly decreased by 14.08%, and the MDA content in leaf for the S1 treatment was significantly decreased by 47.50%, compared with that for the S treatment. No significant differences were found in the MDA content in leaf between the S treatment and A treatment and the MDA content in root between the S1 treatment and the S treatment. The MDA content in leaf for the A1 treatment was significantly decreased by 31.85%, while the MDA content in root was significantly increased by 27.68%, compared with those for the A treatment. For stem-girdling cottons, the MDA content in leaf for the S1-J treatment and the A1-J treatment were significantly decreased by 43.00 and 35.96%, respectively, while the MDA content in root were significantly increased by 19.61 and 73.73%, respectively, compared with those for the A-J treatment (
Effects of compound material on malondialdehyde (MDA) and relative electrical conductivity (REC) of cotton leaf and root under saline and alkaline stresses. S, S1 indicate no compound material was applied in salinized soil, organic polymer was applied in salinized soil, respectively; A, A1 indicate no compound material was applied in alkalized soil, organic polymer was applied in alkalized soil, respectively. Bars represent SD of the mean (
For non-girdling cottons, there were no significant differences in the relative conductivity in leaf and root between the A treatment and the S treatment. The relative conductivity in leaf for the S1 treatment was significantly increased by 24.02% compared with that for the S treatment, while no significant difference was found between the A1 treatment and the A treatment. The relative conductivity in root for the S1 treatment was significantly decreased by 6.00% compared with that for the S treatment, and the relative conductivity in root for the A1 treatment was significantly decreased by 7.45% compared with that for the A treatment. For stem-girdling cottons, there were no significant differences in the relative conductivity in leaf and root between the A1-J treatment and the A-J treatment. However, the relative conductivity in root for the S1-J treatment was significantly decreased by 19.00% compared with that for the S-J treatment, and no significant difference was found in the relative conductivity in leaf (
For non-girdling cottons, the SOD activity in leaf for the A treatment was significantly increased by 21.29% compared with that for the S treatment, and no significant difference was found in the SOD activity in root. The SOD activity in leaf for the S1 treatment was significantly increased by 18.93% compared with that for the S treatment, and no significant difference was found in the SOD activity in root. There was also no significant difference in the SOD activity in leaf and root between the A1 treatment and the A treatment. For stem-girdling cottons, the SOD activity in leaf for the A1-J treatment was significantly increased by 42.22% compared with that for the A-J treatment, and no significant difference was found in the SOD activity in root. There was also no significant difference in the SOD activity in leaf and root between the S1-J treatment and the S-J treatment (
Effects of compound material on Antioxidant enzyme activities of cotton leaf and root under saline and alkaline stresses. S, S1 indicate no compound material was applied in salinized soil, organic polymer was applied in salinized soil, respectively; A, A1 indicate no compound material was applied in alkalized soil, organic polymer was applied in alkalized soil, respectively. Bars represent SD of the mean (
Effects of compound material on osmotic substances in leaf and root of cotton under saline and alkaline stresses. S, S1 indicate no compound material was applied in salinized soil, organic polymer was applied in salinized soil, respectively; A, A1 indicate no compound material was applied in alkalized soil, organic polymer was applied in alkalized soil, respectively. Bars represent SD of the mean (
For non-girdling cottons, the POD activity in root for the A treatment was significantly decreased by 15.41% compared with that for the S treatment, and no significant difference was found in the POD activity in leaf. The POD activity in leaf for the S1 treatment was significantly increased by 24.70% compared with those for the S treatment, and the POD activity in root for the A1 treatment was significantly decreased by 37.10% compared with those for the A treatment. No significant differences were found in the POD activity in leaf between the A1 and the A treatment and in the POD activity in root between the S1 and S treatment. For stem-girdling cottons, the POD activity in leaf for the S1-J treatment was significantly decreased by 8.60% compared with that for the S treatment, and no significant difference was found in the POD activity in root. The POD activity in root for the A1-J treatment was significantly decreased by 13.34% compared with that for the A-J treatment, and no significant difference was found in the POD activity in leaf (
For non-girdling cottons, the CAT activity in root for the A treatment was significantly decreased by 51.15% compared with that for the S treatment, and no significant difference was found in the CAT activity in leaf. There were also no significant differences in the CAT activity in leaf and root between the S1 treatment and the S treatment and between the A1 treatment and the A treatment. For stem-girdling cottons, the CAT activity in root for the S1-J treatment was increased by 25.09% compared with that for the S-J treatment, and the CAT activity in root for the A1-J treatment were increased by 6.91% compared with that for the A-J treatment, and no significant difference was found in the CAT activity in leaf between the S1-J treatment and the A1-J treatment (
For non-girdling cottons, the soluble sugar content in root for the A treatment was significantly increased by 38.04%, and no significant difference was found in the soluble sugar content in leaf, compared with those for the S treatment. The soluble sugar content in leaf for the S1 treatment was significantly increased by 62.14%, and no significant difference was found in the soluble sugar content in root, compared with those for the S treatment. The soluble sugar content in root for the A1 treatment was significantly increased by 49.87%, and no significant difference was found in the soluble sugar content in leaf, compared with those for the A treatment. For stem-girdling cottons, the soluble sugar content in leaf for the S1-J treatment was significantly increased by 30.16%, and no significant difference was found in the soluble sugar content in root, compared with those for the S-J treatment. The soluble sugar content in leaf and root for the A1-J treatment was significantly increased by 14.94 and 11.17%, respectively, compared with those for the A-J treatment (
Effects of compound material on K+ and Na+ contents in leaf and root of cotton under saline and alkaline stresses. S, S1 indicate no compound material was applied in salinized soil, organic polymer was applied in salinized soil, respectively; A, A1 indicate no compound material was applied in alkalized soil, organic polymer was applied in alkalized soil, respectively. Bars represent SD of the mean (
For non-girdling cottons, there were no significant differences in the soluble protein content in leaf and root between the A treatment and the S treatment. The soluble protein content in leaf for the S1 treatment was significantly increased by 24.72% compared with that for the S treatment, while no significant difference was found between the A1 treatment and the A treatment. The soluble protein content in root for the A1 treatment was significantly increased by 23.23% compared with that for the A treatment, while no significant difference was found between the S1 treatment and the S treatment. For stem-girdling cottons, the soluble protein content in leaf for the S1-J treatment was significantly increased by 47.68% compared with that for the S-J treatment, while no significant difference was found between the A1-J treatment and the A-J treatment. There were no significant differences in the soluble protein content in root between the S1-J treatment and the S-J treatment and between the A1-J treatment and the A-J treatment (
After the application of OPCM, the content of K+ in root and leaf were increased compared with that for the control, while the content of Na+ in leaf and root was decreased; the K+ and Na+ contents in leaf were higher than those in root. For non-girdling cottons, the content of K+ and Na+ in leaf for the A treatment were significantly increased by 33.82 and 20.60%, respectively compared with those for the S treatment, while no significant difference was found in the content of K+ and Na+ in root. The content of K+ in root for the S1 treatment was significantly increased by 49.84% compared with that for the S treatment, while no significant differences were found in the content of Na+ in root and K+ and Na+ in leaf. The content of K+ in root for the A1 treatment was significantly increased by 30.63% compared with that for the A treatment, while the content of Na+ in leaf was significantly decreased by 6.49%; there was no significant difference in the content of K+ in leaf and Na+ in root. For stem-girdling cottons, the content of K+ in root for the S1-J treatment was significantly increased by 18.52% compared with that for the S-J treatment, while no significant differences were found in the content of K+ in leaf and Na+ in root and leaf. There was no significant differences in the content of K+ and Na+ in root and leaf between the A1-J treatment and the A-J treatment (
For non-girdling cottons, there was no significant differences in the K+/Na+ ratio in leaf and root between the A treatment and the S treatment. The K+/Na+ ratio in root for the S1 treatment was significantly increased by 65.77% compared with that for the S treatment, while no significant difference was found in the K+/Na+ ratio in leaf. The K+/Na+ ratio in root and leaf for the A1 treatment were significantly increased by 55.84 and 19.10%, respectively compared with those for the A treatment. The K+/Na+ ratio of cotton organs changed significantly under saline and alkaline stresses. For stem-girdling cottons, the K+/Na+ ratio in root for the S1-J treatment was significantly increased by 29.51% compared with that for the S-J treatment, while no significant difference was found in the K+/Na+ ratio in leaf. The K+/Na+ ratio in leaf for the A1-J treatment was significantly increased by 4.68% compared with that for the A-J treatment, while no significant difference was found in the K+/Na+ ratio in root (
Effects of compound material on K+/Na+ ratio of leaf and root under saline and alkaline stresses. S, S1 indicate no compound material was applied in salinized soil, organic polymer was applied in salinized soil, respectively; A, A1 indicate no compound material was applied in alkalized soil, organic polymer was applied in alkalized soil, respectively. Bars represent SD of the mean (
For non-girdling cottons, there was no significant difference in the STK-Na of stem-root and leaf-stem between the A treatment and the S treatment. The STK-Na of leaf-stem for the S1 treatment was significantly increased by 39.59% compared with that for the S treatment, while the STK-Na of stem-root was significantly decreased by 54.47%. The STK-Na of stem-root for the A1 treatment was significantly decreased by 37.27% compared with that for the A treatment, and no significant difference was found in the STK-Na of leaf-stem. For stem-girdling cottons, the STK-Na of stem-root for the S1-J treatment was significantly decreased by 37.55% compared with that for the S-J treatment, while no significant difference was found in the STK-Na of leaf-stem. There was an opposite result in the alkalized soil. The STK-Na of leaf-stem for the A1-J treatment was significantly increased by 32.53%, while the STK-Na of stem-root was significantly decreased by 35.54%, compared with those for the A-J treatment (
Effects of compound material on K+ and Na+ transport coefficients of cotton organs under saline and alkaline stresses.
Treat | STK-Na(leaf/stem) | STK-Na(stem/root) |
---|---|---|
S | 0.69 ± 0.09 b | 3.17 ± 0.08 a |
S1 | 0.96 ± 0.06 a | 1.44 ± 0.04 c |
A | 0.65 ± 0.08 b | 3.36 ± 0.05 a |
A1 | 0.79 ± 0.05 ab | 2.11 ± 0.10 b |
S-J | 0.46 ± 0.04 c | 3.69 ± 0.09 a |
S1-J | 0.55 ± 0.06 c | 2.31 ± 0.05 c |
A-J | 0.70 ± 0.01 b | 3.36 ± 0.17 b |
A1-J | 0.92 ± 0.03 a | 2.16 ± 0.06 c |
S, S1 indicate no compound material was applied in salinized soil, organic polymer was applied in salinized soil, respectively; A, A1 indicate no compound material was applied in alkalized soil, organic polymer was applied in alkalized soil, respectively. Values are means ± SD of three independent replications (
Redundancy analysis was used to analyze the effects of OPCM on K+ and Na+ absorption and physiological characteristics of leaf and root of cottons under saline and alkaline stresses. The results showed that root and leaf was separated by the RDA1 axis. CAT, MDA, and soluble protein (SP) had the highest correlations with the RDA1 axis, and SOD, POD, soluble sugar (SS), K+ content, Na+ content, K+/Na+ ratio, and relative electrical conductivity (REC) had the highest correlations with the RDA2 axis (
Redundancy analysis (RDA) of ion content and physiological characteristics of cotton under saline and alkaline stresses. Hollow legend represents leaf, and solid legend represents root. S, S1 indicate no compound material was applied in salinized soil, organic polymer was applied in salinized soil, respectively; A, A1 indicate no compound material was applied in alkalized soil, organic polymer was applied in alkalized soil, respectively.
Recent studies have shown that exogenous application of betaine and vanillic acid could significantly improve the salt tolerance of crops (
Under saline and alkaline stresses, the OPCM not only improved the physiological and biochemical indexes of cotton organs, but also regulated the transport efficiency of K+ and Na+. The difference in physiological damage could also affect the K+ and Na+ content of cotton under saline and alkaline stresses (
To further study the dynamic change of K+ and Na+, the ion selective coefficient (STK-Na) were calculated. It was found that although the transport efficiency of K+ and Na+ in organs of cotton with stem girdling was lower than that in organs of cotton without stem girdling, there was still a promoting effect (
In this study, the analysis of cotton without girdling treatment showed that the OPCM had different effects on saline stress and alkaline stress on cotton. The Na+ content in leaf and root of cotton under saline stress were lower than those of cotton under alkaline stress. The OPCM could improve the activities of POD and CAT, and further regulate the transport efficiency of K+ and Na+ in cotton leaf and root, to reduce the saline and alkaline stresses on cotton. The analysis of cotton with girdling treatment showed that the OPCM could increase the activities of SOD and CAT in leaf and root and the K+ content, and improve the saline and alkaline tolerance of cotton. The results further confirmed the potential of our self-developed OPCM in regulating NaCl stress and Na2CO3 stress on cotton.
The original contributions presented in the study are included in the article/
KW, XW, and MA conceived, designed, and conducted the experiments. JS and KC helped in conducting experiments. XW analyzed the data results and wrote the manuscript. KW and HF monitored the experimental work and critically commented on the manuscript. All authors contributed to the article and approved the submitted version.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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