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. 2022 Jan 19;11(3):263.
doi: 10.3390/plants11030263.

Potassium and Humic Acid Synergistically Increase Salt Tolerance and Nutrient Uptake in Contrasting Wheat Genotypes through Ionic Homeostasis and Activation of Antioxidant Enzymes

Ghulam Abbas  1 , Sadia Rehman  1 , Manzer H Siddiqui  2 , Hayssam M Ali  2 , Muhammad Ansar Farooq  3 , Yinglong Chen  4   5
Affiliations

Potassium and Humic Acid Synergistically Increase Salt Tolerance and Nutrient Uptake in Contrasting Wheat Genotypes through Ionic Homeostasis and Activation of Antioxidant Enzymes

Ghulam Abbas et al. Plants (Basel). .

Abstract

Salinity limits the growth and nutrient uptake in crop species. Studies show that both potassium (K) and humic acid (HA) improved plant tolerance to salinity. However, the interactive effect of K and HA on plant tolerance to salinity stress remains unknown. This pot study examined the effect of application of K (0, 5 or 10 mM) and HA (0 or 2 g kg-1), alone or in combination, on the growth and physiology under salinity (100 mM NaCl) in two wheat genotypes (SARC 1, salt tolerant; and SARC 5, salt sensitive). The results revealed that salt stress reduced shoot biomass by 35% and 49% in SARC 1 and SARC 5, respectively. Salinity induced overproduction of H2O2 and lipid peroxidation in both genotypes, but the decline in pigments and stomatal conductance was more profound in SARC 5 than in SARC 1. Combined application of 10 mM K and HA was most effective in alleviating salt stress with improved plant biomass by 47% and 43% in SARC 1 and SARC 5, respectively. Combined application of 10 mM K and HA mitigated salt and induced oxidative stress with the activities of APX, CAT, POD and SOD increased by up to 2.8 folds in SARC 1, and by upto 2.5 folds in SARC 5, respectively. Root and shoot Na contents were increased, while K, Fe and Zn contents were decreased under saline conditions. HA combined with K decreased Na and increased K, Fe and Zn contents in both genotypes. Combined application of 10 mM K and HA was more promising for increasing wheat salt tolerance and nutrient uptake and genotype SARC 1 performed better than SARC 5 for cultivation on saline soils.

Keywords: ROS; antioxidants; humic acid; potassium; salinity.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Effect of various treatments: 1; control, 2; salinity, 3; salinity + 5K, 4; salinity + 10K, 5; salinity + HA, 6; salinity + 5K+ HA, 7; salinity + 10K+ HA on growth of salt tolerant (SARC 1) and salt sensitive (SARC 5) wheat genotypes.
Figure 1
Figure 1
Effect of various treatments: 1; control, 2; salinity, 3; salinity + 5K, 4; salinity + 10K, 5; salinity + HA, 6; salinity + 5K+ HA, 7; salinity + 10K+ HA on growth of salt tolerant (SARC 1) and salt sensitive (SARC 5) wheat genotypes.
Figure 2
Figure 2
Effect of potassium (5, 10 mM K) and humic acid (HA, 2 g kg−1) on shoot Na (A), root Na (B), shoot K (C) and root K (D) concentrations of salt tolerant (SARC 1) and salt sensitive (SARC 5) wheat genotypes exposed to exposed to 100 mM NaCl salt stress (S). DW, dry weight. For each trait, bar data with the same letter indicate no significant difference between treatments (p < 0.05).
Figure 3
Figure 3
Effect of potassium (5, 10 mM K) and humic acid (HA, 2 g kg−1) on shoot Fe (A), root Fe (B), shoot Zn (C) and root Zn (D) of salt tolerant (SARC 1) and salt sensitive (SARC 5) wheat genotypes exposed to 100 mM NaCl salt stress (S). DW, dry weight. For each trait, bar data with the same letter indicate no significant difference between treatments (p < 0.05).
Figure 4
Figure 4
Effect of potassium (5, 10 mM K) and humic acid (HA, 2 g kg−1) on H2O2 contents (A), TBARS contents (B) and membrane stability index (C) of salt tolerant (SARC 1) and salt sensitive (SARC 5) wheat genotypes exposed to 100 mM NaCl salt stress (S). FW, fresh weight; TBARS, thiobarbituric acid reactive substances; MSI, membrane stability index. For each trait, bar data with the same letter indicate no significant difference between treatments (p < 0.05).
Figure 5
Figure 5
Effect of potassium (5, 10 mM K) and humic acid (HA, 2 g kg−1) on the activities of SOD (A) CAT (B), POD (C) and APX (D) of salt tolerant (SARC 1) and salt sensitive (SARC 5) wheat genotypes exposed to 100 mM NaCl salt stress (S). For each trait, bar data with the same letter indicate no significant difference between treatments (p < 0.05).
Figure 5
Figure 5
Effect of potassium (5, 10 mM K) and humic acid (HA, 2 g kg−1) on the activities of SOD (A) CAT (B), POD (C) and APX (D) of salt tolerant (SARC 1) and salt sensitive (SARC 5) wheat genotypes exposed to 100 mM NaCl salt stress (S). For each trait, bar data with the same letter indicate no significant difference between treatments (p < 0.05).
Figure 6
Figure 6
Principal component analysis of (A) response variables and (B) treatments and wheat genotypes exposed to 100 mM NaCl salt stress (S) supplemented with/without potassium (5, 10 mM K) and humic acid (HA, 2 g kg−1). V1, SARC 1; V2, SARC 5.
Figure 7
Figure 7
Plant growth, nutrient uptake, pigments, and oxidative stress attributes of salt tolerant (SARC 1) and salt sensitive (SARC 5) wheat genotypes exposed to 100 mM NaCl with and without potas-sium (K) and humic acid (HA). Plants supplemented with combined K and HA showed better salt tolerance and biomass production than without K and HA. Greater salt tolerance of SARC 1 than SARC 5 is mainly attributed to limited uptake of Na and higher activities of antioxidants.
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References

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