Effects of Different Modified Biochars on Growth of Kosteletzkya virginica and Corresponding Transcriptome Analysis

Abstract

Modified biochar can effectively improve the quality and environment of coastal saline-alkali soil, but its effects on the growth and development of halophytes and its mechanism are still unclear. This study systematically evaluated the growth-promoting effects and preliminary mechanisms of H₃PO₄-modified biochar (HBC) and H₃PO₄-kaolinite-biochar composite (HBCK) on the economically important halophyte Kosteletzkya virginica. The results demonstrated that the application of HBC/HBCK significantly enhanced plant growth, resulting in increases of over 55% in plant height and greater than 100% in biomass relative to the control. Multidimensional mechanistic analysis revealed the following: (1) accumulation of nitrogen (N), phosphorus (P), and potassium (K) increased by at least 40%, significantly enhancing nutrient uptake; (2) increases in the activities of superoxide dismutase (SOD) and peroxidase (POD) by over 100% and 70%, respectively, markedly boosting antioxidant capacity and effectively alleviating oxidative stress; (3) molecular regulation via the activation of transcription factor networks (HSP, MYB, TCP, AP2/ERF, bZIP, and NLP) and modulation of key genes in ABA, BR, and JA signaling pathways (CYP707A, CYP90, and OPR2), establishing a multi-layered stress adaptation and growth promotion system. Beyond assessing the growth-promoting effects of modified biochars, this study provides novel insights into the regulatory transcription factor networks and phytohormone signaling pathways, offering theoretical foundations for the molecular design of biochars for saline-alkali soil remediation.

Keywords: Kosteletzkya virginica; modified biochar; phytohormone signaling; salt–alkali tolerance; transcription factor network.

Figure 1

The effects of different modified biochar applications on the growth indicators of K. virginica. (A). Growth morphology of K. virginica after the application of different modified biochars. (B). Statistical chart of the plant height of K. virginica after the application of different modified biochars. (C). Statistical chart of the aboveground biomass of K. virginica after the application of different modified biochars. (D). Statistical chart of the underground biomass of K. virginica after the application of different modified biochars; different small letters in each column indicate significant differences (p < 0.05) among biochars and modified biochar composites. (CK: control group; BC: raw corn straw biochar; HBC: H₃PO₄-modified biochar; BCM: montmorillonite–biochar composite; HBCM: H₃PO₄–montmorillonite–biochar composite; BCK: kaolinite–biochar composite; HBCK: H₃PO₄–kaolinite–biochar composite.).

Figure 2

The effects of different modified biochar applications on the nutrition indicators of K. virginica. (A). The nitrogen content of K. virginica after the application of different modified biochars. (B). The phosphorus content of K. virginica after the application of different modified biochars. (C). The potassium content of K. virginica after the application of different modified biochars; different small letters in each column indicate significant differences among biochars and modified biochar composites; p < 0.05. (CK: control group; BC: raw corn straw biochar; HBC: H₃PO₄-modified biochar; BCM: montmorillonite–biochar composite; HBCM: H₃PO₄–montmorillonite–biochar composite; BCK: kaolinite–biochar composite; HBCK: H₃PO₄–kaolinite–biochar composite.).

Figure 3

The effects of different modified biochar applications on the antioxidant enzyme activity of K. virginica. (A). The effects of applying different modified biochars on the SOD activity of K. virginica. (B). The effects of applying different modified biochars on the POD activity of K. virginica. Different small letters in each column indicate significant differences among biochars and modified biochar composites; p < 0.05. (CK: control group; BC: raw corn straw biochar; HBC: H₃PO₄-modified biochar; BCM: montmorillonite–biochar composite; HBCM: H₃PO₄–montmorillonite–biochar composite; BCK: kaolinite–biochar composite; HBCK: H₃PO₄–kaolinite–biochar composite.).

Figure 4

Volcanic and Venn diagram analysis of differential gene numbers. (A). Volcanic map of differential genes between BC and CK. (B). Volcanic map of differential genes between HBC and CK. (C). Volcanic map of differential genes between HBCK and CK. (D). Venn plots of BC vs. CK and HBC vs. CK. (E). Venn plots of BC vs. CK and HBCK vs. CK. (CK: control group; BC: raw corn straw biochar; HBC: H₃PO₄-modified biochar; HBCK: H₃PO₄–kaolinite–biochar composite.).

Figure 5

GO enrichment classification analysis of differentially expressed genes. (A). GO enrichment classification analysis of differentially expressed genes treated with HBC. (B). GO enrichment classification analysis of differentially expressed genes treated with HBCK. (HBC: H₃PO₄-modified biochar; HBCK: H₃PO₄–kaolinite–biochar composite.).

Figure 6

Differential gene analysis of the co-enrichment of HBC and HBCK. (A). Venn plots of oxidoreductase-activity-related genes co-enriched by HBC and HBCK. (B). Venn plots of transcriptional-regulation-activity-related genes co-enriched by HBC and HBCK. (C). Heat map of the expression of oxidoreductase genes co-enriched with HBC and HBCK. (D). Heat map of the expression of transcription factor genes co-enriched by HBC and HBCK. (CK: control group; HBC: H₃PO₄-modified biochar; HBCK: H₃PO₄–kaolinite–biochar composite; CKX: cytokinin oxidase/dehydrogenase; POD72: peroxidase 72; CYP: cytochrome P450 genes; OPR2: 12-oxophytodienoate reductase 2; NQO1: NAD(P)H: quinone oxidoreductase 1; CP47: photosystem II CP47 reaction center protein gene; LOX2: lipoxygenase 2; HSFA2: heat shock transcription factor A2; HB12: homeodomain-leucine zipper class I, TIE: TCP transcription factor; TINY2: AP2/ERF transcription factor; NLP2: NLP transcription factor; MYB108: MYB transcription factor.).

Figure 7

KEGG enrichment analysis of differentially expressed genes. (A). KEGG enrichment analysis of differentially expressed genes treated with HBC. (B). Waffle diagram of plant hormone-signal-transduction-related genes induced by HBC. (C). KEGG classification analysis of differentially expressed genes treated with HBCK. (D). Waffle diagram of plant hormone-signal-transduction-related genes induced by HBCK. (HBC: H₃PO₄-modified biochar; HBCK: H₃PO₄–kaolinite–biochar composite; IAA: auxin; ABA: abscisic acid; GA: gibberellin; JA: jasmonic acid; SA: salicylic acid; BR: brassinosteroid).

Figure 8

RT-qPCR analysis of differentially expressed genes. ** in each column indicates significant differences among CK and modified biochar composites (HBC and HCBK); p < 0.01. (CK: control group; HBC: H₃PO₄-modified biochar; HBCK: H₃PO₄–kaolinite–biochar composite.).