Among the amendments tested on sugar beet seedlings in saline-alkali soil, sulfuric-acid-modified biochar was associated with the strongest reported growth and physiological responses. Compared with untreated saline-alkali soil, the BS treatment showed 24.75% greater plant height, 15.61% greater leaf area and a 139.44% increase in aboveground dry weight. Fresh weight was 34.30% higher.
The experiment asked whether different acid-modified biochars could improve sugar beet growth and physiology under saline-alkali conditions, including antioxidant activity and membrane permeability. It compared untreated soil with soil receiving 2% unmodified biochar or 2% biochar modified with phosphoric, sulfuric, nitric, fulvic or citric acid. Each of the seven treatment groups had 10 replicates.
The modification process used a final hydrogen-ion concentration of 1 mol L-1. In the reported procedure, 900 g of biochar was mixed with 9 L of acid solution at a 1:10 weight-to-volume ratio, stirred at 200 rpm and 25 ± 2 degrees Celsius for 24 hours, with manual stirring every two hours, then rinsed until the filtrate reached pH 6.5 to 7.0. Treatment means were compared with one-way ANOVA and Tukey post hoc tests. The reported summary values used means ± SD from five biological replicates per treatment, with statistical differences set at P < 0.05.
Growth and photosynthesis moved together
BS also stood out in the leaf pigments measured. Relative to CK, chlorophyll a was 99.63% higher, chlorophyll b was 132.61% higher, carotenoids were 64.95% higher and total chlorophyll was 205.07% higher. The abstract describes the same broad pattern across the acid-modified treatments, with higher physiological performance than under saline-alkali conditions and the strongest reported effects in BS.
Net photosynthesis followed the pattern. BS had an 86.22% higher net photosynthetic rate, or Pn, than CK, with the reported P value below 0.05, the study's threshold for a statistical difference. But the gas-exchange response was not uniformly higher: intercellular CO2 concentration, transpiration rate and stomatal conductance generally decreased across the biochar treatments.
Chlorophyll fluorescence measures gave a similar signal for photosystem II, a part of the photosynthetic machinery tracked by the study. PIABS was 147.35% higher in BS than CK, while Fv/Fm was 4.13% higher. The study also reported higher cross-sectional and specific fluorescence energy flux under BS, along with increases in its listed electron-flow and electron-transport indicators.
The stress response was more complicated
The antioxidant results did not all move in the same direction. Relative to CK, BS was associated with 23.53% lower SOD activity and 22.43% higher CAT activity. Staining showed visibly reduced reactive oxygen species, or ROS, deposition in all acid-modified biochar treatments.
Membrane-related measures were more qualified. Relative electrical conductivity, one of the study's membrane indicators, was 6.79% lower in BS than in CK, and the decrease was statistically significant. MDA, another reported membrane indicator, was 18.01% lower, but that decrease was not significant. The split result means the two measures did not provide equally strong statistical support for a membrane effect.
To examine how the measurements fitted together, the authors used partial least-squares path modeling, or PLS-PM, a statistical model that maps associations among variables. Within BS, the model identified photosynthetic pigment content and osmotic-adjustment substances as primary factors associated with aboveground growth. It also linked chlorophyll variation with light absorption, photosynthetic rates and fluorescence characteristics. Those links are model-based associations, not demonstrations that one process caused another.
A strong result with a narrow reach
The same caution applies to the treatment comparison. The authors report that the physicochemical properties of the modified biochars were not directly characterized, limiting the link between the materials and the plant responses. The experiment was also a short-term pot study at the seedling stage, so it cannot establish whether the pattern would hold beyond that setting.
The clearest conclusion is therefore comparative: BS was the strongest-performing amendment in the reported set. The study leaves open which unmeasured biochar properties account for the differences and whether the same physiological pattern extends beyond the tested seedlings and soil.
Paper data and sources
Original title: Acid-modified biochar improves the adaptability of sugar beet seedlings to saline-alkali soil by enhancing their physiology.
Authors: Chuanhe Zhao, Piao Yunuo, Jean Wan Hong Yong et al.
Journal/Repository: BMC plant biology
Status: Peer-reviewed
First online: 2026-08-20
DOI: 10.1186/s12870-026-09769-z
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