Combination of biochar and silicon influenced the structural and phytochemical characteristics of triticale leaf under soil lead toxicity

Heavy metal (HM) contamination of agricultural soils poses a significant environmental challenge, threatening food security due to decreased plant growth and agricultural production. This study aimed to investigate the synergistic effects of silicon (Si) combined with biochar on the structural and phytochemical properties of triticale leaf under lead (Pb)-contaminated soil. A factorial pot experiment was carried out using a completely randomized design (CRD) to examine the effects of Si (0, 200, and 400 mg Si kg⁻¹ soil) in combination with sheep manure biochar (SMB), rice husk biochar (RHB), and municipal waste biochar (MWB) under Pb toxicity (500 mg Pb kg⁻¹ soil). The application of SMB at 200 mg Si kg⁻¹ (Si200) enhanced leaf weight and area by 108.3% and 29.7%, respectively, compared to the control (without Si and biochar). Increasing the Si application level from 0 to 200 mg kg⁻¹ soil significantly increased the areas of the midrib, metaxylem, and protoxylem; however, a further increase to 400 mg Si kg⁻¹ (Si400) led to a gradual decline in these traits under Pb-contaminated conditions. At Si400, RHB was less effective in mitigating Pb toxicity, resulting in a 25.6% reduction in stomatal area compared to SMB. Additionally, at Si0 and Si200, SMB demonstrated greater efficacy in enhancing the membrane stability index compared to Si400. The application of SMB at Si200 and RHB at Si0 improved total chlorophyll content by 101.3% and 94.5%, respectively. A notable increase in carotenoid content was observed with biochar application under Pb toxicity. The highest values of catalase (CAT) and peroxidase (POX) activity were recorded in SMB at Si200, with increases of 56.6% and 32.9%, respectively, compared to the control. Overall, the application of Si200 with SMB significantly enhanced plant height (19.8%), total dry matter (69.5%), number of grains spike-1 (65.8%), and grain yield (68.0%) compared to the control. These enhancements were related to increases in leaf area, leaf weight, midrib area, chlorophyll content, enzyme activity, and relative water content.农田土壤重金属（Heavy Metal, HM）污染是严峻的环境挑战，因植物生长受抑、农业生产减产而威胁粮食安全。本研究旨在探究硅（Silicon, Si）配施生物炭（Biochar）对铅（Lead, Pb）污染土壤中小黑麦叶片结构及植物化学特性的协同调控效应。本研究采用完全随机设计（Completely Randomized Design, CRD）开展双因素盆栽试验，设置硅施用量梯度为0、200、400 mg Si kg⁻¹ 土壤，分别与羊粪生物炭（Sheep Manure Biochar, SMB）、稻壳生物炭（Rice Husk Biochar, RHB）及城市生活垃圾生物炭（Municipal Waste Biochar, MWB）配施，以探究其在铅胁迫（500 mg Pb kg⁻¹ 土壤）下的作用效果。与未施硅和生物炭的对照组相比，200 mg Si kg⁻¹ 配施羊粪生物炭（Si200处理）可分别使小黑麦叶片重量和叶面积提升108.3%和29.7%。当硅施用量从0提升至200 mg kg⁻¹ 土壤时，叶片中脉、后生木质部及原生木质部面积均显著增加；但进一步将硅施用量提升至400 mg kg⁻¹（Si400处理）时，铅污染条件下上述性状逐渐出现下降趋势。在Si400处理下，稻壳生物炭缓解铅胁迫的效果弱于羊粪生物炭，其气孔面积较羊粪生物炭处理降低25.6%。此外，在Si0和Si200处理下，羊粪生物炭对膜稳定性指数的提升效果优于Si400处理。Si200配施羊粪生物炭、Si0配施稻壳生物炭可分别使总叶绿素含量提升101.3%和94.5%。铅胁迫条件下施加生物炭可显著提升类胡萝卜素含量。过氧化氢酶（Catalase, CAT）和过氧化物酶（Peroxidase, POX）活性的最高值均出现在Si200配施羊粪生物炭处理组，较对照组分别提升56.6%和32.9%。总体而言，与对照组相比，Si200配施羊粪生物炭可显著提升植株株高（19.8%）、总干物质质量（69.5%）、每穗粒数（65.8%）及籽粒产量（68.0%），上述增益效应与叶面积、叶片重量、中脉面积、叶绿素含量、酶活性及相对含水量的提升密切相关。