摘要
摘要:农膜覆盖技术的应用及推广极大地提高了干旱半干旱地区的农业产量，促进了当地农业发展及社会经济效益。然而，由于农膜碎片化程度高、回收难度大、降解周期长，使得残留在土壤中的农膜日益增多，严重威胁着作物生长、土壤健康以及农业可持续发展。尽管农膜残留对土壤质量影响的研究较多，但对于其种类（可降解或不可降解）及残留累积量对作物光生理特征的研究还相对较少。本试验以大豆为研究对象，对比普通聚乙烯（PE）和生物降解（BP）两种农膜（残片大小为0.5~2 cm），研究不同农膜残留累积量（土壤重量的0、0.1%、0.5%、1.0%）下大豆花期及初荚期叶片光合作用光、CO₂响应曲线特征及花期、收获期的植株生物量，探讨塑料类型及残留量对大豆光生理特征及生物量累积的影响。结果表明：PE残留导致大豆叶片光补偿点在花期降低23.96%，而初荚期升高51.38%，说明PE残留导致大豆叶片弱光利用能力在花期提升，但在初荚期被抑制。在初荚期，BP残留使光补偿点降低54.82%，且光饱合点升高58.12%，从而提高了叶片强光适应能力，增大了叶片光能利用范围。同时，PE和BP添加使暗呼吸速率分别增长30.56%和22.28%，从而导致干物质消耗增加。土壤中PE、BP残留量的增加，最大光合力分别降低36.49%和23.56%，表明大豆叶片CO₂利用能力减弱；CO₂补偿点分别降低67.96%和38.91%，从而提高了叶片低浓度CO₂的利用能力，并降低光呼吸速率，从而减少了干物质的消耗。此外，不同农膜及残留量处理下，仅在花期0.1%与0.5%残留量的BP处理中，地下生物量随农膜残留量的增加显著降低，其他各处理间地上及地下生物量无明显变化。光响应及CO₂响应曲线各拟合参数与生物量的Pearson相关性分析结果表明，收获期PE处理下，地上生物量与光补偿点呈显著负相关，而光呼吸速率、CO₂补偿点、初始羧化效率与生物量（地上+地下）的积累有较强相关性。因此，PE农膜残留量增加提高了大豆花期叶片对于弱光的利用能力而减弱初荚期对弱光的利用能力，BP农膜残留量增加则会增强初荚期叶片对弱光的利用，也对大豆叶片适应强光的能力有所提升。
关键词:农膜残留/
大豆/
光合作用光响应曲线/
光合作用CO₂响应曲线/
光生理特征/
生物量
Abstract:Agricultural plastic film mulching technology has greatly promoted the development of agricultural production and social economics, especially in the arid and semi-arid areas of China. However, due to high fragmentation, low recovery, and long-term degradation, the accumulation of plastic residues in the soil has increased annually, which threatens crop growth, soil health, and the sustainable development of agriculture. Although many studies have focused on the effects of agricultural film residues on soil quality, the effects of plastic type (degradable or non-degradable) and the cumulative abundance of plastic on crop photosynthetic characteristics have rarely been reported. In this study, soybean (Glycine max) was investigated for its light and carbon dioxide (CO₂) response characteristics under different plastic residue addition (polyethylene[PE] and biodegradable plastic[BP] mulch film; plastic size:0.5-2 cm; addition levels:0, 0.1%, 0.5%, and 1.0%) at the flowering and early pod stages. Plant biomass and soil samples were collected at the flowering and harvesting stages to examine the effects of the different plastic residues on plant growth and soil quality. The results showed that the light compensation point (LCP) of soybean leaves decreased by 23.96% at the flowering stage and increased by 51.38% at the beginning of the pod stage in the PE treatment groups, suggesting that the weak light utilization ability of soybean leaves increased at the flowering stage and decreased at the beginning pod stage. LCP decreased by 54.82%, and the light saturation point increased by 58.12% in the BP treatment groups at the beginning of the pod stage, which improved the ability of strong light adaptation and increased the range of light energy utilization. The PE and BP residues increased the dark respiration rate (R_d) by 30.56% and 22.28%, respectively, increasing dry substance consumption. With increasing amounts of plastics, the maximum photosynthetic capacity decreased by 36.49% and 23.56% in the PE and BP treatments, respectively, indicating that the CO₂ utilization capacity of soybean was inhibited. Furthermore, the CO₂ compensation point (CCP) decreased by 67.96% and 38.91% in the PE and BP treatments, respectively, which indicated the improved CO₂ utilization capacity of the leaves at low CO₂ levels. The photorespiration rate (R_p) also decreased, reducing dry substance consumption. At the flowering stage in the BP treatment with 0.1% and 0.5% plastic addition, the underground biomass decreased significantly with increased plastic residue (P < 0.05), but there were no significant differences in the aboveground and underground biomass among the other treatments. Pearson correlation analysis was used to analyze the fitting parameters of the light response and CO₂ response curves with biomass. At the harvesting stage in the PE treatments, the aboveground biomass was negatively correlated with LCP, whereas R_p, CCP, and the initial carboxylation efficiency were strongly correlated with biomass accumulation (aboveground + underground). Further research is required to identify the mechanisms by which plastic residues affect crop growth, especially for the photosynthetic properties. Such work will enable a better understanding of the ecological risk of microplastics.
Key words:Plastic residue/
Soybean/
Photosynthetic light response curve/
Photosynthetic CO₂ response curve/
Photosynthetic characteristics/
Biomass



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