Physiological and Biochemical Responses of Two Major Legume Crops to Seed Priming—A Systematic Review

Seed priming is recognized as an environmentally friendly technique to enhance the physiological and biochemical performance of crops. However, its effectiveness varies depending on factors such as crop type, priming agents and climatic conditions. Based on this hypothesis, this comparative, climate- and soil-dependent meta-synthesis study therefore aimed to evaluate how these factors shape plant responses in common bean (Phaseolus vulgaris L.) and soybean (Glycine max L.), while providing insights into sustainable strategies for improving crop performance, food security, and progress toward sustainable development goals. A cross-study synthesis of 31 peer-reviewed articles from Web of Science, Scopus, and Google Scholar evaluated the influence of these factors on key physiological traits, chlorophyll content (CC) and net photosynthesis rate (Pn), and biochemical traits, proline (Pro), superoxide dismutase (SOD), and catalase (CAT) activity. The findings indicated greater priming-induced enhancements in common bean than soybean for most traits: chlorophyll content (36.6% in common bean and 25.6% in soybean), net photosynthesis rate (33.2% in common bean and 19.8% in soybean), proline content (45.2% in common bean and 40.9% in soybean), and SOD activity (37.1% in common bean and 30.5% in soybean). Soybean only showed superior enhancement in CAT activity (40.1% in soybean and 19.5% in common bean). The climatic conditions impacted the outcomes, with physiological traits (CC and Pn) responding more prominently under semi-arid and arid climates, and biochemical traits (Pro, CAT and SOD) showing higher responsiveness in continental and Mediterranean climates. Significant (p < 0.05) correlations were found between CAT activity and priming agents (r = 0.54); SOD and crop type (r = 0.52); and Pn and crop type (0.90). Multivariate analysis revealed that soybean was positively associated with silt, clay, pH, tropical climate and CAT activity, while common bean was linked to nitrogen, arid conditions, SOD activity and proline. These differences could be due to the molecular and genetic variations in the two crops. Unlike previous reviews, this study provides the first quantitative synthesis integrating crop type, priming agents, and climatic variables, aiming to evaluate how these factors influence the responses of two major legume crops to seed priming. Overall, the findings highlight the need for crop- and environment-specific priming protocols to optimize the benefits of seed priming as a cost-effective approach to enhance crop performance and productivity.