Morphological and physiological mechanisms underlying lodging in cotton stems

Abstract Background Cotton lodging has become increasingly prevalent due to extreme environmental conditions and agronomic practices, severely compromising yield, fiber quality, and mechanical harvesting efficiency. However, research on cotton lodging remains limited, with most studies focusing on individual or isolated indices rather than a comprehensive system. This study systematically compared four lodging-resistant varieties (LR-1, LR-2, LR-3, LR-4) and four lodging varieties (L-1, L-2, L-3, L-4) across multiple indices: morphological traits, boll distribution, internode filling degree, stem density, mechanical strength, anatomical structure, and chemical composition. Results The results showed that at the boll-opening stage, lodging-resistant varieties exhibited higher density in the first (increased by 11.6%) and third (increased by 23.5%) basal internodes compared with lodging varieties and significantly greater filling degree in the first (increased by 22.6%), second (increased by 23.1%), and third (increased by 26.1%) basal internodes; significantly higher stem puncture strength (increased by 41.2%) and stem bending resistance (increased by 38.2%); and a significantly lower stem lodging coefficient (19.0% lower in lodging-resistant varieties). Additionally, lodging-resistant varieties showed significantly enhanced anatomical structures, including greater cortex thickness, more mechanical tissue layers, and larger pith cavity, xylem, and phloem areas. Conversely, no significant differences were observed in morphological traits, boll distribution, or chemical composition between the lodging-resistant and lodging types. Conclusion Lodging-resistant varieties exhibited thicker cortical tissue and mechanical tissue layers, along with larger xylem area and phloem area in basal internodes. These structural characteristics provide superior support for the filling degree and density of basal internodes, thereby enhancing stem puncture strength and bending resistance, and ultimately improving lodging resistance in cotton. These findings provide a theoretical basis for reducing the occurrence of cotton lodging.