Dynamic accumulation patterns of ABA, ROS and cell wall materials in the peel and pulp of ‘Nanfeng’ tangerine (Citrus reticulata Blanco) affected by puffing disorder

• As puffing intensified, ABA levels increased in the peel but decreased in the pulp, while H₂O₂ and MDA showed opposite trends. • The peel exhibited a stronger antioxidant system and slower senescence, whereas the pulp underwent accelerated senescence. • Cell wall components decreased in the peel but accumulated in the pulp (except protopectin), indicating tissue-specific remodeling. • Asynchronous peel-pulp senescence drove cell wall metabolism toward degradation (peel) and synthesis (pulp), leading to tissue separation. Puffiness is a physiological disorder in loose-skinned citrus fruit characterized by peel puffing and segment drying, processes linked to senescence and cell wall remodeling. This study investigated the physiological and biochemical mechanisms underlying puffiness in ‘Nanfeng’ tangerine ( Citrus reticulata ) by analyzing the dynamics of abscisic acid (ABA), reactive oxygen species, oxidative stress markers, antioxidant systems, and cell wall metabolism in peel and pulp tissues. With increasing puffing severity, ABA levels rose in the peel but declined in the pulp, while hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) levels decreased in the peel and increased in the pulp. The peel exhibited 2.26- to 10.47-fold higher antioxidant capacity than the pulp, as reflected in the activities of SOD, CAT, APX, POD, and PPO; contents of ascorbic acid (AsA), total phenols, and flavonoids; and DPPH radical scavenging and FRAP values. These results indicate delayed senescence in the peel but accelerated senescence in the pulp. Cell wall components—including lignin, cellulose, hemicellulose, propectin and water-soluble pectin—significantly decreased in puffed peel and correlated negatively with puffing degree, whereas all but propectin increased in the pulp, suggesting cell wall disassembly in the peel and biosynthesis in the pulp. Consistent with these trends, the expression and activity of phenylalanine ammonia-lyase (PAL), a key enzyme in lignin biosynthesis, decreased in the peel while increased in the pulp. Activities of pectin and cellulose-modifying enzymes (PME, β-Gal, and Cel) increased in both tissues, while polygalacturonase (PG) decreased. These findings demonstrate that asynchronous senescence between peel and pulp drives tissue-specific cell wall metabolism: degradation predominates in the peel leading to reduced firmness and tissue loosening, whereas synthesis dominates in the pulp, resulting in drying and shrinkage. The opposing metabolic pathways ultimately lead to peel-pulp separation and the formation of air-filled spaces.