Nutrient Imbalance and Cell-Wall Remodeling Drive Pineapple Translucency: A Two-Season Survey in Hainan, China

Pineapple translucency is a major physiological disorder in ‘Tainong 17’ (Golden Diamond) that severely impairs fruit quality, storability, and market value, yet its physiological basis remains poorly understood. To clarify the underlying mechanisms, we conducted two seasons of field surveys across 24 plots in eleven pineapple orchards in Hainan, China, comparing translucent and healthy fruits in terms of plant growth, nutrient status, fruit quality, cell wall composition, and soil properties. Our results showed that translucency significantly reduced fruit quality, with soluble solids and ascorbic acid contents decreasing by 9.7% and 16.3%, respectively. Translucent plants exhibited markedly increased biomass, whereas fruit dry matter was reduced by 21.6%. In addition, affected plants accumulated 40–70% more nitrogen in leaves, stems, and fruits, accompanied by 23% and 14% reductions in abscisic acid concentrations in leaves and fruits, respectively. Calcium and boron allocation to fruits was impaired, with fruit Ca and B contents decreasing by 25.1% and 50.4%, respectively, despite increased levels in vegetative organs. These nutrient imbalances coincided with a 16.4% decrease in protopectin, a 5.3% decrease in cellulose, and a 15.5% increase in soluble pectin, indicating cell-wall loosening. Collectively, our findings demonstrate that excessive nitrogen input disrupts carbon–nitrogen metabolism and ABA signaling, elevates fruit N/Ca ratios, and accelerates cell-wall remodeling, thereby predisposing fruits to translucency, particularly under humid or rainy conditions.