Postharvest broccoli heads undergo yellowing quickly in unsuitable conditions, which diminishes their quality and commercial value. We investigated the pattern and molecular regulatory mechanism of chlorophyll (Chl) degradation in broccoli under elevated O₂ controlled atmosphere. As results, the 40% O₂ + 5% CO₂ treatment accelerated the Chl degradation and the change in color of postharvest broccoli heads, while the 5% O₂ + 5% CO₂ treatment delayed the yellowing. The results indicated that Chl degradation pattern of postharvest broccoli heads concurrently involved the Pheide a oxygenase (PAO)/phyllobilin and oxidative degradation pathways, and the latter might be the dominant pathway of Chl degradation. The regulatory mechanism of elevated O₂ on Chl degradation may be related to its ability to accelerate cell damage and death, destroy the light-harvesting complex II, and promote up-regulation of genes in the PAO/phyllobilin and oxidative degradation pathways. In contrast, low O₂ treatment may down-regulate the expression of Chl degradation-related genes by increasing H₂O₂ content, thus delaying the yellowing of broccoli heads.

收获后的西兰花头在不合适的条件下会迅速变黄，从而降低其质量和商业价值。我们研究了在升高的 O ₂控制气氛下西兰花中叶绿素 (Chl) 降解的模式和分子调控机制。结果，40% O ₂  + 5% CO ₂处理加速了 Chl 降解和收获后西兰花头部的颜色变化，而 5% O ₂  + 5% CO ₂处理延迟了变黄。结果表明，采后西兰花头部的 Chl 降解模式同时涉及 Pheide a氧化酶（PAO）/叶胆素和氧化降解途径，后者可能是 Chl 降解的主要途径。O ₂升高对 Chl 降解的调控机制可能与其加速细胞损伤和死亡、破坏捕光复合物 II、促进 PAO/叶绿素和氧化降解途径中基因的上调有关。相反，低O ₂处理可能通过增加H ₂ O ₂含量来下调Chl降解相关基因的表达，从而延迟西兰花头部变黄。