Nitric Oxide Extends the Postharvest Life of Water Bamboo Shoots Partly by Maintaining Mitochondrial Structure and Energy Metabolism.

Harvested water bamboo shoots can be stored for only a few days before they lose weight and become soft. Nitrogen oxide (NO) and modified atmosphere packaging (MAP) have previously been used to prolong horticultural crop storage. In the present study, we analyzed the joint effect of these two methods on extending the postharvest quality of water bamboo shoots. Water bamboo shoots were treated with (1) 30 µL L-1 NO, (2) MAP, and (3) a combination of NO and MAP. The NO treatment delayed the softness and weight loss through maintaining the integrity of the mitochondrial ultrastructure and enhancing the ATP level by activating the expressions and activities of succinic dehydrogenase, malic acid dehydrogenase, and cytochrome oxidase. MAP improved the effect of NO on the mitochondrial energy metabolism. These results indicate that NO and MAP treatments are effective at suppressing the quality deterioration of water bamboo shoots, MAP improves the effect of NO in extending postharvest life, and NO may be the main effective factor in the combination of NO and MAP.

Lignin Biosynthesis in Postharvest Water Bamboo (Zizania latifolia) Shoots during Cold Storage Is Regulated by RBOH-Mediated Reactive Oxygen Species Signaling.

Lignification is a major cause of senescence in fresh shoots of water bamboo (Zizania latifolia), which is a popular vegetable in southeast Asia; however, its physiological and molecular mechanisms is less understood. In the present study, lignin content and transcriptome change in postharvested water bamboo shoots under cold storage were investigated. We found that lignin significantly accumulated in the epidermis of the shoots with the increase of firmness. In the cold storage shoots, the major up-regulated genes were involved in phenylpropanoid biosynthesis, plant-pathogen interactions, and starch and sucrose metabolism. The lignin biosynthesis genes PAL, 4CL, C4H, CCoAOMT, CCR, F5H, CAD, and POD family were up-regulated during cold storage, while HCT and C3H were down-regulated. The MAPK signaling pathway was also up-regulated and respiratory burst oxidase homologue (RBOH) genes were strongly up-regulated. Therefore, we investigated the RBOH gene family and their expression profile in water bamboo shoots. The results indicated that 10 ZlRBOHs were up-regulated in cold storage shoots. Diphenyleneiodonium chloride (DPI), an inhibitor of RBOH oxidase, significantly inhibited the expression of genes involved in lignin deposition and biosynthesis, while H2O2 enhanced these processes. These results suggest that lignification of water bamboo shoots is regulated by RBOH-mediated ROS signaling.

Nitric oxide alleviates lignification and softening of water bamboo (Zizania latifolia) shoots during postharvest storage.

Water bamboo shoots quickly deteriorate after harvest as a result of rapid lignification and softening. Nitric oxide (NO) has been used to extend the postharvest life of several other vegetables. Here, we examined the effect of NO on the storage of water bamboo shoots at 4℃ for 28 days. Without NO, fresh weight and firmness decreased quickly, while the cellulose and lignin contents increased sharply during storage. NO treatment delayed softening by maintaining the integrity of the cell wall and inhibiting the degradation of protopectin and the expressions of pectin methylesterase and polygalacturonase. NO treatment also delayed cellulose synthesis by increasing cellulase activity. NO treatment decreased the synthesis of lignin by inhibiting the activities of phenylalanine ammonia-lyase, cinnamyl alcohol dehydrogenase, laccase and peroxidase. These results indicate that NO treatment is effective at suppressing the softening and lignification of water bamboo shoots during postharvest storage.