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Scientia Silvae Sinicae ›› 2022, Vol. 58 ›› Issue (6): 33-46.doi: 10.11707/j.1001-7488.20220604

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Variation in Respiration Pathways of Post-Harvested Treatment Shoots of Moso Bamboo and the Effect of Hyperoxia Treatment

Ruixiang Ma1,2,Manchang Huang1,Jiajia Zhang1,Aoshun Zhao1,Xingcui Ding1,*,Zisheng Luo3,Shenghui Liu1,Zizhang Xiao1,Kai Shen1   

  1. 1. China National Bamboo Research Center, National Forestry and Grassland Administration Key Laboratory of Bamboo High-Efficient Processing of Zhejiang Province Hangzhou 310012
    2. Nanjing Forestry University Nanjing 210037
    3. College of Biosystems Engineering and Food Science, Zhejiang Univesity Hangzhou 310058
  • Received:2021-11-24 Online:2022-06-25 Published:2022-09-24
  • Contact: Xingcui Ding

Abstract:

Objective: This study aims to explore the changes of respiration pathways of postharvest moso bamboo (Phyllostachys edulis)shoot and the effects of high concentration oxygen (H, 90%O2+10%N2) treatment on the respiration, in order to reveal the respiration and aging mechanisms of bamboo shoots and provide theoretical underpinnings of bamboo shoot preservation. Method: The 3-meter bamboo shoots were unexcavated and placed in the atmosphere (A, 21%O2+79%N2) and High-concentration oxygen environments(H, 90%O2+10%N2)in room temperature, respectively. The aging and decay of moso shoots and its ultrafine sections were examined. The respiration rate, activities of key enzymes involved in respiration metabolism were analyzed, including pyruvate kinase (PK), succinate dehydrogenase (SDH), glucose 6-phosphatedehydrogenase (G-6-PDH) and 6-phosphogluconate dehydrogenase (6-PGDH).Thekey metabolic substrates and metabolites such as nicotinamide adenine dinucleotide (NAD), nicotinamide adenine dinucleotide reduced (NADH), nicotinamide adenine dinucleotide phosphate (NADP) and nicotinamide adenine dinucleotide phosphate reduced (NADPH)) were measured, to study the respiration change sof the postharvested moso shoot and the impact of H treatment on them. Result: The mitochondrial structure in the basal part of moso shoots at the slow-growing stage was compact with a lot of cristae. At the fast-growing stage, the mitochondrial structure in the middle part of moso shoots appeared swollen vacuoles withless cristae. During the storage, the number of mitochondria in the shoots with air treatment decreased gradually and the vacuoles swelled on Day 4, but the number of mitochondria by hyperoxia treatment was significantly higher than that by air treatment. In the first 4 days, the oxygen contents in shoot bodies in both A and H treatments remained at a low level and showed little difference with each other. While the oxygen level increased drastically in Day 4-6. On Day 6, the oxygen content of shoot bodies with H treatment was 1.5 times of that withA treatment. The change trendof oxygen content was in accord with the rate of aging and decay. In both A and H treatments. The ethanol contents in moso shoots treated with A and H showed a "slow-fast-slow" increasing pattern. The ethanol content showed no significant difference between the two treatments and the ethanol contents in moso shoots treated with H did not decline significantly. In A treatment, The respiration rate of shoots treated with A decreased gradually, and the enzyme activities of SDH, PK, G-6-PDH and 6-PGDH increased. The content of NAD, a key substrate of glycolysis (EMP) and tricarboxylic acid cycle (TCA cycle), increased initially and decreased later, and the content of NADH increased gradually. The content of NADP, the key substrate of pentose phosphate pathway (PPP), decreased, but the content of NADPH increased. In H treatment, the respiration rate and the activities of key respiration-related enzymes increased significantly (P < 0.05), but the contents of NADH and NADPH, the key metabolites of respiration, significantly decreased (P < 0.05). Conclusion: The respiration pathways of postharvested moso shoots are definitely affected by the ambient oxygen concentration. In A treatment, the aging process of the moso shoot is mainly attributed to anaerobic respiration, not aerobic respiration. EMP, TCA and PPP pathways are changed alternately in aerobic metabolism of postharvested moso shoot. PPP pathway is dominant in Day 0-2, EMP and TCA peaked in Day 2-4, and all three pathways almost stopped in Day 4-6. In H treatment, moso shoot relies primarily on aerobic respiration, supplemented with anaerobic respiration.TCA and PPP metabolic processes are promoted, but anaerobic respiration is inhibited. It has been found that H treatment deterres the aging and decay of postharvested moso shoots by increasing respiration rate, enhancing PPP and TCA and lowering the ethanol content in moso shoot.

Key words: high concentration oxygen, moso bamboo shoot, respiration rate, tricarboxylic acid cycle, glycolysis, pentose phosphate pathway

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