儲運時乙烯及儲運前1-MCP對粗肋草儲後之品質、光合作用、葉綠體及抗氧化反應之影響

Abstract

粗肋草(Aglaonema)為天南星科多年生草本植物，由於臺灣具氣候優勢可全年生產，故有外銷粗肋草盆栽至日本等國的潛力。外銷時儲運環境較密閉不通風，使儲運時從人為或植株等來源產生之乙烯不易擴散，可能降低植株儲後品質。本研究探討儲運時乙烯及儲運前處理乙烯作用抑制劑1-methylcyclopropene (1-MCP)對不同乙烯敏感度粗肋草品種儲運後之品質、光合作用、葉綠體構造及抗氧化反應的影響，以瞭解乙烯造成危害之原因及1-MCP之保護效果。 在16℃黑暗儲運5天期間處理0 - 4.5 μL•L-1乙烯後，‘愛玉’葉片皆無黃化，且維持高品質分級、高葉綠素計讀值與高光系統Ⅱ(PSⅡ)最大光化學潛能(Fv/Fm)。但處理4.5 μL•L-1乙烯之‘斑馬’及處理2.5 μL•L-1乙烯之‘白馬’黃化葉片數顯著較未處理乙烯者高，且品質分級降低。隨乙烯處理濃度由0提高到4.5 μL•L-1，‘斑馬’及‘白馬’於儲後第14天之葉綠素計讀值及Fv/Fm值皆遞減。 ‘愛玉’及‘白馬’進行於16℃黑暗儲運5日(CK)、於儲運期間施用3.0 μL•L-1乙烯(ET)，及儲運前施用600 nL•L-1 1-MCP六小時後於儲運期間施用3.0 μL•L-1乙烯(MCP/ET)等三處理。結果顯示乙烯不影響兩品種葉片之氣孔導度，但會降低‘白馬’最低節位葉片之二氧化碳累積速率及Fv/Fm值；MCP/ET處理之‘白馬’最低節位葉片的二氧化碳累積速率及Fv/Fm值較ET處理者高。‘愛玉’最低節位葉片之柵狀及海綿組織細胞內葉綠體數目於處理間無顯著差異。然而，ET處理之‘白馬’最低節位葉片的葉肉細胞之葉綠體數目較少，葉綠體之質體小球數目較多且面積較大，而葉綠餅堆疊較鬆散，類囊膜空腔間隙較大；MCP/ET處理之最低節位葉片則可維持正常之葉綠體數目和構造。 ‘愛玉’最低節位葉片的過氧化氫、葉綠素濃度及細胞膜相對傷害值(relative injury, RI)在CK、ET及MCP/ET三處理間無顯著差異，RI是經測量並計算細胞離子滲漏液電導度後所得，用以表示膜受損程度。而ET處理之過氧化氫酶(catalase, CAT)活性增加。與CK及MCP/ET處理者比較，ET處理之‘白馬’最低節位葉片的過氧化氫濃度及RI值較高，且葉綠素濃度及過氧化氫酶活性較低。ET處理對‘白馬’剛完全展開葉片之過氧化氫濃度、葉綠素濃度及RI值無顯著影響，而ET處理‘白馬’最低節位葉片之過氧化氫濃度及RI值較CK處理者高，且葉綠素濃度及CAT活性較低。 儲運時處理乙烯對‘愛玉’無顯著影響，而其他五品種處理乙烯後葉片黃化，品質分級、葉綠素計讀值及Fv/Fm值皆降低，其中‘美少女’黃化葉片數較‘銀后’、‘巴黎美人’、‘白馬’及‘黃馬’少，且品質分級、葉綠素計讀值及Fv/Fm值較高。除‘愛玉’外，其他五品種之黃化葉片數隨1-MCP濃度×時間之乘積增加而減少，且葉綠素計讀值及Fv/Fm值增加。1-MCP濃度×時間之乘積為300 nL•L-1•h時，達到對‘美少女’保護效果之飽和點，其他四品種則須處理1-MCP濃度×時間之乘積為400-900 nL•L-1•h才達飽和。儲運前測量六品種最低節位葉片之過氧化氫濃度、抗壞血酸過氧化酶(ascorbate peroxidase, APX)、CAT、超氧化物歧化酶及榖胱甘肽還原酶活性與總抗壞血酸濃度，結果顯示‘愛玉’儲運前之過氧化氫濃度及APX與CAT活性顯著較其他五個品種高。

Aglaonema is an important perennial herbaceous foliage plant. Taiwan has superior climate conditions, and thus has potential for export potted Aglaonema to Japan. Ethylene arising from anthropogenic and biological sources could occasionally accumulated to physiologically active concentrations inside enclosed areas during storage to alternate poststorage quality of foliage plants. This study investigated the effects of ethylene during storage and 1-methylcyclopropene (1-MCP) pretreatment on post-storage leaf senescence as measured by changes in quality, photosynthesis, chloroplasts, and antioxidative reaction of the fully developed leaves and the lowest leaves in Aglaonema cultivars. The purpose was to determine the cause of ethylene damage, and the effectiveness of 1-MCP protection. Potted plants of ‘Chalit’s Fantasy’, ‘Curtisii’ and ‘White Tip’ were treated with 0-4.5 μL•L-1 ethylene during storage at 16℃ for 5 d. ‘Chalit’s Fantasy’ treated with 0 - 4.5 μL•L-1 ethylene did not produce any chlorotic leaves and all stored plants were of excellent quality, with high SPAD-502 and Fv/Fm values. Increased number of chlorotic leaves and reduced quality rating were recorded in ‘Curtisii’ treated with 4.5 μL•L-1 ethylene or ‘White Tip’ treated with 2.5 μL•L-1 ethylene, as compared with 0 μL•L-1 ethylene. Both the SPAD-502 value and Fv/Fm value of ‘Curtisii’ and ‘White Tip’ decreased as ethylene concentration increased from 0 to 4.5 μL•L-1. Potted plants of ‘Chalit’s Fantasy’ and ‘White Tip’ were stored in a dark room at 16℃ for 5 d. Three treatments were employed in this study while plants were being stored. The first treatment (CK) was plants stored without ethylene or 1-MCP treatment. The second treatment (ET) was plants treated with 3.0 μL•L-1 ethylene during storage. The third treatment (MCP/ET) was plants stored with 3.0 μL•L-1 ethylene followed by pretreatment with 600 nL•L-1 1-MCP for 6 h. Results showed that ET treatment did not affect the stomatal conductance in either cultivars or leaves. ET treatment reduced the net CO2 assimilation rate and potential photochemical efficiency of photosystem Ⅱ (Fv/Fm) in the lowest leaves of ‘White Tip’. MCP/ET treatment resulted in increased net CO2 assimilation rate and Fv/Fm in the lowest leaves of ‘White Tip’, as compared with ET treatment. Chloroplast number in a palisade or spongy mesophyll cell did not differ among treatments in the lowest leaves of ‘Chalit’s Fantasy’. However, the lowest leaves of ethylene-treated ‘White Tip’ had fewer chloroplasts in the mesophyll cells, had more and larger plastoglobules in the chloroplasts, and had looser granal stacking with enlarged thylakoid lumens. MCP/ET treatment prevented ethylene injury, and maintained the quantity and structural integrity of chloroplasts. Regardless of the fully developed or the lowest leaves, no differences were found in hydrogen peroxide (H2O2) and chlorophyll concentrations, and relative injury (RI) value among CK, ET and MCP/ET treatments in ‘Chalit’s Fantasy’. In ‘White Tip’, ET treatment resulted in increased H2O2 concentration and RI value, and reduced chlorophyll concentration, APX and CAT activity in the lowest leaves. There were no differences in H2O2 and chlorophyll concentrations and RI value between CK and ET treatments in the fully developed leaves of ‘White Tip’. Ehylene did not alter postharvest performance of ‘Chalit’s Fantasy’. In contrast, ethylene increased number of chlorotic leaves, decreased quality rating, the SPAD-502 value, and Fv/Fm value in ‘Silver Bay’, ‘Silver Queen’, ‘Pattaya Beauty’, ‘White Tip’, and ‘King of Siam’. ‘Silver Bay’ had fewer number of chlorotic leaves and higher quality rating, SPAD-502, and Fv/Fm values than ‘Silver Queen’, ‘Pattaya Beauty’, ‘White Tip’, and ‘King of Siam’. The number of chlorotic leaves decreased, and SPAD-502 and Fv/Fm values increased with increasing 1-MCP concentration × time. Treatment with 1-MCP concentration × time (300 nL•L-1•h) was effective in reducing the number of chlorotic leaves, and maintaining SPAD-502 and Fv/Fm values in ‘Silver Bay’. In other cultivars, higher 1-MCP concentration × time (400-900 nL•L-1•h) was required to maintain poststorage quality. This study also measured H2O2 concentration, CAT, APX, SOD, and GR activity and total ascorbate concentration in the lowest leaves of six cultivars before storage. H2O2 concentration, CAT and APX activity were higher in ‘Chalit’s Fantasy’ than other cultivars.