乙醇汽对青花菜贮藏保鲜效果的影响

通过在20℃避光条件下使用含有不同浓度的乙醇蒸汽(0 g,3 g,6 g,12 g)酒精缓释剂处理青花菜试验发现,对照组青花菜小花在贮藏第3天即开始显著变黄,而且乙烯生成量在第2天和第3天达到峰值,随后逐渐减弱.而经过处理的样品则在5天内未发生明显黄化,总叶绿素含量较对照组无明显差异,而且乙烯产量在5天内均显著小于对照组.对样品中ACC合成酶(ACS)及ACC氧化酶(ACO)活性分析结果显示,该方法可以通过长时间持续缓慢释放乙醇气体来有效抑制ACS和ACO活性,从而减少常温条件下青花菜小花内源乙烯合成,延缓黄化速度.     

1—MCP对红星苹果贮藏期间伤乙烯合成的影响

以红星苹果果实为试材，设机械损伤、机械损伤＋1-MCP、对照3种处理，进行贮藏期间伤诱导乙烯的生物合成过程中ACC合成酶（ACS）活性、ACC积累水平、ACC氧化酶（ACO）活性和乙烯释放速率变化的试验研究。试验结果表明，机械伤刺激了果实ACS和ACO活性，促进了果实乙烯释放，加速了果实衰老；而1-MCP则抑制了受伤果实中ACS和ACO活性，提高了受伤果实贮藏后期ACC积累水平，显著地减少了受伤果实乙烯的释放，改善了受伤果实的贮藏品质。     

外源乙烯对CA贮藏桃果实内源乙烯生物合成的影响

以八月脆桃果实为试材,研究了不同浓度外源乙烯（0μL／L,20～50μL／L,50～80μL/L）对桃果实气调贮藏（9％～11％CO2＋9％-11％O2）期间内源乙烯生成量、ACS和ACO活性变化的影响。结果表明,在整个贮藏过程中,外源乙烯处理果实的内源乙烯生成量显著高于未加外源乙烯的气调贮藏和冷藏对照果实;外源乙烯处理果实ACS活性亦高于气调和冷藏对照果实,但对ACO活性的影响不明显。     

Ca2+参与NO对切花月季瓶插期间乙烯合成的调控

分别用0.1 mmol?L-1 SNP（NO供体）、0.1 mmol?L-1 SNP+0.3 mmol?L-1的TFP（CaM）、0.1 mmol?L-1 SNP+10 mmol?L-1的TFP（Ca2+螯合剂）、6 mmol?L-1 Ca2+、6 mmol?L-1 Ca2++0.05 mmol?L-1的PTIO（NO清除剂）处理切花月季‘Kardinal’,研究切花瓶插期间内源乙烯的生物合成变化以及Ca2+在NO对切花月季瓶插期间乙烯合成调控中的作用。结果表明：Ca2+处理能提高月季瓶插前期花瓣中的NOS活性,保持了花瓣中的NO的较高水平,减缓切花瓶插后期NOS活性的升高,进一步研究表明,Ca2+螯合剂EGTA和CaM的抑制剂TFP处理却可使花瓣中的ACS和ACO活性升高,ACC的含量增加,从而加速了乙烯的生物合成;同时,NO的清除剂PTIO处理也可以抑制由于Ca2+处理导致的ACS和ACO的活性降低以及乙烯合成底物ACC的含量下降。因此,Ca2+和CaM可能参与了NO对切花瓶插期间乙烯的合成调控及其信号转导。     

乙烯利诱导甘蔗ACC合成酶基因家族三成员在茎中表达与乙烯释放量和糖分积累的关系

ACC合酶（ACS）是高等植物乙烯生物合成途径中的限速酶。为明确ACS基因在甘蔗茎中的表达与乙烯释放量、蔗糖积累的关系,在克隆到甘蔗ACS基因3个成员（Sc-ACS1、Sc-ACS2和Sc-ACS3）的基础上,分别以它们作为探针,Northern杂交检验其在茎中的时空表达。结果表明,甘蔗生长后期,ACS基因3个成员在茎中不同品种和节间持续表达,Sc-ACS1和Sc-ACS2表达维持较低水平,Sc-ACS3维持较高水平。乙烯利处理明显提高3个基因在茎的未成熟和正在成熟节间的表达,且Sc-ACS1和Sc-ACS2在未成熟节间的表达持续时间长达一个月,而Sc-ACS3在未成熟节间的较高水平表达可持续45d。该结果与甘蔗节间尤其是未成熟和正在成熟节间的乙烯释放量增加以及糖分积累的效应基本一致。相关分析表明,桂糖17品种乙烯释放量与蔗糖分在处理后14d和28d分别极显著和显著负相关,但巴西固氮品种B1未达显著水平。     

水稻籽粒中乙烯和ACC对土壤水分的反应及其与籽粒灌浆的关系

以武运粳8号(粳稻)和扬稻6号(籼稻)为材,自抽穗后9 d至成熟期进行保持浅水层(WW)、土壤轻度落干(MD)和土壤水分严重亏缺(SD)3种处理。观察在不同土壤水分条件下灌浆期籽粒中乙烯和1-氨基环丙烷1-羧酸（ACC）浓度的变化及其与籽粒灌浆的关系,并使用化学调控物质进行验证。结果表明,MD显著提高籽粒灌浆速率和粒重,SD明显降低籽粒灌浆速率和粒重。籽粒中乙烯释放速率和ACC浓度在MD中降低,在SD中增加。籽粒乙烯释放速率及根系伤流液中ACC浓度与籽粒中ACC浓度呈极显著的正相关。籽粒灌浆速率与乙烯释放速率呈极显著负相关。在花后9~13 d喷施乙烯合成的抑制物质氨基－乙氧基乙烯基甘氨酸(AVG),明显降低籽粒中ACC的浓度和乙烯的释放速率,显著提高了籽粒灌浆速率和粒重以及籽粒中的蔗糖合成酶（SuSase）、ADP葡萄糖焦磷酸化酶（AGPase）和可溶性淀粉合成酶（SSSase）活性;喷施乙烯释放的促进物质乙烯利,结果则相反。表明结实期土壤轻度落干或适度干旱处理可以抑制水稻体内乙烯的产生,促进籽粒灌浆。     

乙烯促进与抑制剂对旱后复水玉米生长、保护酶活性及膜脂过氧化的影响

以玉米品种郑单958为材料,研究了不同程度干旱胁迫与复水条件下乙烯促进与抑制剂处理对春玉米生长、叶片保护酶系活性变化及其对膜脂过氧化作用的影响。结果表明：（1）乙烯利有利于控制玉米的株高,并提高轻度干旱条件下玉米的根重和生物量,而AgNO3（硝酸银）处理的玉米在轻度与重度干旱条件下,生物量明显降低。（2）乙烯利处理可明显抑制水分胁迫条件下玉米MDA（丙二醛）的合成,降低相对电导率,提高可溶性蛋白含量,而AgNO3处理的效果则与乙烯利刚好相反。（3）乙烯利处理可明显提高SOD（超氧化物酶）、CAT（过氧化氢酶）和POD（过氧化物酶）的活性,而AgNO3处理在一定程度上抑制SOD、CAT和POD的活性。     

外源ABA和乙烯利胁迫下斑茅ACO基因表达的实时PCR分析

研究了外源ABA和乙烯利胁迫处理对斑茅1-氨基环丙烷-1-羧酸氧化酶基因（ACO基因）表达情况的影响。在项目组克隆斑茅ACO基因的基础上,应用实时荧光PCR技术分析斑茅ACO基因在ABA、乙烯利胁迫下的表达。结果表明,斑茅ACO基因在ABA的胁迫下,在3h有微弱上调表达,而6h日寸明显抑制,其后表达趋向平缓;在乙烯利的胁迫下,ACO基因在前期受抑制,其后呈明显上调表达,在24h后ACO基因的表达趋向平缓。斑茅ACO基因的表达受乙烯利诱导,而不受外源ABA诱导。     

青花菜采后保鲜技术研究

青花菜采后衰老中呼吸强度呈现跃变型,呼吸高峰出现在采后第2天内,随后黄化率急剧上升;蛋白质含量和Vc含量则随贮期延长而下降。0℃低温与调节气体包装均可抑制青花菜的采后衰老,0℃低温辅以0.04mm厚的聚乙烯袋包装贮藏41天后,青花菜的黄化率为0.0%,失重率低于4.0%,花球青绿无异味,切口鲜度正常。     

薄膜袋包装对青花菜贮藏效应及其生理影响的研究

对青花菜采用不同厚度聚乙烯薄膜包装的贮藏效果及其生理影响进行了研究。薄膜厚度分别为：0．02 mm（M1），0．04 mm（M2），0．06（M3），0．08 mm（M4），对照（Mck）即无薄膜包装贮藏。贮藏温度（0±0．5）℃ ，相对湿度90％～95％。研究结果表明，不同厚度薄膜内积累CO2的浓度差异显著；有膜包装的贮藏效果好于无膜包装；较厚薄膜包装处理的气调效果好于较薄膜包装处理。青花菜贮藏过程中，适宜的CO2浓度为5％～10％。提高CO2浓度对青花菜有抑制呼吸，抑制乙烯释放，推迟乙烯高峰的出现和抑制叶绿素分解的作用。     

Effects of postharvest ethanol vapor treatment on activities and gene expression of chlorophyll catabolic enzymes in broccoli florets

Postharvest yellowing of broccoli (Brassica oleracea L. Italica Group) is an important indicator of quality deterioration and occurs with chlorophyll (Chl) degradation. Postharvest ethanol vapor treatment could delay the yellowing of broccoli florets, through the suppression of Chl degradation. As the first step in identifying the mechanism of this delay, the effects of postharvest ethanol vapor treatment on activities and gene expression of the Chl catabolic enzymes in broccoli were determined. Broccoli branchlets were placed in a perforated polyethylene bag with or without (control) an ethanol pad and stored at 20 °C in darkness. The Chl contents of the control broccoli florets decreased remarkably after three days in storage, whereas the contents of the ethanol-treated broccoli showed no significant changes except at day one. Changes in chlorophyllase activity in the ethanol-treated broccoli were similar to those of the control until three days in storage, but then the activity tended to decease. Mg-dechelatase and Chl-degrading peroxidase activities, which increased greatly with senescence in the controls, remained unchanged in the ethanol-treated broccoli. BoCLH1 expression showed changes almost similar to those of chlorophyllase activity. BoPAO expression in the control broccoli increased greatly at day one in storage and was maintained at a high level until three days. In contrast, this expression in ethanol-treated broccoli was suppressed until two days. BoRCCR expression in the control broccoli increased until two days in storage, while the expression in the ethanol-treated broccoli showed no change during storage. These results show that postharvest ethanol vapor treatment suppressed the activities and gene expression of Chl catabolic enzymes, resulting in delayed yellowing of broccoli florets.     

Apparent synergism between the positive effects of 1-MCP and modified atmosphere on storage life of banana fruit

Fruit of cv. Gros Michel banana were treated with 1-MCP (1000 nL L⁻¹ for 4 h at 25 °C) and then packed in non-perforated polyethylene (PE) bags for modified atmosphere storage (MAP). The bags were placed in corrugated cardboard boxes and stored at 14 °C. Fruit were removed from cool storage and ripened at room temperature using ethephon. The length of storage life was determined by the change in peel color to yellow, after this ethephon treatment. Fruit treated with 1-MCP + MAP had a storage life of 100 days. The storage life of control fruit (no 1-MCP and no MAP) was 20 days. Fruit held in PE bags without 1-MCP treatment had a 40 day storage life, and the same was found in fruit treated with 1-MCP but without PE bags. 1-MCP is an inhibitor of ethylene action, but also inhibited ethylene production, mainly through inhibition of ACC oxidase activity in the peel. MAP inhibited ethylene production mainly through inhibition of ACC oxidase, both in the peel and pulp. The combination of 1-MCP treatment and MAP storage resulted in much lower ethylene production due to inhibition of both ACC synthase and ACC oxidase activity.     

Ethanol vapor treatment maintains postharvest storage quality and inhibits internal ethylene biosynthesis during storage of oriental sweet melons

In order to evaluate the effect of ethanol vapor treatments (0.5 mL/kg and 3 mL/kg) on postharvest storage at 23 °C, quality of oriental sweet melons, and to clarify the mechanism of the inhibition of senescence, we investigated physiological and quality changes induced by ethanol vapor, decay incidence, internal ethylene concentration (IEC) and ethylene-related enzymes activities as well as gene expression. Both ethanol vapor treatments, irrespective of concentration, significantly (P < 0.5) delayed skin color changes, retarded softening and suppressed fruit decay in ethanol vapor-treated fruit. Between the two treatments, 0.5 mL/kg of ethanol vapor maintained better quality in storage than that of 3 mL/kg. Compared with the control, both ethanol vapor treatments resulted in different profiles and composition of aromatic volatile compounds of fruit during storage, and a significant increase of ethyl esters, including ethyl acetate, ethyl butanoate, ethyl hexanoate, ethyl 2-methylbutanoate, 3-(methylthio) propionate and 2-phenethyl acetate, and five new ethyl esters were also detected. Both treatments increased alcohol acyl-transferase (AAT) activity levels, which peaked earlier than in the control, but there were no significant differences in activities of alcohol dehydrogenase (ADH). Both treatments significantly (P < 0.5) suppressed internal ethylene concentrations (IEC) during storage at 23 °C, which was evident from reducing 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS) and ACC oxidase (ACO) activities, and inhibiting ACC biosynthesis, and the effect of the 0.5 mL/kg treatment was better than that of 3 mL/kg. Real-time quantitative PCR (Q-PCR) analysis showed that the expression patterns of CM-ACO1, CM-ACO2, CM-ACS1 and CM-ACS2 were consistent with ethylene production during storage. These results suggest that postharvest ethanol vapor treatments markedly delayed the senescence of harvested oriental sweet melons, maintained better quality in storage and improved levels of volatile aroma compounds, especially the ethyl esters, through suppressing the expression of particular members of ethylene-forming enzyme gene families as well as ethylene biosynthesis, and the effect is dose dependent.     

Specific response of apple skin and pulp tissues to cold stress and 1-MCP treatment

It is now widely accepted that 1-MCP reduces ethylene production and prevents scald disorder in apple skin tissue. However, despite this beneficial effect, very little is known about the effects of 1-MCP on this tissue. This study aimed to determine how this treatment affects ACC metabolism in both skin and pulp tissues in relation to cold storage. Changes in ACC metabolism were monitored in control and 1-MCP treated fruit stored in air and removed after 0, 15, 30, 90 and 150 days of storage. 1-MCP treatment caused an inhibition of ethylene production but also of ACC synthase (ACS) activity and ACC levels both in pulp and skin. Compared to the control, 1-MCP treatment also induced a significant reduction in ACC oxidase (ACO) activity, but the inhibition remained incomplete in both tissues. High levels of MACC were found in 1-MCP treated fruit, showing the presence of a malonyl transferase insensitive to 1-MCP treatment. Collectively, these results showed that apple skin and pulp exhibited similar climacteric behaviour. The results also showed that the different parameters involved in ACC metabolism were differentially inhibited by the 1-MCP treatment during cold storage. ACS was completely inhibited in both tissues, ACO only partially and the treatment was ineffective to prevent MACC accumulation.     

Effect of high temperature stress on ethylene biosynthesis, respiration and ripening of ‘Hayward’ kiwifruit

Temperatures up to 35°C have been shown to increase ethylene production and ripening of propylene-treated kiwifruit (Stavroulakis, G., Sfakiotakis, E.M., 1993. We attempted to study the regulation by high stress temperature of the propylene induced ethylene biosynthesis and ripening in ‘Hayward’ kiwifruit. ‘Hayward’ kiwifruit were treated with 130 μl/l propylene at temperatures from 30 to 45°C up to 120 h. Ethylene biosynthesis pathway and fruit ripening were investigated. Propylene induced normal ripening of kiwifruit at 30–34°C. Fruit failed to ripe normally at 38°C and above 40°C ripening was inhibited. Propylene induced autocatalytic ethylene production after a lag period of 24 h at 30–34°C. Ethylene production was drastically reduced at 38°C and almost nil at 40°C. The 1-aminocyclopropane-1-carboxylic acid (ACC) content was similar at 30–38°C and was very low at 40°C. The 1-aminocyclopropane-1-carboxylate synthase (ACC synthase) and 1-aminocyclopropane-1-carboxylate oxidase (ACC oxidase) activities decreased with a temperature increase above 30°C, but ACC oxidase decreased at a faster rate than ACC synthase. Fruit not treated with propylene showed no ripening response or ethylene production. However, kiwifruit respiration rate increased with temperature up to 45°C, reaching the respiration peak in 10 h. At temperatures up to 38°C, propylene treatment enhanced the respiration rate. After 48 h at 45°C, fruit showed injury symptoms and a larger decrease in CO₂. The results suggest that high temperature stress inhibits ripening by inhibiting ethylene production and sensitivity while respiration proceeds until the breakdown of tissues.     

Control of ripening in transgenic tomatoes

Major progress has been made over the last few years in the identification and regulation of tomato ripening genes. At least 25 genes showing elevated expression during ripening have been cloned and several, including polygalacturonase, which modifies fruit textures, have been shown to be ripening-specific. In addition, genes have been cloned for ACC synthase and ACC oxidase, which control the synthesis of ethylene, which plays a critical role in ripening. Inhibition of expression of polygalacturonase, pectinesterase, ACC synthase, ACC oxidase and phytoene synthase has been achieved in transgenic plants, using antisense technology. The expression of several genes has also been inhibited by sense gene suppression. New traits caused by these transgenes are stably inherited. Antisense tomatoes with reduced polygalacturonase have improved textural qualities which are being exploited commercially for the fresh and processed markets. Overexpression of phytoene synthase has been shown to restore carotenoid production in the yellow flesh mutant and can be used to enhance colour in other cultivars. Antisense fruit in which ACC synthase or ACC oxidase are inhibited show slower ripening and reduced over-ripening. ACC oxidase antisense genes have also been shown to delay leaf senescence. It is to be expected that further genes determining other quality traits will be identified and manipulated soon.     

Effects of auxin and jasmonates on 1-aminocyclopropane-1-carboxylate (ACC) synthase and ACC oxidase gene expression during ripening of apple fruit

1-Aminocyclopropane-1-carboxylate (ACC) synthase and oxidase activities, their gene expression, and ethylene production in apple fruit [Malus sylvestris (L.) Mill. Var. domestica (Borkh.) Mansf.] treated with a synthetic auxin 2,4-dichlorophenoxy-propionic acid (2,4-DP) and n-propyl dihydrojasmonate (PDJ), a jasmonic acid derivative, has been investigated to clarify the action of auxin and jasmonates on ethylene production. The fruit was harvested at 103 d after full bloom (preclimacteric). The expression of MdACS4 messenger RNA (mRNA) at 48 and 96 h after treatment was higher in fruit treated with 2,4-DP than in the untreated control, but those of MdACS1 and MdACO1 were not affected by treatment. The ethylene production in 2,4-DP-treated fruit increased at 96 h after treatment. In contrast, expression of mRNAs hybridized with MdACS1 and MdACO1 probes in the skin of PDJ-treated fruit were higher than those in the untreated control. In addition, ACC synthase activity and ethylene production also increased after treatment. These results show that the ethylene production rate may differ with the kind of genes which were stimulated by auxin or jasmonates.     

Morphological characterisation and agronomic evaluation of transgenic broccoli (Brassica oleracea L. var. italica) containing an antisense ACC oxidase gene

Morphological characterisation and agronomic evaluation was conducted on 12 transgenic broccolilines containing a tomato antisense1-aminocyclopropane-1-carboxylic acid (ACC) oxidase gene. Plants of three cultivars: Shogun (Sh), Green Beauty (Gy) and Dominator (D), were regenerated from hairy root cultures after co-cultivation with Agrobacterium rhizogenes strain A4T harbouring the binary vector pLN35. The T-DNA of pLN35 contains genes encoding a tomato antisense ACC oxidase gene (35S-ACC-5′7′) and a neomycin phosphotransferase II gene (NOS-NPTII-NOS) for kanamycin resistance. The transgenic plants were transferred to a greenhouse and fertile plants obtained. Integration of the foreign DNA into the broccoli genome was confirmed by the polymerase chain reaction and Southern analyses. Transgenic plants showed evidence of hairy root (HR)-induced morphological changes to varying degrees. Of the 12 characterised transgenic lines, three lines(Gy/7, D/1 and D/2) performed within the limits of acceptability for all head quality parameters analysed (size, density, colour, shape and leafiness). The ethylene production from stalks of four field-grown transgenic lines of Green Beauty broccoli showed significant reductions in activity relative to the control 98 h after harvest. The Dominator transgenic lines D/1 and D/2 showed significant improvements in head colour relative to the control from 48 h after harvest. These results are consistent with the ethylene production patterns determined previously for these lines. The head colour results are consistent with previous results suggesting that two enzyme systems may be involved in broccoli senescence, giving two bursts of ethylene production, with only the second burst inhibited by the antisense ACC oxidase gene used. This revised version was published online in August 2006 with corrections to the Cover Date.