间歇升温对冷藏桃果实硬度及有关酶活性的影响

大久保桃果实在２±１℃冷藏期间（３０ｄ），定期将其放回室温下（２５—２８℃）１２、２４、３６ｈ进行间歇升温处理。结果表明，升温时间愈短，果实硬度越大；升温时间愈长，果实硬度愈小。果实硬度受多聚半乳糖醛酸酶（ＰＧ）和果胶甲酯酶（ＰＥ）活性的影响，相关分析结果表明，ＰＧ、ＰＥ活性与果实硬度均呈显著负相关，表明大久保桃果实变软是由ＰＧ、ＰＥ共同作用的结果。     

Effect of wounding on cell wall hydrolase activity in tomato fruit

Changes in the activity of the cell wall hydrolases – polygalacturonase (EC 3.2.1.15), pectinesterase (EC 3.2.1.11) and β-galactosidase (EC 3.2.1.23) – have been investigated following wounding of tomato fruit pericarp tissue (Lycopersicon esculentum cv. Ailsa Craig). In ripening fruit wounding appears to arrest the further synthesis of polygalacturonase. β-Galactosidase synthesis may also have been arrested in ripening fruit. The level of pectinesterase declined over the first 24 h following harvest, and since this was apparent in both wounded and unwounded tissue may be related to a harvest, rather than a wounding effect. There was a recovery of activity in intact fruit by 48 h after harvest but this seems to be impaired in wounded tissue. In the case of pectinesterase, this observation was extended to examine the changes in isoform profile and it appeared that the decline of this enzyme may be associated with the reduction of one specific isoform — PE2. In contrast to ripening fruit, wounding of fruit at the fully ripe stage appears to have no significant effects on the activities of any of these three enzymes.     

柑橘果皮果胶及其酶活性对皱皮果形成的影响

 研究‘红127’甜橙和‘红江橙’的果皮果胶质、果胶甲酯酶( PE) 及皱皮果率的差异。结果表明, 抗皱皮的‘红127’甜橙皱皮果发生率为7.06% , 而‘红江橙’皱皮果发生率高达28.03%; 皱皮出现在阴面果皮占86%以上。‘红江橙’PE在果实成熟时(12月15日) 比成熟前( 10月1日) 增加2.6倍, 水溶性果胶(WP) 增加8.27倍, 总果胶( TP) 增加65% , 盐酸可溶性果胶(HP) 减少54%。‘红127’甜橙果皮的PE变化较小。PE与WP极显著正相关, 与HP极显著负相关。‘红江橙’TP、WP及PE明显高于‘红127’甜橙, 而HP以‘红127’甜橙的高。阴面比阳面果皮有较多的TP、WP和PE, HP则以阳面果皮为高。皱皮果的TP、WP、PE高于正常果, 而HP则少于正常果。六偏磷酸盐可溶性果胶( PP) 在两种果实上没有差异。     

Firmness and activities of polygalacturonase, pectinesterase, β-galactosidase and cellulase in ripening durian harvested at different stages of maturity

The changes in ripening durian aril firmness, water-soluble pectin and polygalacturonase, pectinesterase, β-galactosidase and cellulase activities were determined in fruit harvested at two stages of maturity. Polygalacturonase activity was low in unripe durian aril and increased markedly during ripening. The development of polygalacturonase activity paralleled the formation of water-soluble pectin and decline in firmness. Pectinesterase, β-galactosidase and cellulase activities were high in unripe durian aril and only pectinesterase and β-galactosidase activities increased slightly while cellulase activity was present throughout during ripening. Water-soluble pectin and polygalacturonase and pectinesterase activities were greater in more mature durian aril than in less mature durian aril, whereas firmness and the activities of β-galactosidase and cellulase were less in the more mature durian aril. The roles of polygalacturonase and pectinesterase in softening of ripening durian aril are discussed.     

果胶酶和纤维素酶在桃果实成熟和絮败中的作用

 测定了果胶酶和纤维素酶在桃果实软化和絮败过程中的活性, 分析了贮前加温和中途加温的酶学效应。果实软化的启动似乎与PE、PG和纤维素酶活性的上升有关。endo-PG和纤维素酶活性与果实絮败程度之间呈显著负相关(r = - 0. 9408 , r = - 0. 9234) 。低温胁迫引起桃果实冷害絮败的本质是细胞壁果胶质的降解过程受阻。果胶质降解过程除了受到果胶酶的直接控制之外, 还受到纤维素酶的重要影响。中途加温或贮前加温减轻冷害的原因在于避免了低温胁迫对endo2PG和纤维素酶造成不可逆的伤害, 从而保证了果胶质降解过程的正常进行。