Fruit thinning in ‘Conference’ pear grown under deficit irrigation: Implications for fruit quality at harvest and after cold storage

Fruit thinning in pear is feasible for mitigation of water stress effects. However, it is not well known how fruit quality at harvest and after cold storage is affected by pre-harvest water stress. Even less is known about the effects of fruit thinning on quality under these circumstances. To elucidate these, we applied deficit irrigation (DI) and fruit thinning treatments to ‘Conference’ pear over the growing seasons of 2008 and 2009. At the onset of Stage II (80 and 67 days before harvest in 2008 and 2009, respectively), two irrigation treatments were applied: full irrigation (FI) and DI. FI trees received 100% of crop evapotranspiration (ETc). DI trees received no irrigation during the first three weeks of Stage II to induce water stress, but then received 20% of ETc to ensure tree survival. From bud-break until the onset of Stage II and during post-harvest, FI and DI trees received 100% of ETc. Each irrigation treatment received two thinning levels: no thinning leaving commercial crop load (∼180 fruits tree⁻¹), and hand-thinning at the onset of Stage II leaving a light crop load (∼85 fruits tree⁻¹). Under commercial crop loads, DI trees were moderately water-stressed and this had some positive effects on fruit quality. DI increased fruit firmness (FF), soluble solids concentrations (SSC) and acidity at harvest while no changes were observed in fruit maturity (based on ethylene production). Differences in FF and acidity at harvest between FI and DI fruit were maintained during cold storage. DI also reduced fruit weight loss during storage. But fruit size was reduced under DI. Fruit thinning under DI resulted in better fruit composition with no detrimental effect on fresh-market yield compared to un-thinned fruit. Fruit size at harvest and SSC values after five months of cold storage were higher in fruit from thinned trees than fruit from un-thinned trees. Fruit thinning increased fruit ethylene production, indicating advanced maturity. This may lead to earlier harvest which is desirable in years with impending drought. Fruit thinning is therefore a useful technique to enhance pear marketability under water shortage.     

Inoculation of growing media with the rhizobacterium Variovorax paradoxus 5C-2 reduces unwanted stress responses in hardy ornamental species

Inoculation of growing media with plant growth promoting rhizobacteria (PGPR) has a number of potential benefits for the production of ornamental plants. Certain rhizobacteria synthesise the enzyme ACC deaminase, which cleaves ACC, the precursor of the plant hormone ethylene. Bacterial metabolism is now known to lead to a reduction in [ACC] in the plant transpiration stream and bacteria are hypothesised to act on ACC exuded from roots. This in turn reduces the ethylene generated in plants growing in growing media inoculated with these bacteria. Here we tested if applications of the ACC deaminase containing rhizobacteria Variovorax paradoxus⁵C–²could be of benefit to ornamental growers by reducing ethylene generation in stressed plants. Ethylene is produced at levels that are inhibitory to growth and development under a number of abiotic stresses. The propagation and production of hardy ornamentals is deleteriously affected by abiotic stresses that involve ethylene signalling, including drought and physical wounding. Inoculation of growing media with V. paradoxus 5C-2 lowered ethylene emission from mature leaves of Cytisus × praecox experiencing drought stress. In addition, bacterial inoculation of the growing media resulted in significantly reduced abscission of the mature leaves under drought treatment. Beneficial effects of inoculation where also found in the wounding response of Fargesia murielae following divisional propagation and late season senescence in Aquilegia × hybrida in response to drought stress. Together these results demonstrate that V. paradoxus⁵C–²has real potential for use on ornamental nurseries in situations where plant stresses are unavoidable.     

脂氧合酶与番茄采后成熟的关系

采后番茄果实组织的脂氧合酶（ＬＯＸ）活性随成熟衰老期的进程而改变，从绿熟期（ＭＧ）到转红期（Ｔ）ＬＯＸ酶的活性逐渐增高，然后降低，其模式呈现跃变型果实的特点。利用外源乙烯分别处理绿熟期、发白期和转红期的果实，其ＬＯＸ酶的活性较对照都有明显提高。用ＬＯＸ酶处理番茄果实组织，乙烯产量没有明显提高，然而电导率有大幅度增加，二羟基萘（ＤＨＮ）能部分抑制ＬＯＸ酶的这一作用。ＬＯＸ酶的活性增加需要有果蔬体内乙     

月季切花开花和衰老进程中乙烯变化类型初探

以１４个生产用月季切花品种为试材，测定了开花和衰老过程中花朵的乙烯生成量和呼吸强度变化动态。结果表明：（１）乙烯生成量在萨蔓莎、天使、默西德斯、加布里拉和雅典娜５个品种表现为蕾期较低，随外层花瓣展开逐渐增大，在盛开期达到高峰，然后降低，变化动态类似于跃变型切花和跃变型果实；唐娜小姐品种在整个开花和衰老进程中一直保持在较低水平，类似于非跃变型切花和果实的变化动态；坦尼克、黄金时代、金徽章、金牌、红衣主教、红成功、玛丽娜等品种在蕾期较低，随着开花进程逐渐增大，至盛花后期花朵露心时仍在增加，类似于末期上升型果实的变化特点。（２）上述３个类型月季品种的呼吸强度在瓶插期间的变化趋势一致，即花蕾期相对较低，花朵充分展开前迅速升高并出现高峰，然后降低，呈现典型的呼吸跃变类型，同时，萨蔓莎和天使呼吸跃变高峰的出现都比类似乙烯跃变高峰的出现提前１～２天。说明月季切花乙烯生成量与呼吸强度的变化动态有很大不同     

1-甲基环丙烯对采后猕猴桃果实生理效应的影响

 以美味猕猴桃‘秦美’果实为试材, 研究1-MCP (1-甲基环丙烯) 处理对果实乙烯释放量、硬度、维生素C 含量及SOD (超氧化物歧化酶) 、POD (过氧化物酶) 活性变化的影响。结果表明, 1-MCP 处理能显著降低果实乙烯释放量, 提高SOD、POD 活性, 抑制硬度下降, 推迟软化。     

乙烯抑制剂在采后观赏植物中的应用研究进展

乙烯作为植物衰老激素在观赏植物及切花开花衰老过程中起着关键性的调节作用。利用乙烯抑制剂控制乙烯作用就成为延长观赏植物观赏寿命和提高其观赏价值的主要途径和经济有效的方法,是采后观赏植物研究的主要方向之一。在此,综述了近年来在采后观赏植物研究和生产实践中广为应用的几种乙烯抑制剂,并简要说明了其特点和作用原理。     

表油菜素内酯对提高烟草种子活力机理的研究

本研究表明,用表油菜素内酯(24—Epibrassinolide,简称BR)0.05ppm或0.01ppm浸泡烟草种子24小时后,种子的电导率和渗出液紫外光OD值降低,吸氧量增加,乙烯释放速度和释放量增大;烟草种子萌发时间缩短,其发芽率、萌发系数和发芽势分别高于对照10%、30%和15%以上;幼苗植株干重及根长和根干重明显地增加;幼苗生长势及其抗逆性增强.     

小鼠桑椹胚简易玻璃化冷冻技术再探讨

本试验继小鼠扩张囊胚玻璃化冷冻保存成功后，在室温（２５℃）下利用不同浓度的ＥＦＳ玻璃化溶液，对小鼠的桑椹胚简易玻璃化冷冻技术进行再探讨。结果是胚胎在１０％ＥＧ溶液中预先处理５分钟，再移入事先配置好含有ＥＦＳ３０的０．２５ｍｌ塑料细管中１分钟平衡后直接投入液氮中冷冻，解冻后获得的发育率最高（９４％）。冻胚移植后妊娠率和产仔率分别为５６％（９／１６）及４２％（４９／１１６）。与对照组相比差异不显著（Ｐ＞０．０５）     

1-甲基环丙烯不同时间处理对芒果贮藏生理的影响

以"台农"芒果为材料,测定了1-甲基环丙烯(1-MCP)0-18h处理对芒果贮藏期的呼吸强度、乙烯释放量、可溶性固形物、成熟度指数的影响。结果表明:不同时段的1-MCP处理均能降低呼吸强度,推迟呼吸高峰的到来,延缓乙烯释放量增加,推迟可溶性固形物含量上升,有效延缓后熟进程。其中12、18h处理对延缓成熟的效果优于6h处理,二者之间对成熟度的影响差异不明显,建议使用1-MCP处理12h为宜。     

一氧化氮和外源乙烯处理对肥城桃果实乙烯生物合成的影响

 【目的】研究一氧化氮（NO）和乙烯处理对肥城桃内源乙烯生物合成的影响，并探讨NO与乙烯的拮抗作用。【方法】分别用10 μl•L-1 NO和1 000 μl•L-1 外源乙烯、10 μl•L-1 NO和1 000 μl•L-1 外源乙烯共同处理3种方式处理肥城桃果实，研究果实内源乙烯生物合成的变化。【结果】外源乙烯促进了肥城桃果实的内源乙烯生物合成；而NO通过显著降低果实中ACS和ACO的活性，明显抑制了肥城桃果实内源乙烯的生物合成。NO和外源乙烯共同处理的肥城桃果实内源乙烯生物合成低于外源乙烯单独处理而高于NO单独处理，表明NO对外源乙烯具有拮抗作用。【结论】NO抑制了果实内源乙烯的生物合成，且抑制了外源乙烯对果实乙烯生物合成的催化作用。