采前低温诱发菠萝果实黑心病

采前低温可诱发菠萝果实黑心病,发病率变化范围为６０％－１００％,低于２１℃的采前低温影响是诱发菠萝黑心病的重要因子之一。在华南菠萝生产区,不同品种对黑心病敏感性的峭同。因此,培育和栽培抗黑心病的菠萝新品种,将是一个控制黑心病腐烂的重要措施。     

采后菠萝黑心病诱导因素的研究

本文叙述了外源赤霉素ＧＡ３、低温条件对采后菠萝果实黑心病发展的影响．说明外源赤霉素ＧＡ３和低温条件都是诱导菠萝黑心病的重要因子。菠萝黑心病是一种生理失调症。实验中,未发现化学杀菌剂对此种病症显现出防治效果,而采后贮前４０℃高温处理２４小时．则可以减少和延迟此病的发生,因此．后者是一种可以应用于商品菠萝果实黑心病防治的好方法。     

低温与GA_3诱导菠萝黑心病的生理机制

菠萝黑心病是PPO催化氧化酚类物质形成褐色产物所致。低温或GA_3处理提高了PPO活性及其底物——儿茶酚、绿原酸和咖啡酸的含量,也导致了PAL活性增加;低温还使乙烯释放率增大。这些变化均有利于黑心病的发生和发展。     

低温打蜡对贮藏菠萝黑心病控制的作用

研究了常温、低温、低温加打蜡 3种贮藏条件下菠萝果实硬度、可溶性固形物 (TSS)、可溶性糖醛酸、多聚半乳糖醛酸酶 (PG)和多酚氧化酶 (PPO)等因素的变化 ,及它们对黑心病发生及发展情况的影响。结果表明 ,低温加打蜡可以延缓果肉硬度、可溶性固形物和可溶性糖醛酸含量的下降 ,降低 PG和 PPO的活性 ,降低黑心病的发病率 ,较好的保持果实品质     

雪花梨和鸭梨果实贮藏特性比较（简报）

采后雪花梨和鸭梨果实于20±1℃下均具典型的呼吸跃变过程。后者采后初期对低温敏感,降温过快,导致早期黑心病.12C 下,一周后每 3d降1C 缓慢降温,直至0±0.5C 可控制早期黑心病的发生。前者直接于0C下贮藏效果好。后者对CO_2也敏感,尤其是果心组织,5％～10％的CO_2处理两周,即可导致严重的果心组织褐变,但小于10％的CO_2对前者较安全,且能获得较好的贮藏品质。     

鸭梨黑心病的研究 Ⅰ.温度对黑心病的影响

黑心病是鸭梨贮存过程中经常发生的问题,我们在实验中研究了产地、树龄、采摘期和鸭梨入库贮存时的温度与黑心病的关系。证明:急降温或入库温度低于10℃是造成鸭梨贮存早期发生黑心病的主要原因;调节库温可有效地控制早期黑心病的发生,并有利于防止鸭梨贮存后期黑心病的出现;提前采摘期对控制黑心病有良好效果。     

菠萝VOZ转录因子序列特征及其对非生物胁迫的响应

为探究菠萝(Ananas comosus)维管植物锌指蛋白转录因子(VOZ)家族的序列特征及表达特征,该研究采用生物信息学的方法对菠萝VOZ转录因子家族进行序列分析,并通过qRT-PCR技术研究了NaCl、干旱和低温(4℃)等逆境处理对菠萝VOZ家族基因表达的影响。结果表明:(1)菠萝与拟南芥、水稻的VOZ转录因子家族均含有2个保守区域,且菠萝VOZ蛋白均为亲水酸性蛋白;蛋白质二级结构显示,菠萝VOZ蛋白主要结构元件为α-螺旋和无规则卷曲。(2)qRT-PCR分析显示,不同非生物胁迫下,AcoVOZ1和AcoVOZ2的表达量与对照差异显著,且NaCl、干旱、低温(4℃)、甘露醇、ABA、Eth胁迫下,AcoVOZ1和AcoVOZ2的表达量均呈显著下降趋势。研究推测,菠萝VOZ转录因子家族以负调控的方式参与菠萝抗高盐、干旱、低温(4℃)等非生物胁迫的应答反应,为进一步研究菠萝抗逆分子机制和菠萝抗逆性基因工程改良奠定了技术基础。     

采后处理对菠萝营养成分的影响

贮藏期间,杀菌剂处理可以推迟采后菠萝可溶性糖含量的减少,而对可滴定酸含量没有明显的影响。采后贮前加热４０℃２４ｈ处理的菠萝,其可溶性糖、可滴定酸等营养成分的变化与对照果实没有明显差异。与对照果实相比较,ＧＡ３处理果实除可溶性糖含量下降明显减少之外,可滴定酸和抗坏血酸含量显著增加。     

果实采后对低温逆境的适应性响应及信号转导(综述)

本文综述果实采后对低温逆境的适应性响应,并讨论果实采后低温逆境的信号转导和今后果实低温逆境的研究方向,认为分子生物学和基因工程是开展果实采后低温逆境研究的有效途径。     

菠萝中蛋白酶及其他组份在品种间的差异分析

以湛江地区6个主要菠萝品种巴厘、卡因、台农17号、台农16号、粤脆、香水为对象,研究菠萝的组分在品种间的差异及其与菠萝蛋白酶的产率和酶活力之间的相关性,结果显示,不同的菠萝品种间,各组分的含量以及蛋白酶的得率及酶活有显著差异。菠萝果皮和果肉的不同生长部位的蛋白含量、酶活力及酶得率有显著差异。酶得率与蛋白及纤维素含量呈显著正相关;酶活力与糖酸比、得汁率、纤维素含量及Zn含量呈显著负相关,蛋白含量、纤维素含量、糖酸比、得汁率是衡量菠萝产酶品质的重要指标。     

Low temperature alters plasma membrane lipid composition and ATPase activity of pineapple fruit during blackheart development

Plasma membrane (PM) plays central role in triggering primary responses to chilling injury and sustaining cellular homeostasis. Characterising response of membrane lipids to low temperature can provide important information for identifying early causal factors contributing to chilling injury. To this end, PM lipid composition and ATPase activity were assessed in pineapple fruit (Ananas comosus) in relation to the effect of low temperature on the development of blackheart, a form of chilling injury. Chilling temperature at 10 °C induced blackheart development in concurrence with increase in electrolyte leakage. PM ATPase activity was decreased after 1 week at low temperature, followed by a further decrease after 2 weeks. The enzyme activity was not changed during 25 °C storage. Loss of total PM phospholipids was found during postharvest senescence, but more reduction was shown from storage at 10 °C. Phosphatidylcholine and phosphatidylethanolamine were the predominant PM phospholipid species. Low temperature increased the level of phosphatidic acid but decreased the level of phosphatidylinositol. Both phospholipid species were not changed during storage at 25 °C. Postharvest storage at both temperatures decreased the levels of C18:3 and C16:1, and increased level of C18:1. Low temperature decreased the level of C18:2 and increased the level of C14:0. Exogenous application of phosphatidic acid was found to inhibit the PM ATPase activity of pineapple fruit in vitro. Modification of membrane lipid composition and its effect on the functional property of plasma membrane at low temperature were discussed in correlation with their roles in blackheart development of pineapple fruit.     

A novel aspartic acid protease gene from pineapple fruit (Ananas comosus): Cloning,characterization and relation to postharvest chilling stress resistance

A full-length cDNA encoding a putative aspartic acid protease (AcAP1) was isolated for the first time from the flesh of pineapple (Ananas comosus) fruit. The deduced sequence of AcAP1 showed all the common features of a typical plant aspartic protease phytepsin precursor. Analysis of AcAP1 gene expression under postharvest chilling treatment in two pineapple varieties differing in their resistance to blackheart development revealed opposite trends. The resistant variety showed an up-regulation of AcAP1 precursor gene expression whereas the susceptible showed a down-regulation in response to postharvest chilling treatment. The same trend was observed regarding specific AP enzyme activity in both varieties. Taken together our results support the involvement of AcAP1 in postharvest chilling stress resistance in pineapple fruits.     

Transcriptional regulation of a pineapple polyphenol oxidase gene and its relationship to blackheart

Two genes encoding polyphenol oxidase (PPO) were isolated from pineapple (Ananas comosus[L.] Merr. cv. Smooth Cayenne). Sequence analyses showed that both contained a single intron and encoded typical chloroplast-localized PPO proteins, the sequences of which corresponded to two pineapple PPO cDNAs, PINPPO1 and PINPPO2, recently described by Stewart et al. (2001). Southern blot analyses suggested that pineapple contained only two PPO genes. Analysis of expression of PINPPO1 promoter GUS fusion constructs showed this promoter had a low basal activity and was cold- and wound-inducible, consistent with known mRNA expression profiles. Striking homologies to gibberellin response complexes (GARC) were observed in sequences of both the PINPPO1 and PINPPO2 promoters. Transient assays in mature pineapple fruit and stable expression in transgenic tobacco showed that PINPPO1 promoter-GUS fusions were indeed gibberellin (GA) responsive. A role for the element within the putative GARCs in mediating GA-responsiveness of the PINPPO1 promoter was confirmed by mutational analysis. PINPPO2 was also shown to be GA-responsive by RT-PCR analysis. Mutant PINPPO1 promoter-GUS fusion constructs, which were no longer GA-inducible, showed a delayed response to cold induction in pineapple fruit in transient assays, suggesting a role for GA in blackheart development. This was supported by observations that exogenous GA(3) treatment induced blackheart in the absence of chilling. Sequences showing homology to GARCs are also present in some PPO promoters in tomato, suggesting that GA regulates PPO expression in diverse species.     

黄瓜的冷害及耐冷性

随着蔬菜反季节栽培面积的不断扩大,如何提高黄瓜(Cucumis sativus L.)耐冷性已成为选育新品种的研究重点。系统地综述近几年黄瓜耐冷性的鉴定、获得途径、冷害机理以及遗传和分子遗传学等方面的研究,以促进对黄瓜冷害机制的研究, 加速耐冷品种的培育。耐冷性鉴定时要从耐冷指数、低温发芽能力、MDA (丙二醛)含量和电解质渗漏率等几个方面综合鉴定。耐冷性的获得途径主要有冷驯化、激素处理、热激处理和培育耐低温品种,最重要的途径是耐冷品种选育。黄瓜冷害机理包括细胞膜的流动性降低及透性增加,光合作用被抑制,根系吸收减弱,可溶性糖含量减少,淀粉粒积累增加,微管的稳定性受到破坏等。黄瓜低温发芽能力由非加性基因决定,而幼苗时期主要由加性基因控制。黄瓜 耐冷的分子遗传学研究进展缓慢,目前已克隆出在低温锻炼中特异表达的功能未知的基因CCR18。今后还应研究黄瓜低温胁迫时的信号转导系统,以进一步揭示黄瓜的冷害机理;利用野生资源的抗逆性状,拓宽栽培黄瓜的遗传基础,选育适于保护地栽培的耐低温品种。     

Differential response of photosynthesis in greenhouse- and field-ecotypes of tomato to long-term chilling under low light

Three greenhouse- and four field-ecotype varieties of domestic tomato (Lycopersicon esculentum) were compared for the sensitivity of their photosynthetic apparatus to chilling under low light intensity. After chilling at 12/7 degrees C under 100 micromolm(-2)s(-1) of light for 10 days, they were allowed to recover at 25/18 degrees C and 600 micromolm(-2)s(-1) of light for 10 days. For both pre-chilling and recovered plants, greenhouse-ecotype varieties did not necessarily show higher net CO(2) assimilation rate (A), quantum yield of electron transport at PSII (Phi(PSII)) and photochemical quenching (q(P)) than field-ecotype varieties. However for the post-chilling period, greenhouse-ecotype varieties, exhibited higher A, and Phi(PSII) values than field-ecotype varieties. The difference in Phi(PSII) was found to be largely due to q(P). The absence of ecotypic differences in pre-chilling plants indicates that the trait was not expressed constitutively, but relied mainly on adaptation/acclimation mechanisms. Greenhouse-ecotype varieties were able to adapt to low temperature and low light more quickly, and then exhibited higher A, Phi(PSII), q(P) values and greater re-growth capacity after chilling than field-ecotype varieties. Plant re-growth capacity after chilling was highly correlated with Phi(PSII) and q(P) measured in chilled plants, suggesting the usefulness of Phi(PSII) and q(P) measured at low temperature after defined chilling stresses as screening indexes for chilling tolerance in breeding programs.     

光照条件下低温对水稻籼粳亚种幼苗抗氧化物质含量的影响

与对低温不敏感的粳稻台北309和武育粳相比,对低温敏感的籼稻IR64、CA212和Pusa经光照条件下8℃处理后最大光合速率(Pmax)和原初光化学效率(Fv/Fm)下降较多,出现了O2-·、过氧化氢、氧化型谷胱甘肽(GSSG)和氧化型抗坏血酸(DHA)的大量累积,其GSSG和DHA的含量分别与叶绿素含量的下降呈极显著负相关,表明光照条件下低温胁迫下,还原态的谷胱甘肽(GSH)和抗坏血酸的再生受阻,不能有效地清除活性氧,导致其叶绿素含量降低和光合能力受抑,而汕优63的变化位于上述两种类型之间。其中AsA/DHA和GSH/GSSG的变化与叶绿素含量的变化呈极显著正相关。