超声预处理对半干型荔枝干干燥时间的影响

为探讨半干型荔枝干在干燥前用超声波预处理对其干燥时间的影响,在单因素试验获得效果的基础上,进一步利用响应曲面分析法对超声波预处理条件进行优化,建立了数学回归模型;并对相关机理进行了初步探讨。结果表明：干燥前的超声波预处理能够缩短其干燥时间;预处理的优化条件为：超声频率40 kHz,超声时间32.6 min,超声功率 354 W;在优化条件下预处理后,荔枝干燥至其果肉湿基含水率约为32%时的预测干燥时间为15.65 h,而未处理荔枝所用时间需26.80 h;验证试验实测时间为15.93 h,表明数学回归模型所得的预测值与实测值有较好的一致性;电镜扫描结果表明超声预处理对荔枝内外果皮结构有明显影响,此结果可较好地解释超声预处理能够缩短荔枝干燥时间的机理。     

快速高效提取荔枝幼果和离区组织RNA的新方法）

 以荔枝幼果和离区为材料,以N–十二烷基肌氨酸钠（LSS）为RNA提取液的主要成分,建立了一种简单快速高效适合于荔枝幼果和离区总RNA提取的新方法,简称LSS法。该法提取RNA的过程只需2 h,且质量高,幼果和果柄RNA的28S/18S值分别为1.7和1.9,RNA完整性（RIN）值分别为9.7和10.0,分别为380和450 μg · g-1,A260/A280值分别为1.80和1.89。将提取的RNA经DNA酶消化后反转录成cDNA进行PCR,扩增出预期长度的目的片段,满足进行后续基因表达的要求。LSS法操作简单快速,对微量组织样品是一种有效的RNA提取方法。     

Effects of a phospholipase D inhibitor on postharvest enzymatic browning and oxidative stress of litchi fruit

Membrane lipid degradation catalyzed by phospholipase D (PLD) results in postharvest browning and senescence of litchi fruit. The effects of n-butanol, a specific PLD inhibitor, on enzymatic browning and oxidative stress during storage of litchi fruit at room temperature were evaluated. n-Butanol-treated fruit had a lower browning index and disease index than untreated fruit. n-Butanol treatment also decreased PLD activity. As a result, the decompartmentalization of litchi polyphenoloxidase and substrates was reduced. The conversion of substrates (−)-epicatechin and procyanidin A₂ into quinones was slowed down and enzymatic browning of litchi pericarp tissues was lower after 6 d storage. Additionally, n-butanol-treated fruit possessed significantly lower malondialdehyde contents than untreated fruit after 4 d storage. Analysis of antioxidative enzyme activities showed that n-butanol treatment inhibited oxidative stress mainly by maintaining high catalase activity in litchi pericarp tissues. Consequently, senescence of litchi fruit during storage was moderated.     

Effects of boron-deficiency on anatomical structures in the leaf main vein and fruit mesocarp of pummelo [Citrus grandis (L.) Osbeck]

Summary

Boron (B)-deficiency is a nutritional problem in the citrus industry worldwide. Under B-deficient conditions, symptoms such as corky split veins, small fruit, low tree vigour, and low fruit yield appear. In this study, we investigated the anatomical responses of mature leaves and the albedo of mature fruit of HB pummelo [Citrus grandis (L.) Osbeck] to B-deficiency. Under B-deficient conditions, the numbers of parenchyma cells in the vascular bundles of the leaf and fruit mesocarp increased significantly. The ratio of the area of the phloem to the area of the vascular bundle also increased, while the ratio of the area of the xylem to the area of the vascular bundle decreased in both tissues. Moreover, we observed alterations in the xylem elements under B-deficient conditions. The average lengths of xylem vessels were 216.7 µm and 175.4 µm in leaf main veins and in fruit mesocarp, respectively, both significantly lower than the corresponding values in B-sufficient control plants. However, B-deficiency reduced the average diameter of xylem vessels only in leaf main veins. On the other hand, B-deficiency increased the numbers of pitted vessels to 63 and 59 among 100 xylem vessels sampled at random in leaf main veins and in the fruit mesocarp of B-deficient pummelos, respectively, while the corresponding numbers were 43 and 35, respectively, under B-sufficient conditions. B-deficiency also decreased the numbers of scalariform and reticulated vessels. Possible mechanisms for these anatomical modifications under B-deficient conditions are discussed.     

荔枝古树胚性愈伤组织Fe-SOD成员基因克隆及生物信息学分析

为了解Fe-SOD在荔枝古树胚性愈伤组织保存中的分子机制,选择荔枝古树"宋荔"花药诱导而来的胚性愈伤组织为试验材料,采用同源克隆和RACE方法,获得荔枝Fe-SOD的两个转录本和基因组序列,并对该基因组的内含子进行分析。克隆获得长1 285 bp含有完整开放阅读框的荔枝Fe-SOD核酸序列,其编码1个含有250个氨基酸的蛋白质,将该序列命名为LcFe-SOD7a。生物信息学分析结果表明:该蛋白为稳定的、亲水的、含跨膜结构域的偏酸性蛋白质,定位于微体(过氧化物酶体)和细胞质,具有多样的磷酸化位点。LcFe-SOD7a基因组序列长2 284 bp,含7个内含子,其中第4个内含子较长,达920 bp。同时还得到其中的1条内含子驻留型可变剪接基因,该可变剪接基因提前终止,仅编码207个氨基酸的蛋白质,将该可变剪接基因命名为LcFe-SOD7b。     

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.     

不同物候期妃子笑荔枝叶片光合特性及碳水化合物含量变化分析

【目的】了解不同物候期妃子笑荔枝叶片光合特性和碳水化合物含量变化趋势,为妃子笑荔枝丰产栽培管理提供理论依据。【方法】连续 3 年观测妃子笑荔枝的物候期,并对不同物候期内荔枝叶片光合特性指标及碳水化合物含量的变化进行研究。采用 CIRAS-3 便携式植物光合测定仪测定叶片光合特性指标、蒽酮 -硫酸法测定叶片可溶性糖含量、碘量法测定叶片淀粉含量。【结果】妃子笑荔枝叶片净光合速率呈波浪式变化,枝梢完全老熟后出现最高值 13.04 μmol/m2·s,果实着色期出现最低值 4.73 μmol/m2·s;叶绿素含量在生长期内整体呈现上升趋势,其最大值为 5.2 mg/g。可溶性糖含量呈波浪式变化趋势,花芽分化期处于相对较高水平,最高值 42 mg/g 在生理落果结束后出现,果实成熟期出现最低值 16 mg/g;淀粉含量在花芽分化期呈上升趋势,最高值 237 mg/g 在白点期出现,生理落果期含量下降到最低值 102 mg/g,而后逐渐回升。【结论】从花芽分化期到果实成熟期,叶片净光合速率存在两个峰值,在花芽分化期和果实发育期出现;可溶性糖含量在果实发育期和果实着色期有较大积累,淀粉含量在花芽分化期和果实着色期有较大积累,为后续生长发育储备充足营养。在整个过程中,叶片无明显退绿现象。     

荔枝主要害虫防治技术研究进展与综合治理体系构建

对近 30 年来国内外荔枝害虫防治技术研究情况进行全面总结和梳理：监测预警技术主要用于对荔枝蒂蛀虫、荔枝蝽和鳞翅目食叶害虫防治适期的预测;农业防治措施主要有间伐疏植、回缩修剪、严控冬梢、清理落果、果园生草和间种豆科作物等;生物防治技术包括释放天敌昆虫和施用生物农药等,人工释放平腹小蜂防治荔枝蝽是目前荔枝上较为成功的“以虫治虫”例子,B.t. 和绿僵菌制剂等生物农药对荔枝鳞翅目食叶害虫低龄幼虫有一定的防效;物理防治技术包括色诱、性诱、灯光诱杀和干扰等;化学防治仍是目前防治荔枝害虫最重要的手段,但正式登记的只有拟除虫菊酯类、有机磷类和除虫脲等药剂,而防效更好的甲氨基阿维菌素苯甲酸盐、氯虫苯甲酰胺和噻虫胺等药剂尚有待登记。根据多年研究积累和实践经验,提出在荔枝开花前和谢花后各施药 1 次以防治多种害虫为害或压低虫口基数;释放平腹小蜂防治荔枝蝽以减少农药使用次数;对于荔枝蒂蛀虫要贯彻“兼前 - 抓中 - 控后”和“成虫、卵和初孵幼虫一起杀”的防控策略,在幼果期通过预测预报确定其防治适期可提高防效和减少施药次数;果实及时采收、采后及时修剪,保秋梢、控冬梢和冬季清园等措施都有助于压低虫口基数。     

施用不同pH改良剂对荔枝园酸性土壤性质及荔枝生长的影响

采集华南典型荔枝园酸性土壤[pH(4.2±0.2)],分别在土壤中添加石灰（1 g/kg）、白云石粉（2 g/kg）和2个用量（0.625、4 g/kg）钙镁磷肥,以不添加改良剂为对照,进行土壤培养和荔枝盆栽试验,比较不同物质改良土壤的效果及对荔枝生长的影响。结果表明：施用pH改良剂均可不同程度提高土壤pH,影响土壤的大、中、微量元素养分有效性和酶的活性,土壤性质的变化与改良剂种类、用量及土壤属性本身有关;施用石灰、白云石粉和高量钙镁磷肥均能显著促进荔枝生长,其中石灰和白云石粉的综合作用优于高量钙镁磷肥,但施用低量钙镁磷肥抑制荔枝生长。建议石灰和白云石粉可用作荔枝园酸性土壤pH 改良剂,可否选用钙镁磷肥及其合理用量,则需根据土壤性质而定。     

基于GPRS的荔枝园防盗远程监测系统

针对种植规模大的荔枝园劳动力短缺以致安保管理困难的问题,提出了一种基于GPRS网络的防盗远程监测系统。该系统由单片机控制模块、GPRS通信模块、传感器模块、显示模块、报警模块及远程数据中心6部分组成,借助GPRS数据业务,实时地将荔枝园现场的防盗信息发送至远程数据中心,实现对异常情况的报警。测试结果表明:系统的平均数据传输时间为29.91s,6种传感器相邻安装模式中能正常报警的模式有两种。一种模式是传感器间距为3cm且夹角为30°,人到传感器距离为40cm;另一种模式是传感器间距为6cm且夹角为3 0°,人到传感器距离为7 0 cm。该系统安全性高,使用灵活,相比传统的监控系统更有优势。