Somatic embryogenesis and plant regeneration from litchi protoplasts isolated from embryogenic suspensions

High yields of protoplasts were isolated from litchi embryogenic suspensions, which were maintained by alternative culture in liquid and on solid media containing silver thiosulfate. Protoplasts in liquid culture and agarose beads were unable to divide sustainedly, whereas embedding of protoplasts in Ca-alginate supported cell division to microcalli and the direct formation of somatic embryos from protoplasts. Nurse cells of litchi further enhanced the culture efficiency when protoplasts were cultured in Ca-alginate beads. White non-hyperhydric somatic embryos were developed from protoplast-derived microcalli or proembryos, and 33.1% of white somatic embryos regenerated into plantlets. This revised version was published online in June 2006 with corrections to the Cover Date.     

地膜覆盖棉花、玉米、大豆生育盛期的降温效应

1999～2001年的试验结果表明地膜覆盖在夏季作物旺盛生长期(棉花：开花-吐絮、玉米：抽雄穗-乳熟、大豆：开花-结荚)3种覆盖作物的叶面积均比对照作物大,其叶面积系数分别为：棉花：3．9／3．1、玉米：3．3／2．7、大豆：4．0／3．2。进入作物群体中的光照度(I)主要与叶面积系数(F)有关,而叶面积系数又直接影响消光系数(k)的大小。农田覆盖地膜后,其在作物生育前期的增温保湿作用,使其作物生育速度加快,到作物旺盛生长期因其枝叶茂盛,叶面积系数增大,消光系数减小,白天冠层上部叶片截留的太阳总辐射多,致使最终进入作物群体中下部的光能减少。白天覆盖地虽然蒸发量减少,但因其作物枝叶茂盛,蒸腾量则增大,农田消耗于蒸散(LEc)的能量增多,导致加热土壤(B项)的能量减少。覆盖作物地的土壤温度较对照地低,其中又以白天地面最高温度降温最为明显．棉花、玉米、大豆等3种作物降温幅度分别为3．1C、2．7C和2．5C。地膜覆盖在作物旺盛生长期的降温效应,可减轻夏季高温对作物的危害,夏季白天当温度超过光合作用适宜温度(20～25C)以上时,呼吸作用消耗的有机物质增加,作物生长缓慢,而覆盖作物地因其温度较对照地低,光合强度大,生长活力增强,因而使作物能够增产。     

区域种植业气候适宜度及其对种植活动的响应——以四川省盐亭县为例

在分析盐亭县近63年来(1950—2012)种植业生产发展的基础上,选取该县农村社会经济条件相对稳定的近32年(1981—2012)为研究时段。运用农业生态气候适宜度方法,依据水稻、红薯、玉米、小麦和油菜等5种主要作物生育期的光、热、水等气候条件,分别估算各种作物的资源适宜指数、效能适宜指数和利用指数,构建小尺度区域种植业气候适宜度模型和种植活动对区域种植业气候适宜度的影响度模型,进行小尺度区域种植业气候适宜度以及种植活动对种植业气候适宜度的影响度估算,并对种植业生产对气候变化的适应进行探讨。研究结果表明,(1)近32年来盐亭县大春作物的平均资源适宜指数、效能适宜指数和利用指数(分别为0.578、0.281和48.37%)均大于小春作物(分别为0.304、0.128和42.24%),大春作物的气候适宜度高于小春作物,且作物间的气候适宜度差异较大。(2)受季风气候波动的影响,该县作物气候适宜度有明显的年际波动;该县近32年来气候变化对大春作物气候适宜度有轻微不利影响,而对小春作物气候适宜度趋于有利。(3)盐亭县近32年来种植业平均的资源适宜指数为0.466、效能适宜指数为0.212、利用指数为45.49%;受5种作物资源适宜指数、效能适宜指数,以及作物播种面积与产量年际波动的综合影响,该县种植业气候适宜度亦有明显的年际波动;气候变化对该县种植业气候适宜度总体上有不利影响。(4)近32年来该县种植活动对种植业气候适宜度的影响度平均值为0.00092,其年际波动较大。通过作物种植组合结构的调整,在20世纪90年代中期前对种植业气候适宜度的提高有微弱的正向影响,对气候变化有一定程度的适应;而后期则有负向作用。     

广州市农作物系统与大气的CO2交换

在广泛收集资料和实验分析的基础上,研究了广州市各种农作物系统与大气CO2交换.分析了各种农作物系统净生产力吸收CO2的能力和碳汇功能大小.结果表明:2005年广州市8种农作物系统作物净生产力吸收CO2 4 032 366t·a-1,其土壤CO2排放3981753t·a-1,吸收大于排放,对大气CO2而言,整个农作物系统是一个弱的碳汇;水稻、甘蔗、木薯和果用瓜4种连作或高杆作物系统每年作物净生产力吸收CO2量大于土壤CO2的排放量,系统具有较大的碳汇功能,花生、大豆、花卉和蔬菜4种矮杆作物系统每年作物净生产力吸收CO2量小于土壤CO2的排放量,系统起着碳源作用;果实或经济产量生长在地上部分的作物其单位面积吸收CO2能力比果实(块根)生长在地下的作物大;除花生在生育期间生物量吸收CO2量少于同期土壤排放以外,其余7种作物在生育期间生物量吸收CO2的量大于同期土壤排放,大多数农作物在生育期间具有碳汇功能,在撂荒期才体现碳源作用.     

作物野生近缘种的保护与利用

作物野生近缘种将是保证下一世纪粮食充足的重要因素。近30余年来国际国内非常重视作物野生种质资源的搜集、保存、鉴定、评价和利用的研究。我国作物野生近缘种特别丰富,同时受威胁非常严重。因此,加大力度开展作物及其野生近缘种种质资源的遗传多样性、保存技术、种质创新和利用的研究是刻不容缓的。     

Practical applications of in vitro propagation: Present situation and future prospects

Abstract

This article surveys the techniques and approaches used in the in vitro propagation of economically important plants. The current state of the art for each major class of plants, namely ornamentals, vegetable and agronomic crops, temperate fruits and forest trees is described. The advantages of vegetative propagation in general and the specific advantages which micropropagation offers in the domestication, breeding and conservation of plants are listed. Specific problems associated with in vitro propagation such as juvenility vs maturation, vitrification, rooting and morphological or physiological variations are discussed.     

An improved procedure for protoplast microelectrofusion and culture of Nicotiana tabacum intraspecific somatic hybrids: plant regeneration and initial proofs on organelle segregation

Somatic hybrids were produced between haploid Nicotiana tabacum L. cv. Petite Havana (wild type) and haploid streptomycin resistant (SR1) mutant by an improved version of microelectrofusion of preselected pairs of protoplasts and the culture of fusion products in a nurse culture. Resistance of diploid plants regenerated from 20 somatic hybrid clones was tested at low concentration of streptomycin in the light as well as at high concentrations of streptomycin in the dark. In two independent hybrid lines, plants resistant in the light but sensitive in the dark were found. The existence of this plant type indicates a segregation of chloroplasts and mitocondria in somatic hybrid clones. It is suggested that microelectrofusion of preselected pairs of protoplasts combined with a reliable nurse culture might be a good technique for controlled somatic hybridization, cell reconstitution and partial gene transfer to different plant species. It might also be used to follow and analyse organelle segregation in somatic hybrid clones. The possibility that mitochondria might be resistant to streptomycin in the SR1 mutant is also discussed.     

中国转基因作物风险评估技术研究进展

现代生物技术的发展为利用外源基因培育优良作物品种提供了新的途径,目前国内外已培育出多个高抗害虫的转基因作物。但是,人们对转基因作物潜在的风险尚存在疑问,这是目前转基因作物是否能进一步获准商品化生产的一个重要原因。综述了中国转基因作物研究和转基因产品安全性检测技术取得的主要进展,对我国转基因作物的研究前景进行了展望,并对将来的工作提出了几点建议。     

主要农作物转基因研究现状和展望

近15年来,大豆、水稻、玉米、小麦等主要农作物转基因研究取得了较大进展,几乎各种遗传转化方法在这些作物上都取得了成功,尤其是农杆菌介导法,不仅在难转化的双子叶作物大豆上取得了成功,而且在单子叶作物水稻、玉米、小麦上先后取得了突破。同时,将一些与重要性状改良有关的外源基因转入了主要农作物,包括抗虫、抗病、抗除草剂、抗逆、品质改良、发育调控、营养吸收等。转基因大豆、玉米、棉花、油菜在生产上得到了大面积种植,产生了极大的经济效益,2004年全球转基因作物的种植面积达到了8100万公顷。本文对大豆、玉米、水稻和小麦等主要农作物转基因研究历史和产业化现状进行了综述,并对主要农作物转基因研究中存在的问题进行了分析。     

Autotoxic potential of cucurbit crops

Soil sickness is often observed in cucurbit crops such as Citrullus lanatus, Cucumis melo and Cucumis sativus, but not in cucurbit crops such as Cucurbita moschata, Lagenaria leucantha and Luffa cylindrica. Results showed that root aqueous extracts of Citrullus lanatus, Cucumis melo and Cucumis sativus were autotoxic, but those of Cucurbita moschata, Momordica charantia and Luffa cylindrica were less autotoxic to the radicle elongation of respective species. Plant growth of Citrullus lanatus, Cucumis melo and Cucumis sativus were greatly inhibited by autotoxic substances released from powered root tissue at a rate of 1 g per seedling. Root exudates of Citrullus lanatus, Cucumis melo and Cucumis sativus were autotoxic to radicle elongation and seedling growth of respective species. However, root exudates of Citrullus lanatus did not inhibit radicle elongation of Cucurbita ficifolia, which is commonly used as rootstock for the grafting of Citrullus lanatus, Cucumis melo and Cucumis sativus to decrease soil-borne diseases in commercial production. It seems possible to overcome autotoxicity in cucurbit crops by grafting on Cucurbita ficifolia. This revised version was published online in June 2006 with corrections to the Cover Date.