Mimicking a semi-arid tropical environment achieves dormancy alleviation for seeds of Australian native Goodeniaceae and Asteraceae

Background and Aims: Seed physiological dormancy (PD) limits the use and conservationof some of Queensland's (Qld) native forb species. It was hypothesisedthat optimum dormancy-alleviating treatments would reflect environmentalconditions that seeds experience in situ, and this premise wastested for PD seeds of four species native to south-west Qld. Methods: High temperatures and increased rainfall during summer are characteristicof this semi-arid tropical environment. Ex situ treatments weredesigned to mimic conditions that seeds dispersed in springexperience during the summer months before germinating in coolerautumn temperatures. Seeds received between 4 and 20 weeks ofa dry after-ripening (DAR), warm stratification or dry/wet cyclingtreatment (DAR interspersed with short periods of warm stratification),in darkness, before being transferred to germination test conditions.In addition, natural dormancy alleviation of one of the Goodeniaceaespecies was investigated in situ. Key Results: Dry/wet cycling resulted in higher levels of germination ofActinobole uliginosum (Asteraceae), Goodenia cycloptera andVelleia glabrata (Goodeniaceae) when compared with constantDAR or stratification, while Goodenia fascicularis (Goodeniaceae)responded better to short durations of warm stratification.Long durations of DAR partially alleviated PD of A. uliginosum;however, stratification induced and maintained dormancy of thisspecies. Modifications to the dry/wet cycling treatment andgermination test conditions based on data collected in situenabled germination of G. cycloptera and V. glabrata to be furtherimproved. Conclusions: Treatments designed using temperature, relative humidity andrainfall data for the period between natural seed dispersaland germination can successfully alleviate PD. Differences betweenthe four species in conditions that resulted in maximum germinationindicate that, in addition to responding to broad-scale climatepatterns, species may be adapted to particular microsites and/orseasonal conditions.     

Variation within species and inter-species comparison of seed dormancy and germination of four annual Lamium species

In an ecological context, knowledge of intra-species variation in dormancy and germination is necessary both for practical and theoretical reasons. We used four or five seed batches (replicates) of four closely related annuals co-occurring in arable fields in Sweden: Lamium amplexicaule, L. confertum, L. hybridum and L. purpureum. Seeds used for experiments stemmed from plants cultivated on two sites, each site harbouring one population of each species, thereby ensuring similar environmental history of seeds. Seeds were tested for germination when fresh and after three different pre-treatments (cold or warm stratification, or dry storage) for up to 24 weeks. Seeds were also sown outdoors. Despite substantial intra-species variation, there were clear differences between species. The general seed dormancy pattern, i.e. which environmental circumstances that affect dormancy, was similar for all species; dormancy reduction occurred during warm stratification or dry storage. Even though the response to warm stratification indicates a winter annual pattern, successful plants in Sweden were mostly spring emerged. Germination in autumn occurred, but plants survived winters poorly. Consequently, as cold stratification did not reduce dormancy, strong dormancy in combination with dormancy reduction during dry periods might explain spring germination. It is hypothesised that local adaptations occur through changes mainly in dormancy strength, i.e. how much effort is needed to reduce dormancy. Strong dormancy restricts the part of each seed batch that germinate during autumn, and thus reduces the risk of winter mortality, in Sweden.     

东北刺人参种子萌发影响因子的研究

东北刺人参(Oplopanax elatus Nakai)种子透水性良好,休眠后萌发不受其影响.种皮和胚乳的水提取物中存在萌发抑制物质,胚乳中提取物对白菜种子萌发的抑制效果比种皮更明显.种子自然脱落时胚尚未分化完全,处于心形胚阶段.种子需要先温暖层积以完成胚的分化与生长,然后转入低温层积完成生理后熟.同批种子胚的发育不完全同步,变温层积处理7个月有极少数种子萌发,连续变温层积处理17个月大部分种子萌发.不同年份受气候条件影响,种子产量和发芽率差异较大.种子耐贮性较强,贮藏2年的种子生活力变化不大,仍具有较高的萌发潜力.     

种子休眠与破眠机理研究进展

种子休眠机理主要围绕透性、抑制剂作用和光敏素转化等方面的研究而建立。种皮的阻碍作用可能是由于种皮的物理或化学特性引起．可导致对水、光、气体或溶质的透性改变。抑制剂作用机理是抑制物质可抵消促进细胞分裂和生长发育的激素的作用。光敏素转化机理来源于与休眠有关的生物活性化学物质的合成、活化或破坏受光诱导的观点,由于发现了光敏素蓝色蛋白的活化型（Pfr）和钝化型（Pr）而得到强有力的支持,种子光休眠取决于光敏素蓝色蛋白的活化型（Pfr）含量和Pfr／（Pr＋Pfr）比值。目前,打破休眠的方法一般有机械破皮法、激素处理法、分子生物学技术法、物理处理法（如激光、烟、热等处理技术）、CO2处理法等。激素的平衡由抑制剂占优势向促进物占优势的变化是打破休眠的决定因素。研究破眠机理的分子生物学技术有多种,包括ABA突变体的利用、分子标记、转基因技术、用反义RAN阻止基因的表达、cDNA克隆技术等。用激光照射种子,把适宜的光射入细胞,可增加细胞生物能,促进种子发育,从而可能打破休眠。热处理的机理是由于加热可以增加种皮的透气性。CO2之所以能提高某些物种的萌发率,在于其影响了种子内部乙烯的敏感性。     

濒危植物毛柄小勾儿茶种子休眠与萌发生理的初步研究

毛柄小勾儿茶（Berchemiella wilsonii （Schneid．）Nakai var．pubipetiolata H．Qian）为中国特有种,国家三级保护植物。TTC染色法测得毛柄小勾儿茶种子的生活力较低,仅为32％,空粒和无生活力的种子分别为28％和40％,说明毛柄小勾儿茶发育完全的种子较少。种子吸水速度试验证明毛柄小勾儿茶种皮透水性较差,不利于种子萌发时对水分的吸收,发芽抑制物的生物鉴定结果表明,毛柄小勾儿茶种子的不同部位都存在发芽抑制物,且种胚中的含量最高,不利于种子的萌发,使毛柄小勾儿茶种子处于休眠状态之中。几种不同浓度GA。溶液浸种24h的预处理可以不同程度地提高毛柄小勾儿茶种子的发芽率和发芽指数,其中300mg／L GA3的效果最显著,并且300mg／L GA3的预处理可以在萌发初期（萌发前3天）显著地提高毛柄小勾儿茶种子中过氧化物酶、过氧化氢酶和脱氢酶的活性。毛柄小勾儿茶种子生活力低,且处于休眠状态,再加上与种子发芽力有关的几种酶的活性较低,致使毛柄小勾儿茶种子的发芽率较低,同时这些也是从种子萌发生理方面导致毛柄小勾儿茶濒危的重要原因。     

酵母细胞破碎方法对S-腺苷-L-蛋氨酸提取的影响

考察了不同细胞破碎方法对酵母释放S-腺苷-L-蛋氨酸(SAM)的影响及雷氏盐沉淀分离SAM的影响。结果表 明,用乙酸乙酯处理细胞,再利用0.35moL·L-1硫酸破壁可以使90%以上的SAM从酵母内释放出来,该方法对其它的干扰物 质释放量少,而且能较好地保持SAM的稳定性,有利于SAM的分离和纯化;采用雷氏盐对SAM进行沉淀分离,能有效保持 SAM的稳定性,简化了工艺流程,有利于降低生产成本。     

梨树花芽休眠解除与活性氧代谢的关系

梨树(Pyrus bretschneideri Rehd.)自然休眠和休眠解除时,花芽的活性氧代谢发生变化.O2-·产生速率和H2O2的含量在休眠期间上升,在休眠后期下降.抗氧化系统中SOD活性在自然休眠期呈下降趋势,自然休眠结束活性上升.POD和CAT活性在自然休眠期上升.抗氧化物质AsA和GSH的含量随休眠进行而下降,休眠解除过程中重新升高.APX和GR的活性在休眠期间活性下降,休眠结束活性迅速上升.这些结果表明:花芽的休眠与活性氧的代谢有很大关系.     

杨树和冬小麦在短日照和寒冬中的胞间连丝动态(英文)

Electron microscopic observation revealed that poplar (Populus deltoides Marsh.) and winterwheat ( Triticum aestivum L. cv. Seward 80004) plasmodesmatal structures significantly changed undershort day (SD, 8 h light) and in winter period, and such changes differed also noticeably between these twowoody and herbaceous plants. Under long day (LD, 16 h light), many plasmodesmata with strong stainappeared in the cell wall of both poplar apical buds and winter wheat young leaf tissues, and connections ofcytoplasmic endoplasmic reticulum (ER) with the ER in some plasmodesmata were observed. In addition,the typical “neck type” plasmodesmata were observed in winter wheat young leaf tissues, and their centraldesmotubules (appressed-ER) could be clearly identified. Under SD, many poplar plasmodesmata showedonly a partial structure in the cell wall and appeared to be discontinued; some plasmodesmata swelled in themid-wall, forming the cavity, and no appressed-ER appeared, in winter wheat, however, no noticeablealterations of plasmodesmata occurred, and the plasmodesmatal structure essentially remained the sameas it was under LD. In winter period, poplar plasmodesmata had a similar morphology as those observedunder SD, however, winter wheat manifested at least two types of significant plasmodesmatal alterations:one plugged by electron-dense materials and the other of reduced neck region compared to those underLD. The above dynamic difference of the two species plasmodesmata under SD and winter period revealedthe difference of their dormancy development under those environmental conditions.     

Brassinolide Effect on Growth of Apical Meristems, Ethylene Production, and Abscisic Acid Content in Potato Tubers

Treatment of intact potato (Solanum tuberosum L., cv. Nevskii) tubers with 24-epibrassinolide (EB) resulted in prolonged deep dormancy, increased production of ethylene and higher contents of free and bound abscisic acid (ABA) in buds. EB at the most efficient concentration 0.021 mg dm^–3, applied immediately after tuber harvest, inhibited sprouting by 36 – 38 d, increased ethylene formation after 1 and 7 d of storage by almost 300 and 150%, respectively, and increased the content of both free and bound ABA during the whole period of storage (on average by about 80%). Electron microscopic and morphometric studies showed that EB brings about a decrease in cell volume in tunica and all types of meristems and an increase in the number of vacuoles, accompanied by a decrease in their volume.     

Recipes for successful anhydrobiosis in bdelloid rotifers

We tested the effect of several environmental variables on the ability of three bdelloid rotifers (Macrotrachela quadricornifera, Philodina roseola and Adineta oculata) to recover from the anhydrobiotic state. The variables we examined were (1) rate of water evaporation, (2) relative humidity during anhydrobiosis, (3) temperature during anhydrobiosis, (4) duration of anhydrobiosis, and (5) rehydration rate. Our results indicate that bdelloids can regulate to some degree net water balance during onset and termination of anhydrobiosis.