喀什霸王的结实和种子萌发特性

喀什霸王(Zygophyllum kaschgaricum)是生长于中国新疆南部荒漠环境的稀有种及二级保护植物。当前, 该物种在自然种群中呈分散式及片段化分布, 且种群密度低, 种群老龄化较严重。因此, 为了了解该物种种子萌发特性及其对荒漠环境的响应, 该文采用室内控制实验方法, 对该物种的自然坐果率、结籽率、种子吸水特性、种子休眠和萌发特性及对干旱胁迫的响应进行了比较研究。结果表明: 喀什霸王在自然种群中的坐果率及结籽率较低, 且种子的败育率较高。不同干藏时间种子的吸水速率间存在显著差异; 随着干藏时间的延长, 种子的吸水率逐步增强。刚成熟的种子在不同温度及光周期下均可萌发; 其中高温(10/20 ℃, 20/30 ℃)及黑暗条件下的萌发率比低温(10/5 ℃, 5/2 ℃)及光照条件下的萌发率高。不同干藏时间的种子在不同浓度赤霉素(GA₃)下的萌发率均较高; 但低温储藏时间对该物种种子的打破休眠及萌发率没有促进作用。以上结果说明该物种存在非深度生理休眠; 而干藏时间、高温且黑暗及高浓度(50 mmoloL ^-1) GA₃是打破休眠及促进种子萌发的最合适条件。高温条件下的干旱胁迫对喀什霸王种子萌发具有抑制作用; 春季和秋季降水量决定种子的萌发率。总之, 喀什霸王种子在物候上表现出的春秋季萌动及非深度生理休眠以提高幼苗存活力及保障种群稳定性, 是一种对新疆南部干旱及高温胁迫荒漠环境的适应策略。     

北柴胡胚和胚乳的发育及对其种子萌发的影响

利用常规石蜡制片技术对北柴胡胚和胚乳的发育及对其种子萌发的影响进行了观察。结果表明北柴胡胚的发育属于茄型,基细胞进行一次横分裂后不再分裂,因而胚柄不发达,且很早解体。胚乳的发育属于核型,初生胚孔核的分裂远远早于受精卵的分裂。对果实采收时期胚发育状况进行统计发现,在被测采收期果实中有20%的果实的胚处于球形胚阶段,70%处于心形胚,只有10% 处于鱼雷胚,说明北柴胡种子采收时胚处于不同的发育阶段,存在形态后熟现象,这是北柴胡种子萌发难、萌发率低且出苗不整齐的主要因素。     

Propagation of three orchid genera using encapsulated protocorm-like bodies

Summary Protocorm-like bodies (plbs) of the orchid Dendrobium ‘Sonia’ were obtained from fractionated plb explants on Murashiga and Skoog (1962) medium (MS) supplemented with 4.44 μM 6-benzylaminopurine (BA). The developmental stage of plbs to be encapsulated, concentrations of sodium alginate (2–5%) and calcium chloride (25–100 mM), and concentration of MS salts in the matrix were assessed. Fractionated plbs 13–15 d after culture were at the leaf primordia stage and found suitable for encapsulation studies. The best encapsulation response was observed with 3% sodium alginate upon complexation with 75 mM CaCl₂.2H₂O. An encapsulation matrix prepared with MS medium (three-quarter strength) supplemented with 0.44 μM BA and 0.54 μM α-naphthaleneacetic acid gave 100% conversion of encapsulated plbs to plants after storage. A viability of >85% of encapsulated plbs of Dendrobium ‘Sonia’ was observed for 75 d at 4°C. Encapsulated plbs of orchids Dendrobium, Oncidium, and Cattleya were stored at 4°C for 75, 60 and 30 d, respectively, with >88% germination. All plants survived potting in media having either wood charcoal pieces alone or in combination with brick pieces.     

北柴胡胚和胚乳的发育及对其种子萌发的影响

利用常规石蜡制片技术对北柴胡胚和胚乳的发育及对其种子萌发的影响进行了观察。结果表明北柴胡胚的发育属于茄型,基细胞进行一次横分裂后不再分裂,因而胚柄不发达,且很早解体。胚乳的发育属于核型,初生胚孔核的分裂远远早于受精卵的分裂。对果实采收时期胚发育状况进行统计发现,在被测采收期果实中有20％的果实的胚处于球形胚阶段,70％处于心形胚,只有10％处于鱼雷胚,说明北柴胡种子采收时胚处于不同的发育阶段,存在形态后熟现象,这是北柴胡种子萌发难、萌发率低且出苗不整齐的主要因素。     

Release of dormancy during after-ripening of Agrostemma githago seeds

Freshly harvested seeds of Agrostemma githago L. do not germinate when they are imbibed at 20°C. The block is located in the embryo and is relased by dry storage at 20°C (after-ripening). Freshly harvested seeds complete only a small part of the processes that occur in after-ripened seeds during the lag phase prior to germination (radicle protrusion). After-ripening removed the block on lag phase processes much faster than the block on germination. This was shown both by direct determinations of the completion of lag phase processes and by measurements of the rate of axial protein synthesis, which approximately doubles when seeds are progressing through the lag phase. It is concluded that the percentage germination does not adequately reflect the extent to which the dormancy mechanism has been overcome.     

温带半干旱地区一年生植物种子的萌发特性

在实验室条件下研究了中国温带半干旱地区科尔沁沙地的23种1年生植物的种子萌发特性（新采集种子、冷藏和干藏种子）.大籽蒿、虎尾草、冠芒草、沙蓬和地锦的新种子萌发率达90%左右,11种植物新种子萌发率均低于70%,说明这些植物的新种子具有或多或少的休眠属性.经过150d的冷干藏后,大籽蒿、虎尾草萌发率保持在90%以上,说明这两种植物完全没有休眠机制;冠芒草、沙蓬和地锦的种子萌发率下降较多,可能是储藏的环境条件导致的2次休眠现象;冷藏和干藏处理均能使绿珠藜、毛马唐、细叶益母草、雾冰藜、金狗尾草、苋菜、马齿苋、碱地肤和水稗草的种子在生长季开始时完成生理后熟,萌发率达到80%以上;干藏有利于促进毛马唐、细叶益母草、马齿苋和鹤虱的种子成熟,冷藏有利于促进绿珠藜和金狗尾草的种子成熟;黄蒿、灰绿藜、画眉草和烛台虫实在不同处理下的萌发率都比较低,说明种子内在生理休眠作用较强,具有减少种子一次性萌发数量的风险分摊策略.大多数1年生植物均能在较短时间内达到最终萌发率的90%,表现出迅速萌发的特性;黄蒿、灰绿藜、碱地肤和沙蓬种子则在不同处理中表现出延长萌发时间的策略来适应半干旱地区不确定的环境条件.最后,探讨了几种主要1年生植物的种子萌发对策与其对环境适应机制之间的关系.     

NaCl胁迫对红花种子萌发特性的影响

盐分是影响植物种子萌发和生长的重要因素。为探究NaCl胁迫对红花种子萌发及生长的影响,采用0、0.2%、0.4%、0.6%、0.8%的NaCl溶液处理不同品种红花种子,在盐胁迫条件下测定供试红花品种种子萌发期的发芽率、发芽势、相对发芽率、相对发芽势、根长、芽长、干重及鲜重等指标,比较分析7个红花品种种子萌发期对盐胁迫的耐受性。结果表明：盐胁迫下7个红花品种的发芽率、发芽势、相对发芽率和相对发芽势整体呈下降趋势,盐浓度小于等于0.4%时,3-10和云南红花种子的4个指标均在89.44%以上,种子生活力较强,新疆红花种子活力明显低于其他6个品种。盐胁迫下新疆红花种子萌发的相对盐害率最高,盐浓度大于等于0.4%时,相对盐害率在50%以上,而3-10、BH-1、H-7、四川红花和云南红花5个品种的相对盐害率在-2.34%~3.91%之间,红花种子受伤害程度较轻。3-10和H-7红花品种在盐浓度为0.4%时的根长和芽长的表现优于其他品种;当盐浓度大于等于0.6%时,与其他品种相比,BH-1在根长和芽长方面表现出较强的耐盐性。盐胁迫下7个红花品种的鲜重整体均呈下降趋势,同一处理下新疆红花的鲜重均低于其他品种,0.2%盐处理下,H-7和四川红花的鲜重为2.83 g和2.90 g,与对照相差不大,并且高于同浓度下其他红花品种的鲜重,0.8%盐处理下,BH-1的鲜重高于同浓度下其他红花品种的鲜重;与鲜重相比,盐胁迫对红花幼苗干重的抑制作用小,甚至对干物质的积累有促进作用。综合比较,7个红花品种种子萌发期间耐盐性表现较强的为河南新乡当地红花3-10、BH-1和应举以及云南红花,最弱的为新疆红花。     

Diversity of spore germination in response to inosine and L-alanine and its interaction with NaCl and pH in the Bacillus cereus group

Aims: Our aim was to assess the diversity of the nutrient germination response of Bacillus cereus spores. Methods and Results: B. cereus spore germination was monitored by decrease in optical density using a Bioscreen C analyser in response to the major germinant substances inosine and l -alanine. Spores of a set of 12 strains taken to illustrate the diversity of the B. cereus group showed ranging germination capacities. Two strains never germinated in the presence of l -alanine, at any of the germinant concentrations tested. Both the extent and rate of spore germination were affected by low pH and high NaCl concentration, but differently according to the strain. Conclusions: A broad diversity was observed in nutrient-triggered spore germination among the members of the B. cereus group. Spore germination of some strains occurred at low concentrations of inosine or l -alanine, suggesting high receptor sensitivity to germinants. The activity of these receptors was also affected by pH or high NaCl concentration. Significance and Impact of the Study: The greater ability of some strains to germinate in response to l -alanine and inosine is one criterion among others for B. cereus strain selection in food processing or storage studies, before confirmation in complex food or laboratory media. The diversity in response to germinants found among the B. cereus strains suggests a differential expression and (or) absence of some germination genes involved in the response, mainly to l -alanine.     

Environmental factors affecting dispersal,germination and distribution of <Emphasis Type="Italic">Stipa capensis</Emphasis> in the Negev Desert,Israel

  The effects of postmaturation ambient temperatures, light, as well as chemical and structural properties of the substrate on germination and patch distribution of Stipa capensis in a shrubland landscape were studied. This species is a dominant annual grass in exposed intershrub areas covered with biological loess soil crusts in the northern Negev Desert.Freshly matured caryopses do not germinate. After 7–8months of dry storage at high temperatures, there was a significant reduction in primary dormancy and an increase in the rate and percentage of germination of caryopses stored at high temperatures. The speed and percentages of germination were lower on various sterile substrates, such as organic matter and loose loess soil, in comparison with similar live substrates or the control on filter paper.In 3 of 4years of field observations in semi-arid shrubland, the density of Stipa capensis plants on soil crust in the exposed intershrub areas was significantly higher than below shrubs. The positive effects of higher temperatures on the dry soil during summer, before the season with rains, and of light during germination, can favor germination in exposed patches.Although germination responses to storage temperature and light regime differentiate between patch types before and during germination, other processes may be critical for the pattern of distribution of Stipa capensis. These include dispersal of caryopses, arrival, soil penetration and density of local seed banks, as well as substrate properties affecting germination and plant density, in different landscape patches.     

成熟时间和干贮藏对两种木蓼种子萌发的影响

刺木蓼(Atraphaxis spinosa)和长枝木蓼(A.virgata)为蓼科木蓼属灌木,刺木蓼1a结果2次,分别于6月份和9月份成熟,而长枝木蓼果期较长,于10—11月份成熟。对2种木蓼不同成熟时间及干贮藏后的种子,进行萌发实验,结果表明:不同成熟时间的刺木蓼种子在30℃/20℃的萌发率高,长枝木蓼10月份成熟的种子在15℃/6℃的萌发率低,而11月份成熟的种子在15℃/6℃的萌发率最高。成熟早的刺木蓼种子较小,而长枝木蓼成熟晚的种子较小,不同成熟时间的2种木蓼种子均表现为,小种子的休眠程度低。刺木蓼不同成熟时间的种子在干贮藏的过程中,种子的萌发率先降低后增加。干贮藏明显提高了长枝木蓼种子在15℃/6℃的萌发率,尤其是10月份成熟的种子,10月份和11月份成熟的种子分别贮藏9个月和6个月后解除休眠。     

NaCl胁迫对紫荆花粉萌发特性的影响

以紫荆（Cercis chinensis）为试验材料,采用花粉人工培养法研究不同浓度NaCl对紫荆花粉萌发特性的影响。结果表明：NaCl对紫荆花粉萌发有抑制作用,且抑制程度随培养基中NaCl浓度的增高而加强,NaCl显著抑制(P<0.05)紫荆花粉萌发的浓度为20 mmol/L,显著抑制(P<0.05)花粉管伸长生长的浓度为5 mmol/L。     

Najas marina in Israel: It is a halophyte or a glycophyte?

In Israel Najas marina L. grows mainly in fresh water habitats. The halophytic nature of a population from one such habitat was investigated. NaCl had a positive effect on the growth of Najas , with an optimal concentration of 37–55 μ M . Germination percentage was only slightly reduced by NaCl up to a concentration of 74 μ M . It is thus concluded that the populations of Najas in Israel retain their halophytic nature. In fresh water habitats, Najas grows under suboptimal NaCl concentrations.     

Genetic diversity and population structure of five Ethiopian chicken ecotypes

This study aimed to analyse the genetic diversity and population structure of five Ethiopian chicken ecotypes (N = 155), which were compared with six commercial purebreds (N = 180). For the analysis of genetic diversity, 26 AVIANDIV microsatellite markers were used. The number of alleles in Ethiopian ecotypes ranged from 2 to 19 per locus, with a mean of 6.1. The average observed heterozygosity within ecotype varied between 0.53 and 0.57. The overall heterozygote deficiency (F(IT)) in Ethiopian ecotypes was 0.124 ± 0.037. Over 68% of F(IT) was because of within-ecotype deficiency (F(IS)). In the phylogenetic tree, Ethiopian ecotypes clustered into two groups. The analysis of the relationship between populations using the structure program provided further evidence for the occurrence of at least two subgroups in the Ethiopian ecotypes. Findings of this study may provide the background for future studies to identify the origin of the two gene pools representing the Ethiopian chicken ecotypes and to characterize the gene variants influencing economically important traits.