Dry storage temperatures, duration, and salt concentrations affect germination of local and edaphic ecotypes of Hordeum spontaneum (Poaceae) from Israel

Hordeum spontaneum , the ancestor of cultivated barley, is mainly distributed in the Mediterranean zone of the Near East as well as in the Irano-Turanian steppes and Saharo-Arabian region; these areas receive unpredictable small amounts and distribution of rain followed by long, hot and dry summers. Caryopses of seven local ecotypes of H. spontaneum were collected in Israel from natural populations near Sede Boker, Neve Yaar, Tabigha and Mount Hermon. Three generations of these ecotypes were grown in natural conditions at Sede Boker with additional irrigation. The germination of caryopses of the third generation was tested. Due to the self pollination and atelechoric system of seed dispersal of this species, genetic ecophysiological diversity of afterripening and salt tolerance was found between the ecotypes originating from different areas, even within local populations and patches of plants that grew on different types or depths of soil at a distance of only a few meters from each other. Afterripening is important to prevent the caryopses from germinating shortly after maturation after a late rain at the beginning of the dry summer. Germination of the different ecotypes is regulated by temperature and length of post-maturation dry storage, as well as temperatures during wetting, and salinity.     

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.     

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。     

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。     

Post-maturation of the plastid ribosomal RNA in the plant kingdom

Summary The in vivo fragmentation of the plastid rRNA from plants situated at different places in the evolutionary scale, with the exception ofAlgae, was analysed by electrophoresis using fully denaturing conditions. This fragmentation corresponds to an in vivo post-maturation. It exists only in some bacteria and is not random. Five main groups of fragments with the following real molecular weights (Mr) are found in 23 S:ca 0.9 × 10⁶; 0.7 × 10⁶; 0.45 × 10⁶; 0.35 × 10⁶ and 0.15 × 10⁶. The existence of a large fragment (Mr = 0.9 × 10⁶) corresponds to a primitive type of fragmentation found in some archaic plants. Dicotyledons and several other groups have the same pattern of 23 S fragmentation, often comprising all the fragments mentioned above, whilstGraminaceae (Monocotyledons) constitute a special group with a very predominant 0.35 × 10⁶ dalton fragment and the absence of the 0.45 × 10⁶ dalton fragment. The plastid 16 S rRNA in all plants studied here has aMr of 0.54 × 10⁶ which is smaller than the 16 S ofEscbericbia coli taken as reference (0.56 × 10⁶ dalton).