THE ESTABLISHMENT OF TWO SETS OF ALIEN ADDITION LINES OF WHEATWHEATGRASS

The procedure and method for the transfer of two sets of 14 pairs of wheatgrass (Agropyron interrnedium) chromosomes into common wheat to establish two sets of wheat-wheatgrass alien addition lines are reported. Meanwhile, observations and analyses have been made on the phenotypicaI characters of all the 14 alien addition lines established. It is determined that wheatgrass chromosomes in some of the established addition lines carry the rustresistant genes. In addition, questions concerning the location and distribution of certain agriculturally important genes of wheatgrass chromosomes have been discussed.     

RNP STRUCTURE IN METAPHASE CHROMOSOMES OF Vicia faba

The results of studies on ultrastructural and cytochemical features of metaphase chromosomes of Vicia faba are reported. In conventionally stained specimens are observed many electron-lucent compartments, in which exists an internal fibrillar-granular structure. When stained with the Bernhard's technique, the internal structure is found to consist of ribonucleoprotein (RNP) fibrilsand granules that measure about 15 to 20 nmin diameter. In the transverse section of metaphase chromosomes, the RNP structures are distributed in both the central and the peripheral regions of chromatids. It is conceivable that this RNP structure constitutes a special component of chromosomes. The distribution of the RNP structure in a chromosome and some questions related to the chromosomal scaffold are discussed on the basis of these data.     

两套小冰麦异附加系的建立

本文报道了把天兰冰草(Agropyrn intermedium)的两个染色体组的14对染色体分别加入小麦,建立起两套小冰麦异附加系列的程序和方法,并对所建立的14种异附加系的表型特征进行了观察分析,查明有些小冰麦异附加系中的冰草染色体上携带有抗锈病基因。此外,本文还讨论了与一些农艺性状有关的基因在不同冰草染色体上的分布。     

ULTRASTRUCTURE OF THE NUCLEOLUS AND REPLICATION SITES OF RIBOSOMAL DNA IN Allium cepa

Our conventional EM observations indicate that the nucleolus of Allium cepa is composedof the fibrillar centre (FC), fibrillar component (F) and granular region (G). FC is an elec-tron-lucid zone which contains condensed or loosened chromatin. F is a circular, highly elec-tron-dense component which surrounds FC and consists of compact fibrils. EM autoradiographic(EM ARG) studies with ~3H- UdR reveal that the synthesis of ribosomal RNA (rRNA) takesplace in F. G is situated around F and composed of granules about 25 to 30 nm in diameter.EM ARG studies with ~3H- TdR demonstrate that silver grains are predominantly located in Gof the nucleolar periphery and the region of the nucleolus-associated chromatin. In addition,~3H- TdR labels are also present, but with a much lower frequency, in FC. F and G of the nu-cleolar interior. According to the distribution and sphere of silver grains in different compo-nents of the nucleolus, we suggest that the replication sites of ribosomal DNA (rDNA) aremainly located in     

洋葱核仁的超微结构与rDNA复制位置

本文通过常规电子显微镜观察看到洋葱核仁是由纤维中心(FC)、纤维部分(F)和颗粒区(G)构成。FC是电子透明区,其内部有集缩或松散的染色质。F是围绕FC的环状结构部分,由密集的纤维构成,电子密度很高。用~3H-尿嘧啶核苷标记的电子显微镜放射自显影观察表明,它是rRNA合成的部位。颗粒区位于F外侧,由直径约25—30nm的颗粒组成。用~3H-胸腺嘧啶脱氧核苷标记的电子显微镜放射自显影观察表明,银粒大多分布在核仁边缘的颗粒区和核仁伴随染色质,在FC和F以及核仁内部颗粒区也有银粒出现,但频率很低。根据银粒分布频率和银粒范围的大小,推测rDNA复制的位置主要在核仁周边颗粒区和核仁伴随染色质,但在FC也有一些DNA区段开始复制,然后向核仁周边转移。     

蚕豆中期染色体内的RNP结构

本文对蚕豆中期染色体的超微结构和细胞化学特点进行了研究。在常规染色样品中发现,染色体内存在着一些低电子密度区域,该区域中有一种内在结构。Bernhard染色结果表明,这种内在结构是由直径15至20 nm的RNP颗粒和纤维组成的。这种RNP结构有的分布在染色体横切面的近中央区,有的分布在近边缘区。根据上述观察结果,本文讨论了这种RNP结构在染色体中的分布特点和有关染色体骨架的一些问题。