Changes in the anatomical structure of the shoot apex ofSenecio vulgaris L. during ontogenis in relation to the formation of leaves and inflorescence

An investigation was made of the anatomical structure of the shoot apex ofSenecio vulgaris L. a photoperiodically neutral plant, and compared with the formation of successive leaf primordia along the axis up to the initiation of the terminal inflorescence. In the shoot apex of a germinating plant a central zone can first be distinguished from the peripheral zone which is composed of small and intensely stained cells. Later, a rib meristem appears. At the time of the initiation of the middle (the largest) leaves, the shoot apex has a distinct small central zone and a well developed peripheral zone and rib meristem. Between these zones there is a group of cells dividing in all directions, the subcentral zone. At the time of initiation of the last leaves, the central zone extends to the flanks and gradually ceases to be distinguishable. At the same time, the subcentral zone increases in size. This is caused first by cell division and later, with the initiation of the last, most reduced leaves, by enlargement of the cells. Vacuolization in the inner part of the apex and the arrangement of the superficial cells in rows parallel to the surface of the apex, is a preparatory step to the initiation of the inflorescence.     

The influence of EDTA on the mutagenic activity of ethyl methanesulphonate (EMS) inArabidopsis thaliana

Nebyl prokázán sensibilizující ú?inek EDTA na muta?ní aktivitu EMS uArabidopsis thaliana.     

Bemerkungen zur Variabilität vonSaxifraga marginata

Saxifraga marginata Sternb. is divided into three subspecies:S. m. subsp.marginata, S. m. subsp.bubakii (Rohlena)Chrtek etSoják,S. m. subsp.karadzicensis (Degen etKo?anin)Chrtek etSoják (environments of Skopje, Macedonia).     

正丁酸钠对人胃腺癌细胞染色体数目和DNA含量的影响

培养的人胃腺癌MGc 80-3细胞经过正丁酸钠处理7天后,生长抑制率达50.7%,约有90%的细胞形态发生分化,其超微结构亦有显著改变。而且,在染色体数目上,超二倍体细胞由对照组的78%增加到实验组的96%,超三倍体和超四倍体细胞则分别从6%和14%下降至2%。同时应用~3H-TdR放射自显影和福尔根细胞光度法测定未标记细胞(G_1期)DNA含量,结果显示实验组比对照组降低了。而且在实验组的同一制片中,未分化细胞DNA含量平均为超六倍体值(DI=3.67和3.56),其中90%的细胞超过6C;分化细胞DNA含量则平均为近四倍体值(DI=2.03和1.99),其中近60%的细胞少于4C。两者差异统计显著,表明形态分化的人胃腺癌细胞的遗传物质含量明显减少,但这些细胞并非就是正常二倍体细胞。     

甘蔗幼叶切段培养中的体细胞胚胎发生

本文从形态学和组织学方面研究了甘蔗幼叶胚性愈伤组织发生及体细胞胚胎的形成过程。甘蔗幼叶片切段培养于含2.4—D1.5mg/1的MS培养基上,4—6天后切段开始形成愈伤组织,约10天后愈伤组织表面出现白色颗粒状结构。将含有白色颗粒状结构的愈伤组织转移至不含激素的培养基中,7—10天后可见有小植株长出。组织学和形态学观察表明,甘蔗离体再生植株是通过体细胞胚胎发生途径。