高等真菌的营养繁殖和无性繁殖

在高等真菌中,有许多是食用真菌、药用真菌和其他具有经济意义的真菌。因此,概括和总结高等真菌营养繁殖和无性繁殖的种类和形式,不仅在真菌教学中很重要,而且也对经济真菌的驯化研究、遗传育种和人工栽培等有直接的促进作用。     

中国藓类植物无性繁殖体的初步观察

无性生殖在苔藓植物的生活史中起着重要的作用,并且常通过各种无性繁殖体来完成。无性繁殖体的形态常被用来辅助鉴定一些不育的藓类植物。本文通过对38种藓类植物的无性繁殖体进行显微观察,结果显示：无性繁殖体在不同的藓类植物之间已经过多次演化;无性繁殖体的形态在种内是相对稳定的,且与其着生位置、配子体的分枝方式密切相关,而与植物的系统位置以及生境并无直接的关系;无性繁殖体的颜色与其胞壁的厚度以及表面纹饰密切相关。此外,无性繁殖体的产生常常与假根、原丝体有共存关系。在研究中发现,藓类植物的无性繁殖体主要包括原丝体芽胞、无性芽胞（叶生芽胞、中肋芽胞、枝生芽胞）、芽体、假根芽胞和假根状块茎;其中原丝体芽胞和无性芽胞最为常见。     

Molecular Genetic Variation in a Clonal Plant Population of Leymus chinensis （Trin.） Tzvel.

Randomly amplified polymorphic DNA （RAPD） analysis was used to investigate the genetic variation among populations, between populations, and within populations, relationships between genetic distance and geographic distance, and the molecular variation and population size. The effects of geographic and genetic distances, as well as of genetic differentiation and population size, on genetic variations of Leymus chinensis （Trin.） Tzvel. are discussed. The present study showed that there was significant RAPD variation between the Baicheng region population and the Daqing region population, with a molecular variance of 6.35% （P 〈 0.04）, and for differentiation among area populations of the Daqing region, with a molecular variance of 8.78% （P 〈 0.002）. A 21.06% RAPD variation among all 16 populations among two regions was found （P 〈 0.001）, as well as 72.59% variation within populations （P 〈 0.001）. Molecular variation within populations was significantly different among 16 populations.     

文冠果种群繁殖方式及其在种群更新中的作用

以黄土高原丘陵区文冠果天然种群为研究对象,通过样地调查,分析了不同生境文冠果种群的有性和无性繁殖方式及其在种群更新中的地位.结果表明：不同坡向文冠果种群均能进行有性繁殖和无性繁殖,在阳坡、半阴坡生境,文冠果以有性繁殖为主,实生苗数量和占据空间的能力均大于萌生苗,有性繁殖在这2个生境中对种群的更新贡献较大;在半阳坡生境,文冠果以无性繁殖为主,萌生苗数量和占据空间的能力均大于实生苗,无性繁殖对种群更新的贡献较大.在相同生境条件下,文冠果幼苗生长状况均表现为萌生苗＞实生苗.同一起源的文冠果幼苗生长状况均表现为阳坡＞半阳坡＞半阴坡.2种繁殖的瓶颈期在实生苗的种子-幼苗阶段和萌生苗的幼树-成株阶段.黄土丘陵区文冠果种群在新生境定居下来的过程中,首先以实生苗入侵,当水分、光照、养分条件较好时,文冠果又以无性繁殖方式迅速占领空间,繁衍后代.     

科学家发现雌性无性繁殖蚂蚁

美国亚利桑纳大学生物学家安娜·希姆勒尔率领的科研小组．最近在巴西的亚马逊地区首次发现完全由雌性组成的无性繁殖蚂蚁。他们对这种名为Mycocepurussmithii的蚂蚁进行了一系列实验,发现这种蚂蚁能开发多种真菌养殖,且没有雄性个体。在对这种蚂蚁的DNA进行研究时,科学家们发现所有的蚂蚁都由蚂蚁群落中的雌性蚁后繁殖,且这些雌性蚂蚁没有性行为能力,它们的性器官不运转。雄性通过未经授精的卵进行无性繁殖在昆虫世界中是普遍现象,     

Cloning and characterization of a FLORICAULA/LEAFY ortholog, PFL, in polygamous papaya

The homologous genes FLORICAULA （FLO） in Antirrhinum and LEAFY （LFY） in Arabidopsis are known to regulate the initiation of flowering in these two distantly related plant species. These genes are necessary also for the expression of downstream genes that control floral organ identity. We used Arabidopsis LFY cDNA as a probe to clone and sequence a papaya ortholog of LFY, PFL. It encodes a protein that shares 61% identity with the Arabidopsis LFY gene and 71% identity with the LFY homologs of the two woody tree species： California sycamore （Platanus racemosa） and black cottonwood （Populus trichocarpa）. Despite the high sequence similarity within two conserved regions, the N-terminal proline-rich motif in papaya PFL differs from other members in the family. This difference may not affect the gene function of papaya PFL, since an equally divergent but a functional LFY ortholog NEEDLY of Pinus radiata has been reported. Genomic and BAC Southern analyses indicated that there is only one copy of PFL in the papaya genome. In situ hybridization experiments demonstrated that PFL is expressed at a relatively low level in leaf primordia, but it is expressed at a high level in the floral meristem. Quantitative PCR analyses revealed that PFL was expressed in flower buds of all three sex types - male, female, and hermaphrodite with marginal difference between hermaphrodite and unisexual flowers. These data suggest that PFL may play a similar role as LFY in flower development and has limited effect on sex differentiation in papaya.     

滇重楼的无性繁殖

滇重楼[Paris polyphylla var.yunnanensis(Fr.)Hand.-Muzz.]根茎的各部位切段都能繁殖出新植株。这些后代的四年生根茎,其增长速度比同龄实生苗快3—6倍。但切段间表现出较大的差异性:带顶芽切段能于种植的第一年成苗,并开花、结实,是根茎中生活力最强的部位,但其地上茎一般为单轴;中间和末端的切段,它们的出苗情况和有性繁殖相似,第一年只有极少数出苗,第二年才大量出土成苗,但不开花,地上茎出现较多的多轴现象。后代根茎和地上茎的主要成份与野生滇重楼基本相同。     

浅谈克隆动物技术

浅谈克隆动物技术徐存拴（河南师范大学生物系,４５３００２）图１绵羊的生活史１克隆动物技术１１动物细胞结构生物体是由一个个具有相同和不相同功能的细胞构成,例如,人体约由１５０亿个细胞构成、绵羊约由１３０亿个细胞构成。细胞的基本结构包括细胞膜、细胞质和...     

经济植物无性繁殖讲座（六）：压条和埋条技术的应用

压条和埋条也是一种重要的无性繁殖技术,对于必须用自根扦插繁殖又难以生根的植物,则可用压条或埋条方法。例如:随着各种果树矮化砧木的发展,砧木的繁殖非常重要,为了使砧术表现一致,就必须发展无性系。砧木是利用其根系,所以不能用嫁接繁殖,但是用扦插繁殖又不易成活。这种情况最好用压条方法。埋条法介于插条和压条之间,可提高插条的成活率,下面重点介绍这两种技术的具体应用。