A Cytological Observation on Six Mosses of Northeast China

In this paper the chromosome number of 6 mosses species are reported. The materials used for investigation were taken from immature capsules. Meiosis in spore mother cells were observed, and the results are as follows: Brachythecium plumosum, n=15. Entodon obtusatus, n = 11. E.okamurae, n = 11. Anoectangium aestivum, n= 13. Bryum argenteum, n= 10. Eurhynchium eustegium, n = 20+ 2m. The chromosome number of the former three species are re-ported for the first time.     

Cytological Investigation of the Mechanism of Parthenogenesis in Drosophila mercatorum

Thelytokous parthenogenesis (female progeny only) in animals is believed to arise initially in unfertilized eggs produced by bisexual females via the fusion of two haploid nuclei following meiosis, to produce diploid female progeny. The transition from sexual to parthenogenetic mechanisms of reproduction requires that the egg replace the paternal contributions of a haploid genetic complement and the basal body, which is thought to be essential for centrosome formation. The transitional facultative parthenogenetic stage is usually associated with a high rate of failed or abortive development, but the molecular and mechanistic reasons for this failure remain unclear. We show that a facultatively parthenogenetic strain of Drosophila mercatorum produces a high percentage of unfertilized eggs competent to restore diploidy and form centrosomes de novo following meiosis. The female meiotic products replicate and divide by an acentrosomal mechanism in most oocytes and cytoplasmic centrosomes form in 35% of the oocytes. However, after pronuclear replication the cytoplasmic centrosomes must "capture" two haploid nuclei in order to restore diploidy. In practice, this process frequently fails due to centrosome-mediated capture events of single or more than two haploid nuclei, as well as multiple nuclear capture events in a single embryo when excess free centrosomes are not inactivated following formation of the first zygotic nucleus. Additionally, as development proceeds, many of the centrosomes that initiate syncytial development do not remain functional, possibly due to centrosome maturation defects, and later stages of syncytial development fail. The combined effect of the high error rate associated with nuclear capture and the failure of centrosome maturation during later developmental prevents successful parthenogenesis in most of the eggs that initiate development. This shows that the high rate of failed development associated with the transition from sexual to parthenogenetic reproduction is limited by the low probability of the formation of a diploid zygotic nucleus with the correct complement of centrosomes in D. mercatorum.     

Mosses in biotechnology

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苔藓植物耐旱机制研究进展

耐旱藓类快速脱水并存活的能力可由快速建立起来的对环境变化的耐受机制来反映,保护细胞完整性的组成型机制与修复细胞损伤的诱导机制协同作用使苔藓植物渡过干旱胁迫.再水化时光合系统原初恢复非常迅速;ABA处理可显著改变PSⅡ的生理特征;基因表达的变化主要由翻译调控引起;脱水组织中贮存mRNPs既保护了mRNAs,又加快了再水化修复速度.山墙藓(Tortula ruralis)是耐旱研究较多的一个种,已建立了表达序列文库(EST),将会成为耐旱研究的重要模式植物.     

Cytological Investigation of Taiwania flousiana Gaussen (Taxodiaceae)

The present paper deals with the cytological investigation of Taiwania flousiana Gaussen. The somatic chromosomes in root-tip cells of the plant are found to be 2n=22 for the first time, all with median and submedian constrictions. According to the terminology defined by Levan et al.^[11], the karyotype formula is K(2n)=16m+6sm, which belongs to “2B” of Stebbins'^[16,17] karyotypic symmetry and is generally regarded as a relatively primitive one. The species' chromosome complement is 2n=22=4L+6M₂+8M₁+4s according to the standard defined by Kuo et al.^[10] based on relative length. The nucleolus number in resting root-tip cells of T. flousiana is found to be 1-5 (Table 3). The percentage of cells with two nucleoli is 77.6%, and those with five nucleoli, the highest number ever found by me, is only 1.6%. A few cells with many micronuclei are found in this species for the first time (Plate 1, 1). Although T. flousiana and T. cryptomerioider have the same “2B” type of karyotypic symmetry, the differences in the arm ratio and the index of the karyotypic asymmetry (Table 2) show that the karyotype of the former is less symmetrical than that of the latter, so the former may be a little more advanced than the latter. The basic karyotype (2B) of Taiwania is more related to that of Cunninghamia (1B)^[3] than to that (1A) of Metasequoia^[5], Glyptostrobus^[4] and Cryptomeria^[3]. Wang et al.^[1], have reached the similar conclusion from the embryological study.     

低等植物蓝光受体信号传导研究

拟南芥含有5个已分离的蓝光受体和至少1个未鉴定的蓝光/紫外光-A受体.隐花色素(CRY1、CRY2和CRY3) 调节植物的形态建成、开花和生物节律性,而向光素 (PHOT1和PHOT2) 调节植物的向光性、叶绿体运动和气孔开放.黄素可以吸收蓝光和紫外光-A,是CRY和PHOT蓝光受体的生色团.对这些光受体的结构和作用模式已了解很多.苔藓植物小立碗藓中含有2个已分离的隐花色素(CRY1a和CRY1b),负责调节侧枝形成和调控生长素反应;有4个向光素(PHOTA1,PHOTA2,PHOTB1,PHOTB2) 调节叶绿体的运动.苔藓细胞内蓝光/紫外光-A引发的信号转导有Ca2+参与.     

中国藓类植物新记录

在研究新疆喀纳斯自然保护区的苔藓植物时 ,发现新疆藓类 4个新记录 ,包括硬叶拟白发藓Paraleucobryumenerve (Thed.)Loesk .,长枝砂藓Racomitriumericoides (Hedw .)Brid .,弯叶卷叶藓Ulotacurvifolia (Wahl.)Lilj.和柔弱明叶藓Vesiculariaflaccida (Sull.etLesq .)Iwats.,其中弯叶卷叶藓和柔弱明叶藓亦为中国新分布。在文中讨论了它们的形态特性     

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。     

苔藓植物蓝光/紫外光-A 信号传导的研究

种子植物含有5个已分离的光受体和至少1个未鉴定的蓝光/紫外光-A受体。隐花色素(CRY1、CRY2和CRY3) 调节植物的生长发育,而向光蛋白(PHOT1和PHOT2) 调节植物对光的营养反应。黄素可以吸收蓝光和紫外光-A,是生色团。对这些光受体的结构和作用模式已了解很多。苔藓植物小立碗藓中含有2个已分离的隐花色素(CRY1a和CRY1b),负责调节侧枝形成和生长素代谢;有4个向光蛋白(PHOTA1,PHOTA2,PHOTB1,PHOTB2) 调节叶绿体的运动。苔藓细胞内蓝光/紫外光-A刺激引发的信号转导有Ca2+参与。     

Cytological Studies in the Laminariales

A cytological investigation of British members of the orderLaminariales has revealed the presence of a very large X-chromosomein dividing nuclei of female gametophytes and young sporophytesof Saccorhiza polyschides. This chromosome pairs with a smallY-chromosome at meiosis. A chromosome which is conspicuouslylarger than the others has also been detected in the femalegametophytes (and young sporophytes) of Laminaria spp., Chordafilum, and Alaria esculenta. There is some evidence that thisalso pairs with a smaller chromosome. Chromosome numbers determinedduring the work are as follows: Laminaria digitata, L. saccharina,L. hyperborea, L. ochroleuca, Saccorhiza polyschides, hap-loid31 and diploid 62; Alaria esculenta, haploid 28 and diploid56; Chorda filum, haploid c. 28 and diploid c. 56