A comparative ultrastructural analysis of exine pattern development in wild-typeArabidopsis and a mutant defective in pattern formation

Summary In order to identify factors necessary for the establishment of the reticulate pollen wall pattern, we have characterized a T-DNA tagged mutant ofArabidopsis thaliana that is defective in pattern formation. This study reports the results of an ultrastructural comparison of pollen wall formation in the mutant to wall development in wild-type plants. Pollen wall development in the mutant parallels that of wild-type until the early tetrad stage. At this point in wild-type plants, the microspore plasma membrane assumes a regular pattern of ridges and valleys. Initial sporopollenin deposition occurs on the ridges marking the beginning of probacula formation. In contrast, the plasma membrane in the mutant appears irregular with flattened protuberances and rare invaginations. As a result, the wild-type regular pattern of ridges and valleys is not formed. Sporopollenin is randomly deposited on the plasma membrane and aggregates on the locule wall; it is not anchored to the membrane. Our finding that the mutation blocks the normal invagination of the plasma membrane and disrupts the proper deposition of sporopollenin during wall formation suggests that the mutation could be in a gene responsible for pattern formation. These results also provide direct evidence that the plasma membrane plays a critical role in the establishment of the pollen wall pattern.     

Plant regeneration from coleoptile tissue of wheat (Triticum aestivum L.)

Plant regeneration was achieved from coleoptile tissue of wheat (Triticum aestivum L. cv. Kharachia-65). Coleoptiles (1.0 - 3.5 cm long) were excised from 2- to 5-d-old seedlings and cultured on Murashige and Skoog's (MS) medium supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D - 0.5, 2.5, and 5.0 mg dm^-3). Cream, friable callus was obtained after 6 weeks of inoculation. This callus was sub-cultured on MS medium supplemented with 2,4-D (2.5 mg dm^-3) and 5 % coconut water. After 6 weeks of sub-culturing white, cream or pale, friable, nodular callus was obtained. Plant regeneration occurred when this callus was sub-cultured on MS medium supplemented with 0.2 mg dm^-3 1-naphthalene acetic acid + 1.0 mg dm^-3 6-benzylaminopurine. For rooting, regenerated shoots or plantlets were transferred on MS medium supplemented with 0.5 mg dm^-3 indole-3-acetic acid. Rooted plantlets were directly transferred into pots and grown under field conditions. Seed setting invariably occurred in all plants. This revised version was published online in July 2006 with corrections to the Cover Date.     

Somatic embryogenesis from chickpea (Cicer arietinum L.) inmature cotyledons: The effect of zeatin, gibberellic acid and indole-3-butyric acid

Studies were conduced to test the effects of various cytokinins on somatic embryogenesis from chickpea (Cicer arietinum L.) immature cotyledons. Zeatin (13.7 μmol) added, to B5 basal medium, supplemented with 1.5 % sucrose and 0.2 μmol indole-3-acetic acid, was the most effective cytokinin. Lobular structures obtained from cotyledons cultures were transferred to B5 basal medium supplemented with gibberellic acid and indole-3-butyric acid at different concentrations. The most effective treatment was B5 medium containing 14.4 μmol gibberellic acid plus 1.0 μmol indole-3-butyric acid in which 42.8 % of lobular structures cultured formed normal somatic embryos. High conversion of embryos into plantlets (61.0–65.2 % embryos regenerated plants) was observed when germinated embryos were placed on plant development medium.     

枸杞胚性细胞分化的超微结构和ATP酶的细胞化学定位研究

枸杞的胚性细胞多由愈伤组织表层的薄壁细胞分化而来,与愈伤组织中未分化的细胞相比,胚性细胞呈卵圆形,细胞核大,核仁明显,细胞质浓厚并含有丰富的细胞器,细胞壁较薄,细胞间有胞间连丝相通;胚性细胞发育到晚期细胞壁加厚,胞间连丝逐渐消失,细胞核向一端偏移,有大液泡形成;胚性细胞的第一次分裂多为均等分裂,形成二细胞原胚,继续分裂形成多细胞原胚;组成多细胞原胚胚体的细胞核大,核形状不规则,细胞质浓厚,细胞器丰富,在质体中出现淀粉的积累。在胚性细胞发育的早期,ATP酶活性主要位于质膜上,随后在液泡内和细胞核中都出现ATP酶活性的分布;随着胚性细胞壁的加厚,细胞壁加厚处和细胞间隙中也出现ATP酶活性反应;当多细胞原胚形成后,ATP酶活性反应主要定位于液泡膜上。由此分析了结构特征、ATP酶活性定位变化与胚性细胞分化的关系。     

Functional expression of opioid receptor—like receptor and its endogenous specific agonist nociceptin／orphanin FQ during mouse embryogenesis

INTRODUCTIONOpioidreceptorsbelongtotheG-protein-coupledreceptorfamilythatischaracterizedbytheseventransmembranespanningdomainsinstructure.Threesubtypesoftheopioidreceptors(H,6,andK)havebeenclonedandcharacterizedthroughtheir1.CorrespondingauthorFunctionalexpressionofORLIandN/OFQduringmouseembryogenesisdistinctaffinitiesfordifferentopioidligands.TheseopioidreceptorsareallcoupledtotheinhibitoryGprotein(Gi)andnegativelyregulateadenylatecyclase[1].Opioidreceptor--likereceptor(ORLI),anew…     

国产葛属植物花粉形态的研究

对国产葛属ＰｕｅｒａｒａｉＤＣ．７种１变种植物花粉的光学显微镜、扫描电镜以及２种１变种的透射电镜观察表明：花粉形态各具特征;表面纹饰类型包括穿孔状（一般直径小于网脊直径或稍等,孔穴中无或少颗粒）、细网纹（网眼直径约与网脊直径相等或略细,网眼内具颗粒）、粗网纹（网眼直径大于网脊直径、网眼内具成片的众多颗粒）;孔沟类型为具孔膜或孔盖,孔膜常成孔桥．上述结果,表明葛属植物７种１变种的花粉形态是有区别的,从覆盖层等形态结构可以推测其亲缘关系,亦可看到部分的演化．     

中国蒿属植物比较形态和解剖学研究 Ⅱ花粉形态

本文通过光学显微镜和扫描电镜,观察国产菊科蒿属２亚属７组５８种代表物的花粉形态,结合有关资料以及菊科１２族,３０属代表植物花粉作比较,分析研究,取得以下结果：１．蒿属的花粉特征具有高度的一致性。主要体现在：花粉呈球形或近球形,极面观的三形圆形,赤道面观为圆形或椭圆形。     

Influence of enhanced UV-B radiation on biomass allocation and pigment concentrations in leaves and reproductive structures of greenhouse-grown Brassica rapa

We assessed the effects of enhanced ultraviolet-B radiation (UV-B; 280–320 nm) on biomass allocation to roots, shoots, leaves and flowers in the annual Brassica rapa. In addition, we investigated how concentrations of chlorophyll and UV-B-absorbing compounds in leaves, ovaries and pollen changed in response to enhanced UV-B. Plants were grown for 38 d in a greenhouse under lampbanks providing daily biologically effective UV-B doses equivalent to those under ambient mid-March stratospheric ozone levels or 16% (low-enhanced UV-B) or 32% (high-enhanced UV-B) ozone depletion levels for Morgantown, WV, USA. Total and aboveground biomass of plants was less under low-enhanced UV-B, but similar to ambient controls under high-enhanced UV-B. Concentrations of UV-B-absorbing compounds in leaves (area basis) increased under high-enhanced UV-B by about 20%, but were similar to ambient controls under low-enhanced UV-B. More effective protection due to higher screening-compound concentrations in plants under high-enhanced UV-B may explain why biomass production was not reduced. Plants under high-enhanced UV-B also had more reproductive biomass and produced more flowers, and had less root mass, than plants under ambient or low-enhanced UV-B. Concentrations of leaf total chlorophyll were not affected by UV-B treatment. While UV-B treatment had no affect on concentrations of UV-B-absorbing compounds in ovaries, concentrations in pollen from plants under both enhanced-UV-B treatments were >40% greater than ambient controls.     

The initiation of callus and regeneration from callus culture ofTulipa gesneriana

Cold treatment of seeds, obtained from crosses between cultivars ofT. gesneriana L., affects the developmental stage of embryos, which in turn influences the frequency of callus induction and the development of different callus types. Cold-treated, mature embryos and basal segments ofin vitro-derived bulblets, were suitable explants for the initiation of regenerative callus on medium with 2,4-dichlorophenoxyacetic acid. The bulblets were initiated on flower-stalk segments from cold-stored bulbs ofT. gesneriana ‘Christmas Marvel.’ Histological analyses of regenerative callus revealed the regeneration of bulb-like structures. The influences of culture medium, culture conditions, growth regulators and acetylsalicylic acid, an inhibitor of ethylene, on the initiation and establishment of regenerative callus cultures are discussed.     

Histology of somatic embryo initiation and organogenesis from rhizome explants of Musa spp.

The origin of somatic embryos derived from rhizome explants of triploid Musa cv. Grand Nain was the subject of histological studies during different phases of ontogenetic development. The investigation revealed that the majority of somatic embryos showed normal root formation and consisted of highly vacuolated cells in the poorly structured shoot apex. The embryogenic mass and somatic embryos were mostly derived from several morphologically competent cells. Single cell origin depended on the presence of organogenetically functional vascular cells of rhizome explants and occurred infrequently. The implications of these findings for genetic improvement of banana and plantain by in vitro mutation breeding and gene technology are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.