Lip anatomy and its implications for the pollination mechanisms of Bulbophyllum species (Orchidaceae)

BACKGROUND AND AIMS: The lip structure of six Brazilian and one Asiatic species of Bulbophyllum with wind-assisted fly pollination (B. involutum, B. ipanemense and B. weddellii) and non-wind-assisted fly pollination (B. epiphytum, B. glutinosum, B. regnellii and B. rothschildianum) was studied to investigate the presence of secretory tissues related to these pollination mechanisms. METHODS: The lip study was carried out through scanning electron microscopy (lip surface) and light microscopy (anatomical features). KEY RESULTS: In most of the species studied, the osmophores (odour glands) were located in the lobes and in the upper surface of the lip callus. Differences in the lip structure were observed between the two groups (the presence of a nectary and the extent of osmophore surface), depending on the mechanism of pollination. Nectaries were found in the cavity callus in B. ipanemense, B. involutum and B. weddellii, even though their pollinators were presumably attracted by the instinct to oviposit. CONCLUSIONS: These findings corroborate the hypothesis that, because pollination in these species is dependent on an unpredictable external factor (wind), nectar is necessary to keep the insect in the flower for a long period. Despite the occurrence of a liquid-like nectar in the flowers of B. epiphytum, B. glutinosum, B. regnelli and B. rothschildianum, no anatomical evidence for nectaries was found in the lips of these species, although a similar structure may occur in another region of the flowers. This observation agrees with the fact that pollination by lip movement in the latter species requires only gravity, with no additional mechanism being needed to keep the flies in the flower.     

耳河螺生殖器官和精子的形态学研究

耳河螺「Ｒｉｖｕｌａｒｉａ ａｕｒｉｃｕｌａｔａ （Ｍａｒｔｅｎｓ）」为雌雄异体。雄性生殖器官由精巢,输精小管,贮精囊,输精管,前列腺和阴茎组成。精巢内有精子,精子有典型精子和非典型精子两种。扫描电镜下,典型精子头部呈螺旋状,尾端只有一根较粗壮;非典型精子头部和中部为棒状,尾部呈扫帚状,由８－１５根鞭毛组成。     

Relictual vegetative anatomical characters in Cactaceae: the genusPereskia

The genusPereskia, which contains numerous morphological features considered relictual in the Cactaceae, has numerous anatomical features that we consider to be relictual also. These were studied to establish a basis for determining the ways that morphogenic mechanisms and anatomical characters diversified as the family evolved. ThesePereskia features may be relictual in the family: epidermis predominantly unistratose and lacking crystals; hypodermis absent or of about three layers of weakly collenchymatous cells with druses; cortex thin and predominantly parenchyma with druses and mucilage cells but lacking cortical bundles; secondary phloem without early differentiation of sclerenchyma but with secondary sclereids developing later, either idioblastically or in clusters; ergastic substances lacking from old secondary phloem; wood with a matrix of libriform fibers (mostly septate and nucleate), scanty paratracheal parenchyma, vessels solitary or in small clusters, perforations simple, pitting circular, oval or very broad; wide-band tracheids absent; ray cells slightly thick-walled, lignified, upright, isodiametric or procumbent; all primary rays narrow; pith without medullary bundles; leaves lacking hypodermis, with only weak development of palisade mesophyll; veins of four orders, strongly distinct in size, none with fibers; vessels in leaves narrower than those in stems.     

Anatomical and ultrastructural changes of the floral nectary ofPisum sativum L. during flower development

Summary The floral nectary ofPisum sativum L. is situated on the receptacle at the base of the gynoecium. The gland receives phloem alone which departed the vascular bundles supplying the staminal column. Throughout the nectary, only the companion cells of the phloem exhibited wall ingrowths typical of transfer cells. Modified stomata on the nectary surface served as exits for nectar, but stomatal pores developed well before the commencement of secretion. Furthermore, stomatal pores on the nectary usually closed by occlusion, not by guard-cell movements. Pore occlusion was detected most frequently in post-secretory and secretory glands, and less commonly in pre-secretory nectaries. A quantitative stereological study revealed few changes in nectary fine structure between buds, flowers secreting nectar, and post-secretory flowers. Dissolution of abundant starch grains in plastids of subepidermal secretory cells when secretion commenced suggests that starch is a precursor of nectar carbohydrate production. Throughout nectary development, mitochondria were consistently the most plentiful organelle in both epidermal and subepidermal cells, and in addition to the relative paucity of dictyosomes, endoplasmic reticulum, and their associated vesicles, the evidence suggests that floral nectar secretion inP. sativum is an energy-requiring (eccrine) process, rather that granulocrine.Abbreviations ER endoplasmic reticulum - GA glutaraldehyde - SEM scanning electron microscopy     

Mycorrhizal synthesis between <Emphasis Type="Italic">Boletus edulis</Emphasis> species complex and rockroses (<Emphasis Type="Italic">Cistus</Emphasis> sp.)

Ectomycorrhizas of Boletus aereus, Boletus edulis, and Boletus reticulatus were synthesized with Cistus sp. under laboratory conditions using synthesis tubes filled with a mixture of sterilized peat-vermiculite and nutrient solution. The fungal strains isolated from sporocarps were identified by molecular techniques. The inoculated seedlings were grown for 4–5 months. The ectomycorrhizas formed were described based on standard morphological and anatomical characters. The three ectomycorrhizas described were very similar, with white monopodial-pinnate morphology, a three-layered plectenchymatous mantle on plan view and boletoid rhizomorphs.     

Structural features of mycorrhizal associations in two members of the Monotropoideae, Monotropa uniflora and Pterospora andromedea

Species in the subfamily Monotropoideae (family Ericaceae) are achlorophyllous and myco-heterotrophic. They have become highly specialized in that each plant species is associated with a limited number of fungal species which in turn are linked to autotrophic plants. This study provides an updated and comprehensive examination of the anatomical features of two species that have recently received attention with respect to their host-fungal specificity. Root systems of Monotropa uniflora and Pterospora andromedea collected from the field were characterized by light microscopy and scanning electron microscopy. All roots of both species were associated with fungi, each root having a well-developed mantle, paraepidermal Hartig net, and intracellular fungal pegs within epidermal cells. The mantle of M. uniflora was multi-layered and numerous outer mantle hyphae developed into cystidia of two distinct morphologies. Large calcium oxalate crystals were present, primarily on the mantle surface. The outer mantle of P. andromedea was more loosely organized, lacked cystidia, and had smaller plate-like as well as cylindrical crystals on the surface and between outer mantle hyphae. Fungal pegs in M. uniflora originated from inner mantle hyphae that penetrated the outer tangential wall of epidermal cells; in P. andromedea, these structures were initiated either from inner mantle hyphae or Hartig net hyphae and penetrated radial walls of epidermal cells. With respect to function, fungal pegs occurred frequently in both host species and, although presumed to be the sites of active nutrient exchange, no direct evidence exists to support this. Differences between these two monotropoid hosts, resulting from the mycorrhizal fungi with which each associates, are discussed.     

Mechanical adaptations of cleavers (Galium aparine)

BACKGROUND AND AIMS: Cleavers (Galium aparine) is a fast-growing herbaceous annual with a semi-self-supporting, scrambling-ascending growth habit. Mature plants often use upright species for support. It is common in hedgerows and on waste ground. This study aims to characterize the mechanical behaviour of the stem and roots of cleavers and relate this to the arrangement of structural tissue, the net microfibrillar orientations in the cell walls, and plant growth habit. METHODS: The morphology and mechanics of mature cleavers was investigated using plants grown in pots and ones collected from the grounds at the University of Lincoln, Lincoln, UK. Tensile tests were carried out on the stem and the basal section of the first-order lateral roots. The net orientation of cellulose microfibrils in the cell walls was investigated using polarized light microscopy. KEY RESULTS: Results show that the basal regions of the stem and first-order lateral roots were highly extensible. Breaking strains of 24 +/- 7% were recorded for the stem base and 28 +/- 6% for the roots. Anatomical observations showed that the lower stem (base + 100 mm) was circular in cross-section with a solid central core of vascular tissue, whereas further up the stem the transverse section showed a typical four-angled shape with a ring-like arrangement of vascular tissue and sclerenchyma bundles in the corners. The net orientation of wall microfibrils in the secondary xylem diverges from the longitudinal by between 8 and 9 degrees . CONCLUSIONS: The basal region of the stem of cleavers is highly extensible, but the mechanism by which the stem is able to withstand such high breaking strains is unclear; reorientation of the cellulose fibrils in the stem along the axis of loading is not thought to be responsible.     

Features of visual function in the naked mole-rat <Emphasis Type="Italic">Heterocephalus glaber</Emphasis>

The eyes and visual capacity of the naked mole-rat, Heterocephalus glaber, a subterranean rodent, were evaluated using anatomical, biochemical, and functional assays, and compared to other rodents of similar body size (mouse and gerbil). The eye is small compared to mouse, yet possesses cornea, lens, and retina with typical mammalian organization. The optic nerve cross-sectional area and fiber density are ~10% and ~50% that of gerbil, respectively. Levels per unit retinal area of 11-cis and all-trans retinal, derivatives of vitamin A associated with the visual cycle, are comparable to mouse. The corneal electroretinogram (ERG) exhibits early and late negative components that scale with flash strength; raising the body temperature of this poikilothermic animal from 30°C (normal for H. glaber ) to 37°C (normal for mouse) revealed an ERG response with typically mammalian features, but greatly attenuated and with slower kinetics. Leaving the nest chamber was a behavior correlated with light onset displayed preferentially by breeding females. Optical models of five mole-rat eyes suggest reasonable, but variable, image formation at the retina, possibly related to age. Results are consistent with amorphous light detection, possibly useful for circadian entrainment or escape behavior in the event of tunnel breeches.     

A Permian nurse log and evidence for facilitation in high‐latitude Glossopteris forests

The biology of trees that grew in high‐latitude forests during warmer geological periods is of major interest in understanding past and future ecosystem dynamics. As we study the different plants that composed these forests, it becomes possible to make comparisons with ecosystem processes that occur today. Here we describe a silicified late Permian (Lopingian) glossopterid (seed fern) trunk from Skaar Ridge, central Transantarctic Mountains, Antarctica, with evidence of glossopterid rootlets growing into its wood. The specimen is interpreted as a nurse log similar to those seen in some extant forests. Together with evidence of glossopterid roots growing within the lacunae of older roots, this new specimen suggests the existence of facilitative interactions among the glossopterid trees that dominated the high‐latitude forests of Gondwana during the late Permian. More generally, the existence of self‐facilitation might have favoured the expansion of glossopterids within various environments, especially those at high palaeolatitudes, during the Permian icehouse to greenhouse transition.     

四眼斑龟消化、呼吸系统的解剖

解剖测量了 8只成年四眼斑龟的消化系统和呼吸系统 ,结果表明 :消化管总长 ( 6 0 4 3± 99.2 )mm ,为背甲长的 3 75～ 5 77倍。舌不能伸缩 ;食管扩展性强 ;胃呈囊状 ,被肝叶覆盖 ;小肠较长 ,为消化的主要场所 ,约占消化道总长的 4 8% ;盲肠不发达。肝较大 ,重约 ( 14 12± 8 2 4 )g ,分左、中、右三叶 ,占体重的 6 %左右 ,绿色胆囊位于右叶小肝内 ;胰腺长条形 ,分布于十二指肠肠系膜内。肺长囊形 ,内壁有复杂的间隔 ,把内腔分隔成蜂窝状小室 ,紧贴在背甲的内表面 ,位于肩带和腰带之间 ;气管较长 ,由 6 5～ 85个软骨环连接而成 ;支气管较短 ,由 30～ 4 0个软骨环连接而成