Generative Cell Division and Sperm Cell Association in the Pollen Grain of Sambucus nigra

Generative cell division in tricellular pollen grains of Sambucusnigra L. (Caprifoliaceae) has been examined with light and electronmicroscopy. During division the generative cell is located inthe centre of the pollen grain, near to the nucleus of a surroundingvegetative cell. Conventional mitosis of the generative cellis followed by cytokinesis through centrifugal cell plate formation.Two sister sperm cells remain in spatial contact with each otherand are surrounded, as formerly their progenitor cell was, bythe vegetative cell. From the changes of shape of the generativecell during division and of the sperm cells it may be assumedthat the space between these cells and the vegetative one containsa labile, non-rigid, wall material. No plastids have been observedin the generative cell and its mitochondria appear to be unequallydistributed between the two future sperm cells during division. Sambucus nigra L., generative cell division, pollen, sperm cell association     

Phylogenetic relationships of a new genus and species of microteiid lizard from the Atlantic forest of north-eastern Brazil (Squamata, Gymnophthalmidae)

A new genus and species of a short limbed and slightly elongate gymnophthalmid lizard is described from the Atlantic rain forests of north-eastern Brazil. The new genus is also characterized by short and stout pentadactyl limbs, presence of prefrontals, absence of frontoparietals, distinctive ear opening and eyelid, two pairs of genials, a distinct collar, smooth, quadrangular, dorsal scales, quadrangular ventrals, fused postfrontal and postorbital bones, and two pairs of sternal ribs. The geographical distribution of the new taxon extends from the state of Rio Grande do Norte to the northern bank of the Rio São Francisco in the state of Alagoas. All specimens were obtained in leaf litter, an observation which agrees with the fossorial habits suggested by the body shape and massive aspect of the head of this species. A phylogenetic analysis based on external morphology, osteology, and molecular data recovered the new lizard as the sister genus to Anotosaura , and Colobosauroides as the sister group to these two.  © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society , 2005, 144 , 543−557.     

Hemicellulosic Polysaccharides from the Xylopodium of Ocimum nudicaule: Changes in Composition in Dormancy and Sprouting

Changes in the yield and composition of hemicelluloses fromthe underground organs (xylopodia) of Ocimum nudicaule wereinvestigated. Hemicelluloses constituted about 12% of the delipidizedpowder in sprouting and about 30 % in dormant phases. Xyloseis the major component of hemicelluloses A and B (and is alsopresent in C), followed by arabinose, galactose, glucose, rhamnoseand mannose. The amounts of hemicellulose B decreased by sixtimes between dormancy and sprouting, whereas the yields ofhemicelluloses A and C remained constant. This, together withthe higher solubility of hemicellulose B and its higher susceptibilityto hemicellulase in sprouting indicates that this fraction constitutesa cell-wall bound storage polysaccharide, which may play a rolein the onset of xylopodia bud sprouting. Ocimum nudicaule, hemicelluloses, cell-wall storage polysaccharide