We describe a water fern spore assemblage from the Maastrichtian La Colonia Formation, Chubut Province, Patagonia, Argentina. The includes three species of Azolla (A. andreisii sp. nov., A. coloniensis, and 1), two Azollopsis intermedia tomentosa), Crybelosporites pannuceus, Gabonisporis cristata, Ghoshispora sp., Grapnelispora loncochensis, Molaspora (M. lobata M. reticulata), Paleoazolla pata...

Protein ubiquitination is critical for numerous processes in eukaryotes. The ubiquitin-conjugating enzyme (E2) is required for ubiquitination. The Arabidopsis genome has approximately 37 E2 genes, but in vivo functions for most of them remain unknown. In this study we observed that knockout mutants of Arabidopsis UBC22 had much-reduced silique length and seed number, with nearly 90% of ovules a...

The present investigation deals with morphological and embryological studies of Rhynchelytrum repens (Willd) C.E. Hubbard. The development of anther walls are found to be Monocotyledonous type. The tapetal cells are substantially large, glandular and uninucleate. The middle layer is ephemeral and their cells are small in size. It is sandwiched between endothecial and tapetal layer. The endothec...

INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597 Linkage intensity between the factor pairs Su su and Ta tu in maize. .................... 598 The relative frequency of crossing over between S, su and Tu tu in megaspore and microspore development. ...................................................

INTRODUCTION Unlike animals, in which male and female gametes are derived from germline stem cells, plants produce their gametes from somatic cells that are directed onto specialised pathways based on their position within the reproductive organ, rather than their lineage (Huala and Sussex, 1993; Nonomura et al., 2007). Formation of the female gametophyte (FG) in Arabidopsis ovules begins with ...

The ultrastructure of the Late Cretaceous (Santonian-?early Campanian) megaspore Glomerisporites pupus and its associated microspores has been examined in an attempt to resolve a number of problems concerning the interpretation of their morphology. The new observations presented are based on an analysis of entire, fragmentary, and thin-sectioned specimens under scanning and transmission electro...

In most plants, the female germline starts with the differentiation of one megaspore mother cell (MMC) in each ovule that produces four megaspores through meiosis, one of which survives to become the functional megaspore (FM). The FM further develops into an embryo sac. Little is known regarding the control of MMC formation to one per ovule and the selective survival of the FM. The ICK/KRPs (in...