Although genetically modified (GM) plants have improved commercially important traits, such as biomass and biofuel production, digestibility, bioremediation, ornamental value, and tolerance to biotic and abiotic stresses, there remain economic, political, or social concerns over potential ecological effects of transgene flow from GM plants. The current solution for preventing transgene flow fro...

INTRODUCTION. .. ............................................................... 417 Relative frequency of crossing over in males and females. ............................. 418 Previous investigations. ...................................................... 418 Crossing over between B b and Lg I , and between C c and Sh sh in microsporogenesis and megasporogenesis. .................................

The development of gametophytes relies on the establishment of a haploid gametophytic generation that initiates with the specification of gametophytic precursors. The majority of flowering plants differentiate a single gametophytic precursor in the ovule: the megaspore mother cell. Here we show that, in addition to argonaute9 (ago9), mutations in other ARGONAUTE (AGO) genes such as ago4, ago6, ...

Female gametogenesis in most flowering plants depends on the predetermined selection of a single meiotically derived cell, as the three other megaspores die without further division or differentiation. Although in Arabidopsis thaliana the formation of the functional megaspore (FM) is crucial for the establishment of the gametophytic generation, the mechanisms that determine the specification an...

Meiosis, the key step of sexual reproduction, persists in facultative apomictic plants functional to some extent. However, it still remains unclear how and why proportions of reproductive pathways vary under different environmental stress conditions. We hypothesized that oxidative stress mediates alterations of developmental pathways. In apomictic plants we expected that megasporogenesis, the s...

Cytochemical methods are used to examine the distribution and localization of acid phosphatase, non-specific esterase, ribonuclease and peroxidase activity in the walls of the spores of the heterosporous Marsileaceae before and during germination. In the quiescent spore, the principal activity is associated with the perine layer of the wall and the intine, with some activity in the outer, gelat...

Here we investigate megaspores from 10 Triassic‒Jurassic localities of southern Sweden and Bornholm, Denmark, based on collections housed in the Swedish Museum Natural History. We identify describe 19 megaspore taxa belonging to three stratigraphically constrained assemblages, representing Rhaetian, Hettangian Pliensbachian, respectively. Megaspores are abundant diverse (12 taxa) Rhaetian assem...

Salak palms (Salacca spp.) are important fruit species in Southeast Asia, but the morphogenesis of their reproductive organs is unknown. To observe female gametogenesis, pistil S. wallichiana and subsequent fertilization were observed. The ovary contained three ovule primordia months before flowering (BF). one mono-nucleate megaspore at center degenerated megaspores on chalazal side two BF, a e...