The role of gravimorphoses in moss adaptation to extreme environment

Gravisensitivity of mosses at different stages of their ontogenesis has an adaptive value and contributes to the functional activity of the gametophyte and its stability under extreme conditions in microhabitats. The aim of our research was to determine the participation of gravimorphoses in the adaptive plasticity of mosses depending on thermal conditions of their habitats and UV radiation effect. The objects of the study were sterile cultures of the following moss protonemata: Weissia tortilis, collected in different thermal conditions of Zaporizhzhya and Lviv regions (Ukraine), Bryum caespiticium from Lviv Region (Ukraine), as well as B. caespiticium and Polytrichum arcticum collected in Antarctica (Galindez Island). In all moss cultures, the gravisensitivity of protonemata, the morphological structure and morphogenesis of stolons were analysed. The protonemata of W. tortilis from two populations in Ukraine and of B. caespiticium from Antarctica and Ukraine, growing under conditions of different UV levels, were compared in terms of their sensitivity to UV radiation. Gravity-dependent morphoses of terrestrial dendrites of W. tortilis under arid conditions, branching of apical cells of gravitropic stolons of Antarctic mosses P. arcticum and B. caespiticium as well as the rapid development of shoots on them demonstrate participation of gravimorphogenesis in adaptation of mosses to stressful environmental conditions. Gravisensitivity and ability to form buds at the apex of a gravitropic stolon are considered an important adaptive morphogenetic process. It has been found that plants of W. tortilis from Zaporizhzhya Region were more resistant to UV irradiation than those from Lviv Region. Antarctic moss after UV irradiation showed significantly higher antioxidants activity and contained larger amount of phenolic compounds and flavonoids.

3D Dissection of Structural Membrane-Wall Contacts in Filamentous Moss Protonemata

In conventional light microscopy, the adjacent cell walls of filamentous moss protonemata are seen from its narrow side thereby obscuring the major area of cell–cell connection. Optical sectioning, segmentation and 3D reconstructions allow the tilting and rotation of intracellular structures thereby greatly improving our understanding of interaction between organelles, membranes and the cell wall. Often, the findings also allow for conclusions on the respective functions. The moss Physcomitrium (Physcomitrella) patens is a model organism for growth, development and morphogenesis. Its filamentous protonemata are ideal objects for microscopy. Here, we investigated the cell wall between two neighboring cells and the connection of membranes towards this wall after plasmolysis in 0.8 M mannitol. An m-green fluorescent protein (GFP)-HDEL cell line was used to visualize the endoplasmatic reticulum (ER), the plasma membrane (PM) was stained with FM4-64. Our studies clearly show the importance of cell–cell contacts in P. patens protonemata. In 86% of the investigated cell pairs, at least one of the protoplasts remained fully attached to the adjacent cell wall. By tilting of z-stacks, volume renderings and 3D reconstructions, we visualized the amount of attached/detached PM and ER components after plasmolysis and membrane piercings through the wall of cell neighbors.

Preemergence Control of Silvery Threadmoss (Bryum argenteum) Grown from Spores and Bulbils in Axenic Culture

Silvery threadmoss naturally reproduces through spore and bulbil production, both of which have potential to be controlled prior to establishment. Studies have not evaluated effects of turf protection products on moss protonema or gametophyte growth from spores or bulbils; consequently, most moss is controlled POST on putting greens. Initial studies were performed to determine the optimal growth temperature for spores and bulbils in sterile culture. Protonemata from spores grew optimally at 29.5 C and gametophytes from bulbils grew optimally at 22.5 C. Three subsequent in vitro studies were conducted to evaluate effects of turf protection products on moss development from spores or bulbils in axenic culture at a constant 24 C. Carfentrazone, which effectively controls mature silvery threadmoss gametophytes POST, also reduced green cover of moss protonemata and gametophyte production from spores and bulbils. All combinations with carfentrazone reduced area under the progress curve (AUPC) for green cover of moss for both spores and bulbils by 80% or more by 3 wk after treatment. Sulfentrazone, oxyfluorfen, oxadiazon, saflufenacil, flumioxazin, and pyraflufen-ethyl reduced AUPC of moss equivalent to carfentrazone for both propagule types. The two fosetyl-Al products, phosphite, and mineral oil caused an increase in silvery threadmoss cover between 22 and 113% of the nontreated for spores; however, only methiozolin positively influenced AUPC (90.2%) compared to the nontreated for bulbils. Though silvery threadmoss is typically targeted POST on putting greens, there are products that can provide PRE control, including the industry standard of carfentrazone. These data suggest that differences may occur between turf protection products in their ability to suppress silvery threadmoss establishment from spores or bulbils.

Evidence against mediation of adenosine-3',5'-cyclic monophosphate in the bud-inducing effect of cytokinins in moss protonemata

Effects Oif adenosdne-3',5'-cyclic monophosphate (cAMP), N⁶,O²-dibuityryl adenosine-3',5'-cyclic monophosphate (DBcAMP), caffeine and theophylline on the bud-inducing activity of cytokinin in the protonema of two moss species, <i>Ceratodon purpureus</i> and <i>Funaria hygrometrica</i> were examined. The sub-stances have been found ineffective as gametophore bud inducers. Some synergism between cytokinin and cAMP or DBcAMP was observed with relation to the buds' growth, but this effect is nonspecific since it can be obtained with 5'-AMP or 5'-GMiP as well, The results seem to exclude the possibility of an involvement of cAMP as a second messenger in the mechanism of cytokinin action on morphogenetic processes in moss protonemata.