Search

Collaboration between two biologists and a physicist resulted in the example of tattooing being used as a motivator to support discussion across several scientific fields (cell biology, microbiology, human health, and physics). Although often viewed as self-destructive and rebellious in the Western world, tattooing has a deep and rich history full of meaning, for example as a rite of passage. Our main objective was to use a culturally relevant topic as a way to increase student engagement and learning while linking biological phenomena and physics. We describe this experience and provide a brief background on how the art and history of tattooing can aid in teaching young biologists.

To identify developmental mechanisms that might have been involved in the evolution of axial sporophytes in early land plants, we examined the effects of auxin-regulatory compounds in the sporophytes of the hornwort Phaeoceros personii, the liverwort Pellia epiphylla, and the moss Polytrichum ohioense, members of the three divisions of extant bryophytes. The altered growth of isolated young sporophytes exposed to applied auxin (indole-3-acetic acid) or an auxin antagonist (p-chlorophenoxyisobutyric acid) suggests that endogenous auxin acts to regulate the rates of axial growth in all bryophyte divisions. Auxin in young hornwort sporophytes moved at very low fluxes, was insensitive to an auxin-transport inhibitor (N-[1-naphthyl]phthalamic acid), and exhibited a polarity ratio close to 1.0, implying that auxin moves by simple diffusion in these structures. Emerging liverwort sporophytes had somewhat higher auxin fluxes, which were sensitive to transport inhibitors but lacked any measurable polarity. Thus, auxin movement in liverwort sporophytes appears to result from a unique type of apolar facilitated diffusion. In young Polytrichum sporophytes, auxin movement was predominantly basipetal and occurred at high fluxes exceeding those measured in maize coleoptiles. In older Polytrichum sporophytes, acropetal auxin flux had increased beyond the level measured for basipetal flux. Insofar as acropetal and basipetal fluxes had different inhibitor sensitivities, these results suggested that moss sporophytes carry out bidirectional polar transport in different cellular pathways, which resembles the transport in certain angiosperm structures. Therefore, the three lineages of extant bryophytcs appear to have evolved independent innovations for auxin regulation of axial growth, with similar mechanisms operating in moss sporophytes and vascular plants. Key words: auxin; axial growth; bryophyte sporophytes; hornworts; liverworts; mosses; polar auxin transport.

Student engagement during the development of a three-dimensional visual aid or teaching model can vary for a number of reasons. Some students report that they are not "creative" or "good at art," often as an excuse to justify less professional outcomes. Student engagement can be low when using traditional methods to produce a model, but 3D printing gives both the teacher and the student new ways of experiencing classroom activities. The simple (and free) software offers students valuable skills, "professional" modeling results, a stronger understanding of the topic at hand, and new confidence.

Lycopodium is a commonly ignored plant in the forest understory and in fire ecological studies in spite of the well-documented explosive nature of their spores. Therefore, in order to understand how fire may affect Lycopodium, burn studies were carried out on varying sporophyte life cycle stages. Strobili exhibited varying degrees of sporophyll opening and closing in response to the burning and age was directly correlated to the length of the burn. Spores that were burned and plated on axenic media showed a decrease in germination time, from 9 months to 3 weeks, after being subjected to fire. Beyond providing baseline understanding of the effects of fire on Lycopodium and its reproduction, these studies also provide clues about the possible role of fire in Paleozoic forests. [ABSTRACT FROM AUTHOR]

This review represents the first effort ever to survey the entire literature on auxin (indole-3-acetic acid, IAA) action in all plants, with special emphasis on the green plant lineage, including charophytes (the green alga group closest to the land plants), bryophytes (the most basal land plants), pteridophytes (vascular non-seed plants), and seed plants. What emerges from this survey is the surprising perspective that the physiological mechanisms for regulating IAA levels and many IAA-mediated responses found in seed plants are also present in charophytes and bryophytes, at least in nascent forms. For example, the available evidence suggests that the apical regions of both charophytes and liverworts synthesize IAA via a tryptophan-independent pathway, with IAA levels being regulated via the balance between the rates of IAA biosynthesis and IAA degradation. The apical regions of all the other land plants utilize the same class of biosynthetic pathway, but they have the potential to utilize IAA conjugation and conjugate hydrolysis reactions to achieve more precise spatial and temporal control of IAA levels. The thallus tips of charophytes exhibit saturable IAA influx and efflux carriers, which are apparently not sensitive to polar IAA transport inhibitors. By contrast, two divisions of bryophyte gametophytes and moss sporophytes are reported to carry out polar IAA transport, but these groups exhibit differing sensitivities to those inhibitors. Although the IAA regulation of charophyte development has received almost no research attention, the bryophytes manifest a wide range of developmental responses, including tropisms, apical dominance, and rhizoid initiation, which are subject to IAA regulation that resembles the hormonal control over corresponding responses in seed plants. In pteridophytes, IAA regulates root initiation and vascular tissue differentiation in a manner also very similar to its effects on those processes in seed plants. Thus, it is concluded that the seed plants did not evolve de novo mechanisms for mediating IAA responses, but have rather modified pre-existing mechanisms already operating in the early land plants. Finally, this paper discusses the encouraging prospects for investigating the molecular evolution of auxin action. [ABSTRACT FROM AUTHOR]