Botany seminars

Leonardo Fernandes Fraceto explores the development of nanoherbicides for more efficient, sustainable weed control. This Spanish-language webinar covers design strategies, interactions between nanomaterials and plants, controlled release, reduced herbicide doses and potential reductions in environmental impact. It examines how these principles could support more precise crop management and discusses the practical benefits, barriers and opportunities associated with adopting nanoherbicides in real agricultural systems. Speaker: Dr. Leonardo Fernandes Fraceto, Universidade Estadual Paulista, Brazil. The registration page also lists Dr. Ingrid Montes, Universidad de Puerto Rico, Recinto de Río Piedras. Co-produced by ACS Webinars and Sociedad Química de México. Wednesday 30 September 2026, 14:00–15:00 America/New_York (EDT); the live registration page confirms 20:00 CEST. Online via Zoom Events, free registration required. Follow Regístrese Gratuitamente on the ACS event page to the verified Zoom Events registration page. A free ACS ID may be required. Slides are scheduled to be available on the webinar day.

Jennifer Brophy presents two methods for programming when and where genes are expressed in plants and their associated microbes. One creates a chemical signal using the noncanonical amino acid O-methyl-L-tyrosine. Engineered Arabidopsis, tomato and poplar produce the signal, while engineered Bacillus subtilis and soil bacteria respond by activating gene expression. Restricting signal production to selected plant tissues allows local control of microbial activity. The second approach builds a genetic circuit that counts successive branching events in roots. It produces different expression patterns at different branch orders, helping researchers distinguish the contributions of roots that otherwise have similar molecular identities. Together, the approaches support experiments on plant development and the engineering of plant–microbe partnerships.

Sanne Evers introduces the first forecasting challenge organized by the European Ecological Forecasting Initiative. The challenge uses long-running observations from Doñana National Park in southern Spain to support short-term predictions of vegetation indices and the abundance of multiple shrub species. Forecasting these changes can inform habitat management, productivity assessments and conservation decisions under climatic and hydrological pressures. The seminar explains why Doñana’s range of habitats and monitoring infrastructure offer a useful setting for comparing predictions before new observations become available. It also discusses lessons from developing the challenge and planned next steps, with participation encouraged across ecological disciplines and levels of forecasting experience.

Jérôme Chave examines how tropical forests respond to warming and rising carbon dioxide. Their carbon uptake is constrained by physiology, ecological interactions and extreme conditions. Long-term field observations, analytical methods and models are used to investigate future carbon storage, biodiversity and the persistence of forest communities under global change.

Living Systems often seem to follow, in addition to external constraints and interactions, an intrinsic predictive model of the world — a defining trait of Anticipatory Systems. Here we study rhythmic behaviour in Caulerpa, a marine green alga, which appears to predict the day/night light cycle. Caulerpa consists of differentiated organs resembling leaves, stems and roots. While an individual can exceed a meter in size, it is a single multinucleated giant cell. Active transport has been hypothesized to play a key role in organismal development. It has been an open question in the literature whether rhythmic transport phenomena in this organism are of autonomous circadian nature. Using Raspberry-Pi cameras, we track over weeks the morphogenesis of tens of samples concurrently, while tracing at resolution of tens of seconds the variation of the green coverage. The latter reveals waves propagating over centimeters within few hours, and is attributed to chloroplast redistribution at whole-organism scale. Our observations of algal segments regenerating under 12-hour light/dark cycles indicate that the initiation of the waves precedes the external light change. Using time-frequency analysis, we find that the temporal spectrum of these green pulses contains a circadian period. The latter persists over days even under constant illumination, indicative of its autonomous nature. We further explore the system under non-circadian periods, to reveal how the spectral content changes in response. Time-keeping and synchronization are recurring themes in biological research at various levels of description — from subcellular components to ecological systems. We present a seemingly primitive living system that exhibits apparent anticipatory behaviour. This research offers quantitative constraints for theoretical frameworks of such systems.

We have characterised the motility of the swimming microalga Chlamydomonas reinhardtii as a function of day/night cycles, to which the microalgal growth is entrained. Intriguingly, we find that the microalgae swim almost twice as fast during the night than during the day. I will connect this result with the bioenergetics of flagellar propulsion, discussing consequences for the distributions of cells in lab-based and environmental water columns.

Three complementary lectures explain the development and applications of optogenetics. Gero Miesenböck traces optical control of neuronal activity from early experiments to studies of sleep, including neurons that respond to accumulated sleep need and molecular mechanisms governing sleep pressure. Peter Hegemann connects microbial photobiology to channelrhodopsins that control neuronal membrane voltage. He discusses their use in studying development and learning, and prospects for extending optical control to enzymes, transcription and translation. Georg Nagel follows the discovery and expression of microbial rhodopsins with light-sensitive transport and enzymatic functions. His examples include Channelrhodopsin-2 and its H134R variant, halorhodopsin, the more light-sensitive ChR2/XXL, the rhodopsin guanylyl cyclase Cyclop, and anion-channelrhodopsins in tobacco plants. Together, the talks connect molecular mechanisms with experimental control of neural and plant systems.