Stomatal acclimation to dynamic light: implications for photosynthesis and water use efficiency

Although stomata typically occupy only a small portion of the leaf surface (0.3-5%), stomata control approximately 95% of all gas exchange between the leaf interior and external environment.Therefore, stomatal behaviour has major consequences for photosynthetic CO2fixation and water loss from leaf to canopy levels, influencing carbon and hydrological cycles at global scales. Plant acclimation to growth light environment has been studied extensively; however, the majority of these studies have focused on constant light intensity and photo-acclimation, with few studies exploring the impact of dynamic growth light on stomatal acclimation and behaviour. Initially, in this thesis natural variation in the response of stomatal conductance (gs) to light was assessed in the model tree species Populus nigra. Dynamic growth light regimes (varying in intensity and pattern) were subsequently used, to explore how stomatal acclimation to growth light impacts stomatal behaviour, photosynthesis (A) and water use efficiency (Wi). The rate, magnitude and diurnal behaviour of the response of gs to light varied significantly between genotypes and growth light treatments, which promoted differences in A and therefore Wiover the course of the day. The findings in this study illustrate the impact of growing plants in dynamic light regimes, similar to those experienced by plants in the natural environment, on the physiology and performance of model species Populus nigraand Arabidopsis thaliana. Furthermore, it emphasizes that growing plants under laboratory conditions and square-wave illumination does not accurately represent plant acclimation anddevelopment under a natural environment. Highlighting the need to potentially rethink how we grow plants as a community if we are to infer results from the lab to the field. Finally, this study highlights the importance of considering plant acclimation togrowth light, and the impact this has on the functional response of stomata, when attempting to model the response of gsacross leaf to ecosystem and global scales

Spatio-temporal patterns act as computational mechanisms governing emergent behavior in robotic swarms

Our goal is to control a robotic swarm without removing its swarm-like nature. In other words, we aim to intrinsically control a robotic swarm emergent behavior. Past attempts at governing robotic swarms or their self-coordinating emergent behavior, has proven ineffective, largely due to the swarm's inherent randomness (making it difficult to predict) and utter simplicity (they lack a leader, any kind of centralized control, long-range communication, global knowledge, complex internal models and only operate on a couple of basic, reactive rules). The main problem is that emergent phenomena itself is not fully understood, despite being at the forefront of current research. Research into 1D and 2D Cellular Automata has uncovered a hidden computational layer which bridges the micro-macro gap (i.e., how individual behaviors at the micro-level influence the global behaviors on the macro-level). We hypothesize that there also lie embedded computational mechanisms at the heart of a robotic swarm's emergent behavior. To test this theory, we proceeded to simulate robotic swarms (represented as both particles and dynamic networks) and then designed local rules to induce various types of intelligent, emergent behaviors (as well as designing genetic algorithms to evolve robotic swarms with emergent behaviors). Finally, we analysed these robotic swarms and successfully confirmed our hypothesis; analyzing their developments and interactions over time revealed various forms of embedded spatiotemporal patterns which store, propagate and parallel process information across the swarm according to some internal, collision-based logic (solving the mystery of how simple robots are able to self-coordinate and allow global behaviors to emerge across the swarm)

Acclimation to fluctuating light impacts the rapidity and diurnal rhythm of stomatal conductance.

Plant acclimation to growth light environment has been studied extensively, however, the majority of these studies have focused on light intensity and photo-acclimation, with few studies exploring the impact of dynamic growth light on stomatal acclimation and behavior. In order to assess the impact of growth light regime on stomatal acclimation, we grew plants in three different lighting regimes (with the same average daily intensity); fluctuating with a fixed pattern of light, fluctuating with a randomized pattern of light (sinusoidal), and non-fluctuating (square wave), to assess the effect of light regime dynamics on gas exchange. We demonstrated that gs acclimation is influenced by both intensity and light pattern, modifying the stomatal kinetics at different times of the day resulting in differences in the rapidity and magnitude of the gs response. We also describe and quantify response to an internal signal that uncouples variation in A and gs over the majority of the diurnal period, and represents 25% of the total diurnal gs. This gs response can be characterized by a Gaussian element and when incorporated into the widely used Ball-Berry Model greatly improved the prediction of gs in a dynamic environment. From these findings we conclude that acclimation of gs to growth light could be an important strategy for maintaining carbon fixation and overall plant water status, and should be considered when inferring responses in the field from laboratory based experiments

Diurnal Variation in Gas Exchange: The Balance between Carbon Fixation and Water Loss

Stomatal control of transpiration is critical for maintaining important processes, such as plant water status, leaf temperature, as well as permitting sufficient CO2 diffusion into the leaf to maintain photosynthetic rates (A). Stomatal conductance often closely correlates with A and is thought to control the balance between water loss and carbon gain. It has been suggested that a mesophyll-driven signal coordinates A and stomatal conductance responses to maintain this relationship; however, the signal has yet to be fully elucidated. Despite this correlation under stable environmental conditions, the responses of both parameters vary spatially and temporally and are dependent on species, environment, and plant water status. Most current models neglect these aspects of gas exchange, although it is clear that they play a vital role in the balance of carbon fixation and water loss. Future efforts should consider the dynamic nature of whole-plant gas exchange and how it represents much more than the sum of its individual leaf-level components, and they should take into consideration the long-term effect on gas exchange over time

Synthesis and evaluation of designed PKC modulators for enhanced cancer immunotherapy.

Bryostatin 1 is a marine natural product under investigation for HIV/AIDS eradication, the treatment of neurological disorders, and enhanced CAR T/NK cell immunotherapy. Despite its promising activity, bryostatin 1 is neither evolved nor optimized for the treatment of human disease. Here we report the design, synthesis, and biological evaluation of several close-in analogs of bryostatin 1. Using a function-oriented synthesis approach, we synthesize a series of bryostatin analogs designed to maintain affinity for bryostatin's target protein kinase C (PKC) while enabling exploration of their divergent biological functions. Our late-stage diversification strategy provides efficient access to a library of bryostatin analogs, which per our design retain affinity for PKC but exhibit variable PKC translocation kinetics. We further demonstrate that select analogs potently increase cell surface expression of CD22, a promising CAR T cell target for the treatment of leukemias, highlighting the clinical potential of bryostatin analogs for enhancing targeted immunotherapies

Temporal Dynamics of Stomatal Behavior: Modeling and Implications for Photosynthesis and Water Use.

An analysis of stomatal behavior reveals the importance of modeling slow stomatal responses and the impacts on photosynthesis under dynamic light environments

Light, power, action! Interaction of respiratory energy and blue light induced stomatal movements

Although the signalling pathway of blue light (BL)-dependent stomatal opening is well characterized, little is known about the interspecific diversity, the role it plays in the regulation of gas exchange and the source of energy used to drive the commonly observed increase in pore aperture. Using a combination of red and BL under ambient and low [O₂] (to inhibit respiration), the interaction between BL, photosynthesis and respiration in determining stomatal conductance was investigated. These findings were used to develop a novel model to predict the feedback between photosynthesis and stomatal conductance under these conditions. Here we demonstrate that BL-induced stomatal responses are far from universal, and that significant species-specific differences exist in terms of both rapidity and magnitude. Increased stomatal conductance under BL reduced photosynthetic limitation, at the expense of water loss. Moreover, we stress the importance of the synergistic effect of BL and respiration in driving rapid stomatal movements, especially when photosynthesis is limited. These observations will help reshape our understanding of diurnal gas exchange in order to exploit the dynamic coordination between the rate of carbon assimilation (A) and stomatal conductance (gs), as a target for enhancing crop performance and water use efficiency

Blue Light Induces a Distinct Starch Degradation Pathway in Guard Cells for Stomatal Opening

Stomatal pores form a crucial interface between the leaf mesophyll and the atmosphere, controlling water and carbon balance in plants [1]. Major advances have been made in understanding the regulatory networks and ion fluxes in the guard cells surrounding the stomatal pore [2]. However, our knowledge on the role of carbon metabolism in these cells is still fragmentary [3-5]. In particular, the contribution of starch in stomatal opening remains elusive [6]. Here, we used Arabidopsis thaliana as a model plant to provide the first quantitative analysis of starch turnover in guard cells of intact leaves during the diurnal cycle. Starch is present in guard cells at the end of night, unlike in the rest of the leaf, but is rapidly degraded within 30 min of light. This process is critical for the rapidity of stomatal opening and biomass production. We exploited Arabidopsis molecular genetics to define the mechanism and regulation of guard cell starch metabolism, showing it to be mediated by a previously uncharacterized pathway. This involves the synergistic action of β-amylase 1 (BAM1) and α-amylase 3 (AMY3) - enzymes that are normally not required for nighttime starch degradation in other leaf tissues. This pathway is under the control of the phototropin-dependent blue-light signaling cascade and correlated with the activity of the plasma membrane H+-ATPase. Our results show that guard cell starch degradation has an important role in plant growth by driving stomatal responses to light

A qualitative study of health care professionals' views and experiences of paediatric advance care planning

Background: Good end-of-life care planning is vital to ensure optimal care is provided for patients and their families. Two key factors are open and honest advance care planning conversations between the patient (where possible), family, and health care professionals, focusing on exploring what their future wishes are; and the development of an advance care plan document. However, in paediatric and neonatal settings, there has been little research to demonstrate how advance care planning conversations take place. This study explored health care professionals' views and experiences of paediatric advance care planning in hospitals, community settings and hospices. Methods: A qualitative methodology was employed using purposive sampling of health care professionals involved in the end-of-life care for children aged 0-18 years known to the hospital palliative care team, and had died at least three months before, but less than 18 months prior to the study. Ethics committee approval was obtained for the study. Located in the North of England, the study involved three hospitals, a children's hospice, and community services. Data were collected using semi-structured, digitally recorded, telephone interviews. All interviews were transcribed verbatim and subjected to thematic analysis. Results: Twenty-one health care professionals participated, including generalist paediatric staff as well as specialist palliative care staff. Two themes were generated from the study: The timing of planning conversations, including waiting for the relationship with the family to form; the introduction of parallel planning; avoiding a crisis situation. Secondly, supporting effective conversations around advance care planning, including where to have the conversation; introducing the conversation; and how to approach the topic encompassing the value of advance care planning and documentation for families. Conclusion: The timing of when to start the advance care planning conversations remains an issue for health care professionals. The value of doing it in stages and considering the environment where the conversations are held was noted. Timely planning was seen as vital to avoid difficult conversations at a crisis point and for co-ordination of care. Good advance care planning is to provide the best person-centred care for the child and experience for the family