OBJECTIVE: Light is essential for plants, and local populations exhibit adaptive photosynthetic traits depending on their habitats. Although plastic responses in morphological and/or physiological characteristics to different light intensities are well known, adaptive divergence with genetic variation remains to be explored. This study focused on Saxifraga fortunei (Saxifragaceae) growing in sun-exposed and shaded habitats.
METHODS: We measured the leaf anatomical structure and photosynthetic rate of plants grown in their natural habitats and in a common greenhouse (high- and low-intensity light experimental sites). To assess differences in ecophysiological tolerance to high-intensity light between the sun and shade types, we evaluated the level of photoinhibition of photosystem II and the leaf mortality rate under high-intensity light conditions. In addition, population genetic analysis was conducted to investigate phylogenetic origins.
RESULTS: Clear phenotypic differences were found between the sun and shade types despite their recent phylogenetic origin. The leaf anatomical structure and photosynthetic rate showed plastic changes in response to growing conditions. Moreover, the sun type had a well-developed palisade parenchyma and a higher photosynthetic rate, which were genetically fixed, and a lower level of photoinhibition under high-intensity light.
CONCLUSIONS: Our findings demonstrate that light intensity is a selective pressure that can rapidly promote phenotypic divergence between the sun and shade types. While phenotypic changes in multiple photosynthetic traits were plastic, genetic divergence in specific traits related to adaptation to high-intensity light would be fundamental for ecotypic divergence to different light regimes.

暂无摘要。

暂无摘要。

Recent discoveries related to the habitability and astrobiological relevance of the outer Solar System have expanded our understanding of where and how life may have originated. As a result, the Icy Worlds of the outer Solar System have become among the highest priority targets for future spacecraft missions dedicated to astrobiology-focused and/or direct life detection objectives. This, in turn, has led to a renewed interest in planetary protection concerns and policies for the exploration of these worlds and has been a topic of discussion within the COSPAR (Committee on Space Research) Panel on Planetary Protection. This paper summarizes the results of those discussions, reviewing the current knowledge and the history of planetary protection considerations for Icy Worlds as well as suggesting ways forward. Based on those discussions, we therefore suggest to (1) Establish a new definition for Icy Worlds for Planetary Protection that captures the outer Solar System moons and dwarf planets like Pluto, but excludes more primitive bodies such as comets, centaurs, and asteroids: Icy Worlds in our Solar System are defined as all bodies with an outermost layer that is believed to be greater than 50 % water ice by volume and have enough mass to assume a nearly round shape. (2) Establish indices for the lower limits of Earth life with regards to water activity (LLAw) and temperature (LLT) and apply them into all areas of the COSPAR Planetary Protection Policy. These values are currently set at 0.5 and -28 °C and were originally established for defining Mars Special Regions; (3) Establish LLT as a parameter to assign categorization for Icy Worlds missions. The suggested categorization will have a 1000-year period of biological exploration, to be applied to all Icy Worlds and not just Europa and Enceladus as is currently the case. (4) Have all missions consider the possibility of impact. Transient thermal anomalies caused by impact would be acceptable so long as there is less than 10-4 probability of a single microbe reaching deeper environments where temperature is >LLT in the period of biological exploration. (5) Restructure or remove Category II* from the policy as it becomes largely redundant with this new approach, (6) Establish that any sample return from an Icy World should be Category V restricted Earth return.

Solar energy is the most promising among many renewable energy sources to meet the increasing demand. Photovoltaic (PV) based power generating solutions are expected to gain popularity as a power source for different applications, including independent and grid connected loads, due to their cleanliness, high performance, and high dependability. The efficacy of photovoltaic systems is impacted by several elements, including geographical location, positioning, shadowing effects, and local climate conditions. In order to fulfil the demands of loads, an interleaved boost converter is utilized, which has a reduced number of filters with less stress on the devices. Solar powered systems employ several maximum power point tracking (MPPT) methodologies. However, when there is partial shading, many power peaks arise, which complicates the identification of the overall peak. Although MPPT approaches are designed to measure and maintain the global maximum power point (GMPP), there are still significant oscillations observed around the GMPP with subpar settling time, tracking efficiency, and conversion efficiency. In this work, novel hybrid MPPT technique called artificial neural network supported adaptable stepped-scaled perturb and observe (ANN-ASSPO) method and water cycle optimization based perturb and observe (WCO-PO) have been proposed. Artificial neural network (ANN) has been used to determine the best scaling factor in ANN-ASSPO MPPT. Performance is enhanced in ANN-ASSPO MPPT by using the optimum scaling factor, particularly in situations when the irradiance is rapidly changing/partial shading conditions. Similarly, in WCO-PO MPPT water cycle optimization is used to determine the peak power when the PV panel is subjected to partial shading conditions. The performances of proposed hybrid MPPT ANN-ASSPO and WCO-PO techniques have been compared in terms of power generated, output voltage, average settling time and conversion efficiency. The MATLAB/Simulink tool is employed to carry out the experiment for this study.

We look at what astronomy from the Moon might be like over the next few decades. The Moon offers the possibility of installing large telescopes or interferometers with instruments larger than those on orbiting telescopes. We first present examples of ambitious science cases, in particular ideas that cannot be implemented from Earth. After a general review of observational approaches, from photometry to high contrast and high angular resolution imaging, we propose as a first step a 1-metre-class precursor and explore what science can be done with it. We add a proposal to use the Earth-Moon system to test the quantum physics theory. This article is part of a discussion meeting issue \'Astronomy from the Moon: the next decades (part 2)\'.

All known life on Earth inhabits environments that maintain conditions between certain extremes of temperature, chemical composition, energy availability, and so on (Chapter 6). Life may have emerged in similar environments elsewhere in the Solar System and beyond. The ongoing search for life elsewhere mainly focuses on those environments most likely to support life, now or in the past-that is, potentially habitable environments. Discussion of habitability is necessarily based on what we know about life on Earth, as it is our only example. This chapter gives an overview of the known and presumed requirements for life on Earth and discusses how these requirements can be used to assess the potential habitability of planetary bodies across the Solar System and beyond. We first consider the chemical requirements of life and potential feedback effects that the presence of life can have on habitable conditions, and then the planetary, stellar, and temporal requirements for habitability. We then review the state of knowledge on the potential habitability of bodies across the Solar System and exoplanets, with a particular focus on Mars, Venus, Europa, and Enceladus. While reviewing the case for the potential habitability of each body, we summarize the most prominent and impactful studies that have informed the perspective on where habitable environments are likely to be found.

The materials that form the diverse chemicals and structures on Earth-from mountains to oceans and biological organisms-all originated in a universe dominated by hydrogen and helium. Over billions of years, the composition and structure of the galaxies and stars evolved, and the elements of life, CHONPS, were formed through nucleosynthesis in stellar cores. Climactic events such as supernovae and stellar collisions produced heavier elements and spread them throughout the cosmos, often to be incorporated into new, more metal-rich stars. Stars typically form in molecular clouds containing small amounts of dust through the collapse of a high-density core. The surrounding nebular material is then pulled into a protoplanetary disk, from which planets, moons, asteroids, and comets eventually accrete. During the accretion of planetary systems, turbulent mixing can expose matter to a variety of different thermal and radiative environments. Chemical and physical changes in planetary system materials occur before and throughout the process of accretion, though many factors such as distance from the star, impact history, and level of heating experienced combine to ultimately determine the final geophysical characteristics. In Earth\'s planetary system, called the Solar System, after the orbits of the planets had settled into their current configuration, large impacts became rare, and the composition of and relative positions of objects became largely fixed. Further evolution of the respective chemical and physical environments of the planets-geosphere, hydrosphere, and atmosphere-then became dependent on their local geochemistry, their atmospheric interactions with solar radiation, and smaller asteroid impacts. On Earth, the presence of land, air, and water, along with an abundance of important geophysical and geochemical phenomena, led to a habitable planet where conditions were right for life to thrive.

While Earth contains the only known example of life in the universe, it is possible that life elsewhere is fundamentally different from what we are familiar with. There is an increased recognition in the astrobiology community that the search for life should steer away from terran-specific biosignatures to those that are more inclusive to all life-forms. To start exploring the space of possibilities that life could occupy, we can try to dissociate life from the chemistry that composes it on Earth by envisioning how different life elsewhere could be in composition, lifestyle, medium, and form, and by exploring how the general principles that govern living systems on Earth might be found in different forms and environments across the Solar System. Exotic life-forms could exist on Mars or Venus, or icy moons like Europa and Enceladus, or even as a shadow biosphere on Earth. New perspectives on agnostic biosignature detection have also begun to emerge, allowing for a broader and more inclusive approach to seeking exotic life with unknown chemistry that is distinct from life as we know it on Earth.

Microbial organisms have been implicated in several mass extinction events throughout Earth\'s planetary history. Concurrently, it can be reasoned from recent viral pandemics that viruses likely exacerbated the decline of life during these periods of mass extinction. The fields of exovirology and exobiology have evolved significantly since the 20th century, with early investigations into the varied atmospheric compositions of exoplanets revealing complex interactions between metallic and non-metallic elements. This diversity in exoplanetary and stellar environments suggests that life could manifest in forms previously unanticipated by earlier, more simplistic models of the 20th century. Non-linear theories of complexity, catastrophe, and chaos (CCC) will be important in understanding the dynamics and evolution of viruses.