The rise of baobab trees in Madagascar.

The baobab trees (genus Adansonia) have attracted tremendous attention because of their striking shape and distinctive relationships with fauna1. These spectacular trees have also influenced human culture, inspiring innumerable arts, folklore and traditions. Here we sequenced genomes of all eight extant baobab species and argue that Madagascar should be considered the centre of origin for the extant lineages, a key issue in their evolutionary history2,3. Integrated genomic and ecological analyses revealed the reticulate evolution of baobabs, which eventually led to the species diversity seen today. Past population dynamics of Malagasy baobabs may have been influenced by both interspecific competition and the geological history of the island, especially changes in local sea levels. We propose that further attention should be paid to the conservation status of Malagasy baobabs, especially of Adansonia suarezensis and Adansonia grandidieri, and that intensive monitoring of populations of Adansonia za is required, given its propensity for negatively impacting the critically endangered Adansonia perrieri.

Sustainable versatile chitin aerogels: facile synthesis, structural control and high-efficiency acoustic absorption.

Bio-based materials with excellent acoustic absorption properties are in great demand in architecture, interior, and human settlement applications for efficient noise control. In this study, crayfish shells, a form of kitchen waste, are utilized as the primary material to produce ultralight and multifunctional chitin aerogels, which effectively eliminate noise. Different replacement solvents and freezing rates were employed to regulate the porous structures of chitin aerogels, and their resulting acoustic absorption performance was investigated. Results demonstrate that employing deionized water as the replacement solvent and utilizing a common-freeze mode (frozen via refrigerator at -26 °C) can produce chitin aerogels with larger porosity (96.26%) and apertures, as well as thicker pore walls. This results in superior broadband acoustic absorption performance (with a maximum absorption coefficient reaching 0.99) and higher Young's modulus (28 kPa). Conversely, chitin aerogels solvent-exchanged with tert-butyl alcohol or subjected to quick-freeze mode (frozen via liquid nitrogen) exhibit smaller porosity (92.32% and 94.84%) and apertures, thereby possessing stronger diffuse reflection of visible light (average reflectance of 94.30% and 88.18%), and enhanced low-frequency (500 to 1600 Hz) acoustic absorption properties. Additionally, the acoustic absorption mechanism of fabricated chitin aerogels was predicted using a simple three-parameter analysis Johnson-Champoux-Allard-Lafarge (JCAL) model. This study presents a novel approach to developing multifunctional biomass materials with excellent acoustic absorption properties, which could have a wide range of potential applications.

Effects of Freeze-Drying Processes on the Acoustic Absorption Performance of Sustainable Cellulose Nanocrystal Aerogels.

Cellulose aerogels have great prospects for noise reduction applications due to their sustainable value and superior 3D interconnected porous structures. The drying principle is a crucial factor in the preparation process for developing high-performance aerogels, particularly with respect to achieving high acoustic absorption properties. In this study, multifunctional cellulose nanocrystal (CNC) aerogels were conveniently prepared using two distinct freeze-drying principles: refrigerator conventional freezing (RCF) and liquid nitrogen unidirectional freezing (LnUF). The results indicate that the rapid RCF process resulted in a denser CNC aerogel structure with disordered larger pores, causing a stronger compressive performance (Young's modulus of 40 kPa). On the contrary, the LnUF process constructed ordered structures of CNC aerogels with a lower bulk density (0.03 g/cm3) and smaller apertures, resulting in better thermal stability, higher diffuse reflection across visible light, and especially increased acoustic absorption performance at low-mid frequencies (600-3000 Hz). Moreover, the dissipation mechanism of sound energy in the fabricated CNC aerogels is predicted by a designed porous media model. This work not only paves the way for optimizing the performance of aerogels through structure control, but also provides a new perspective for developing sustainable and efficient acoustic absorptive materials for a wide range of applications.

Adaptive evolution of the chrysanthemyl diphosphate synthase gene involved in irregular monoterpene metabolism.

BACKGROUND: Chrysanthemyl diphosphate synthase (CDS) is a key enzyme in biosynthetic pathways producing pyrethrins and irregular monoterpenes. These compounds are confined to plants of the tribe Anthemideae of the Asteraceae, and play an important role in defending the plants against herbivorous insects. It has been proposed that the CDS genes arose from duplication of the farnesyl diphosphate synthase (FDS) gene and have different function from FDSs. However, the duplication time toward the origin of CDS and the evolutionary force behind the functional divergence of the CDS gene are still unknown. RESULTS: Two duplication events were detected in the evolutionary history of the FDS gene family in the Asteraceae, and the second duplication led to the origin of CDS. CDS occurred after the divergence of the tribe Mutisieae from other tribes of Asteraceae but before the birth of the Anthemideae tribe. After its origin, CDS accumulated four mutations in sites homologous to the substrate-binding and catalysis sites of FDS. Of these, two sites were involved in the binding of the nucleophilic substrate isopentenyl diphosphate in FDS. Maximum likelihood analyses showed that some sites in CDS were under positive selection and were scattered throughout primary sequences, whereas in the three-dimensional structure model they clustered in the large central cavity. CONCLUSION: Positive selection associated with gene duplication played a major role in the evolution of CDS.

Modeling impacts of climate change on the potential distribution of six endemic baobab species in Madagascar.

Madagascar, a globally renowned biodiversity hotspot characterized by high rates of endemism, is one of the few remaining refugia for many plants and animal species. However, global climate change has greatly affected the natural ecosystem and endemic species living in Madagascar, and will likely continue to influence species distribution in the future. Madagascar is home to six endemic baobab (Adansonia spp., Bombacoideae [Malvaceae]) species (Adansonia grandidieri, A. suarezensis, A. madagascariensis, A. perrieri, A. rubrostipa, A. za), which are remarkable and endangered plants. This study aimed to model the current distribution of suitable habitat for each baobab species endemic to Madagascar and determine the effect that climate change will have on suitable baobab habitat by the years 2050 and 2070. The distribution was modeled using MaxEnt based on locality information of 245 occurrence sites of six species from both online database and our own field work. A total of seven climatic variables were used for the modeling process. The present distribution of all six Madagascar's baobabs was largely influenced by temperature-related factors. Although both expansion and contraction of suitable habitat are predicted for all species, loss of original suitable habitat is predicted to be extensive. For the most widespread Madagascar baobab, A. za, more than 40% of its original habitat is predicted to be lost because of climate change. Based on these findings, we recommend that areas predicted to contract in response to climate change should be designated key protection regions for baobab conservation.

Fertilization increases paddy soil organic carbon density.

Field experiments provide an opportunity to study the effects of fertilization on soil organic carbon (SOC) sequestration. We sampled soils from a long-term (25 years) paddy experiment in subtropical China. The experiment included eight treatments: (1) check, (2) PK, (3) NP, (4) NK, (5) NPK, (6) 7F:3M (N, P, K inorganic fertilizers+30% organic N), (7) 5F:5M (N, P, K inorganic fertilizers+50% organic N), (8) 3F:7M (N, P, K inorganic fertilizers+70% organic N). Fertilization increased SOC content in the plow layers compared to the non-fertilized check treatment. The SOC density in the top 100 cm of soil ranged from 73.12 to 91.36 Mg/ha. The SOC densities of all fertilizer treatments were greater than that of the check. Those treatments that combined inorganic fertilizers and organic amendments had greater SOC densities than those receiving only inorganic fertilizers. The SOC density was closely correlated to the sum of the soil carbon converted from organic amendments and rice residues. Carbon sequestration in paddy soils could be achieved by balanced and combined fertilization. Fertilization combining both inorganic fertilizers and organic amendments is an effective sustainable practice to sequestrate SOC.