Living in Drylands: Functional Adaptations of Trees and Shrubs to Cope with High Temperatures and Water Scarcity

Plant functioning and survival in drylands are affected by the combination of high solar radiation, high temperatures, low relative humidity, and the scarcity of available water. Many ecophysiological studies have dealt with the adaptation of plants to cope with these stresses in hot deserts, which are the territories that have better evoked the idea of a dryland. Nevertheless, drylands can also be found in some other areas of the Earth that are under the Mediterranean-type climates, which imposes a strong aridity during summer. In this review, plant species from hot deserts and Mediterranean-type climates serve as examples for describing and analyzing the different responses of trees and shrubs to aridity in drylands, with special emphasis on the structural and functional adaptations of plants to avoid the negative effects of high temperatures under drought conditions. First, we analyze the adaptations of plants to reduce the input of energy by diminishing the absorbed solar radiation through (i) modifications of leaf angle and (ii) changes in leaf optical properties. Afterwards, we analyze several strategies that enhance the ability for heat dissipation through (i) leaf size reduction and changes in leaf shape (e.g., through lobed leaves), and (ii) increased transpiration rates (i.e., water-spender strategy), with negative consequences in terms of photosynthetic capacity and water consumption, respectively. Finally, we also discuss the alternative strategy showed by water-saver plants, a common drought resistance strategy in hot and dry environments that reduces water consumption at the expense of diminishing the ability for leaf cooling. In conclusion, trees and shrubs living in drylands have developed effective functional adaptations to cope with the combination of high temperature and water scarcity, all of them with clear benefits for plant functioning and survival, but also with different costs concerning water use, carbon gain, and/or leaf cooling.This research was funded by Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA) grant number RTA2015-00054-C02-01, by Ministerio de Ciencia e Innovación grant number PID2019-106701RR-I00/AEI/10.13039/501100011033 and INERTIA project (PID-2019-111332-C22), project IMAGINA (Prometeu program/2019/110, GVA) and from Gobierno de Aragón H09_20R research group. Work of D.A.F. is supported by a FPI-INIA contract BES-2017-081208. CEAM is funded by Generalitat Valenciana

Molecular and biochemical analysis of the diet of the black rhinoceros

The black rhinoceros, Diceros bicornis, is listed as critically endangered. The black rhinoceros population in the Great Fish River Reserve (GFRR) has increased steadily to a current estimate of one hundred animals since the re-introduction of four animals in 1986. In an effort to contribute to the effective conservation and management of this species, dietary composition was studied in the medium Portulcaria thicket vegetation of the GFRR. This study used a molecular approach to determine the diet of the black rhinoceros of the GFRR by sequencing the ribulose bisphosphate carboxylase large subunit (rbcL) gene in plants and dung. Twenty-three plant species were collected from the reserve, and 802 bp of the rbcL gene were sequenced. These plant sequences were used as a reference database for the identification of plant sequences generated from black rhinoceros dung. Initial studies investigated the amplification, cloning and sequencing of DNA extracted from the dung samples which indicated the viability of the molecular approach. Thereafter, dung generated rbcL DNA was analyzed by GS FLX sequencing. Of the plant sequences identified by comparison to the GenBank database, Carissa bispinosa was the most prevalent. The study further characterized the antioxidant activities and phenolic content of plants eaten by the black rhinoceros using four different assays. Phyllanthus verrucosus, Putterlickia pyracantha, Maytenus capitata, Euclea undulata and Ozoroa mucrunata consistently had high antioxidant activities when assayed against 2,2-azinobis (3-ethyl benzothiazolium-6-sulfonic acid) (ABTSʹ⁺), 2,2-diphenyl-1-picrylhydrazyl (DPPHʹ), and ferric reducing antioxidant potentials (FRAP) and phenolic content when evaluated using the Folin-Ciocalteu assay. The majority of plants investigated showed low antioxidant potentials and low phenolic content. The extent to which antioxidants influenced the browse selection by the black rhinoceros remains inconclusive

Plant Responses and Tolerance to Salt Stress: Physiological and Molecular Interventions

Overall, the 19 contributions in this Special Issue “Plant Responses and Tolerance to Salt Stress: Physiological and Molecular Interventions” discuss the various aspects of salt stress responses in plants. It also discusses various mechanisms and approaches to conferring salt tolerance on plants. These types of research studies provide further directions in the development of crop plants for the saline environment in the era of climate change

Implications of leaf anatomy and stomatal responses in the Clusia genus for the evolution of Crassulacean acid metabolism

PhD ThesisThe tropical genus Clusia which contains species with C3, Crassulacean acid metabolism and C3/CAM properties is an interesting model to dissect anatomical, physiological and molecular traits that underpin the evolution of CAM photosynthesis. About 7 % of higher plants perform CAM, a specialised photosynthetic pathway, characterized by CO2 uptake during the night mediated via the enzyme phosphoenolpyruvate carboxylase (PEPC) and keeping stomata shut for much of the day. CAM confers high water use efficiency (WUE) and has long been considered an adaptation to drought stress and high irradiance. In some species like Clusia CAM facilitates remarkable photosynthetic plasticity in dealing with changing environments. Thus, CAM plants are important and challenging model organisms for investigating plant responses to global climate change and for examining the anatomical and physiological traits that underpin enhanced water use efficiency. In this thesis strong relationships were found between the magnitude of CAM photosynthesis in eight species of Clusia (C. hilariana, C. alata, C. rosea, C. lanceolata, C. aripoensis, C. grandiflora, C. tocuchensis and C. multiflora) and six leaf anatomical traits (stomatal size, stomatal density, % intercellular air space, length of mesophyll exposed to air space, cell size and specific leaf area) . These relationships point to leaf anatomical features as important in the evolution of CAM, and also have implications for the behaviour of stomata and their response to light. It was found that CAM species of Clusia have lower densities of larger stomata compared with C3 species of Clusia. The CAM species of Clusia still maintain a high WUE and it was hypothesised that this was a consequence of robust circadian control of stomatal conductance which was maintained under different light regimes. To examine the response of CAM stomata to contrasting light regimes and to test if circadian oscillations in stomatal conductance are disrupted under different wavelengths of light, gas exchange measurements were recorded during 48 hours under constant light regimes (either white light, blue light, red light or darkness) for C. rosea a constitutive CAM plant, and C. multiflora, a constitutive C3 plant. It was found that the species responded differently to variation in light regimes and the response of stomata to blue light in the CAM Clusia had not been lost, as proposed by previous workers. The larger stomata of C. rosea responded faster to changes in light intensity during the photoperiod compared with those of C. multiflora, but this did not happen during the night. It was hypothesised that the kinetic responses of the CAM stomata might be important for optimising carbon gain and reducing water loss under changing environmental conditions at the start and end of the day.. Furthermore, circadian control of stomatal conductance was found to be mediated by both photoreceptors and metabolism, including photosynthesis and carbohydrate metabolism in CAM and C3 Clusia plants. A molecular approach was taken to probe the mechanisms underpinning the contrasting responses to light. The differential transcript abundance, of photoreceptors involved in stomatal opening (phototropin 1 and phototropin 2) and circadian regulation (cryptochrome 2 and phytochrome A) was examined for C. rosea and C. multiflora under different constant light regimes using semi-quantitative reverse transcription- PCR and Real Time PCR. Diel expression patterns of phototropins were found to differ between the C3 and CAM species in terms of transcript abundance, the level of control exerted by circadian clock over the transcripts and the response of transcripts to different light regimes. It was concluded that stomatal responses to light in Clusia species must be mediated by a coordinated labour of different photoreceptors to exert control over water loss and CO2 assimilation. Further work is required to assess the expression and regulation of photoreceptors at the stomatal guard cell level. Having more knowledge regarding the function of stomata in CAM plants and their implications for WUE should help inform efforts for improving the water use of crop species in the light of environmental challenges such as desertification and global warming.Colfuturo: NUIPS: The School of Biology of Newcastle University

Remote Sensing in Agriculture: State-of-the-Art

The Special Issue on “Remote Sensing in Agriculture: State-of-the-Art” gives an exhaustive overview of the ongoing remote sensing technology transfer into the agricultural sector. It consists of 10 high-quality papers focusing on a wide range of remote sensing models and techniques to forecast crop production and yield, to map agricultural landscape and to evaluate plant and soil biophysical features. Satellite, RPAS, and SAR data were involved. This preface describes shortly each contribution published in such Special Issue

The mechanisms of evolutionary flexibility in earthworm genomes

Many individual organisms have latent phenotypic potentials which are never realised within their lifespans. This potential can include a huge diversity of dormant adaptations across the tree of life, such as the ability to tolerate radical changes in temperature, survive restricted nutrient availability, and resist toxins and parasites. Prior to unrealised phenotypic potentials are necessarily information potentials residing in a dormant state also. This thesis investigates the systematic interactions of facultative morphologies and atavistic adaptivity with the evolutionary systems which propagate them. Earthworms as models are for these purposes an almost archetypal form of a high-latent-potential organism. Examples abound of their thriving as peregrine species with near-global ranges

Regulation of Central Carbon and Amino Acid Metabolism in Plants

Due to their lightweight and high specific strength, Mg-based alloys are considered as substitutes to their heavier counterparts in applications in which corrosion is non-relevant and weight saving is of importance. Furthermore, due to the biocompatibility of Mg, some alloys with controlled corrosion rates are used as degradable implant materials in the medical sector. The typical processing route of Mg parts incorporates a casting step and, subsequently, a thermo–mechanical treatment. In order to achieve the desired macroscopic properties and thus fulfill the service requirements, thorough knowledge of the relationship between the microstructure, the processing steps, and the resulting property profile is necessary. This Special Issue covers in situ and ex situ experimental and computational investigations of the behavior under thermo–mechanical load of Mg-based alloys utilizing modern characterization and simulation techniques. The papers cover investigations on the effect of rare earth additions on the mechanical properties of different Mg alloys, including the effect of long-period stacking-ordered (LPSO) structures, and the experimental and computational investigation of the effect of different processing route

Plant Signaling Molecule: Role and Regulation under Stressful Environments

Plant Signaling Molecule: Role and Regulation under Stressful Environments explores tolerance mechanisms mediated by signaling molecules in plants for achieving sustainability under changing environmental conditions. Including a wide range of potential molecules, from primary to secondary metabolites, the book presents the status and future prospects of the role and regulation of signaling molecules at physiological, biochemical, molecular and structural level under abiotic stress tolerance. This book is designed to enhance the mechanistic understanding of signaling molecules and will be an important resource for plant biologists in developing stress tolerant crops to achieve sustainability under changing environmental conditions