Control of Substrate Water Availability Using Soil Sensors and Effects of Water Deficit on the Morphology and Physiology of Potted Hebe andersonii

Many plant producers tend to overwater crops to prevent water stress and salt-induced damage. These practices waste irrigation water and cause leaching that harms the environment and increases production costs. In order to optimize water consumption and minimize the environmental impact of plant production, this study aimed to determine the physiological and morphological responses of Hebe andersonii to three substrate volumetric water contents (49%, 39%, and 32%). The experiment was conducted in a greenhouse with an irrigation protocol that consisted of adding small volumes of water to avoid leaching while monitoring substrate moisture with dielectric soil sensors. The results showed that moderately low substrate moisture improved the water-use efficiency, while growth was significantly reduced under more severe water deficit conditions (but without leaf chlorosis or abscission). The photosynthetic activity of Hebe was primarily controlled by the stomatal aperture, which was co-determined by the substrate moisture and seasonal temperature. Hebe leaves promoted non-photochemical quenching when carbon assimilation was limited by a water deficit, and accumulated solutes through an osmotic adjustment process (especially Cl−, Na+, and K+) to maintain their water status. Overall, Hebe andersoni cv. Variegata could successfully grow and improve its water-use efficiency in low substrate moisture and under a non-draining irrigation regime.

Anomalous Arctic Sea Ice Melting Linked to Recent Warming Amplification

This study investigates the mechanism of seasonal sea ice variation and recent warming amplification. Seasonal temperature changes in the vertical structure reveal that the autumn and winter seasons are warming more than summer. The thermodynamic processes of sea-ice-air interactions via the heat flux component have been studied. The summer Arctic Sea ice has receded by half (∼52%), producing excessive heat. This sea ice loss plays a significant role in determining the heat exchange between the ocean and atmosphere in the following season. During a warm season, the ocean heats up due to incident solar radiation. As a result, delayed ice growth and atmospheric warming occur. Sea ice and heat flux feedbacks explain a large part of Arctic atmospheric warming. These abrupt changes are closely coupled to accelerated Arctic Sea ice loss and atmospheric warming, which are still uncertain.

Intensified paraglacial slope failures due to accelerating downwasting of a temperate glacier in Mt. Gongga, southeastern Tibetan Plateau

Topographic development via paraglacial slope failure (PSF) represents a complex interplay between geological structure, climate, and glacial denudation. Southeastern Tibet has experienced amongst the highest rates of ice mass loss in High Mountain Asia in recent decades, but few studies have focused on the implications of this mass loss on the stability of paraglacial slopes. We used repeat satellite- and unpiloted aerial vehicle (UAV)-derived imagery between 1990 and 2020 as the basis for mapping PSFs from slopes adjacent to Hailuogou Glacier (HLG), a 5 km long monsoon temperate valley glacier in the Mt. Gongga region. We observed recent lowering of the glacier tongue surface at rates of up to 0.88 m a−1 in the period 2000 to 2016, whilst overall paraglacial bare ground area (PBGA) on glacier-adjacent slopes increased from 0.31 ± 0.27 km2 in 1990 to 1.38 ± 0.06 km2 in 2020. Decadal PBGA expansion rates were ∼ 0.01 km2 a−1, 0.02 km2 a−1, and 0.08 km2 in the periods 1990–2000, 2000–2011, and 2011–2020 respectively, indicating an increasing rate of expansion of PBGA. Three types of PSFs, including rockfalls, sediment-mantled slope slides, and headward gully erosion, were mapped, with a total area of 0.75 ± 0.03 km2 in 2020. South-facing valley slopes (true left of the glacier) exhibited more destabilization (56 % of the total PSF area) than north-facing (true right) valley slopes (44 % of the total PSF area). Deformation of sediment-mantled moraine slopes (mean 1.65–2.63 ± 0.04 cm d−1) and an increase in erosion activity in ice-marginal tributary valleys caused by a drop in local base level (gully headward erosion rates are 0.76–3.39 cm d−1) have occurred in tandem with recent glacier downwasting. We also observe deformation of glacier ice, possibly driven by destabilization of lateral moraine, as has been reported in other deglaciating mountain glacier catchments. The formation, evolution, and future trajectory of PSFs at HLG (as well as other monsoon-dominated deglaciating mountain areas) are related to glacial history, including recent rapid downwasting leading to the exposure of steep, unstable bedrock and moraine slopes, and climatic conditions that promote slope instability, such as very high seasonal precipitation and seasonal temperature fluctuations that are conducive to freeze–thaw and ice segregation processes.

The Future of Climate Resilience in Wheat

As the most widely cultivated crop globally - providing 20% of all human calories and protein - there is an urgent need to increase wheat’s resilience to harsher climates [1]. The risk of simultaneous crop failures due to heat and/or drought in global “breadbaskets” has risen and is projected to rise further [2-4]. Severe water scarcity events are predicted for up to 60% of the world’s wheat-growing areas by the end of this century [5]. Furthermore, for each 1°C increase in average seasonal temperature, it is predicted that wheat yields will decrease by 6% on average globally, and much more in some already marginal environments where wheat is a traditional staple food [6,7]. At the current rate of yield gain, wheat production is predicted to fall well short of future demand due to population growth alone. Emerging environmental threats only make the challenge harder. On top of this, demand by consumers, farmers and the food industry is predicted to increase due to wheat’s high grain-protein content relative to other cereals, wide growing range and adaptability to most environmental stresses. Since farmer adoption of improved cultivars is a critical part of adaptation [8], new and more targeted breeding efforts are needed to ensure that wheat's climate resilience is maximized [9-11]. This article briefly outlines research that has been conducted and current research needs to develop climate resilient wheat.

The Response of Tomato Fruit Cuticle Membranes Against Heat and Light

Two important biophysical properties, the thermal and UV-Vis screening capacity, of isolated tomato fruit cuticle membranes (CM) have been studied by differential scanning calorimetry (DSC) and UV-Vis spectrometry, respectively. A first order melting, corresponding to waxes, and a second order glass transition (Tg) thermal events have been observed. The glass transition was less defined and displaced toward higher temperatures along the fruit ripening. In immature and mature green fruits, the CM was always in the viscous and more fluid state but, in ripe fruits, daily and seasonal temperature fluctuations may cause the transition between the glassy and viscous states altering the mass transfer between the epidermal plant cells and the environment. CM dewaxing reduced the Tg value, as derived from the role of waxes as fillers. Tg reduction was more intense after polysaccharide removal due to their highly interwoven distribution within the cutin matrix that restricts the chain mobility. Such effect was amplified by the presence of phenolic compounds in ripe cuticle membranes. The structural rigidity induced by phenolics in tomato CMs was directly reflected in their mechanical elastic modulus. The heat capacity (Cprev) of cuticle membranes was found to depend on the developmental stage of the fruits and was higher in immature and green stages. The average Cprev value was above the one of air, which confers heat regulation capacity to CM. Cuticle membranes screened the UV-B light by 99% irrespectively the developmental stage of the fruit. As intra and epicuticular waxes contributed very little to the UV screening, this protection capacity is attributed to the absorption by cinnamic acid derivatives. However, the blocking capacity toward UV-A is mainly due to the CM thickness increment during growth and to the absorption by flavone chalconaringenin accumulated during ripening. The build-up of phenolic compounds was found to be an efficient mechanism to regulate both the thermal and UV screening properties of cuticle membranes.

Evaluating sources of variability in inflorescence number, flower number and the progression of flowering in Sauvignon blanc using a Bayesian modelling framework

The time of flowering is key to understanding the development of grapevines. Flowering coincides with inflorescence initiation and fruit set, important determinants of yield. This research aimed to determine between and within-vine variability in 4-cane-pruned Sauvignon blanc inflorescence number per shoot, number of flowers per inflorescence and flowering progression using an objective method of assessing flowering via image capture and statistical analysis using a Bayesian modelling framework. The inflorescence number and number of flowers per inflorescence were measured by taking images over the flowering period. Flowering progression was assessed by counting open and closed flowers for each image over two seasons. An ordinal multinomial generalised linear mixed-effects model (GLMM) was fitted for inflorescence number, a Poisson GLMM for flower counts and a binomial GLMM for flowering progression. All the models were fitted and interpreted within a Bayesian modelling framework. Shoots arising from cane node one had lower numbers of inflorescences compared to those at nodes 3, 5 and 7, which were similar. The number of flowers per inflorescence was greater for basal inflorescences on a shoot than apical ones. Flowering was earlier, by two weeks, and faster in 2017/18 when compared to 2018/19 reflecting seasonal temperature differences. The time and duration of flowering varied at each inflorescence position along the cane. While basal inflorescences flowered later and apical earlier at lower insertion points on the shoot, the variability in flowering at each position on the vine dominated the date and duration of flowering.This is the first study using a Bayesian modelling framework to assess variability inflorescence presence and flower number, as well as flowering progression via objective quantification of open and closed flower counts rather than the more subjective method of visual estimation in the field or via cuttings. Although flower number differed for apical and basal bunches, little difference in timing and progression of flowering by these categories was observed. The node insertion point along a shoot was more important. Overall, the results indicate individual inflorescence variation and season are the key factors driving flowering variability and are most likely to impact fruit set and yield.

A wMel Wolbachia variant in Aedes aegypti from field-collected Drosophila melanogaster with increased phenotypic stability under heat stress

Mosquito-borne diseases such as dengue, Zika and chikungunya remain a major cause of morbidity and mortality across tropical regions. Population replacement strategies involving the wMel strain of Wolbachia are being used widely to control mosquito-borne diseases transmitted by Aedes aegypti. However, these strategies may be influenced by environmental temperature because wMel is vulnerable to heat stress. wMel infections in their native host Drosophila melanogaster are genetically diverse, but few transinfections of wMel variants have been generated in Ae. aegypti mosquitoes. Here we successfully transferred a wMel variant (termed wMelM) originating from a field-collected D. melanogaster population from Victoria, Australia into Ae. aegypti. The new wMelM variant (clade I) is genetically distinct from the original wMel transinfection (clade III) generated over ten years ago, and there are no genomic differences between wMelM in its original and transinfected host. We compared wMelM with wMel in its effects on host fitness, temperature tolerance, Wolbachia density, vector competence, cytoplasmic incompatibility and maternal transmission under heat stress in a controlled background. wMelM showed a higher heat tolerance than wMel, with stronger cytoplasmic incompatibility and maternal transmission when eggs were exposed to heat stress, likely due to higher overall densities within the mosquito. Both wMel variants had minimal host fitness costs, complete cytoplasmic incompatibility and maternal transmission, and dengue virus blocking under standard laboratory conditions. Our results highlight phenotypic differences between closely related Wolbachia variants. wMelM shows potential as an alternative strain to wMel in dengue control programs in areas with strong seasonal temperature fluctuations.

Calculation of temperature waves in kurums

The article indicates the relevance of the study of heat transfer processes in kurums. Boundary value problems of vertical temperature change in kurums and in the underlying rock base are solved, when the temperature on the surface of kurums changes according to a given periodic law, which simulates daily and seasonal temperature fluctuations. The cases when the rock base is a heat-conducting medium and permafrost are considered. Some regularities of temperature propagation along the depth are revealed.

Dynamic analysis of a malaria reaction-diffusion model with periodic delays and vector bias

<abstract><p>One of the most important vector-borne disease in humans is malaria, caused by <italic>Plasmodium</italic> parasite. Seasonal temperature elements have a major effect on the life development of mosquitoes and the development of parasites. In this paper, we establish and analyze a reaction-diffusion model, which includes seasonality, vector-bias, temperature-dependent extrinsic incubation period (EIP) and maturation delay in mosquitoes. In order to get the model threshold dynamics, a threshold parameter, the basic reproduction number $ R_{0} $ is introduced, which is the spectral radius of the next generation operator. Quantitative analysis indicates that when $ R_{0} &lt; 1 $, there is a globally attractive disease-free $ \omega $-periodic solution; disease is uniformly persistent in humans and mosquitoes if $ R_{0} &gt; 1 $. Numerical simulations verify the results of the theoretical analysis and discuss the effects of diffusion and seasonality. We study the relationship between the parameters in the model and $ R_{0} $. More importantly, how to allocate medical resources to reduce the spread of disease is explored through numerical simulations. Last but not least, we discover that when studying malaria transmission, ignoring vector-bias or assuming that the maturity period is not affected by temperature, the risk of disease transmission will be underestimate.</p></abstract>