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Sea-buckthorn is a multi-purpose plant that provides food, feed, fuel, and medicine. Climate conditions affect its adaptability more than the terrain characteristics. Limited research has focused on its leaf functional traits important for climate adaptation. This study characterized seventy sea-buckthorn accessions from five locations in Gilgit region of northern Pakistan (2444–3172 m.a.s.l) for leaf-functional traits (leaf angle, hairs, rolling, groove, and wettability – summarized as leaf traits and physiological traits including stomatal conductance (gs), leaf relative water content (RWC), transpiration (E), water use efficiency (WUE) and photosynthesis (A)). Leaf surface structures were observed under a scanning electron microscope. Majority of accessions at Misgar (higher altitude) showing 0–20% inward leaf rolling, medium groove, and semi-erect leaf angle had higher E, gs, and lower WUE, RWC, moderate A, and hydrophilic leaf surface. Comparatively, most of accessions at middle altitudes (Passu) indicated adaptive leaf characters i.e., semi-droopy leaves, light leaf groove, 20–40% leaf rolling, moderate trichome density with hydrophobicity (> 90°) and high drop rolling efficiency (< 15°), and had higher A (8.9 ± 1.4 µmol CO 2 m −2 s −1 ), WUE (4.8 ± 0.4 mmol CO 2 mol −1 H 2 O), and fruiting (~ 67%). Moreover, the positive association of WUE with fruit yield indicated high photosynthetic productivity of such accessions. Umbrella-shaped peltate leaf trichomes were 151–175 μm long, with higher densities on abaxial surface, appressed to the epidermis and two layers with overlapping rays-shields. Stomatal density was higher on the abaxial surface, mostly covered by the trichomes. This study provides theoretical backgrounds of an ideotype suited for climate resilience supporting sea buckthorn germplasm conservation.

Leaf wettability and drainage characteristics of different taxa are often hypothesised to have emerged as a result of evolutionary selection, perhaps to limit the duration of leaf wetness, or to direct water toward efficiently to the soil and root system, rather than suffering loss to evaporation. Methods for quantifying leaf wetting and drainage are however not well‐developed. The present work describes a low‐cost, electro‐mechanical tilting table intended to facilitate precise and reproducible measurements of droplet shedding from leaves, describe by the roll‐off angle αroll. The new tilting table uses widely‐available components (microcontroller, stepper motor and driver, liquid‐crystal display (LCD) and custom operating code) to achieve controlled tilting through the range 0° to >90° at user‐controlled rates of tilting. It is suitable for field use, such that leaf specimens can be tested within minutes of collection. Water shedding tests on juvenile leaves from Homolanthus populifolius, native to the wet tropics of northern Queensland, Australia, show that testing of whole leaves (rather than small excised samples) reveals quite complex behaviour in which the open leaf surface is hydrophobic but major adaxial veins are strongly hydrophilic and can trap droplets. These can remain attached to the leaf at inclinations beyond vertical. Moreover, the apparent droplet roll‐off angles are dependent on the tilt speed applied. Droplet roll‐off tests used to characterise the propensity for leaf wetting or water shedding require controlled and reproducible experimental conditions, and a device suitable for studying the whole intact leaf surface. Preliminary results on H. populifolius show complex adaxial leaf surface characteristics, with mixed hydrophobic and hydrophilic components. This suggests that overall propensity to retain or shed water droplets is likely to depend on the size and intensity of rain or canopy drip from above. This makes the inferring of evolutionary costs or advantages more challenging and more likely to co‐vary with regional environmental conditions.

Key message Leaf CA measurement should take into account angle variation during measurement time. Leaf wettability of common deciduous forest plants is characterized by wetting contact angles ranging from 60° to 140° with a significant variation between species of the same family. Leaf wettability is an important phenomenon that has an influence on several processes such as the hydrological cycle, plant pathogen growth, or pollutant and pesticide absorption/deposition. The main objective of this research was to investigate the leaf wettability differences of 19 species (16 trees and 3 shrubs) of deciduous plants commonly occurring in Polish forests (temperate climate). The measurements were gathered as follows: 20 undamaged leaves were selected for each species and the wettability was determined by contact angle measurements with an optical goniometer CAM 100 using the sessile drop method. The contact angle was measured with 1-s intervals during 2 min from droplet deposition on adaxial and abaxial leaf surface. Laboratory analyses were completed during the summer of 2016 during full vegetation growth. A general CA decrease with time was observed on both leaf sides. The contact angle values ranged from 60° to 140° depending on species and leaf side. Differences between contact angle values at the beginning and the end of measurement reached 23.6° and engendered changes of wetting classes for some species. In many cases, no wettability class change was observed despite a CA lowering of 20°. The abaxial side was found to be the more repellent for 14 out of 19 species. Altogether, the leaves were classified from highly wettable to highly non-wettable, probably depending on the plant-survival strategy.

Plants provide many ecosystem services in urban environments, including improving ambient air quality. Leaves of plants permit the deposition of particulate matter (PM) and, depending on their leaf traits, PM may be immobilized within the epicuticular wax (EW) layer, on trichomes, on hyphae of fungi, or inside stomatal cavities. In this study, leaves of 96 perennial urban plant species consisting of 45 deciduous broadleaf/needle-like trees, 32 deciduous broadleaf shrubs, 12 evergreen needle/scale-like trees, 5 evergreen broadleaf trees, and 2 climber species were investigated in June and September 2016 to determine the effectiveness of distinct leaf surfaces in PM immobilization after leaf washing treatment. The leaf surfaces were washed vigorously using a vortex shaker. The magnetizable component of accumulated and immobilized PM on the leaf surfaces was estimated using saturation isothermal remanent magnetization (SIRM) of the unwashed and washed leaves, respectively. In June, the washed leaf SIRM of deciduous (broadleaf/needle-like) tree and shrub species ( n = 77) ranged between 0.1 and 13.9 μA. In September, the washed leaf SIRM of all investigated plant species ( n = 96) ranged between 1.2 and 35.0 μA. Outcomes of this study indicate that leaves of Buddleja davidii , Viburnum lantana , and Sorbus intermedia showed the highest washed leaf SIRM and thus were the most effective in immobilizing PM on their leaf surfaces while leaves of Populus alba , Robinia pseudoacacia , and Abies fraseri with lowest washed leaf SIRM were the least effective. On average, more than half (i.e., 60%) of the magnetic signal still remained after vigorous washing but a large variation exists between species (9–96%). The leaf SIRM of washed leaves of deciduous broadleaf tree and shrub species was significantly higher compared to leaves of evergreen needle/scale-like species. Evidently, the magnetic signal of unwashed leaves was higher than washed ones and higher in September than in June. Leaf traits significantly influenced the magnetic signal of both washed and unwashed leaves: leaves with a high trichome density or high leaf wettability showed a higher unwashed and washed leaf SIRM compared to leaves with no trichomes or low leaf wettability. The effect of epicuticular wax structure types on leaf SIRM was indicated to be only marginally significant. Moreover, also the immobilized fraction of PM was significantly affected by trichome density and leaf wettability, thus substantiating that plant species with high trichome density and/or leaf wettability not only accumulate more PM but are also less prone to PM re-suspension than other species. In general, the results also indicate that leaf SIRM of unwashed leaves can be a good indicator to determine the effectiveness of a plant species in PM immobilization. Plant species effective in immobilizing PM on their leaf surfaces may likely improve ambient air quality when planted in urban environments. However, it is vital that leaves of these plant species (i.e., with high PM immobilization abilities) are carefully recycled as they may be polluted.

BackgroundPlants use different mechanisms to transport the collected fog water. Leaf traits of wheat play an important role in directing fog water through leaf rolling and leaf angle into the root zone, where it can be stored for consumption. Wheat leaf traits can enhance fog capturing under drought stress. To examine this, 200 wheat genotypes were characterized for leaf rolling and leaf angle under optimal conditions in the field using a randomized complete block design. Seven different phenotypic combinations for leaf traits were observed. A core set of 44 genotypes was evaluated under drought stress.ResultsResults show that variability for leaf traits existed among genotypes. An association was found between leaf rolling and leaf angle, moisture capturing, physiological parameters, and yield contributing traits using correlation. Physiological parameters, especially water use efficiency, were positively correlated with grain yield and moisture capturing at both growth stages. The genotypes (G11 at tillering and G24 at booting phonological phases) with inward to twisting type rolling and erect to semi-erect leaf angle capture more water (12–20%) within the root zone. Twenty-one genotypes were selected based on moisture capturing efficiency and evaluated for leaf surface wettability. Association was found between fog capturing and wettability. This shows that it was due to the leaf repellency validated from static contact angle measurements.ConclusionThese results will give insights into fog capturing and the development of drought-tolerant crops in the semi-arid and arid regions.

Crop production and quality safety system have the potential to nurture human health and improve environmental sustainability. Providing a growing global population with sufficient and healthy food is an immediate challenge. However, this system largely depends on the spraying of agrochemicals. Crop leaves are covered with different microstructures, exhibiting distinct hydrophilic, hydrophobic, or even superhydrophobic wetting characteristics, thus leading to various deposition difficulties of sprayed droplets. Here, the relationship between wettability and surface microstructure in different crop leaves from biological and interfacial structural perspectives is systematically demonstrated. A relational model is proposed in which complex microstructures lead to stronger leaf hydrophobicity. And adding surfactant with a faster dynamically migrating velocity and reducing droplet size can improve agrochemical precise deposition. These contribute toward highly accurate and efficient targeted applications with fewer agrochemicals use and promote sustainable models of eco‐friendly agriculture systems.

Leaf wettability, the affinity of a leaf surface to water droplets, affects the interactions between leaves and external environments. This study aimed to determine the interspecific and seasonal variabilities of leaf wettability across 30 common landscape plants, and their relationships with leaf functional traits, surface micromorphology and rainfall interception in Hefei city, China. Results indicated that leaf wettability was species-specific, and the adaxial and abaxial contact angles ranged from 63° to 134° and 66° to 134°, respectively, with the adaxial surface proving more wettable. Leaf wettability gradually increased from spring to winter. Classification of life forms revealed that there were no significant wettability differences among trees, shrubs and herbs, and between evergreen and deciduous plants, but deciduous plants’ wettability increased more significantly in winter. Leaf wettability was not significantly correlated with any leaf functional traits. Single surface microscopic parameters also had low correlations with leaf wettability. Instead, the low-wettability species were found to possess more prominent epidermis cells, dense waxy layers or trichomes on leaf surfaces. Leaf wettability was the best predictor of surface rainwater storage within all functional traits. Our results highlighted that leaf wettability was variable between different species and growth periods due to micromorphological differences, and significantly affected rainfall interception at the leaf scale, which may have great significance for evaluating plant hydrological function in urban areas.

Foliar water uptake (FWU) is one of the primary water sources for desert plants. Desert plants’ water uptake capacity is essential in maintaining the balance of carbon and water. However, there are few studies on FWU capacity in desert plants and the physiological and ecological characteristics that lead to differences in FWU capacity. In order to clarify FWU strategies and the influencing factors of plants in desert ecosystems, this study measured the contact angle, FWU parameters, and hydraulic parameters to explore six desert plants’ FWU capacity and the effects of leaf wettability and hydraulic parameters on FWU capacity. The results showed that all six plants had FWU capacity, among which the leaves of Nitraria sibirica Pall. and Halimodendron halodendron (Pall.) Voss had a high foliar water uptake rate (k) and high foliar water uptake accumulation (FWU storage), and the leaves of Glycyrrhiza uralensis Fisch. had a high k and low FWU storage. The leaves of Populus euphratica Oliv., Apocynum hendersonii Hook. f., and Alhagi sparsifolia Shap. had a low k and low FWU storage. Additionally, FWU capacity was mainly affected by stomatal regulation compared with leaf wettability and leaf structure. The results of this study will help to improve the understanding of the physiological and ecological adaptability of desert plants.

Many wetland plants have gas films on submerged leaf surfaces. We tested the hypotheses that leaf gas films enhance CO₂ uptake for net photosynthesis ($P_{N}$) during light periods, and enhance O₂ uptake for respiration during dark periods. Leaves of four wetland species that form gas films, and two species that do not, were used. Gas films were also experimentally removed by brushing with 0.05% (v/v) Triton X. Net O₂ production in light, or O₂ consumption in darkness, was measured at various CO₂ and O₂ concentrations. When gas films were removed, O₂ uptake in darkness was already diffusion-limited at 20.6 kPa (critical O₂ pressure for respiration, $COP_{R}$ $\\geqalant$ 284 mmol O₂ m⁻³), whereas for some leaves with gas films, O₂ uptake declined only at approx. 4 kPa ($COP_{R}$ 54 mmol O₂ m⁻³). Gas films also improved CO2 uptake so that, during light periods, underwater $P_{N}$ was enhanced up to sixfold. Gas films on submerged leaves enable continued gas exchange via stomata and thus bypassing of cuticle resistance, enhancing exchange of O₂ and CO₂ with the surrounding water, and therefore underwater $P_{N}$ and respiration.

An altitudinal gradient of leaf wettability is often observed between and within species. To understand its functional significance, positional variation of leaf surfaces within plants should be taken into account. In rosette-forming plants, rosette leaves are near the ground and their adaxial surfaces are exposed, whereas cauline leaves are lifted from the ground throughout the reproductive season, and their abaxial surfaces are more exposed. Here, we investigated leaf wettability of cauline and rosette leaves of Arabidopsis halleri subsp. gemmifera growing in contrasting montane habitats along an altitudinal gradient at Mt Ibuki, Japan. We conducted field investigations and a growth chamber experiment to determine whether field-observed variation in leaf wettability was caused by genetic differentiation. We further performed gene expression analysis of a wax-related gene, i.e. AhgCER1, a homologue of A. thaliana ECERIFERUM1 (CER1) that may be involved in differentiation of leaf wettability. We found cauline-leaf specific genetic differentiation in leaf wettability between contrasting montane habitats. Cauline leaves of semi-alpine plants, especially on abaxial surfaces, were non-wettable. Cauline leaves of low-altitudinal understorey plants were wettable, and rosette leaves were also wettable in both habitats. AhgCER1 expression corresponded to observed leaf wettability patterns. Low wettability of cauline leaves is hypothesized to keep exposed surfaces dry when they are wrapping flowering buds in early spring, and presumably protects flowering buds from frost damage. The genetic system that controls wax content, specifically for cauline leaves, should be involved in the observed genetic differentiation, and AhgCER1 control is a strong candidate for the underlying genetic mechanism.