Influence of surface water and groundwater gradient on spatial distribution of typical vegetation in the hinterland of Taklamakan desert.

Water resources are essential for desert oases and are key drivers of local ecological processes critical to the growth of desert vegetation. In this study, the oasis in the hinterland of the Taklamakan Desert, China, was selected as the research subject. Using high-precision classification of oasis vegetation through machine learning, surface water within the oasis was identified and extracted from multi-year Landsat remote sensing data. The spatial distribution patterns of the main community-building species, Populus euphratica and Tamarix ramosissima, were studied under different moisture gradients using environmental covariates and measured groundwater depth to invert its spatial distribution and K-mean clustering to construct surface water and groundwater moisture gradients. The results indicated that the classification accuracy for the two species reached 0.917. Gradients 1-5 were used to categorize the water resources, dividing surface water and groundwater into five gradients. Gradient 3 exhibited the optimal moisture conditions, with a high surface water distribution frequency (0.017) and shallow groundwater depth (3.158 m), while Gradient 4 showed the least optimal moisture conditions, characterized by a low surface water distribution frequency (0.008) and deep groundwater depth (4.820 m). The water gradient decreased in the following order: Gradient 3 > Gradient 5 > Gradient 1 > Gradient 2 > Gradient 4. The optimum gradients for growth of P. euphratica and T. ramosissima were gradients 5, 1, and 2. The normalized vegetation index spatial distribution patterns of the two species were consistent with that of the moisture gradient. Tamarix ramosissima was found to be more tolerant to salinity and drought than P. euphratica. Overall, this study provides valuable information on the effect of the spatial distribution of water resource gradients on oasis vegetation and can guide future water delivery policies in oases.

Moisture Power Generation: From Material Selection to Device Structure Optimization.

Moisture power generation (MPG) technology, producing clean and sustainable energy from a humid environment, has drawn significant attention and research efforts in recent years as a means of easing the energy crisis. Despite the rapid progress, MPG technology still faces numerous challenges with the most significant one being the low power-generating performance of individual MPG devices. In this review, we introduce the background and underlying principles of MPG technology while thoroughly explaining how the selection of suitable materials (carbons, polymers, inorganic salts, etc.) and the optimization of the device structure (pore structure, moisture gradient structure, functional group gradient structure, and electrode structure) can address the existing and anticipated challenges. Furthermore, this review highlights the major scientific and engineering hurdles on the way to advancing MPG technology and offers potential insights for the development of high-performance MPG systems.

Response of the root anatomical structure of Carex moorcroftii to habitat drought in the Western Sichuan Plateau of China.

MAIN CONCLUSION: The anatomical structures of Carex moorcroftii roots showing stronger plasticity during drought had a lower coefficient of variation in cell size in the same habitats, while those showing weaker plasticity had a higher coefficient of variation. The complementary relationship between these factors comprises the adaptation mechanism of the C. moorcroftii root to drought. To explore the effects of habitat drought on root anatomy of hygrophytic plants, this study focused on roots of C. moorcroftii. Five sample plots were set up along a soil moisture gradient in the Western Sichuan Plateau to collect experimental materials. Paraffin sectioning was used to obtain root anatomy, and one-way ANOVA, correlation analysis, linear regression analysis, and RDA ranking were applied to analyze the relationship between root anatomy and soil water content. The results showed that the root transverse section area, thickness of epidermal cells, exodermis and Casparian strips, and area of aerenchyma were significantly and positively correlated with soil moisture content (P < 0.01). The diameter of the vascular cylinder and the number and total area of vessels were significantly and negatively correlated with the soil moisture content (P < 0.01). The plasticity of the anatomical structures was strong for the diameter and area of the vascular cylinder and thickness of the Casparian strip and epidermis, while it was weak for vessel diameter and area. In addition, there was an asymmetrical relationship between the functional adaptation of root anatomical structure in different soil moisture and the variation degree of root anatomical structure in the same soil moisture. Therefore, the roots of C. moorcroftii can shorten the water transport distance from the epidermis to the vascular cylinder, increase the area of the vascular cylinder and the number of vessels, and establish a complementary relationship between the functional adaptation of root anatomical structure in different habitats and the variation degree of root anatomical structure in the same habitat to adapt to habitat drought. This study provides a scientific basis for understanding the response of plateau wetland plants to habitat changes and their ecological adaptation strategies. More scientific experimental methods should be adopted to further study the mutual coordination mechanisms of different anatomical structures during root adaptation to habitat drought for hygrophytic plants.

A Natural Moisture Gradient Affects Soil Fungal Communities on the South Shore of Hulun Lake, Inner Mongolia, China.

Soil moisture content (SWC) can change the diversity and composition of soil fungal communities by affecting soil texture and soil nutrients. To explore the response of soil fungal communities to moisture in the grassland ecosystem on the south shore of Hulun Lake, we set up a natural moisture gradient that was subdivided into high (HW), medium (MW), and low (LW) water contents. Vegetation was investigated by quadrat method, and aboveground biomass was collected by the mowing method. Soil physicochemical properties were obtained by internal experiments. The composition of the soil fungal community was determined using high-throughput sequencing technology. The results showed significant differences in soil texture, nutrients, and fungal species diversity under the moisture gradients. Although there was significant clustering of fungal communities in different treatments, the fungal community composition was not significantly different. According to the phylogenetic tree, the Ascomycota and Basidiomycota were the most important branches. The fungal species diversity was smaller when SWC was higher, and in this environment (HW), the fungal-dominant species were significantly related to SWC and soil nutrients. At this time, soil clay formed a protective barrier for the survival of the dominant classes Sordariomycetes and Dothideomycetes and increased their relative abundance. In summary, the fungal community responded significantly to SWC on the southern shore of the Hulun Lake ecosystem in Inner Mongolia, China, and the fungal community composition of the HW group was stable and easier to survive.

Above- and below-ground plant traits are not consistent in response to drought and competition treatments.

BACKGROUND AND AIMS: Our understanding of plant responses to biotic and abiotic drivers is largely based on above-ground plant traits, with little focus on below-ground traits despite their key role in water and nutrient uptake. Here, we aimed to understand the extent to which above- and below-ground traits are co-ordinated, and how these traits respond to soil moisture gradients and plant intraspecific competition. METHODS: We chose seedlings of five tropical tree species and grew them in a greenhouse for 16 weeks under a soil moisture gradient [low (drought), medium and high (well-watered) moisture levels] with and without intraspecific competition. At harvest, we measured nine above- and five below-ground traits of all seedlings based on standard protocols. KEY RESULTS: In response to the soil moisture gradient, above-ground traits are found to be consistent with the leaf economics spectrum, whereas below-ground traits are inconsistent with the root economics spectrum. We found high specific leaf area and total leaf area in well-watered conditions, while high leaf dry matter content, leaf thickness and stem dry matter content were observed in drought conditions. However, below-ground traits showed contrasting patterns, with high specific root length but low root branching index in the low water treatment. The correlations between above- and below-ground traits across the soil moisture gradient were variable, i.e. specific leaf area was positively correlated with specific root length, while it was negatively correlated with root average diameter across moisture levels. However, leaf dry matter content was unexpectedly positively correlated with both specific root length and root branching index. Intraspecific competition has influenced both above- and below-ground traits, but interacted with soil moisture to affect only below-ground traits. Consistent with functional equilibrium theory, more biomass was allocated to roots under drought conditions, and to leaves under sufficient soil moisture conditions. CONCLUSIONS: Our results indicate that the response of below-ground traits to plant intraspecific competition and soil moisture conditions may not be inferred using above-ground traits, suggesting that multiple resource use axes are needed to understand plant ecological strategies. Lack of consistent leaf-root trait correlations across the soil moisture gradient highlight the multidimensionality of plant trait relationships which needs more exploration.

Hydrotropism: Analysis of the Root Response to a Moisture Gradient.

Plant adaptation to environmental stress generated by low water availability requires continuous search for moisture niches in the soil. Thus, roots have evolved a hydrotropic response to sense differences in water potential of the soil, and through asymmetric growth, roots can bend to avoid lower water potential sites. Different experimental systems have been devised for hydrotropism assays, which usually rely on air moisture or split agar assays. This latter system uses plates containing an osmolyte only in a region of the plate in order to generate a water potential gradient. Seedlings are placed on the agar plate containing normal medium (NM) so that their root tips are near the junction between NM and the region supplemented with the osmolyte. As a result, a hydrotropic response is elicited to avoid the low water potential medium, which is reflected in the root curvature angle.

Recent changes in high-mountain plant community functional composition in contrasting climate regimes.

High-mountain plant communities are strongly determined by abiotic conditions, especially low temperature, and are therefore susceptible to effects of climate warming. Rising temperatures, however, also lead to increased evapotranspiration, which, together with projected shifts in seasonal precipitation patterns, could lead to prolonged, detrimental water deficiencies. The current study aims at comparing alpine plant communities along elevation and water availability gradients from humid conditions (north-eastern Alps) to a moderate (Central Apennines) and a pronounced dry period during summer (Lefka Ori, Crete) in the Mediterranean area. We do this in order to (1) detect relationships between community-based indices (plant functional leaf and growth traits, thermic vegetation indicator, plant life forms, vegetation cover and diversity) and soil temperature and snow duration and (2) assess if climatic changes have already affected the vegetation, by determining directional changes over time (14-year period; 2001-2015) in these indices in the three regions. Plant community indices responded to decreasing temperatures along the elevation gradient in the NE-Alps and the Apennines, but this elevation effect almost disappeared in the summer-dry mountains of Crete. This suggests a shift from low-temperature to drought-dominated ecological filters. Leaf trait (Leaf Dry Matter Content and Specific Leaf Area) responses changed in direction from the Alps to the Apennines, indicating that drought effects already become discernible at the northern margin of the Mediterranean. Over time, a slight increase in vegetation cover was found in all regions, but thermophilisation occurred only in the NE-Alps and Apennines, accompanied by a decline of cold-adapted cushion plants in the Alps. On Crete, xeromorphic shrubs were increasing in abundance. Although critical biodiversity losses have not yet been observed, an intensified monitoring of combined warming-drought impacts will be required in view of threatened alpine plants that are either locally restricted in the south or weakly adapted to drought in the north.

Changes in rheology, quality, and staling of white breads enriched with medium-polymerized inulin.

The objective of this study was to evaluate the changes that occurred during processing white breads enriched with 5, 7.5, and 10% of medium-polymerized inulin (MPI). Farinographic analysis revealed that enrichment caused the development time and dough stability to increase by up to 69.9% and 62.8%, respectively, when 7.5% of MPI was incorporated into wheat flour. This indicated that the added MPI strengthened the doughs. Conversely, alveographic analysis demonstrated that MPI was harmful to the gluten network. The specific volume and humidity of breads with up to 7.5% MPI were similar to those of the control (MPI-free) bread. During bread storage for 10 days, we noticed that the retrogradation rate increased only for the bread sample with 10% MPI. However, MPI enrichment, regardless of concentration, promoted an increase in the Avrami exponent and affected bread firmness. Bread staling analysis indicated that the moisture difference between crumb and crust was higher for the MPI-enriched breads than for the control. Moreover, we prepared more consistent doughs and fresh breads with MPI contents of up to 7.5%, which presented good quality and were good fiber sources; however, we determined that inulin did not present an anti-staling effect.

Shoot: root ratio of seedlings is associated with species niche on soil moisture gradient.

Surviving the seedling phase is crucial for the establishment of plant individuals and populations. In ecosystems with dynamic water availability such as temperate grasslands, seedlings should adjust their growth strategy not only to match the current conditions but also to secure resource acquisition in the future. Here, we explored evolutionary adaptations determining plant early growth strategies in herbaceous species of temperate grasslands differing in their requirements for soil water availability. We chose 15 plant genera, within which we selected species differing in their Ellenberg indicator values for moisture. We cultivated the seedlings under standard conditions with sufficient water supply for 4 weeks. Subsequently, we measured length-based and mass-based shoot:root ratio to investigate seedling growth strategy and its association with species ecological niche. Seed size and content of soil-borne nutrients were considered as potential covariates affecting this association. Linear mixed-effect models identified the length-based shoot:root ratio of seedlings was positively associated with soil moisture requirements in a congeneric species comparison. Nitrogen and phosphorus seed concentrations had an additional negative effect on the shoot:root ratio. Neither of these trends was found for the mass-based shoot:root ratio. We demonstrated for the first time that there might be a general adaptation modifying the seedling shoot:root ratio according to the species niche position on the soil moisture gradient in temperate grassland species across a broad range of angiosperm phylogeny. This adaptation seems to be affected by seed mineral nutrient reserves and may operate in parallel to the well-known phenotypic plasticity.

Assay system for mesocotyl elongation and hydrotropism of maize primary root in response to low moisture gradient.

We designed and validated a test system that simulates a growth environment for Zea mays L. maize seedlings under conditions of low moisture gradient in darkness. This system allowed us to simultaneously measure mesocotyl elongation and the primary root hydrotropic response in seedlings before the emergence phase in a collection of maize hybrids. We found great variation in these two traits with statistically significant reduction of their elongations under the low moisture gradient condition that indicate the richness of maize genetic diversity. Hence, the objective of designing a new test system that evaluates the association between these underground traits with the potential use to measure other traits in maize seedlings related to early vigor was achieved.

[Nutrient resorption patterns of Phragmites australis leaves and its response to soil moisture in Yangguan wetland, Dunhuang, Northwest China]. / æ•¦ç Œé˜³å ³æ¹¿åœ°èŠ¦è‹‡å¶ç‰‡å »åˆ†é‡å¸æ”¶æ¨¡å¼åŠå ¶å¯¹åœŸå£¤æ°´åˆ†çš„å“åº”.

Nutrient resorption of leaves is an important nutrient conservation mechanism for plants in nutrient-poor habitats. Understanding the responses of leaf nutrient resorption to soil moisture is helpful to reveal the adaptation strategies of plants to the environment. In this study, the dominant plant in the Yangguang wetland of Dunhuang Phragmites australis was used as research material, to explore nitrogen and phosphorus resorption patterns of P. australis leaves and their responses to soil moisture under different moisture regimes, i.e. high (33.5%±1.9%), medium (26.4%±1.3%) and low (11.3%±1.5%). The results showed that: 1) With the decreases of soil moisture, soil N concentration decreased significantly, and N concentrations in mature and senescent leaves increased significantly, the P concentration in mature and senescent leaves as well as in soil did not change. 2) N resorption efficiency of leaves under high moisture condition was 76.1%, which was significantly higher than the medium (65.5%) and low (62.5%) moisture conditions. P resorption efficiency varied among different moisture conditions. 3) The N concentrations of mature and senescent leaves were negatively correlated with N resorption efficiency. There was no significant correlation between P concentration and P resorption efficiency in mature leaves, but the P concentration of senescent leaves was negatively correlated with P resorption efficiency of leaves. As a result, water scarcity is not conducive to leaf N resorption.

[Effects of annual whole-film mulching on freezing-thawing characteristics, moisture, and temperature distribution of maize soil in semi-arid area]. / åŠå¹²æ—±åŒºå‘¨å¹´å ¨è†œè¦†ç›–å¯¹çŽ‰ç±³ç”°åœŸå£¤å†»èžç‰¹æ€§å’Œæ°´çƒ­åˆ†å¸ƒçš„å½±å“.

Based on a 3-year field experiment (2015-2017) with two treatments, annual whole-film mulching (PM) and uncovered (CK), we analyzed the relationship between soil temperature, moisture, and soil hydrothermal movement in semi-arid area. The results showed that freezing-thawing processes under both PM and CK were one-way freezing and two-way melting. Compared with CK, the freezing period in PM treatment was lagged, freezing rate was slowed down, freezing depth was 20 cm shallower, but melting rate was faster, and melting period was shortened by 6-7 days. In freezing period, soil temperature gradients of PM and CK were positive, with heat being transmitted toward top soil layer, and the conduction strength in PM treatment was greater than CK. During the melting period, soil temperature gradient of PM was also positive, with heat being transmitted toward upper soil layer, and that of CK was conversed. Soil water in PM treatment transported to upper soil layer during freezing-thawing period, but it appeared a "down-up-down" movement mode under CK in freezing period, "up-down" in thawing period. There was positively correlation between temperature and moisture gradient in the freezing period under both PM and CK treatments, with closer correlation in PM than CK. During melting period, soil temperature and moisture gradient was positively correlated in PM treatment with soil heat and moisture moved upward synchronously, while that in CK was negatively correlated with soil heat and moisture simultaneously moved to the lower layer soil. Driven by soil temperature and moisture gradient, soil temperature in 0-10 cm, 10-20 cm and 20-30 cm layers increased by 1.13-1.34 ℃, 0.96-1.24 ℃ and 0.89-1.32 ℃, while average soil water content increased by 3.4%-5.6%, 1.4%-2.2% and 6.7%-7.8%, respectively in PM treatment before sowing. Our results indicated that PM could provide water and heat protection for re-greening of winter crop and sowing, emergence and seedling of spring-sown crops in semi-arid areas.

Effect of moisture gradient on rice yields and greenhouse gas emissions from rice paddies.

Fluxes of methane (CH4) and nitrous oxide (N2O) from two rice varieties, Huayou 14 and Hanyou 8, were monitored using closed chamber/gas chromatography method. Huayou 14 is a commonly grown variety of rice whereas Hanyou 8 is a water-saving and drought-resistant rice (WDR) variety. Low soil volumetric water content (VWC) existed in the treatments on the slope (W5 < W4 < W3 < W2). On the slope, rice yields of Hanyou 8 decreased by 12-39%, and Huayou 14 by 11-46% as compared to the plots on the flat. The total compatible solutes in Hanyou 8 had a greater variational range than Huayou 14. Compared to W1, CH4 emissions from W2-W5 decreased by 58-86% in Hanyou 8 and 38-86% in Huayou 14, whereas those of N2O increased by 26-121% in Hanyou 8 and 49-189% in Huayou 14 across both two seasons, which was mainly because the VWC varied in W2-W5 treatment. Under the treatments in the slope (W2, W3, W4, and W5), the global warming potential (GWP) was dominated by N2O emissions, which accounted for 69-90% of the GWP. Hanyou 8 had greater tolerance for water stress than Huayou 14 did, as evident from the smaller reductions in rice yield and greater variational range of total compatible solutes content. Water stress could reduce CH4 emissions but decrease N2O emissions for both rice varieties. This results suggest that planting WDR varieties under water shortage irrigation (such as W4, W5) will be able to maintain rice yields and reduce the GWP with less water.

A method for rapid analysis of the root hydrotropic response in Arabidopsis thaliana.

The system for analyzing the hydrotropic curvature with a moisture gradient in wild-type Arabidopsis roots was modified. Optimal conditions were determined for detecting a hydrotropic curvature of 90° just after 4 h of stimulation. This system only requires 15 ml of a solution of K2CO3 with a density of 1.48 g·ml-1 to generate a rapid moisture gradient inside a square Petri dish without decreasing root growth. In this, the root growth rate observed in hydrostimulated wild-type and miz1 mutant, utilized as a negative control, increases sixfold compared with those roots examined using the former method.

Relating Bryophyte Assemblages to a Remotely Sensed Depth-to-Water Index in Boreal Forests.

Given the habitat moisture (air humidity or soil moisture) preferences of many forest bryophytes, we explored whether the depth-to-water (DTW) index, derived from remotely sensed Light Detection and Ranging (LiDAR) data, was related to fine-scale patterns of spatial variation in bryophyte abundance, diversity, and composition. The goal was to assess the utility of the topographic DTW index as a tool to decipher trends in bryophyte assemblages along a site wetness gradient in the boreal mixedwood forest. Discrete Airborne Laser Scanning (ALS) data were acquired over the entire Ecosystem Management Emulating Natural Disturbance (EMEND) experimental site located in northwestern Alberta, Canada (56° 46' 13″ N, 118° 22' 28″ W), based on which we calculated a mathematical index of approximate depth to water at or below the soil surface at 1 m resolution using the Wet-Areas Mapping model. Bryophytes (mosses and liverworts) were sampled in permanent sample plots in unmanaged forest stands of varying dominant canopy tree composition. The relationships between DTW and bryophyte cover, richness, diversity, and composition in broadleaf (deciduous)-, mixed, and conifer-dominated boreal forest stands were analyzed using linear mixed-effect models and multivariate analyses. Bryophyte cover was highest in conifer-dominated forest, which occupied the wetter end of the DTW gradient, followed by mixed forest, whereas broadleaf forest, which occupied the drier end of the DTW gradient, had the lowest cover but highest bryophyte diversity. Bryophyte cover in conifer-dominated forests was positively related to site moisture (negatively related to the DTW index). In contrast, bryophyte species richness and diversity were negatively related to site moisture (increased at higher DTW values) in all forest types. DTW explained significant variation in bryophyte species composition in mixed forests, while indicator species analysis identified species with preferences for wet, moist, and dry site conditions in each forest type. Our results corroborate the importance of site moisture as a driver of bryophyte assemblages but, interestingly, there were important differences among forest types, which themselves are distributed across a gradient of site moisture. Our study demonstrates the utility of the topographic DTW index for understanding fine-scale (plot-level) variation in bryophyte assemblages in forested landscapes.

Tree diversity in relation to maximum tree height: evidence for the harshness hypothesis of species diversity gradients.

Marks et al. (Ecology Letters, 19, 2016, 743) showed tree species richness correlates with maximum tree height, and interpret this as evidence that the environmental stressors that limit tree height also act as ecological filters on species richness. Here, we strengthen these arguments by further addressing the roles of environmental covariates and beta diversity.

Tree diversity in relation to tree height: alternative perspectives.

Marks et al. (Ecol. Lett., 19, 2016, 743-751) show that tree diversity increases with tree height in North America and argue it reflects habitat 'suitability'. This finding conflicts with classical results, lacks controls for covariates of tree height, and can be explained alternatively using the modified Janzen-Connell effect and regional variance in habitats.

Productivity and species richness in longleaf pine woodlands: resource-disturbance influences across an edaphic gradient.

This study examines the complex feedback mechanisms that regulate a positive relationship between species richness and productivity in a longleaf pine-wiregrass woodland. Across a natural soil moisture gradient spanning wet-mesic to xeric conditions, two large scale manipulations over a 10-yr period were used to determine how limiting resources and fire regulate plant species diversity and productivity at multiple scales. A fully factorial experiment was used to examine productivity and species richness responses to N and water additions. A separate experiment examined standing crop and richness responses to N addition in the presence and absence of fire. Specifically, these manipulations addressed the following questions: (1) How do N and water addition influence annual aboveground net primary productivity of the midstory/overstory and ground cover? (2) How do species richness responses to resource manipulations vary with scale and among functional groups of ground cover species? (3) How does standing crop (including overstory, understory/midstory, and ground cover components) differ between frequently burned and fire excluded plots after a decade without fire? (4) What is the role of fire in regulating species richness responses to N addition? This long-term study across a soil moisture gradient provides empirical evidence that species richness and productivity in longleaf pine woodlands are strongly regulated by soil moisture. After a decade of treatment, there was an overall species richness decline with N addition, an increase in richness of some functional groups with irrigation, and a substantial decline in species richness with fire exclusion. Changes in species richness in response to treatments were scale-dependent, occurring primarily at small scales (≤10 m2 ). Further, with fire exclusion, standing crop of ground cover decreased with N addition and non-pine understory/midstory increased in wet-mesic sites. Non-pine understory/midstory standing crop increased in xeric sites with fire exclusion, but there was no influence of N addition. This study highlights the complexity of interactions among multiple limiting resources, frequent fire, and characteristics of dominant functional groups that link species richness and productivity.

An individual-based forest model links canopy dynamics and shade tolerances along a soil moisture gradient.

Understanding how forested ecosystems respond to climatic changes is a challenging problem as forest self-organization occurs simultaneously across multiple scales. Here, we explore the hypothesis that soil water availability shapes above-ground competition and gap dynamics, and ultimately alters the dominance of shade tolerant and intolerant species along the moisture gradient. We adapt a spatially explicit individual-based model with simultaneous crown and root competitions. Simulations show that the transition from xeric to mesic soils is accompanied by an increase in shade-tolerant species similar to the patterns documented in the North American forests. This transition is accompanied by a change from water to sunlight competitions, and happens at three successive stages: (i) mostly water-limited parkland, (ii) simultaneously water- and sunlight-limited closed canopy forests featuring a very sparse understory, and (iii) mostly sunlight-limited forests with a populated understory. This pattern is caused by contrasting successional dynamics that favour either shade-tolerant or shade-intolerant species, depending on soil moisture and understory density. This work demonstrates that forest patterns along environmental gradients can emerge from spatial competition without physiological trade-offs between shade and growth tolerance. Mechanistic understanding of population processes involved in the forest-parkland-desert transition will improve our ability to explain species distributions and predict forest responses to climatic changes.

Hydrotropism: Analysis of the Root Response to a Moisture Gradient.

Hydrotropism is a genuine response of roots to a moisture gradient to avoid drought. An experimental system for the induction of hydrotropic root response in petri dishes was designed by pioneering groups in the field. This system uses split agar plates containing an osmolyte only in a region of the plate in order to generate a water potential gradient. Arabidopsis seedlings are placed on the MS agar plate so that their root tips are near the junction between plain MS medium and the region supplemented with the osmolyte. This elicits a hydrotropic response in Arabidopsis roots that can be measured as the root curvature angle.