Soil Water Absorption Research Articles

Regulation of a plant aquaporin by a Casparian strip membrane domain protein-like.

The absorption of soil water by roots allows plants to maintain their water status. At the endodermis, water transport can be affected by initial formation of a Casparian strip and further deposition of suberin lamellas and regulated by the function of aquaporins. Four Casparian strip membrane domain protein-like (CASPL; CASPL1B1, CASPL1B2, CASPL1D1, and CASPL1D2) were previously shown to interact with PIP2;1. The present work shows that CASPL1B1, CASPL1B2, and CASPL1D2 are exclusively expressed in suberized endodermal cells, suggesting a cell-specific role in suberization and/or water transport regulation. When compared with wild-type plants, and by contrast to caspl1b1*caspl1b2 double loss of function, caspl1d1*caspl1d2 double mutants showed, in some control or NaCl stress experiments and not upon abscisic acid (ABA) treatment, a weak enlargement of the continuous suberization zone. None of the mutants showed root hydraulic conductivity (Lpr ) phenotype, whether in control, NaCl, or ABA treatment conditions. The data suggest a slight negative role for CASPL1D1 and CASPL1D2 in suberization under control or salt stress conditions, with no major impact on whole root transport functions. At the molecular level, CASPL1B1 was able to physically interact with PIP2;1 and potentially could influence the regulation of aquaporins by acting on their phosphorylated form.

Effects of mycorrhizae and water conditions on perennial ryegrass growth in rare earth tailings.

Mycorrhizal symbioses, which include plant roots and arbuscular mycorrhizal fungi (AMF), can significantly enhance plant resistance and promote the absorption of soil nutrients by plants. A greenhouse experiment was conducted to investigate the effects of three AMF species (Glomus mosses, Glomus etunicatum and Glomus versiforme) on the height, biomass, malondialdehyde (MDA) and proline contents and antioxidant enzyme activities of perennial ryegrass (Lolium perenne) under different water supply treatments. Potted experimental soil samples were collected from the abandoned rare earth tailings in Ganzhou, Jiangxi. The results showed that all three AMF species infected ryegrass under the different treatments. Under severe drought stress, G. mosses had the most significant effects on the promotion of ryegrass performance. After inoculation, the height and whole-plant biomass of ryegrass increased by 60.44% and 150%, respectively. In addition, inoculation with AMF significantly reduced the content of MDA and proline in the ryegrass leaves in all water supply treatments except the moderate drought stress treatment, in which there was no effect. The leaf antioxidant enzyme activity was also measured. The results showed that under severe drought stress, inoculation with Glomus mosses significantly increased the activities of CAT and SOD in ryegrass and enhanced the resistance of plants. A possible reason that AMF promotes host plant growth and enhances drought resistance is that AMF directly increases the absorption of soil water and minerals by host plant roots and indirectly improves the physiological metabolism of plants.

Presowing fertigation effects on soil moisture absorption and consumption of cotton in arid regions

To increase the yield and water-use efficiency of cotton in arid regions, irrigation and fertilizer management must be optimized. This study evaluated the effects of two irrigation levels (i.e., with (W80) and without (W0) presowing irrigation) combined with two basal fertilization methods (i.e., surface application (F10) and deep application (F30)) on soil water absorption and transport, and relationships with water-use efficiency. Our results showed significantly positive relationships between water-use efficiency and the root surface area in the 0–30 cm soil layer (RSA-30), root vigor in the 0–30 cm soil layer (RV-30), root vigor in the 60–80 cm soil layer (RV-80), the leaf transpiration rate, stomatal conductance, sap flow, and water productivity. Principal component analysis showed that the W80F10 treatment initially positively influenced RSA-30, RV-30, and RV-80 and that these parameters affected the leaf transpiration rate, stomatal conductance, sap flow, and leaf area (i.e., the main transpiration area), which finally influenced water productivity and water-use efficiency. In addition, the W80F10 treatment increased the ability of aerial parts to compete for water after 69 days after emergency. These findings indicate that the combination of presowing irrigation and basal fertilizer surface application can enhance the ability of aerial parts to compete for water and increase water-use efficiency by promoting water absorption and consumption after the full flowering stage. This research provides valuable information on agricultural management in aridregions.

An experimental irrigation tool for creating a water gradient across soil depths under terminated rainfall conditions

An experimental irrigation tool to research the response of plants to soil drying from deep to shallow soil layers observed under limited rainfall conditions was tested. Water was supplied from the tips of 4-mm-diameter tubes measuring 0.1, 0.3, 0.6, and 0.85 m in the length inserted into the soils. Each tube was set from shallowest to deepest at intervals of 1.5–3.0 m in the field. Control by the irrigation system was evaluated in rice and spring wheat fields under rain-protected shelters, where two cultivars with different root depths were planted. The irrigation tool created a series of different soil water profiles in which wet soil layers decreased with increasing irrigation depth due to the inserted tube lengths in both fields. In fine sandy soils more than sand, continuous decreases in soil water content were well simulated. Leaf conductance, leaf green color (SPAD value), and aboveground plant dry weight in both fields decreased with increasing irrigation depth in shallow root cultivars to a greater extent than that in deep root cultivars. The lower reducing effect of deep irrigation on plant dry weight in wheat compared to that in rice suggested that the irrigation depth based on tube length should be changed depending on the root distribution traits in the tested crops. These results indicated that the irrigation tool can conveniently simulate a diverse and continuous soil water content profile closer to that of an actual water gradient under limited rainfall conditions and contribute to studies on crop responses to different soil water absorption traits.

Effects of rainfall and vegetation to soil water input and output processes in the Mu Us Sandy Land, northwest China

Soil water plays a critical role in vegetation growth and restoration in semiarid regions, and has highly spatiotemporal variability. Gaining a comprehensive understanding of the soil water input and output processes is critical to the study of the hydrological cycle. To further unveil and quantify soil water dynamics, we embarked on a research program to quantify hydrological processes under three sites (i.e., shifting dune, shrub-dominated community, and herb-dominated community) with continuously monitored soil water content at 10-min intervals in the Mu Us Sandy Land between April and October 2012. The results indicated that soil water input and output processes were strongly affected by rainfall infiltration and surface characteristics. Rainfall affects the fluctuation of soil water content in deeper layers (60–80cm) by altering rainfall amount and soil texture; vegetation affects the soil water input process by altering the canopy rainfall interception, hydraulic lift, and soil organic matter content and so on. The effects of rainfall on the soil water output process mainly contributed to direct leakage and evaporation. Plant root distribution was a vital factor affecting the soil water output process. In addition, a state of dynamic equilibrium existed between the absorption of soil water and non-rainfall replenishment of soil water content during the output process over a long period of time. With limited soil water input and relatively larger soil water uptake by deeper roots, the soil water varied up to ~80% under the herb-dominated community. Our results imply that the increment of the deeper layer (60–80cm) would enhance shrub expansion in the Mu Us Sandy Land of China.

丛枝菌根真菌与植物共生对植物水分关系的影响及机理

PDF HTML阅读 XML下载 导出引用 引用提醒 丛枝菌根真菌与植物共生对植物水分关系的影响及机理 DOI: 10.5846/stxb201306091556 作者: 作者单位: 兰州大学草地农业生态系统国家重点实验室,兰州大学草地农业生态系统国家重点实验室,兰州大学草地农业生态系统国家重点实验室,兰州大学草地农业生态系统国家重点实验室,兰州大学信息科学与工程学院,兰州大学草地农业生态系统国家重点实验室,兰州大学草地农业生态系统国家重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(31070372);国家科技支撑计划(2012BAD14B10);科技部国际合作项目(2013DFA30950);国家星火计划项目(2012GA860003);国家自然科学基金青年科学基金(61201421);甘肃省青年科技基金计(1208RJYA058);甘肃省科学院开发与应用基金项目(2012JK-03);国家公益性行业(气象)科研专项(GYHY201106029-2);高等学校博士学科点专项科研基金(20110211110022) Effects of arbuscular mycorrhizal fungi and plant symbiosis on plant water relation and its mechanism Author: Affiliation: State Key Laboratory of Glassland and Agro-Ecosystems,Institute of Arid Agroecology,School of Life Sciences,Lanzhou University,State Key Laboratory of Glassland and Agro-Ecosystems,Institute of Arid Agroecology,School of Life Sciences,Lanzhou University,State Key Laboratory of Glassland and Agro-Ecosystems,Institute of Arid Agroecology,School of Life Sciences,Lanzhou University,State Key Laboratory of Glassland and Agro-Ecosystems,Institute of Arid Agroecology,School of Life Sciences,Lanzhou University,School of Information Science and Engineering,Lanzhou University,State Key Laboratory of Glassland and Agro-Ecosystems,Institute of Arid Agroecology,School of Life Sciences,Lanzhou University,State Key Laboratory of Glassland and Agro-Ecosystems,Institute of Arid Agroecology,School of Life Sciences,Lanzhou University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:自1885年Frank首次提到菌根(mykorhiza)概念以来,大量的试验证实了丛枝菌根真菌(AMF)与植物根系之间形成具有一定结构和功能的共生体,促进植物生长并提高干旱耐受能力,在干旱生态系统中发挥重要的作用。该研究多集中在对宿主植物生理生态的影响及其机制方面,然而菌根共生对宿主植物水分吸收和信号产生、传递的影响研究少而分散,缺少系统总结。综述了最近四十多年丛枝菌根真菌与植物共生体对宿主植物干旱适应性影响研究进展,讨论了菌根共生对植物根冠通讯的影响及机理。干旱胁迫下AMF与植物共生,通过影响宿主植物一系列生理生态过程,提高宿主植物横向根压和纵向蒸腾拉力。经典的Ohm吸水模型是该方向最有代表性的研究成果,该模型揭示了菌根共生的根外菌丝具有不同于根细胞的细胞结构和水分运输性能,这为宿主植物提供一种特殊的快速吸水方式,可提高植物对土壤水分的吸收和运输能力。研究表明,AMF会影响宿主植物根冠通讯过程,如诱发信号级联反应,诱导根系尽早感知水分胁迫并产生非水力根源信号,提高宿主对干旱的耐受性。讨论了AMF在根冠通讯分子机制研究方面存在的问题及可能的解决途径,展望了AMF在干旱农业生产中的应用潜力。 Abstract:Since Frank proposed "mykorhiza" for the first time in 1885, extensive studies have demonstrated the formation of mycorrhizae between arbuscular mycorrhizal fungi (AMF) and plant roots, and the functioning of mycorrhizae in improving plant gowth and drought adaptability under drought stress particularly in semiarid and arid ecosystems. However, information is limited on the mechanisms how AMF could affect the host plant water uptake, root signal generation and transfer, while most studies have focused on effects of AMF on their physiological and ecological changes in host plants. In this review, progresses in how AMF could balance water relations and affect root to shoot communications are summarized from studies in the last four decades, and possibly related mechanisms are also concluded. These mechanisms include enhanced water uptake, root hydraulic conductance, antioxidant activity, altered hormone relations, osmotic adjustment, aquaporin expression and nutrition absorption. Studies have showed that AMF associated symbioses have usually altered eco-physiological characteristics, e.g. stomatal conductance, plant size and abscisic acid (ABA) content, and thus enhancing the lateral root pressure and vertical transpiration to benefit for host plant's water absorption. The Ohm's law model, which is the most representatively traditional progress in water uptake mechanisms, could further reveal how AMF is able to improve soil water absorption and transport. This mode reveals that mycorrhizal hyphae, which are different from plant root cells, having aseptate or coenocytic and elastic hyphal wall at the tip, and only infrequent, adventitious septa, can contribute to transport water rapidly in host plants under drought stress. Thus, AMF in plant root may be able to feel drier soil more quickly and produce non-hydraulic root-sourced signals earlier. AMF can also affect root to shoot communications, such as inducing signaling cascades for root-sourced signal generation and the improvement of drought tolerance from cellular to whole plant level. Nevertheless, the composition of root exudates are complex, and the mechanisms of root to shoot communications still need to be solved: 1) how AMF help root cells to perceive root water stress; 2) relationships between early drought-gene expression and non-hydraulic root-sourced signal (nHRS); and 3) relationships between late drought-gene expression and hydraulic root-sourced signal (HRS). Possible pathways may further reveal the unknown mechanisms in root to shoot communications that are affected by AMF: 1) the differences in their composition among root exudates and root ingredient under moisture gradients, which may have potential in indicating the perception of water stress signal component; 2) the ABA-binding factor (ABF), which may be as one of the important transcripts to respond to the early drought stress, and Ca2+ as a second messenger collaborating ABA to regulates the open and close of guard cells. Therefore, studies on their distribution of ABA and Ca2+ in root, stem and leaf under moisture gradients may provide insight into relationships between early drought-gene expression and nHRS; and 3) relationships between the whole plant drought tolerance (e.g. plant type and biomass allocation) and the cell drought tolerance (e.g. antioxidant enzymes and penetration substances), which may address mechanisms involving in the late drought-gene expression and HRS. With the further progresses are made on the contribution of AMF symbiosis to plant water uptake and drought tolerance, we believe that AMF will have potential application in semi-arid and arid agricultural production. 参考文献 相似文献 引证文献

Nanoclay Performance On Resistance of Clay Under Freezing Cycles

This study aims to investigate effect of nanoclay on resistance of the exposed clay soils in freezing in vitro conditions. The clay sample was selected from the considered land. Then they were mixed on water in 1.5, 3, 4.5 and 6 percents as well as without nanoclay. There were prepared cylinders with 3.81 cm diameter and 7.62 cm height, which they have been placed in conditions without freezing, one cycle, two cycles and three cycles of freezing. Then they were tested under uniaxial experiment. Then they were analyzed by SPSS software. The results show that adding nanoclay with 1.5, 3, 4.5 and 6 percents will reduce soil strength during freezing cycles. It can be occurred because adding nanoclay will result to increase special surface of the samples; consequently, increasing electrical load increases water absorption, which it can be partly cause of non-effective increasing nanoclay in soil resistance. There is also a significant difference between pressure strength of soils with lower humidity and those with higher humidity. It confirms that increasing humidity decreases strength level, which increasing water absorption of samples by nanoclay is reason of decreasing strength. There is an inverse significant relationship between increasing nano and soil water absorption, which its reason may be that adding nanoclay because of increasing samples special surface and consequently, increasing electricity load will increase water absorption and samples’ plasticity. It can be expected that samples’ permeability will decline by increasing their plasticity. There is also a significant relationship between increasing nano and soil liquid and doughiness limit that its reason can be increasing rate of water absorption in samples due to presence of nanoclay.© JASEM Keywords : Nanoclay, Resistance, Freezing, Sample, Uniaxial

Water mass balance in the case of vertical infiltration

Water movement in the unsaturated zone is an important hydrological process. Richard’s equation is windily used to describe both soil water infiltration and soil water absorption. Various methods have been developed to solve Richard’s equation. Wang et al. (2003) have developed an algebraic model for the description of soil water infiltration, based on Parlange’s solution of Richard’s equation and on soil retention curve and hydraulic conductivity equation given by Brooks and Corey. Their model utilizes experimental measurements of the cumulative infiltration volume and the wetting front distance as functions of time in order to describe soil water infiltration. The objective of this paper is to test the accuracy of the Wang et al. algebraic model for the one-dimensional (vertical) soil water infiltration. A vertical infiltration experiment was conducted on a sandy soil, for the measurement of the cumulative infiltration volume and the wetting front distance. Soil water content was determined at selected times and positions, using gamma ray absorption. Additionally the hydraulic conductivity K(θ) and the soil retention curve Ψ(θ) were determined. The algebraic model developed by Wang et al., was found simple to use since the required data are the cumulative infiltration (F), the wetting front distance (zf) and the initial and saturated soil water content (θi and θs respectively). The results show a fair agreement between calculated and measured values on soil water content profiles, hydraulic conductivity and on the water mass balance.

Pengaruh Perubahan Penggunaan Lahan terhadap Sifat Biofisik Tanah dan Kapasitas Infiltrasi di Kota Malang

Land use management causes the changes of the function of the land in the city. The change of the function of uncultivated land to be cultivated land has a potential to change soil biophysical characteristic, and at the same time, it decreases the absorption of soil water. This research aims: (1) to study the influence of the landuse change towards soil biophysical characteristics, (2) to study the correlation between soil biophysical characteristics and infiltration capacity, and (3) to study the influence of the landuse change towards the infiltration capacity. The landuse change is studied by comparing the ongoing mapping documents. Soil biophysical characteristics consist of root biomass, number of worms, soil organic matter (SOM), and porosity. The root biomass is obtained by root density, the number of worms is identified with monolith and hand sorting method, the SOM is identified with fraction analysis, and the porosity is identified with cylinder and pignometer method. The water absorption is measured with the plot experiment. The influence of the landuse towards soil biophysical traits is analyzed T-test and the influence of landuse change towards infiltration capacity is analyzed correlatively. This research gains the results that: (1) the landuse change causes the change of soil biophysical traits, too, and the soil biophysical traits change causes, furthermore, the declining of the land capability in absorbing water, and (2) the amount of the infiltration capacity is caused by soil biophysical traits, mostly by root biomass, number of worms, and the SOM, and (3) the landuse change causes the declining of infiltration capacity.

Seeding depth and soil packing affect pure live seed emergence of cuphea

Cuphea viscosissima Jacq. × C. lanceolata f. silenoides W.T. Aiton is a new crop being developed in the north-central USA as an industrial oilseed crop. Adequate plant stand is essential for successful commercial production of cuphea. The objective of this study was to determine the effect of seeding date, depth and soil packing on stand establishment and subsequent crop performance. The study was conducted at Carrington and Prosper, ND, in 2005 and 2006. The experimental design was a randomized complete block with four replicates, with a split–plot arrangement, where the whole plot was a factorial arrangement (2 × 2) of two seeding dates, optimum and late, with or without soil packing after seeding. The subplot treatments were three seeding depths (surface, 13, and 25 mm). The same plot planter was used to adjust seeding depth to 13 and 25 mm. Each experimental unit had six rows 4.6-m long with a between-row spacing of 0.31 m. Traits evaluated were pure live seed emergence (PLSE), plant stand, plant height at harvest and seed yield. The main effect for seeding date did not have an effect on PLSE and resulted in adequate stands from both late May and mid June plantings averaged across environments. The seeding depth by soil packing interaction was significant for PLSE, plant stand and seed yield. Pure live seed emergence, plant stand, and seed yield were greater if the soil was packed compared with non-packed for the surface seeded treatment. The soil packing treatment did not influence PLSE, plant stand, or seed yield at the 13- and 25-mm seeding depths. Plant stands obtained from the non-packed surface and 13-mm seeding depths was adequate for high seed yield, as the plants branched to compensate for the lower plant density. Although surface seeding with packing produced satisfactory plant stands, reliance on timely rainfall is required for this to be successful. For this reason, the recommendation for seeding at the 13-mm depth without soil packing would ensure a better chance for sufficient soil water absorption by the seed to initiate germination. If surface seeding is practiced, a roller-packer to incorporate seeds and firm the seedbed after planting is recommended.

Numerical analysis of crack generation in saturated deformable soil under row-planted vegetation

Desiccation cracks play an important role in the drainage of excess water via the subsurface drainage system in clayey puddled paddy fields. The present study focuses on the linear inter-row cracks induced by water absorption from row-planted rice. The shrinkage behavior of clayey puddled soil, which can be regarded as the consolidation of saturated soil subject to pore water suction, was simulated using a numerical model based on the Biot's two-dimensional consolidation theory. The model demonstrates how row-planted crops' absorption of soil water induces the deformation of the soil and the development of tensile effective stress. The model requires parameters to specify the mechanical and hydraulic properties of the soil. These parameters can be determined from the e–log p (void ratio and mean stress) relationship and the e–log k (void ratio and saturated hydraulic conductivity) relationship. The calculations were performed using the finite element method (FEM). The simulation demonstrated a concave distribution of suction between rows and showed the induced deformation of the soil fabric. It showed that the peaks of tensile effective stress are not necessarily located at the center of the rows; the peaks are typically found near the Fronts of a Suction Rise (FSR), where the suction is about to rise. Further numerical experiments demonstrated that the distribution of tensile effective stress is characterized by either single or double peaks, depending on the following conditions. Greater transpiration flux, wider row-spacing, and a thinner soil layer induce the double-peaked distribution of tensile effective stress. This phenomenon corresponds to the field observation that the linear inter-row cracks running parallel to the rows are single in narrower row-spacing, and double in wider row-spacing.

Comment on “Analytical decomposition of the nonlinear unsaturated flow equation” by Sergio E. Serrano

Keywords: approximate analytical solution ; Richards' equation ; soil water absorption ; Bruce and Klute formula ; soil water diffusivity Reference ECOL-ARTICLE-2002-012doi:10.1029/2001WR000421 URL: http://www.agu.org/journals/wr/ Record created on 2005-12-09, modified on 2016-08-08

Scaling of soil water absorption by seeds: an experiment using seed analogues

AbstractScaling of water absorption and water loss by seeds on various soil surfaces was simulated using seed analogues constructed with paper pulp. Three sizes of analogue seeds (large, medium and small) were laid on three types of soil surface (coarse, medium and fine texture). To estimate the amount of water absorbed by a seed during a fixed time interval, the difference in seed weight from the start of the experiment was used. The scaling of water absorption necessary for germination was also studied using actual seeds of 14 species representing a range of seed sizes. Scaling coefficients between the amount of absorbed water by an analogue seed (net water gain) and seed mass were usually lower than 1: small seeds absorbed water more rapidly than large ones. The water loss of analogue seeds was also correlated with seed mass with a scaling coefficient lower than 1, but the amount of water loss itself was far smaller than the absorption. On the other hand, the germination of actual seeds revealed that the amount of water necessary to start germination was proportional to seed mass. Thus, smaller seeds have an advantage over larger seeds in more rapidly attaining the water content necessary for germination. Moreover, small seeds can penetrate through small cracks in the soil surface and thus enjoy a double advantage in a microsite that promotes water absorption and minimizes desiccation.

土壌の水分特性曲線と吸水特性に関する研究

Soil can be regarded as a source and a storage of water in soil-plant-atmosphere continum (SPAC). To make clear the characteristics of moisture retention of the soil in relation to other soil properties is part of the basic work of water dynamic analysis in SPAC. In this study, water retention characteristic curves and other soil properties were measured for 50 samples representing 5 different kinds of soil from the northeastern region of China.From the results, a new empirical equation for moisture characteristic curve was proposed. The parameters of the equation had physical meaning and could be estimated by the percentage of micro-aggregate and the organic matter content in the soil, and the geometric mean of soil particle size. Furthermore, an equation to describe the rate of soil water absorption was also proposed. Parameters in the equation depended upon the specific surface area of the soil, the organic matter content in the soil and the percentage of soil particles less than 0.01mm.

Non-linear absorption of soil water from a disc source

Non-linear absorption of water from a surface-disc source is examined. The solution can be evaluated only by numerical techniques. However, results can be generalized in a dimensionless form invariant to disc radius, saturated hydraulic conductivity, and capillary length. Gravity effects are negligible for small time and for small disc radii. For the limiting effect of gravity for large times, Wooding's equation gives the ratio of excess flow due to gravity as πr 0/(4 λ c) compared to 1, where r 0 is the disc radius and λ c the capillary length. Examples are presented by using two sets of empirical hydraulic functions as well as an estimate of the product of saturated hydraulic conductivity and capillary length from field data.

A Study on the Application of Quick-Lime Consolidated Briquette Piles in Loose Sandy Soils

ABSTRACT During earthquakes, saturated loose sandy soils often liquefy, causing serious damage to buildings and underground structures. Various construction methods have been employed to stabilize these soils against liquefaction, the most popular being those which increase their density. Vibration and impact methods are commonly employed, but these are often a problem in urban areas. We studied the usage of a composite soil improvement material called Quick-Lime Consolidated Briquette. This material is placed to form cylinders, resulting in static consolidation of the surrounding soil due to absorption of soil water and consequent swelling. In our study, static consolidation increased density, and the swollen material became aggregate-like soon after placement, thus quickly stabilizing the surrounding soil. This report examines the preventive effect of quick-lime consolidated briquette piles against liquefaction as well as a method of determining optimum pile diameter and pitch.

Development and Testing of Root Effectiveness Function for Soil Water Uptake

AbstractFor soil water uptake studies under cropped conditions, root effectiveness for soil water absorption is of great significance. For development of root effectiveness function, information on the age of roots present at any soil depth at any time during the crop growth period is needed. For estimation of root age and root effectiveness function, a methodology has been developed. Wheat crop was used as a test crop. It has been observed that root effectiveness for water uptake remains constant during the early period of root growth and thereafter it decreases exponentially with root age. The application of the proposed root effectiveness function was tested successfully using macroscopic model of soil water dynamics which yielded 7.83 per cent variation between observed and simulated soil water content on overall basis in the crop root zone for the entire crop growth season.

Non-uniform soil water extaction by plant roots

Using the technique of Computer Assisted Tomography applied to gamma ray attenuation measurement of soil water content, it has been shown that the assumption of uniform absorption of soil water along a plant root is clearly erroneous and that drawdown distance is a function of time. The results suggest that the plant sequentially removes water from the top to the bottom of the root as soil hydraulic resistance becomes a major limiting factor in the upper layers, even at the high soil water potential (−0.30 MPa) used.

Soil Moisture and Absorption of Water by Tree Roots

Shade trees undergo periodic dehydration because the rate of absorption of soil water lags behind the rate of transpirational water loss from tree crowns. The rate of absorption of water from wet, warm, and well-aerated soil is controlled largely by the rate of transpiration. However, absorption of water often is impeded by low soil moisture content, a small or slow-growing root system, poor soil aeration, low soil temperature, a high concentration of the soil solution, or combinations of these. As the soil dries down from field capacity, the rate of absorption of water is reduced because of increased resistance to water movement in the soil and within the tree as well as loss of soil-root contact. Poor soil aeration in compacted or flooded soils decreases water absorption by inhibiting root growth, inducing decay of roots, and suppressing development of mycorrhizae. Low soil temperature reduces absorption of water by decreasing the permeability of roots, increasing the viscosity of water, and inhibiting root growth. High concentrations of deicing salts and fertilizers in the soil solution may reduce absorption of water by osmotic effects.

An investigation of the lattice and interlayer water vibrational spectral regions of muscovite and vermiculite using Raman microscopy. A Raman microscopic study of layer silicates

AbstractThe micro Raman spectrum of ∼100fg of the clay materials Muscovite and Vermiculite in the region of 600 cm−1 −3300 cm−1 is reported. An attempt has been made to assign the observed Raman shifts in particular those of H‐bonded OH−, which may have significance to an understanding of the role which clay plays in the absorption of soil water.