Root Elongation Rate Research Articles

Dual pathways for regulation of root branching by nitrate.

Root development is extremely sensitive to variations in nutrient supply, but the mechanisms are poorly understood. We have investigated the processes by which nitrate (NO3-), depending on its availability and distribution, can have both positive and negative effects on the development and growth of lateral roots. When Arabidopsis roots were exposed to a locally concentrated supply of NO3- there was no increase in lateral root numbers within the NO3--rich zone, but there was a localized 2-fold increase in the mean rate of lateral root elongation, which was attributable to a corresponding increase in the rate of cell production in the lateral root meristem. Localized applications of other N sources did not stimulate lateral root elongation, consistent with previous evidence that the NO3- ion is acting as a signal rather than a nutrient. The axr4 auxin-resistant mutant was insensitive to the stimulatory effect of NO3-, suggesting an overlap between the NO3- and auxin response pathways. High rates of NO3- supply to the roots had a systemic inhibitory effect on lateral root development that acted specifically at the stage when the laterals had just emerged from the primary root, apparently delaying final activation of the lateral root meristem. A nitrate reductase-deficient mutant showed increased sensitivity to this systemic inhibitory effect, suggesting that tissue NO3- levels may play a role in generating the inhibitory signal. We present a model in which root branching is modulated by opposing signals from the plant's internal N status and the external supply of NO3-.

Ecological significance of root tip rotation for seedling establishment of Oryza sativa L.

How plant seeds secure root penetration into soil to obtain good seedling establishment is one of the basic ecological problems. In this study, seminal root growth was investigated to clarify the cause of varietal difference of seedling establishment in direct seeding of rice in flooded paddy fields, with special reference to root tip rotation. In a field experiment, seedling establishment percentage had a weak correlation with seminal root elongation rate but was not correlated with apparent seedling weight in water, which has been reported to be the cause of floating seedlings resulting in poor seedling establishment. Root tip rotation was analyzed for indoor‐grown seedlings using spectrum analysis: the maximum entropy method (MEM) was used. Maximum entropy method power spectrum analysis clarified that maximum MEM power density (practically corresponds to spiral angle) detected in the frequency range above 0.1 cycles mm‐1 was highly and positively correlated to seedling establishment percentage in the field experiment. Maximum MEM power density in high correlation with seedling establishment was mostly found around frequencies of 0.2 cycles mm–1, which corresponded to 2.0–3.4 cycles of root tip rotation per day. From these results, root tip rotation (circumnutation) with a larger spiral angle was suggested to play an important role in the establishment of rice seedlings on flooded and very soft soil. A possible explanation for why a larger spiral angle was advantageous for seedling establishment is that if buoyancy and seedling weight are constant, a larger pushing force of the seminal root is available without causing floating of a seedling, due to the upward force being a reaction of the seminal root pushing force.

Change in apoplastic aluminum during the initial growth response to aluminum by roots of a tolerant maize variety

Root elongation, hematoxylin staining, and changes in the ultrastructure of root-tip cells of an Al-tolerant maize variety (Zea mays L. C 525 M) exposed to nutrient solutions with 20 &mgr;M Al (2.1 &mgr;M Al3+ activity) for 0, 4, and 24 h were investigated in relation to the subcellular distribution of Al using scanning transmission electron microscopy and energy-dispersive x-ray microanalysis on samples fixed by different methods. Inhibition of root-elongation rates, hematoxylin staining, cell wall thickening, and disturbance of the distribution of pyroantimoniate-stainable cations, mainly Ca, was observed only after 4 and not after 24 h of exposure to Al. The occurrence of these transient, toxic Al effects on root elongation and in cell walls was accompanied by the presence of solid Al-P deposits in the walls. Whereas no Al was detectable in cell walls after 24 h, an increase of vacuolar Al was observed after 4 h of exposure. After 24 h, a higher amount of electron-dense deposits containing Al and P or Si was observed in the vacuoles. These results indicate that in this tropical maize variety, tolerance mechanisms that cause a change in apoplastic Al must be active. Our data support the hypothesis that in Al-tolerant plants, Al can rapidly cross the plasma membrane; these data clearly contradict the former conclusions that Al mainly accumulates in the apoplast and enters the symplast only after severe cell damage has occurred.

Callose production as indicator of aluminum toxicity in bean cultivars

The response of seven cultivars of beans to aluminum (Al) stress was assessed by using root elongation rate and callose accumulation in 5 mm root tips as early markers of injury. Bean seedlings were grown in acid nutrient solution (pH 4.5) and exposed to 0, 20, and 50 μM Al for 24 h. Root elongation was recorded at frequent intervals and callose accumulation was determined spectrofluorometrically. Based on the root elongation rate, Strike and Contender were Al‐sensitive and F‐15 and Superba were the most Al‐tolerant cultivars. The cultivars Hilds maxi, Hinrichs riesen, and Saxa showed an intermediate behavior. Callose synthesis positively correlated with internal Al concentration and negatively correlated with root elongation rate. Both callose accumulation and root elongation rate were useful in classifying the bean cultivars for aluminum tolerance, but root elongation rate was a more sensitive parameter. Root callose deposition can serve as an early marker for Al toxicity and tolerance in beans.

Water relations and root activities of Buchloe dactyloides and Zoysia japonica in response to localized soil drying

Effects of localized soil drought stress on water relations, root growth, and nutrient uptake were examined in drought tolerant ‘Prairie’ buffalograss [Buchloe dactyloides (Nutt.) Engelm.] and sensitive ‘Meyer’ zoysiagrass (Zoysia japonica Steud.). Grasses were grown in small rhizotrons in a greenhouse and subjected to three soil moisture regimes: (1) watering the entire 80-cm soil profile (well-watered control); (2) drying 0–40 cm soil and watering the lower 40 cm (partially dried); (3) and drying the entire soil profile (fully dried). Drying the 0–40 cm soil for 28 days had no effect on leaf water potential (Ψ leaf ) in Prairie buffalograss compared to the well-watered control but reduced that in Meyer zoysiagrass. Root elongation rate was greater for Prairie buffalograss than Meyer zoysiagrass under well-watered or fully dried conditions. Rooting depth increased with surface soil drying; with Prairie buffalograss having a larger proportion of roots in the lower 40 cm than Meyer zoysiagrass. The higher rates of water uptake in the deeper soil profile in the partially dried compared to the well-watered treatment and by Prairie buffalograss compared to Meyer zoysiagrass could be due to differences in root distribution. Root 15N uptake for Prairie buffalograss was higher in 0–20 cm drying soil in the partially dried treatment than in the fully dried treatment. Diurnal fluctuations in soil water content in the upper 20 cm of soil when the lower 40 cm were well-watered indicated water efflux from the deeper roots to the drying surface soil. This could help sustain root growth, maintain nutrient uptake in the upper drying soil layer, and prolong turfgrass growth under localized drying conditions, especially for the deep-rooted Prairie buffalograss.

Root growth dependence on soil temperature for Opuntia ficus‐indica: influences of air temperature and a doubled CO2 concentration

1. Root elongation as a function of soil temperature was determined for the CAM succulent Opuntia ficus‐indica, under three different day/night air temperatures (15 °C/5 °C, 25 °C/15 °C and 35 °C/25 °C) and an ambient (360 μmol mol–1) vs a doubled CO2 concentration (720 μmol mol–1) at 25 °C/15 °C, the optimum temperature for net CO2 uptake. 2. Root elongation occurred at soil temperatures from 12 °C (at 15 °C/5 °C) to 43 °C (at 35 °C/25 °C) with optimum temperatures of 27–30 °C, similar to other CAM succulents and consistent with the distribution of this shallow‐rooted species in warm regions. Although a doubled CO2 concentration did not alter the optimum or limiting soil temperatures, increases of up to 5 °C in these temperatures accompanied the 20 °C increase in day/night air temperatures. 3. Root elongation rates at optimum soil temperatures ranged from 5·4 mm day–1 (15 °C/5 °C), through 6·6 mm day–1 (25 °C/15 °C), to 10·4 mm day–1 (35 °C/25 °C) with a 25% increase under a doubled CO2 concentration. Highest root elongation rates at 35 °C/25 °C may reflect changing root vs shoot sink strengths in a species with a highly plastic root system. 4. At limiting soil temperatures, the length of the cell division zone was reduced by an average of 20% and cell length at the mid‐point of the elongation zone by 10%. Increased root elongation rates under a doubled CO2 concentration reflected increased cell elongation. 5. The temperature response for the roots of O. ficus‐indica and stimulation of elongation by a doubled CO2 concentration indicate that root growth for this highly productive species should be enhanced by predicted global climate change.

Water stress induced by PEG decreases the maximum growth pressure of the roots of pea seedlings

Roots of plants growing in dry soil often experience large mechanical impedance because the decreased soil water content is associated with increases in soil strength. The combined effect of mechanical impedance and water stress hinders the establishment of seedlings in many soils, but little is known about the interaction between these two stresses. A method has been designed that, for the first time, measured the maximum axial force exerted by a root growing under controlled water stress. Using this technique the axial force exerted by a pea radicle was measured using a shear beam, while the seedling was suspended in an aerated solution of polyethylene glycol 20000 at osmotic potentials between 0 and -0.45 MPa. The maximum growth force was then divided by the cross-sectional area of the root to give the maximum axial growth pressure. The value of maximum axial growth pressure decreased linearly from 0.66 to 0.35 MPa as the osmotic potentials of the solution of PEG decreased from 0 to -0.45 MPa. In dry soil, therefore, the maximum strength of soil that a root can penetrate is decreased because of the decrease in maximum growth pressure. The elongation rates of unimpeded roots were similar whether the roots were subject to either a matric potential in soil or to an osmotic potential in a solution of PEG.

Water stress induced by PEG decreases the maximum growth pressure of the roots of pea seedlings

Roots of plants growing in dry soil often experience large mechanical impedance because the decreased soil water content is associated with increases in soil strength. The combined effect of mechanical impedance and water stress hinders the establishment of seedlings in many soils, but little is known about the interaction between these two stresses. A method has been designed that, for the first time, measured the maximum axial force exerted by a root growing under controlled water stress. Using this technique the axial force exerted by a pea radicle was measured using a shear beam, while the seedling was suspended in an aerated solution of polyethylene glycol 20 000 at osmotic potentials between 0 and −0.45 MPa. The maximum growth force was then divided by the crosssectional area of the root to give the maximum axial growth pressure. The value of maximum axial growth pressure decreased linearly from 0.66 to 0.35 MPa as the osmotic potentials of the solution of PEG decreased from 0 to −0.45 MPa. In dry soil, therefore, the maximum strength of soil that a root can penetrate is decreased because of the decrease in maximum growth pressure. The elongation rates of unimpeded roots were similar whether the roots were subject to either a matric potential in soil or to an osmotic potential in a solution of PEG.

Priority for allocation of water‐soluble carbohydrate reserves during regrowth of Lolium perenne

A glasshouse study was undertaken to determine the priority within the perennial ryegrass (Lolium perenne L.) plant for leaf and root growth and daughter tiller initiation after defoliation, in relation to various levels of water‐soluble carbohydrate (WSC) reserves at defoliation. Individual plants were arranged in mini‐swards, and underwent varying defoliation frequencies and ambient temperatures before defoliation, and harvest heights at defoliation, to obtain a gradient of WSC content at H1, the date when all plants were defoliated. Defoliation interval consisted of defoliating either three times at the one new leaf tiller–1 stage (1‐leaf stage) of regrowth, or once only at the 3‐leaf stage, up to H1, while night temperature in the week prior to H1 was altered from 15°C to either 8 or 20°C. At H1, plants were defoliated to a stubble height of either 20 or 50 mm. Plants were subsequently destructively harvested at days 4, 6, 8, 12, 18 and 27. Leaf and root extension and tiller dynamics were also measured.On a regrowth timescale, tiller initiation was most sensitive, root regrowth moderately sensitive, and leaf regrowth relatively insensitive to a decrease in WSC. The time of daughter tiller initiation also coincided with replenishment of stubble WSC levels.In contrast to this sequence of regrowth events following defoliation, the quantitative effects on growth were different, with elongation and survival of roots most affected by reduced WSC levels. A 30‐fold difference in stubble WSC at H1 between high and low WSC plants (1·52 vs. 0·05 mg tiller–1) produced only a 4‐fold increase in leaf dry matter (DM) after 27 d (2·2 vs. 0·6 g plant−1), while tiller number plant−1 increased 6‐fold (138 vs. 23% increase in tiller number from H1). Root elongation rate was 59 times higher in the high than in the low WSC plants (1·18 vs. 0·02 mm d−1).From a pasture management perspective, the study confirms that defoliation, coinciding with the 3‐leaf stage of regrowth and around a stubble height of 50 mm, optimizes persistence and productivity of perennial ryegrass. By allowing more rapid replenishment of WSC reserves, this optimal defoliation strategy enables a greater proportion of WSC to be allocated to maintain a more active root system, and promotes tillering, compared with more frequent and close defoliation.

The tropic response of plant roots to oxygen: oxytropism in Pisum sativum L.

Plant roots are known to orient growth through the soil by gravitropism, hydrotropism, and thigmotropism. Recent observations of plant roots that developed in a microgravity environment in space suggested that plant roots may also orient their growth toward oxygen (oxytropism). Using garden pea (Pisum sativum L. cv. Weibul's Apollo) and an agravitropic mutant (cv. Ageotropum), root oxytropism was studied in the controlled environment of a microrhizotron. A series of channels in the microrhizotron allowed establishment of an oxygen gradient of 0.8 mmol mol-1 mm-1. Curvature of seedling roots was determined prior to freezing the roots for subsequent spectrophotometric determinations of alcohol dehydrogenase activity. Oxytropic curvature was observed all along the gradient in both cultivars of pea. The normal gravitropic cultivar showed a maximal curvature of 45 degrees after 48 h, while the agravitropic mutant curved to 90 degrees. In each cultivar, the amount of curvature declined as the oxygen concentration decreased, and was linearly related to the root elongation rate. Since oxytropic curvature occurred in roots exposed to oxygen concentrations that were not low enough to induce the hypoxically responsive protein alcohol dehydrogenase, we suspect that the oxygen sensor associated with oxytropism does not control the induction of hypoxic metabolism. Our results indicate that oxygen can play a critical role in determining root orientation as well as impacting root metabolic status. Oxytropism allows roots to avoid oxygen-deprived soil strata and may also be the basis of an auto-avoidance mechanism, decreasing the competition between roots for water and nutrients as well as oxygen.

Time Lapse Analysis of Root Elongation Rates of Rice and Sorghum During the Day and Night

This paper describes a technique to monitor the root elongation rate (RER) per hour for several days, and variation in RER during the day and night. Rice (Oryza sativaL.) and sorghum (Sorghum bicolorMoench) were grown in root boxes placed inside a growth chamber set at 25 °C with a 12 h photoperiod. Seminal root axes were sandwiched between a transparent acrylic board and filter paper placed on a loamy sand soil. The roots were photographed under dim green light using a CCD camera connected to a time lapse video recorder. The environment of the root, including temperature, light, nutrient, water and air supply, was controlled precisely and maintained constant. RER fluctuated hourly in sorghum and to a greater extent in rice. Maximum RERs were 1.4 to 4.4 times faster than minimum rates. RERs during the day and night did not differ statistically when temperatures were the same.

Large Sunflower Seeds are Characterized by Low Embryo Vigor

The cause for the differences in germination ability of large and small confection sunflower (Helianthus annuus L.) seeds was investigated over 3 years. The source-sink relationship was manipulated to better explore the differences between seeds of various sizes and to study the role of the embryo and the pericarp (hull) in controlling germination ability. Percent germination of large seeds was significantly lower than that of small seeds when tests were performed at 15 °C. Increasing the ratio of leaf area to number of developing seeds caused an increase in mean seed mass, but resulted in a lower percentage of germination. Seed vigor, as measured by mean time to germination or to emergence of hulled seeds or by rate of root elongation, was negatively correlated with embryo mass, indicating that the low vigor of large seeds is not due to the mechanical barrier imposed by the hull. Analysis of electrolyte leakage confirmed the hypothesis that the low quality of large seeds results from a disturbance during the process of seed development.

Loblolly Pine Root Growth and Distribution under Water Stress

AbstractA rhizotron study was conducted to assess the relationship between soil water availability and shoot and root growth of loblolly pine (Pinus taeda L.) under conditions where O2 availability and mechanical resistance were considered not limiting. Relationships between soil water availability and (i) root growth rate, (ii) root distribution, (iii) growth periodicity, and (iv) above‐ and belowground allocation were evaluated under four watering regimes ranging from maintaining profile near field capacity (WK 1) to withholding moisture for 4 wk (WK 4). The final distribution of cumulative root growth was similar among watering treatments, even though root growth shifted downward with depth during the growing period due to water depletion in surface soils. Relative root elongation rates were found to be linearly related to soil water potential. The strength of this relationship was improved by considering only periods of active root growth. Reductions in above‐ and belowground growth were proportional among water‐restricting treatments. Stem volume and root growth in the driest treatments were reduced 46 and 41%, respectively, compared with the WK 1 cells, indicating that patterns of biomass allocation above and below ground were similar among treatments. In the absence of other limiting soil factors, flushes of root growth in this study were a function of relatively short‐term changes in soil water potential. Our results indicate that when maximum tree biomass is desired, management efforts in establishing pine should be aimed at reducing any restrictions to root growth during establishment.

Root Response to Magnetostatic Field

Magnetostatic stimuli were fairly applied to the tip of seminal roots of Maize and the response was observed. At 72 hours after sowing, the test seminal roots with almost equal length of 60 mm started to be exposed to seven levels of magnetic field strength, 0.5, 1.6, 5, 16, 50, 160 and 500-G (Gauss) in magnetic flux density, during 48 hours. Start-up drops and rapid recovering in elongation rate clearly appeared to occur for all test roots, and the recovering elongation rates reached about ten times as high as controls. Within 6 hours after the exposure-on to magnetic filed, the high increases in elongation rate of test roots relaxed and decreased to the almost same value of controls. Stimuli by exposure-off of magnetic field induced no significant variations in a rate of root elongation.

Root Growth and Oxygen Relations at Low Water Potentials. Impact of Oxygen Availability in Polyethylene Glycol Solutions1

AbstractPolyethylene glycol (PEG), which is often used to impose low water potentials (ψw) in solution culture, decreases O2 movement by increasing solution viscosity. We investigated whether this property causes O2 deficiency that affects the elongation or metabolism of maize (Zea mays L.) primary roots. Seedlings grown in vigorously aerated PEG solutions at ambient solution O2partial pressure (pO2) had decreased steady-state root elongation rates, increased root-tip alanine concentrations, and decreased root-tip proline concentrations relative to seedlings grown in PEG solutions of above-ambientpO2 (alanine and proline accumulation are responses to hypoxia and low ψw, respectively). Measurements of root pO2 were made using an O2 microsensor to ensure that increased solutionpO2 did not increase rootpO2 above physiological levels. In oxygenated PEG solutions that gave maximal root elongation rates, rootpO2 was similar to or less than (depending on depth in the tissue) pO2 of roots growing in vermiculite at the same ψw. Even without PEG, high solution pO2 was necessary to raise rootpO2 to the levels found in vermiculite-grown roots. Vermiculite was used for comparison because it has large air spaces that allow free movement of O2 to the root surface. The results show that supplemental oxygenation is required to avoid hypoxia in PEG solutions. Also, the data suggest that the O2 demand of the root elongation zone may be greater at low relative to high ψw, compounding the effect of PEG on O2 supply. Under O2-sufficient conditions root elongation was substantially less sensitive to the low ψwimposed by PEG than that imposed by dry vermiculite.

Analysis of cell division and elongation underlying the developmental acceleration of root growth in Arabidopsis thaliana.

To investigate the relation between cell division and expansion in the regulation of organ growth rate, we used Arabidopsis thaliana primary roots grown vertically at 20 degreesC with an elongation rate that increased steadily during the first 14 d after germination. We measured spatial profiles of longitudinal velocity and cell length and calculated parameters of cell expansion and division, including rates of local cell production (cells mm-1 h-1) and cell division (cells cell-1 h-1). Data were obtained for the root cortex and also for the two types of epidermal cell, trichoblasts and atrichoblasts. Accelerating root elongation was caused by an increasingly longer growth zone, while maximal strain rates remained unchanged. The enlargement of the growth zone and, hence, the accelerating root elongation rate, were accompanied by a nearly proportionally increased cell production. This increased production was caused by increasingly numerous dividing cells, whereas their rates of division remained approximately constant. Additionally, the spatial profile of cell division rate was essentially constant. The meristem was longer than generally assumed, extending well into the region where cells elongated rapidly. In the two epidermal cell types, meristem length and cell division rate were both very similar to that of cortical cells, and differences in cell length between the two epidermal cell types originated at the apex of the meristem. These results highlight the importance of controlling the number of dividing cells, both to generate tissues with different cell lengths and to regulate the rate of organ enlargement.

Spatial distributions of tissue expansion and cell division rates are related to irradiance and to sugar content in the growing zone of maize roots

We have investigated the way in which the radiation absorbed by leaves affects the rate of elongation of maize (Zea mays L.) roots. In five repeated growth chamber experiments, plants previously grown at a photon irradiance of 23 mol m–2 d–1 received either 7 or 34 mol m–2 d–1 from day 10 to day 20 after germination. The elongation rate of primary roots steadily decreased for 4 d after reduction in irradiance and then stabilized at 60% of that in plants at high irradiance. The elongating zone was slightly shorter after 2 d at low irradiance, and was further reduced after 8 d. The concentrations of sucrose and glucose in the elongating zone were greatly decreased after 2 d at low irradiance and the gradient of both sugars was suppressed. The longer period at low irradiance affected neither sugar content nor gradient. In the same way, cell production rate was reduced after 2 d at low irradiance and was not appreciably decreased afterwards. The root zone with cell division was shorter in plants at low irradiance, but cell division rate remained nearly constant temporally and spatially, and was unaffected by the irradiance treatment. Our results suggest that primary events after a reduction in irradiance were a change in cell flux and sugar content in the elongating zone. Change in elongation rate was slower and probably the result of a time‐related developmental effect, which may be related to the change in cell production.

PH influence on root growth and nutrient uptake of Pinus pinaster seedlings

Two-week old Pinus pinaster seedlings were grown at four pH values ranging from 3.5 to 6.5. Root elongation rate progressively decreased with the duration of treatment at 3.5 and 6.5 pH. After 4 weeks 3.5 pH gron roots showed the lowest lenth and the highest biomass because of their marked thickening. The pH of the culture solution did not influence lateral root initiation, whereas it affected their length, that was highest at 3.5 pH and lowest at 6.5 pH. Mineral nutrition was affected by the pH of the culture solution. The P, Fe and Al concentration in roots was higher in the 3.5 pH and 4.5. pH solutions. On the contrary a lower K, Ca, Mg and especially Mn content of roots was measured in the 3.5 pH grown seedlings. These results suggest that P pinaster is able to grow on a wide range of acidic soils changing the morphology of the root system in relation to soil conditions.

Root and shoot elongation of rhizotron-grown seedlings of Eucalyptus nitens and Eucalyptus globulus in relation to temperature

Information on the growth response of a crop plant in relation to temperature can be helpful in selecting genotypes to suit local environments, scheduling favourable time of planting and forecasting growth and yield. To determine the effects of varying temperature on root and shoot elongation of eucalypt seedlings, elongation rates of roots and shoots were measured in rhizotrons for two species (Eucalyptus nitens (Deane and Maiden) Maiden, and Eucalyptus globulus Labill.) at a temperature range of 5–23 °C. Within this range of temperatures, elongation rates of roots and shoots of both species increased with an increase in temperature. Roots of E. globulus were more sensitive and shoots less sensitive to temperature than those of E. nitens. However, the threshold temperature corresponding with zero elongation rate predicted from the regression of elongation rate against temperature was similar for the roots (∼5 °C) and shoots (∼0 °C) of both species. Hysteresis did not appear to have a significant influence on root or shoot elongation of both species during warming compared with cooling. Results are discussed highlighting the importance of the interaction between development and growth of plant components.

Characterization and Distribution of Soils at Lambir Hills National Park in Sarawak, Malaysia, with Special Reference to Soil Hardness and Soil Texture.

For the rehabilitation of the degraded and abandoned land in the tropical area, it needs to define the various characteristics of remaining natural forests. This work was done to find out a physical hazard for root elongation of plant at Lambir Hills National Park, Miri, Sarawak, Malaysia, with special reference to soil hardness and soil texture. Furthermore, soil moisture and soil temperature were monitored at the hill ridge and at the valley to show their annual fluctuation. Soil physico-chemical properties at the hill ridge and the valley were also investigated. At the hill ridge, well-developed soils with a deep solum were found. Organic matter content was high only at the surface horizon (0-5 cm) where a root mat develops. Although soil moisture content fluctuated significantly, the soil was dry throughout the monitoring period. On the other hand, at the valley, soil moisture content was relatively stable even after the frequent rainfall. The small particles and nutrients at the valley have been brought by the continuous water and eroded particles supply from surroundings. Based on the topographical investigation, the study area was roughly divided into 3 categories: 1) Steep slope area : Soil and vegetation status may be often affected and modified by the land slide or soil erosion. Soil texture was sandy loam, loamy sand, or loam. Gravelly materials often appeared in the subsurface layer at the depth of 20-40 cm, which are hard for root to penetrate into. This layer can be regarded as the one with physical hazard against root penetration. 2) Gentle slope area : Soil and vegetation status are relatively stable for a long time. Soil texture was light clay or heavy clay. Transported clayey materials were accumulated to a depth below 20 cm, and/or the in-situ weathering in the deeper part could have occurred because of the relatively stable topography. 3) Ridge area : Although soil and vegetation status looks stable in view of topography, moisture condition much fluctuated. Soil texture was clay loam or sandy clay loam, which was the middle range between that of a steep slope area and a gentle slope area. The physical hazard in the soil might not be found, but the rates of root elongation and plant growth may be slow since the soil is prone to be dry.