Root Moisture Research Articles

Adaptive Responses of Soybean and Cotton to Water Stress: I. Transpiration Changes in Relation to Stomatal Area and Stomatal Conductance

The adaptive responses of soybean and cotton to various irrigation levels were explored in terms of transpiration, stomatal role in transpiration, leaf temperature (Tl) and CO2 assimilation rate (An). Compared with cotton, soybean showed a lower flow rate of stem sap (FRSS), transpiration rate (E), stomatal conductance (gs), stomatal density and An and had a smaller stomatal area but larger leaf area, heavier root dry matter and higher Tl at all irrigation levels. Under water stress conditions, FRSS, E, gs, and An decreased and Tl increased more in soybean than in cotton. Stomatal area decreased in response to water stress though nonsignificantly but stomatal density was not affected by water stress in soybean. Stomatal area decreased significantly in response to water stress in cotton. We concluded that soybean and cotton adapted to water stress differently. Soybean adapted to water stress by reducing transpiration while cotton adapted to water stress by maintaining higher transpiration as compared with soybean. Soybean reduced the transpiration rate by reducing gs. Reduction of gs in soybean was due to reduced FRSS, which might have resulted from the lower root moisture absorption efficiency. The higher transpiration in cotton was due to a higher gs, which was supported by a higher FRSS, larger stomatal area, and probably the diaheliotropism. The higher gs and transpiration rate suppressed the increase in Tl thus preventing the decrease of An in response to water stress.

Compositional and Sensory Analyses of Sweetpotatoes after X-ray Irradiation Quarantine Treatment

Sweetpotato [Ipomoea batatas (L.) Lam.] roots of two Hawaii-grown clones were treated with 100 to 600 Gy X-ray irradiation and evaluated for quality before and after cooking. Root moisture content, surface color, and glucose and fructose concentrations were not affected by irradiation treatment for either the red-skin, yellow-flesh (RY) or the white-skin, purple-flesh (WP) clones. Firmness decreased at higher doses for RY roots, but not for WP roots. The alcohol insoluble solids and the starch concentrations of raw roots decreased linearly in response to increasing dose for both clones. Maltose decreased at higher doses in cooked RY roots only. Irradiation had the greatest effect on sucrose concentrations, which increased linearly in response to dose as starch concentrations decreased. A sensory panel perceived sweetpotato roots treated with 600 Gy irradiation as sweeter than control roots. Panelists found the overall acceptability to be the same for control and 600 Gy treated roots for both clones.

NON-STRUCTURAL CARBOHYDRATE CONTENT AS AN AID FOR INTERPRETING QUALITY TESTING OF NURSERY STOCK PLANTS

The effects of lifting date and increasing drought stress on root electrolyte leakage (REL) and moisture content of seedlings of Carpinus betulus, Fagus sylvatica and Picea abies were assessed to obtain threshold values for predicting plant quality. The relationships of REL and moisture content to survival were determined. Lifting date influenced REL and moisture content; a higher shoot moisture content (SMC) was found in October and March/April, while highest REL and moisture percentage of the roots was found in October. Furthermore, interpreting values of REL and moisture content without knowledge of the 'hardened' or 'dehardened' state of the plant could lead to wrongly classifying plant quality. Seasonal observations of bud dormancy showed that bud dormancy is insufficient for indicating the 'hardened' and thus more stress supporting state of the plant. Seasonal changes of nonstructural carbohydrates indicated that for the studied species the presence of raffinose and/or stachyose in bud or stem tissue were good indicators for 'hardened plants' and could help to interpret REL values and moisture content levels with respect to plant quality assessment.

Forced-air drying of ginseng roots: 2. Control strategy for three-stage drying process

Previous research showed that a three-stage (38–50–38 °C) drying process produced equivalent dried root quality in a shorter time relative to drying at a constant temperature of 38 °C which is typical in commercial ginseng dryers. However, unless air temperature changes occurred at specific moisture levels, there were unacceptable changes in root colour. Digital images of roots were used to monitor volume shrinkage as an indirect measure of moisture content and to confirm critical points to adjust drying air temperature. Volume shrinkage was limited when root moisture was less than 18% (wet basis) so the drying end point at 10% moisture (wet basis) was estimated with a kinetic model. Model parameters depended on root size and shape and were estimated from thin-layer drying experiments. Quality of roots dried by a three-stage process was not significantly different from roots dried at a constant air temperature of 38 °C in terms of internal colour and ginsenoside content. Drying times were in the range of 100–150 h for the three-stage process compared to 180–200 h at 38 °C.

The impact of storage, desiccation and planting date on seedling quality and survival of woody plant species

A comparative study of nine tree species was carried out to investigate the effects of ambient storage, desiccation and planting date on seedling quality. The ability of plant morphological and physiological indicators to detect damage and predict field performance after out‐planting was also tested. After lifting from the nursery bed, plants were either stored under ambient conditions or subjected to desiccation for 3 h, and seedling condition was assessed by measuring fine root electrolyte leakage, fine root moisture content, root moisture content, shoot moisture content and shoot water potential. Treated and control seedlings were planted in the experimental fields. Ambient storage affected the pre‐planting vitality indicators of some species, but no consistent and significant effects were found in survival between the control and stored planting stock. Pre‐planting measurements showed a significant effect of treatments on plant condition. Desiccation adversely affected the physiological parameters and survival of most plants. Seedlings planted in March showed reduced survival compared with those planted in February. Pre‐planting measurements were related to spring survival means but the results were very poor in autumn when survival was very low.

Effects of Root Drying Temperature and Moisture Content on the Levels of Active Ingredients in Echinacea Roots

ABSTRACT The effects of drying temperature and final moisture contents on the levels of cichoric acid, echinacoside, chlorogenic acid and polysaccharides in roots of Echinacea purpurea, Echinacea angustifolia, and Echinacea pallida were studied. Increases in drying temperature increased the level of cichoric acid in Echinacea purpurea, and Echinacea pallida. Increases in root moisture increased the level of echinacoside in Echinacea angustifolia, and Echinacea pallida, and increased the level of chlorogenic acid in Echinacea angustifolia. Polysaccharide contents were significantly affected by moisture levels only in Echinacea angustifolia, and Echinacea pallida.

Effects of desiccation and freezing on vitality and field performance of broadleaved tree species

) and freezing (–5 °C, darkness).The effect of stress factors on seedling quality was assessed using root electrolyte leakage, water potential and moisture content offine roots. After treatments, seedlings were outplanted in a field site. The effects of desiccation and freezing on planting stock quali-ty and field performance varied and depended upon the length of exposure and species. Root electrolyte leakage values were signifi-cantly related to field performance rates of seedlings exposed to both stress factors. Root moisture content and root water potentialwere related to survival only in the case of desiccation treatment. seedling quality / survival / planting stock / desiccation / freezingResume – Effets du dessechement et de la congelation sur la vitalite et la performance des plants d’especes arborees platy-phylles. Des plants d’Acer pseudoplatanus L., Fraxinus ornusL. et Castanea sativa Miller, ont ete soumis a des traitements condi-tionnes controles de dessechement (15 °C, 50 % HR, mouvement d’air 0.3 ms

Effects of temperature and moisture on carbon respired from decomposing woody roots

Controls of temperature and moisture on root decomposition have not been well studied despite their direct relevance to climate change impacts on root carbon flux. The main objective of this laboratory study was to examine the respiration response of Sitka spruce, Douglas-fir, western hemlock, ponderosa pine, and lodgepole pine decomposing roots (1–3 cm in diameter) to temperature and moisture change. Roots of Sitka spruce, Douglas-fir and western hemlock, and ponderosa pine and lodgepole pine were collected from Cascade Head, H.J. Andrews, and Pringle Falls site, respectively. Dead root respiration increased with temperature and reached the maximum at 30–40°C, and then decreased. Analysis of covariance indicated that the Q 10 of root decomposition rate was influenced significantly ( p<0.01) by incubation temperature range 5–40°C, but not by species, decay class or the direction of temperature change. At 5–10°C, Q 10 averaged 3.99 and then decreased to 1.37 at 30–40°C. Over a range of 5–60°C, Q 10 could be predicted by a single-exponential model using temperature as the independent variable. Analysis of variance showed that the respiration rate of dead roots was significantly ( p<0.01) influenced by root moisture, species, and decay class as well as temperature. Dead root respiration increased with root moisture, reached the optimum range when moisture was between 100 and 275% and then decreased. Moreover, there were apparent interactions of root moisture and temperature on root respiration. Our study showed the direction of temperature and moisture change did not significantly influence root respiration, indicating that hysteresis may not occur for the temperature and moisture ranges examined. To better model global climate warming effects on root carbon flux, we suggest a temperature dependent Q 10 function should be incorporated into current root dynamics models. The short-term laboratory incubation approach provided a good way to examine temperature and moisture controls on root decomposition, although we are cautious about long-term mass-loss extrapolations based on these short-term results.

The effect of pre-planting desiccation stress and root pruning on the physiological condition and subsequent field performance of one year old Prunus avium and P. cerasifera seedlings

SummarySevere desiccation of dormant seedlings of wild cherry (Prunus avium) and cherry plum (P. cerasifera) did not affect their immediate survival, but caused significant reductions in subsequent shoot growth and root volume which were not recovered in a single growing season. Damage to the fine roots, as indicated by the physiological plant quality measures of tetrazolium absorbance and root electrolyte leakage, increased rapidly over drying periods of ca. 6 h, further damage requiring progressively longer periods of desiccation. Root pruning prior to planting did not mitigate desiccation damage and severe pruning was highly injurious to subsequent growth. Generally the removal of the fine roots was equivalent to a relatively short desiccation period, but pruning of fine roots prior to, instead of after, desiccation in P. cerasifera resulted in more lateral shoots, possibly indicating the production of growth retardant substances by the dried root systems. All measures of physiological plant quality at the beginning of the growing season were effective as predictors of plant performance at the end. In the species tested, the most cost-effective routines are likely to be fine root electrolyte leakage and root moisture content, with tetrazolium testing and stem water potential measurements requiring both greater reproducibility and more sophisticated equipment.

Fine root electrolyte leakage and moisture content: indices of Sitka spruce and Douglas-fir seedling performance after desiccation

In spring 1992, 2-year-old bare-rooted seedlings of Sitka spruce (Picea sitchensis (Bong.) Carr.) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) were exposed for 0, 0.5, 1.0, 1.5, or 3 h in a controlled environment room at 20°C. Plants were desiccated in batches during February and March; 100 seedlings of each species were planted in 5 20-plant plots at each of 6 planting sites using the normal planting times and methods of each area. The effect of exposure was assessed within 24 h of desiccation on a subsample of plants by measuring fine root moisture content and electrolyte leakage and, in a limited number of cases, needle water potential. These measures were related to survival and growth after the first and second growing seasons.

The introduction of macroscale hydrological complexity into land surface-atmosphere transfer models and the effect on planetary boundary layer development

The importance of surface hydrological processes on land surface-atmospheric fluxes is currently a major topic of investigation. It has been shown that the division of available energy into latent and sensible heat is sensitive to the prevailing hydrological conditions. Planetary boundary layer development is indicative of the amount of sensible heat being supplied to the lower atmosphere. Feedback mechanisms imposed by the boundary layer on the evaporative potential near the surface are also important. This paper uses a simple slab planetary boundary layer (PBL) model to show how PBL development is affected under a range of hydrological model scenarios. The investigation commences using a one-dimensional, single soil moisture root zone store model, which will represent the hydrological representation seen in current SVAT (soil-vegetation-atmosphere transfer) models. This model is the benchmark against which more complex models are tested and is also used to show the sensitivity of the PBL model to antecedent soil moisture conditions. A further level of complexity is added using the topographically derived distribution function model TOPMODEL. TOPMODEL introduces a water table that interacts with the root zone stores. The role of laterally redistributed water within a catchment or grid cell on the PBL is demonstrated; under certain circumstances, a spatially varying water table can substantially change the development of the PBL. A distribution function structure model showing a hydrological structure that includes spatially varying available water capacity (AWC) is also described. It is shown that the PBL development is sensitive to the spatial variability of available water and so can be highly dependent on the hydrological scenario at the land surface.

A root moisture sensor for plants in microgravity

Development of components for bioregenerative life-support systems is a vital step toward long-term space exploration. The culturing of plants in a microgravity environment may be optimized by the use of appropriate sensors and controllers. This paper describes a sensor developed for determining the amount of fluid (nutrient solution) available on the surface of a porous ceramic nutrient delivery substrate to the roots of conventional crop plants. The sensor is based on the change in thermal capacitance and thermal conductance near the surface as the moisture content changes. The sensor could be employed as a data acquisition and control sensor to support the automated monitoring of plants grown in a microgravity environment.

Some Methods of Cold Storage can Seriously Affect Root Growth Potential and Root Moisture Content and Subsequent Forest Performance of Sitka Spruce and Douglas Fir Transplants

Some Methods of Cold Storage can Seriously Affect Root Growth Potential and Root Moisture Content and Subsequent Forest Performance of Sitka Spruce and Douglas Fir Transplants

Effects of Russian wheat aphid infestation on barley plant response to drought stress

The influence of Russian wheat aphid (Diuraphis noxia Mordvilko) infestation on the response of barley (Hordeum vulgare L. ev Hazen) plants to drought stress was investigated. Fourteen‐day‐old plants were infested with eight apterous adult aphids, which were removed 7 days later with systemic insecticide. Leaves previously infested with aphids had lower relative water content, reduced stomatal conductance, more negative water potential, lower levels of chlorophyll and higher levels of amino‐N, proline and glycinebetaine than corresponding leaves from uninfested plants. When water was withheld for a period of 7 days after aphids were removed, the relative water content of previously infested plants dropped steadily from 0.89 to 0.60, while the relative water content of uninfested plants remained at about 0.94 for the first 4 days of the drought stress period followed by a steady drop to about 0.77 by the end of the drought stress period. Leaf water potentials dropped steadily during the drought stress period in both previously infested (‐1.14 to ‐1.91 MPa) and unin‐fested (‐0.54 to ‐1.52 MPa) plants. Analysis of glycinebetaine and proline levels at the end of the drought stress period indicated that leaves of previously infested plants accumulated lower levels of these solutes than leaves from uninfested plants. Upon alleviation of drought stress, plants previously infested with aphids showed little increase in dry weight while younger leaves and tillers from uninfested plants showed large increases. It is concluded that Russian wheat aphids cause drought‐stress symptoms in leaves of infested plants even in the presence of ample root moisture. The observations of low levels of glycinebetaine and proline present in leaves after water was withheld from roots and lack of leaf growth upon alleviation of drought stress in previously‐infested plants, suggest that aphid infestation limits the capacity of barley plants to adjust successfully to drought stress.

Application of an Extraction‐Term Model to the Study of Moisture Flow to Plant Roots1

AbstractA one‐dimensional extraction‐term model is used to simulate the moisture flow and removal process in the vicinity of plant roots. The dependence of model results on root depth and soil type are investigated. Moisture contents, root moisture absorption rates and soil moisture fluxes are computed and discussed for several hypothetical root systems in a sandy soil and in a clay soil.The model is solved numerically with a procedure based on the Douglas‐Jones predictor‐corrector method. Results indicate that moisture extraction by the roots from soil in their immediate vicinity is the dominant process, with Darcian flow in the root zone playing a smaller but often significant role.Extraction‐term models are versatile and seem able to describe many of the phenomena associated with moisture removal by the roots of transpiring plants.

Root Moisture Extraction Profiles of Various Weeds

Root moisture extraction profiles varied from 20 square feet for Kochia scoparia (L.) Schrad, (kochia to 44 square feet for Xanthium pennsylvanicum Wallr. (cocklebur). Weeds within the extremes with increasing root moisture extraction profiles were Eragrostis pectinacea (Michx) Ness (tufted lovegrass), Solanum rostratum Dunal. (buffalobur), Digitaria sanguinalis (L.) Scop. (large crabgrass), Tribulus terrestris L. (puncturevine), Salsola kali L., var. tenuifolia Tausch (Russian thistle), Amaranthus palmeri S. Wats. (Palmer amaranth) and sorghum.