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  • 1
    Electronic Resource
    Electronic Resource
    Concurrent measurements of stem density, leaf and stem water potential, stomatal conductance and cavitation on a spaling of Thuja occidentalis L. (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 7 (1984), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Concurrent estimates of stem density, leaf and stem water potential, stomatal conductance and ultrasonic acoustic emissions (cavitations) in an excised sapling of Thuja occidentalis L. were made. As the sapling dehydrated in air, the decline in leaf water potential to about - 2.0 MPa was followed by apparent rehydration of the foliage while the stem showed no sign of rehydration. The rate of acoustic emissions peaked prior to the onset of rehydration which coincided with virtual stomatal closure. There was a significant decline in stem density until maximum foliage rehydration level was reached. From this point, leaf water potential, stem water potential and stem density continued a relatively slow decline while acoustic emission rate and stomatal conductance remained low.Removal of the bark and majority of foliage from the sapling resulted in increased cavitation and more rapid deelines in leaf and stem water potential and stem density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11592146
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  • 2
    Electronic Resource
    Electronic Resource
    Water relations of the tomato during fruit growth (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 15 (1992), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Fruit and stem water potentials of tomato plants were measured continuously for several days using automated psychrometers. A linear voltage displacement transducer was used to simultaneously measure diameter changes on an adjacent fruit. A strong correlation was observed between the water potential gradient of the fruit and stem, and changes in fruit diameter. Fruit diameter increased when the apoplasmic water potential gradient favoured solution flow into the fruit and fruit shrinkage occurred only when the water potential gradient was inverted. Based on our data and other published data (Ehret & Ho 1986; Lee 1989a) on phloem transport in tomato, we have concluded that low stem water potentials have an immediate and direct effect on phloem turgor; reducing the driving force for sap flow into the fruit. Since fruit water potential remained relatively constant, the diurnal variation in stem water potential was sufficient to account for the correlation with changes in fruit diameter. There are consequences with respect to predicting the accumulation of dry matter in tomato fruit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1992.tb01027.x
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  • 3
    Electronic Resource
    Electronic Resource
    A new stem hygrometer, corrected for temperature gradients and calibrated against the pressure bomb (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 7 (1984), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract A simple stem hygrometer for attachment to a bared section of sapwood or a cross-sectional cut end of a shoot is described. Two welded chromelconstantan thermocouples inside the chamber, one touching the sample and the other in the chamber air, allowed measurement of and correction for the temperature gradient between the sample and the dewpoint measuring junction. The instrument was attached to the cut end of an apical shoot of Thuja occidentalis L. protuding from a Scholander-Hammel pressure bomb. Cut-end water potential (ψhyg), measured using the stem hygrometer, was compared to xylem pressure potential (ψxp) while the latter was manipulated in the pressure bomb. After an initial equilibration time of 3–4 h, hygrometer equilibrium values were achieved within 1.5–4.0 min of changing ψxp in the pressure bomb. The half-time (ψ1/2) for vapour pressure equilibration was 15–40 s. Stable temperature gradients between the sample and dewpoint measuring junction of 0.01–0.1°C were measured. Correcting ψhyg for the temperature gradient resulted in excellent agreement with ψxp.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11572454
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  • 4
    Electronic Resource
    Electronic Resource
    Field measurement of leaf water potential with a temperature-corrected in situ thermocouple psychrometer (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 11 (1988), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. The construction and evaluation of a temperature-corrected in situ thermocouple psychrometer for measurement of leaf water potential (Ψ) is described. The instrument utilized two chromel-constantan thermocouples which allowed for detection of both the psychrometric zero offset and the temperature differential between the sample and the Peltier measuring junction. The psychrometer was subjected to stable temperature gradients while in contact with reference solutions of sodium chloride, and the effects of thermal gradients were quantified. Regression analysis indicated that temperature differentials were responsible for errors in water potential determinations of approximately –7.73 MPa°C−1. When installed on leaves of field-grown cotton (Gossypium hirsutum L.), corn (Zea mays L.) and soybean (Glycine max L. Merr) the instrument detected temperature differentials up to 0.1°C (–6.0 μV) which were associated with relatively small shifts in psychrometric zero offsets (–0.05––0.75 μV). Results indicated that substantial errors in apparent Ψ were caused by non-isothermal conditions between the leaf and the psychrometer measuring junction. The relative magnitude of these errors could be quantified and the corrected results showed good agreement with conventional psychrometric determination of Ψ on excised samples during a diurnal cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1988.tb01137.x
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  • 5
    Electronic Resource
    Electronic Resource
    Stomatal resistance of three potato cultivars as influenced by soil water status, humidity and irradiance (1997)
    Springer
    Potato research 40 (1997), S. 47-57 
    Details
    ISSN: 1871-4528
    Keywords: minimum stomatal resistance ; soil water ; Solanum tuberosum L. ; photosynthetic photon flux density ; vapour pressure deficit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Leaf stomatal resistance varies considerably in response to changes in environmental conditions. Understanding cultivar differences in the response of stomata to these conditions is important for effectively simulating water-use and growth. In this study the stomatal resistance of three field grown potato (Solanum tuberosum L.) cultivars Atlantic. Monona and Norchip was observed in response to photosynthetic photon flux density, leaf to air vapour pressure difference and root zone available soil water. Substantial variation in stomatal resistance was accounted for by functions of the environmental variables for both Monona and Norchip. The explained variation for Atlantic was considerably less. Light saturation occurred near 500 μmol m−2 s−1. Increasing stomatal resistance above 1000 μmol m−2s−1 was also observed but is likely an artifact of stomatal closure on days in which mid-day leaf water potentials dropped below critical levels. Although the leaf presumably insufficient to obtain substantial effects. The soil water status was partially linked to the average 1000 h to 1500 h stomatal resistance on clear, sunny days. Significant differences were observed among the cultivars in the response of stomata to changes in the available soil water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02407561
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  • 6
    Electronic Resource
    Electronic Resource
    Non-destructive estimation of potato leaf area index using a fish-eye radiometer (1994)
    Springer
    Potato research 37 (1994), S. 393-402 
    Details
    ISSN: 1871-4528
    Keywords: measurement ; LAI ; Solanum tuberosum L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Leaf area index (LAI) is widely used in many facets of potato (Solanum tuberosum L.) modelling but direct measurements have historically been difficult. This investigation tested the accuracy of a commercially available instrument (LI-COR LAI-2000) for measuring LAI non-destructively on a potato crop. Accurate estimates of LAI were difficult to obtain with small plots of≈1 m2. Results from larger field plots were extremely favourable and indicate that non-destructive measurements of LAI in situ can routinely be estimated within 5 to 10% of the destructively measured LAI. Six thinning tests performed on four potato cultivars produced average root mean square error measurements of LAI that ranged from 0.09 to 0.27.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02358353
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  • 7
    Electronic Resource
    Electronic Resource
    Patterns of stem water potential in field grown potatoes using stem psychrometers (1997)
    Springer
    Potato research 40 (1997), S. 35-46 
    Details
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; in situ
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The first large scale outdoor measurements of potato (Solanum tuberosum L.) stem water potential (SWP) usingin situ temperature-corrected stem psychrometers were performed on three cultivars common to Ontario, Canada (Atlantic, Monona and Norchip). Potato plants were examined under three soil water treatments which included rainfed, irrigated and stressed through the use of rain shelters. Cultivar variations in SWP under both irrigated and rainfed conditions were slight (P〉0.05), although some significant (P〈0.05) differences in mid-day SWP were evident, especially under conditions conducive to high atmospheric water demand. Under these conditions. cv. Atlantic maintained the lowest SWP with cv. Monona highest and cv. Norchip was intermediate. Few differences in pre-dawn SWP were detected between the three cultivars under well watered and rainfed conditions. Under low soil water, significant differences (P〈0.05) were observed. The similar trend of Atlantic maintaining the lowest SWP with Monona the highest was consistent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02407560
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  • 8
    Electronic Resource
    Electronic Resource
    Estimating potato leaf area index for specific cultivars (1997)
    Springer
    Potato research 40 (1997), S. 251-266 
    Details
    ISSN: 1871-4528
    Keywords: LAI ; canopy expansion ; radiation use efficiency ; Solanum tuberosum L. ; soil water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The growth and duration of crop leaf area determines the amount of solar radiation intercepted by the canopy and therefore influences the extent of photosynthesis, evaporation, transpiration and final dry matter yield. The objective of this study was to develop cultivar specific relationships to estimate the daily leaf area index (LAI) for the potato crop (Solanum tuberosum L.) that included the effects of available soil water. The model is divided into three LAI growth stages, the durations of which are partially related to potato heat units (PHU). The LAI in the first stage is estimated from a cultivar specific leaf area-based radiation use efficiency index with a soil water reduction factor. The second stage involves the maintenance of a constant LAI with the duration related to both PHU and a soil water index that can accelerate senescence. The final stage includes a decrease in the LAI from a maximum to zero in response to a cultivar specific PHU accumulation. Model simulations compared favourably with independent LAI measurements obtained with a LI-COR plant canopy analyzer over two seasons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02358007
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  • 9
    Electronic Resource
    Electronic Resource
    Verification of sap flow by heat balance method on three potato cultivars (1997)
    Springer
    Potato research 40 (1997), S. 267-276 
    Details
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; transpiration estimates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A heat balance method for measuring sap flow in actively growing plants was tested on three potato (Solanum tuberosum L.) cultivars Monona, Norchip and Atlantic. The method is based on applying a known heat source to the stem of an intact plant: by measuring the axial and radial heat dissipation the magnitude of sap flow can be quantified. The technique shows promise as 24 h accumulated sap flow measurements were highly correlated (r2=0.935, n=36) with gravimetric measurements of transpiration and produced an average root mean square error (RMSE) of 20 g d−1. The accuracy of the method improved as daily accumulated flow increased. Under low daily flow rates overall RMSE increased, supporting the need for a heat storage term in the heat balance equation. Short term flow rates were less significantly correlated (r2=0.764, n=1572) and produced an average RMSE of 2.89 g h−1. Identification of these short term flow rates during high flow periods may be difficult. The presence of water potential gradients and the likelihood of re-hydration during high flow events may have also affected the short term performance of the method. At low flow rates, many different errors may be introduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02358008
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  • 10
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    Canopy Gas Exchange Response to Moisture Stress in Old and New Maize Hybrid (1997)
    Wiley
    Details
    Publication Date: 1997-01-01
    Print ISSN: 0011-183X
    Electronic ISSN: 1435-0653
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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