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Ning Li and Larry S. Daley

The goal of our project is to develop a non-invasive means to monitor the physiological status of plants. Spectral image acquisition is a powerful analytical approach for determining chemically distinct species in heterogeneous materials. It was found by Callis and Brukner that the combination of a continuously tunable monochromatic light with a thermoelectric-cooled CCD detector offered the best approach. In the in vivo spectra of leaf, researches has been focused on interpreting the visible spectra in terms of the profile of various types of chlorophyll-protein complexes and relating these to selected aspects of plant pathology and physiology. A computer interfaced imaging spectrometer employing a CCD detector was constructed. It can record the transmitted spectra of up to 31,680 positions for each sample. The instrument was used to study in vivo spectra of sugar cane and barley leaves. The light harvesting complex proteins were then `interpreted from the spectra and were shown graphically. Excellent results were also obtained when we measured the relative respiration rate of plant roots. A pH sensitive dye Resazurin was used to show the pH changes around a soybean root. The spectral images changing as a function of time were recorded and the relative respiration rate of any position of the root could be determined.

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S. Miyamoto, J. Henggeler and J. Benton Storey

Irrigated production of pecans in the southwestern United States started with notoriously inefficient flood irrigation along river basins. Today, most surface-irrigated orchards are laser-leveled, and many orchards in upland areas are under sprinkler or drip irrigation. Technical and scientific knowledge for improving water management also has evolved from studying drought effects on tree performance to an improved understanding of water relations, salt effects, evapotranspiration processes, and the distribution of water and salts in irrigated fields. Yet, many growers still experience difficulties with water management and may benefit from maintaining the soil water suction above saturation but below 30 to 40 cb until shuck opening. The soil salinity should be kept below 2.5 dS·m−1, and irrigation water should be applied to essentially the entire root zone for optimum tree growth. Due to extreme soil variability existing in most irrigated fields of the southwestern region, these guidelines alone are not adequate. Soil profiles, root distributions, water quality, and irrigation methods may have to be examined to improve water management.

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John M. Ruter

Temperatures producing heat damage in leaves of Ilex ×meserveae S.Y. Hu `Blue Prince' and Ilex rugosa × cornuta Lindl. & Paxt. `Mesdob' (China Boy) were evaluated using electrolyte leakage and chlorophyll fluorescence techniques. Whole leaves were exposed to temperatures from 30 to 65C for 30 minutes to determine critical midpoint heat-killing temperatures (TJ using electrolyte leakage techniques. The Tm for `Blue Prince' and `Mesdob' was 52.4 ± 0.lC and 53.8 ± 0.lC, respectively. Dark-adapted leaves were heated for 30 minutes in darkness at temperatures between 30 and 57C before chlorophyll fluorescence was measured. Initial (F0) and peak fluorescence measurements were higher at 54 and 55C for `Mesdob' than for `Blue Prince'. Cultivar had no effect on variable fluorescence (F,). Based on the Fv: Fo ratio, `Mesdob' was estimated to have a higher optimal plant growth temperature than `Blue Prince'. The physiologic data support the hypothesis that I. cornuta as a parent conferred heat tolerance to the interspecific hybrid in this study.

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William R. Graves, Robert J. Joly and Michael N. Dana

Honey locust (Gleditsia triacanthos var. inermis Wind.) and tree-of-heaven Ailanthus altissima (Mill.) Swingle] sometimes are exposed to high root-zone temperatures in urban microclimates. The objective of this study was to test the hypothesis that seedlings of these species differ in how elevated root-zone temperature affects growth, leaf water relations, and root hydraulic properties. Shoot extension, leaf area, root: shoot ratio, and root and shoot dry weights were less for tree-of-heaven grown with the root zone at 34C than for those with root zones at 24C. Tree-of-heaven with roots at 34C had a lower mean transpiration rate (E) than those grown at 24C, but leaf water potential (ψ1) was similar at both temperatures. In contrast, shoot extension of seedlings of honey locust grown with roots at 34C was greater than honey locust at 24C, E was similar at both temperatures, and ψ1 was reduced at 34C. Hydraulic properties of root systems grown at both temperatures were determined during exposure to pressure in solution held at 24 or 34C. For each species at both solution temperatures, water flux through root systems (Jv) grown at 34C was less than for roots grown at 24C. Roots of tree-of-heaven grown at 34C had lower hydraulic conductivity coefficients (Lp) than those grown at 24C, but Lp of roots of honey locust grown at the two temperatures was similar.

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M. Ahmedullah and C. R. Rom

86 ORAL SESSION (Abstr. 512-519) CROSS-COMMODITY STRESS PHYSIOLOGY

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Roger Kjelgren and Bradley H. Taylor

86 ORAL SESSION (Abstr. 512-519) CROSS-COMMODITY STRESS PHYSIOLOGY

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Gary W. Stutte

86 ORAL SESSION (Abstr. 512-519) CROSS-COMMODITY STRESS PHYSIOLOGY

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William A. Retzlaff, Ted M. DeJong and Larry E. Williams

86 ORAL SESSION (Abstr. 512-519) CROSS-COMMODITY STRESS PHYSIOLOGY

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Thomas E. Marler

86 ORAL SESSION (Abstr. 512-519) CROSS-COMMODITY STRESS PHYSIOLOGY

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G.A. Picchioni, S. Miyamoto and J.B. Storey

86 ORAL SESSION (Abstr. 512-519) CROSS-COMMODITY STRESS PHYSIOLOGY