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Judith A. Abbott and Louis A. Liljedahl

Sonic vibrational characteristics of intact apples are related to flesh elasticity which is, in turn, related to firmness. Firmness changes in Golden Delicious and Delicious apples were followed during accelerated ripening and under storage conditions. Firmness was measured by Magness-Taylor puncture force and by compression of tissue cylinders (modulus of elasticity and rupture strength) for comparison with sonic vibrational characteristics of intact apples. Influences of apple temperature, size, shape, and skin on sonic spectra were investigated. Sonic resonant frequencies were significantly correlated with destructive firmness measurements and decreased as storage time increased. Sonic amplitudes were not closely related to firmness. Regression equations incorporating sonic data and size were developed to predict Magness-Taylor force. Use of sonic vibrational characteristics is proposed as a rapid nondestructive method for firmness sorting of apples.

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Robert E. Rouse, Sandra P. Perez and Sally B. Davenport

The Minolta chlorophyll meter SPAD-502 (Minolta Camera Company, 101 Williams Drive, NJ 07446, USA) was evaluated as an accurate, nondestructive means to measure chlorophyll content in citrus leaves. Meter readings from leaves of sweet orange and grapefruit citrus cultivars were used to develop a standard curve for citrus. A significant correlation value of 0.96 was calculated between the chlorophyll meter readings and actual chlorophyll extraction levels. The development of a standard curve using the SPAD-502 chlorophyll meter had not been established on citrus. The SPAD-502 chlorophyll meter proved to be a quick, accurate, simple, and nondestructive way to determine chlorophyll content in citrus leaves.

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Julia L. Whitworth, Andy Mauromoustakos and Michael W. Smith

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F.J. Montero, J.A. de Juan, A. Cuesta and A. Brasa

The importance of rapid, nondestructive, and accurate measurements of leaf area (LA) in agronomic and physiological studies is well known, but a search of the literature revealed little information available for grape (Vitis vinifera L.). The results described herein include a comparison of 12 different mathematical models for estimating leaf area in `Cencibel'. The simplest, most accurate regression equations were: LAi = 0.587 LW (R 2 = 0.987) and LAi = 0.588 LW (R 2 = 0.994), where LAi is leaf area measured using image analysis and LW is leaf length × maximum width. Use of maximum width (W), leaf length (L), petiole length (Lp), and dry weight of leaves (DML) as single variables in the regression equations were not as closely associated with total leaf area, although their R 2 values were also highly significant.

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S. Gamiely, W.M. Randle, H.A. Mills and D.A. Smittle

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N.H. Furness, A. Upadhyaya and M.K. Upadhyaya

Surface areas of differently shaped vegetables, namely beet (Beta vulgaris L.), cucumber (Cucumis sativus L.), carrot (Daucus carota L.), and parsnip (Pastinaca sativa L.) were determined by Baugerod's (a linear) method, a shrink-wrap replica method, and image analysis. Values obtained using these methods did not differ significantly for carrots and beets. Surface area values obtained using image analysis were higher than those obtained by Baugerod's method for parsnips (by 23.5%), and higher than Baugerod's and shrink-wrap replica methods for cucumbers (by 11.3% and 12.6%, respectively). A method was considered reproducible if surface area values from five measurements on the same product did not differ significantly (P ≤ 0.05). Surface area values for an individual product varied in the range of 4.7% for Baugerod's method for parsnips, and 6.6% for the shrink wrap replica method for carrots. No significant variation was observed for any of the vegetables when repeated measurements were made using the image analysis method. Image analysis offers rapidity, lack of adverse effect on produce, and the ability to collect and analyze data simultaneously. However, in absence of the necessary equipment for image analysis, Baugerod's method may be used for a product symmetrical around its central axis, after comparing it with a more direct procedure (e.g., shrink-wrap replica method).

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Jennifer R. DeEll, Robert K. Prange and Dennis P. Murr

Chlorophyll fluorescence was evaluated as a rapid and nondestructive technique to detect low-O2 or high-CO2 stress in apples (Malus domestica Borkh.) during storage. `Marshall' McIntosh apples were held for 5, 10, 15, 20, or 25 days at 3C in 1) standard O2 (2.5% to 3%) and low CO2 (<1%), 2) low O2 (1% to 1.5%) and low CO2 (<1%), 3) standard O2 (2.5% to 3%) and standard CO2 (4% to 4.5%), or 4) standard O2 (2.5% to 3%) and high CO2 (11% to 12%). Only 10% of the apples had skin discoloration after 5 days in 1% to 1.5% O2; 80% developed skin discoloration after 20 days in low O2. Small desiccated cavities in the cortex, associated with CO2 injury, developed in 10% of the apples after 20 days in 11% to 12% CO2. Five days in 1% to 1.5% O2 or 11% to 12% CO2 caused variable fluorescence (Fv) of apple fruit to decrease compared to those held in standard atmospheres. Additional exposure did not significantly affect Fv in either the low-O2 (1% to 1.5%) or high-CO2 (11% to 12%) treatment. Our results suggest that chlorophyll fluorescence techniques can detect low-O2 and high-CO2 stress in apples before the development of associated disorders.

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Angela Knerl, Brendon Anthony, Sara Serra and Stefano Musacchi

Leaf area is evaluated as leaf area index (LAI), the ratio of leaf to ground area, and is known to be crucial to understanding forests and high-quality fruit production in orchards. Nondestructive tools have been available for decades that pair hemispherical photography with gap fraction theories to understand LAI. Those tools do not allow for rapid assessment in the field, and there is no standardized protocol to acquire accurate estimates yet. This experiment has developed an optimized method with the CID Plant Canopy Imager (CI-110) in a high-density apple orchard. This novel tool for LAI estimation allows image acquisition and processing in real time in the field. LAI assessments of hemispherical images were taken under five light environments, at three imaging heights, processed with two thresholding methods, and were compared with destructive LAI values for accuracy. The difference between estimated and destructive LAI (∆LAI) was determined for trees on an individual or grouped by a three tree basis. Estimations for triplet groupings were more accurate, and the significantly lower ∆LAI in each treatment occurred for the no-net environment, 10 cm from the ground and processed with the Otsu threshold. When combined as triplet groupings, this methodology sequence yielded an LAI estimation with a 13% prediction error (∆LAI = 0.19). The use of the CI-110 with this methodology can give useful, real-time information regarding orchard canopies to address pruning and training decisions for high-quality fruit production.

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Nadia Hakam, Jennifer R. DeEll, Shahrokh Khanizadeh and Claude Richer

Chlorophyll fluorescence (CF) was evaluated as a technique to assess chilling injury of rose (Rosa sp.) leaves exposed to low temperatures. In the more susceptible genotypes, variable fluorescence (Fv) decreased dramatically as the temperature was lowered. In the less susceptible genotypes, Fv was more stable and decreased more slowly as temperature fell. Our results suggest that measurement of CF may provide a rapid method to prescreen genotypes for chilling susceptibility, as required in plant breeding.

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Gustavo H. de A. Teixeira, Valquiria G. Lopes, Luís C. Cunha Júnior and José D.C. Pessoa

levels of these compounds at the moment they are received by the industry. On the other hand, nondestructive methods can be applied to overcome these limitations and NIR spectroscopy is a fast, nondestructive, noninvasive method with a high penetration of