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Marc W. van Iersel and Lynne Seymour

Respiration is important in the overall carbon balance of plants, and can be separated into growth (Rg) and maintenance respiration (Rm). Estimation of Rg and Rm throughout plant development is difficult with traditional approaches. Here, we describe a new method to determine ontogenic changes in Rg and Rm. The CO2 exchange rate of groups of 28 `Cooler Peppermint' vinca plants [Catharanthus roseus (L.) G. Don.] was measured at 20 min intervals for 2 weeks. These data were used to calculate daily carbon gain (DCG, a measure of growth rate) and cumulative carbon gain (CCG, a measure of plant size). Growth and maintenance respiration were estimated based on the assumption that they are functions of DCG and CCG, respectively. Results suggested a linear relationship between DCG and Rg. Initially, Rm was three times larger than Rg, but they were similar at the end of the experiment. The decrease in the fraction of total available carbohydrates that was used for Rm resulted in an increase in carbon use efficiency from 0.51 to 0.67 mol·mol-1 during the 2-week period. The glucose requirement of the plants was determined from Rg, DCG, and the carbon fraction of the plant material and estimated to be 1.39 g·g-1, while the maintenance coefficient was estimated to be 0.031 g·g-1·d-1 at the end of the experiment. These results are similar to values reported previously for other species. This suggests that the use of semicontinuous CO2 exchange measurements for estimating Rg and Rm yields reasonable results.

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J.J. Steiner and K. Opoku-Boateng

We investigated the effects of variation in ambient air temperature on seed production in the field during the reproductive development phase of `Salinas' head-type lettuce (Luctuca sativa L.) in the central San Joaquin Valley of California where daytime maxima may exceed 38C for many consecutive days during reproduction. Florets were tagged daily for 41 days and harvested seeds were sampled to determine temperature-sensitive periods during seed development. The number of seeds per inflorescence (NOS), seed mass (SM), and seedling root length (SRL) were reduced and percentage germination (GERM) increased with increasing minimum (LT) and maximum (HT) temperatures. Daily HT > 35C greatly reduced NOS. Increasing LT reduced SM and SRL, but to a lesser extent than NOS (r2 = 0.23 and 0.40; P = 0.01 and 0.001, respectively). The advantage of increasing HT on GERM (r2 = 0.20; P = 0.01) was overshadowed by the severe reduction in NOS and the vigor components SM and SRL. The periods of greatest sensitivity to high air temperature for NOS, SM, GERM, and SRL were - 1 to +1, - 4, +1, and - 4 to - 3 days from anthesis, respectively. The hours of peak sensitivity for these variables occurred during the same days at - 36, - 101, + 15, and - 83 hours from anthesis, respectively. Using Box-Jenkins time series analysis, diurnal periodicity in temperature sensitivity for the four variables was determined.

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Wei-Chin Lin, Dietmar Frey, Gordon D. Nigh, and Cheng C. Ying

understood. It was found that in some cultivars such as Derby and Meteor, three preceding weekly yields gave a good estimate of current yield by using time series analysis ( Verroens et al., 2006 ). They also found that the inclusion of environmental

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E. E. Gemoets, L. A. Gemoets, T. E. Cannon, and R. G. McIntyre

Abstract

U. S. production of pecan (Carya illinoensis (Wang) K. Koch) has been characterized by highly irregular variations in crop size from season to season. Spectral analysis is applied to the U. S. pecan production system to identify cycles. In analysis of U. S. pecan production data for 1919 through 1974, a first order autoregressive process with a negative constant of −0.39 to −0.62, a biennial alternating process, was found. Also identified were cycles of 2½, 4, and 11 – 16 years statistically significant at the 95% and higher levels for all pecans, native pecans and improved pecans.

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Taku Shimizu, Kazuma Okada, Shigeki Moriya, Sadao Komori, and Kazuyuki Abe

The development of new high-quality apple (Malus ×domestica) cultivars that are resistant to flesh browning is needed to expand the use of apples in the food service and catering industry. However, conventional methods for evaluating apple flesh browning can be both time-consuming and costly, thereby rendering such methods unsuitable for breeding programs that must characterize a large number of product samples. Therefore, it is necessary to develop new, simple, and inexpensive methods. The aim was to develop a method for simultaneously measuring the color values of 42 apple samples using a digital camera. The processing time per sample was reduced to less than one-tenth of that of the conventional method. The measurement dispersion [sd of the color difference between two colors (ΔEab*)] of this system was less than 0.08, equivalent to the nominal value of a general colorimeter. Time-series analysis of six apple cultivars using this method showed that the calculated browning index values correlated well with the degree of browning judged by human perception. Further, the measurement data showed that the CIE L* a* b* value trends associated with browning in reddish- and watercored-flesh samples, was different from the corresponding trends in yellowish-flesh samples. This work reports the development of a high-throughput analytical system of apple browning and provides cautionary notes for evaluating reddish- and watercored-flesh browning, which should be measured on a different basis from that used for normal-flesh browning.

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Fabio Orlandi, Carlo Sgromo, Tommaso Bonofiglio, Luigia Ruga, Bruno Romano, and Marco Fornaciari

(northwest Spain): A survey to forecast the onset and daily concentrations of the pollen season Grana 43 101 110 Sirois, A. 1998. A brief and biased overview of time series analysis or how to find that evasive trend. WMO report No. 133: WMO

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Waltram Ravelombola, Ainong Shi, Jun Qin, Yuejin Weng, Gehendra Bhattarai, Bazgha Zia, Wei Zhou, and Beiquan Mou

except for Bayesian Information Criterion for trifoliate leaf chlorophyll (Supplemental Table 4). Therefore, ANOVA involving time series analysis for chlorophyll contents was conducted based on an unstructured covariance matrix type. Time by genotype

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Leah L. Granke, Layla E. Crawford, and Mary K. Hausbeck

strawberry Plant Dis. 88 878 881 Box, G. Jenkins, G. 1976 Time series analysis forecasting and control. Holden-Day, San Francisco, CA Braun, U. Cook, R.T.A. Inman, A.J. Shin, H.D. 2002 The taxonomy of the powdery mildew fungi, p. 13–55. In: Belanger, R.R., W

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Bandara Gajanayake, K. Raja Reddy, Mark W. Shankle, and Ramon A. Arancibia

status is one of the crucial and readily manageable variables to produce a profitable crop ( Taylor et al., 1983 ). Fig. 2. Time-series analysis of storage root development in two sweetpotato cultivars, Beauregard and Evangeline, across five soil moisture

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Eugene K. Blythe and Donald J. Merhaut

the experimental units used in a study. Nonconstancy of the error variance may call for use of weighted least squares. Nonindependence of the error terms, as can occur in time series analysis, may call for use of a model that accounts for correlated