We evaluated spring phenology changes from 1965 to 2001 in northeastern USA utilizing a unique data set from 72 locations with genetically identical lilac plants (Syringa chinensis, clone "Red Rothomagensis"). We also utilized a previously validated lilac-honeysuckle "spring index" model to reconstruct a more complete record of first leaf date (FLD) and first flower date (FFD) for the region from historical weather data. In addition, we examined mid-bloom dates for apple (Malus domestica) and grape (Vitis vinifera) collected at several sites in the region during approximately the same time period. Almost all lilac sites with significant linear trends for FLD or FFD versus year had negative slopes (advanced development). Regression analysis of pooled data for the 72 sites indicated an advance of -0.092 day/year for FFD (P=0.003). The slope for FLD was also negative (-0.048 day/year), but not significant (P=0.234). The simulated data from the "spring index" model, which relies on local daily temperature records, indicated highly significant (P<0.001) negative slopes of -0.210 and -0.123 day/year for FLD and FFD, respectively. Data collected for apple and grape also indicated advance spring development, with slopes for mid-bloom date versus year of -0.20 day/year (P=0.01) and -0.146 (P=0.14), respectively. Collectively, these results indicate an advance in spring phenology ranging from 2 to 8 days for these woody perennials in northeastern USA for the period 1965 to 2001, qualitatively consistent with a warming trend, and consistent with phenology shifts reported for other mid- and high-latitude regions.
Nitsch, J. P., C. Pratt, C. Nitsch, and N. J. Shaulis (Cornell U., Ithaca, N. Y.) Natural growth substances in Concord and Concord Seedless grapes in relation to berry development. Amer. Jour. Bot. 47(7): 566–576. Illus. 1960.—A comparative study was made of the development of the grape berry in the ‘Concord’ variety and its presumed mutant, ‘Concord Seedless.’ This study included fresh and dry weight determinations, embryological observations, measurements of growth substances active on the oat first‐internode test and preliminary determination of other growth factors stimulating the growth of excised Jerusalem artichoke tissues in aseptic cultures. Four phases could be distinguished in the growth of the ‘Concord’ berry: Period O—limited growth and low growth‐substance content; Period I—rapid growth and high growth‐substance concentration; Period II—marked slowing down in growth and sudden drop in the growth‐substance level; and Period III—resumption of active increase in fresh and dry weight with no increase in growth‐substance concentration. In the ‘Concord Seedless’ variety, growth of the nucellus and production of growth substances increased faster during Period 0 than in ‘Concord,’ but degeneration of the endosperm and reduction in the growth‐substance level followed during the middle of Period I. Period II was inconspicuous. Early growth‐substance production in both varieties seemed to be associated with nucellus rather than with endosperm development. Some 6 different substances promoting growth in the Avena first‐internode test could be separated on paper chromatograms. None of them was chemically identified.
In a previous study of factors affecting the composition of Concord grape juice (ll), the sugar-acid ratio was found to be affected most by two factors, season and pruning severity. Trellis height exerted a lesser influence. When maturity was defined in terms of soluble solids accumulation, heat units were not particularly useful as a measure of maturity. Indications that acid contents were less affected than sugar contents by cultural practice variations encouraged the present investigation into the changes in acidic constituents of Concord grape juice during ripening and from season to season. The acids of grapes have been the object of much research since the nineteenth century (3), but the causes of their variation are still subject to much conjecture (2,8). E X P E R I M E N T A LThe grapes used in this study were obtained from vines of the Concord variety grown in New York State. Vine training, pruning, and sampling procedures and juice preparation have been described in a previous publication (11).Total acid was determined by titration to pH 8.0 and is expressed as tartaric acid. Tartaric acid was determined by the metavanadate method ( 5 ) . Malic acid was determined by the method of Goodban and Stark (4).Heat units for each day were determined by subtracting 50 from the average of the maximum and minimum temperatures in degrees Fahrenheit. The daily units were accumulated from date of bloom to date of harvest. RESULTSIn 1956 comparisons were made (Table 1) of the sugar, acid, and tartrate changes in Concord grapes as affected by very severe, medium, and very light prunings (10). Ten, 40, and 70 buds, respectively, were left on the vine for the initial pound of prunings and 10 buds for each additional pound. Pruning exerted a pronounced effect on sugar content ( Fig. l ) , but had little, if any, effect on the acidity of the grape. As the grapes ripened a change occurred it1 the character of the acidic constituents. On September 6, when the grapes were still in the red stage, tartrates comprised less than 30% of the acids, but as ripening progressed, there was little change in the tartrate content while the total acids decreased gradually so that tartaric acid became the mijor fraction at harvest (Figure 2).Since the acids were unaffected by pruning severity differences, the sugar-acid ratio values follow the same pattern as that of the soluble solids readings.In view of the relative stability of the acids of grapes to changes in pruning severity, it was thought probable that the acids would be less influenced than sugars by factors affecting the leaf-to-fruit ratio such as leaf exposure, crop load, and cluster thinning. With this in mind, it was decided to reasstss the value of heat units froin the standpoint of acid content of the grapes. Samples of grape juice were available for eight different years. For each of these samples the dates of bloom and harvest and appropriate temperature data were available. These samples were aidyzed for tna1:c acid content, total acid, and soluble solids ( Table 2 ) .
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