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Potted `Cabernet Sauvignon' and `Pinot noir' grapevines (Vitis vinifera L.) grown in a sunlit phytotron were used to study the influence of cluster light exposure during various stages of fruit development on berry growth and composition. Clusters grown without light during berry development stages I and II, stage III, or stages I, II, and III, were compared to clusters exposed to light throughout fruit development (control). The temperature of light-exposed and nonexposed fruit was similar. The weights and diameters of berries grown without light during stages I and II, or stages I, II, and III, were similar and significantly lower than those of the control. Fruit softening in both cultivars, as well as the initiation of berry coloration, was delayed when berries were grown without light during stages I and II. Following fruit softening, berries grown without light during stages I, II, and III were lower in sugar than the control. On the final sample date, `Cabernet Sauvignon' berries grown without light during stages I, II, and III were higher in malate compared to the control. `Pinot noir' berries grown without light during stages I and II, or stages I, II, and III, were lower in malate before fruit softening, and higher in malate following fruit softening, than the control. Control berries had greater skin anthocyanins and phenolics compared to the remaining treatments. Berries grown without light during stages I and II, or stage III, were greater in anthocyanins and phenolics than fruit grown without light during stages I, II, and III. Light had no effect on fruit tartrate concentration or juice pH. Light had its greatest impact on fruit development during the initial stages of berry growth. Berry growth was reduced and ripening delayed when fruit were grown without light during stages I and II. Normal fruit development was not fully restored when these fruit were exposed to light during stage III.

Phosphoenolpyruvate (PEP) carboxylase activity in immature 'Carignane' grape berries (Vitis vinifera L.) had a temperature optimum of about 38 C, whereas malic enzyme activity rose with increasing temperature between 10 and 46 C. In vitro temperature inactivation rates for the PEP carboxylase were markedly greater than for the malic enzyme activity. From the simultaneous action of malic acidproducing enzymes (PEP carboxylase and malic dehydrogenase) and malic acid-degradating enzyme (malic enzyme) systems at different temperatures, the greatest tendency for malic acid accumulation in immature grape berries was at 20 to 25 C. Time-course measurements of enzymic activity from heated, intact berries revealed greater in vivo temperature stability for the malic enzyme activity than for the PEP carboxylase activity.

SUMMARY: The concentration of eight free amino acids, total nitrogen, amino‐acid fraction nitrogen, and nonamino‐acid‐fraction nitrogen in the juices of 26 red‐ and 23 white‐wine varieties of grapes was determined at early and late stages of fruit maturity. Proline was the most prominent amino acid in 31 of the varieties at early harvest and in 45 of the varieties at late harvest while arginine was the main amino acid in 16 and 3 varieties at early and late harvest, respectively. “Salvador” and “Scarlet” were the only varieties in which α‐alanine was the predominant amino acid. The concentration of total nitrogen in the juices of the various varieties ranged from 44 to 256 mg/100 ml and the amino‐acid fraction nitrogen ranged from 26 to 171 mg/100 ml juice. The amino acid fraction and nonamino acid fraction nitrogen in the juices ranged from 53 to 76% and 23 to 56% of total Kjeldahl nitrogen respectively. Alanine, γ‐aminobutyric acid, arginine, aspartic acid, glutamic acid, proline, serine and theronine accounted for 29 to 72% of the total nitrogen and 47 to 96% of the amino acid fraction nitrogen. Arginine contributed the most nitrogen of the amino acids, accounting for 6 to 44% of the total nitrogen in the juices of the various fruits.

Summary. Glucose, fructose, galaotose, sucrose, mfaltose, melibiose, raffinose, and stachyose were identified in the leaves, bark, 'roots, and berries of Vitis vinifera L. var. Thompson Seedless. In addition to these sugars, verbascose and manninotriose were found in the leaves and bark. Malic, tartaric, citric, isocitric, ascorbic, cis-aconitic, oxalic, glycolic, glyoxylic, suc- (17) showed that 12 to 27 % of the total acidity and 0.5 to 12 % of the reducing sugars in grape leaves is not accounted for by malic and tartaric acids and glucose and fructose, respectively. The introduction of chromatography has greatly facilitated the study of sugars and organic acids by offering a relatively simple method of separating and identifying individual componenlts of rather complex mixtures of these substances. For a review o,f the literature pertaining to organic acids and sugars in grapevi,nes, see Amerine (1, 2), Amerine and Winkler (3), and Kliewer (13,14,15).In the present study, 11 different parts of the grapevine were investigated for their free organic acid and sugar components. Various tests were conducted to identify individual organic acids and sugars. Glucose, fructose, sucrose, malate, tartrate, and citrate were determined quantitatively in the various parts

Phosphoenolpyruvate (PEP) carboxykinase activity was found in crude extracts of 'Pinot noir' grape berries. The enzyme required ATP, Mn'+ plus Mg, a pH of 6.6, and a temperature of 40 C for maximum activity. The range in concentration of oxaloacetic acid needed for maximum phosphoenolpyruvate carboxykinase activity was 5 to 10 mM, and the Km for HC03-in the exchange of 1CO2 into oxaloacetic acid was 26.8 mM.Changes in the activity of PEP carboxykinase and PEP carboxylase in berries were studied at weekly intervals throughout fruit development. PEP carboxykinase had maximum activity 4 weeks after flowering, and during the following 11 weeks remained relatively constant. The activity of PEP carboxylase was 2-to 4-fold higher than PEP carboxykinase throughout fruit development, and changed little except for a sharp reduction at the onset of ripening.

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SUMMARY —The concentration of eight amino acids, total free amino acids, total nitrogen and free amino acid fraction nitrogen in the juices of 28 table varieties of grapes was determined at both early and a late stage of fruit maturity. Arginine, proline, glutamic acid and alanine were the most prominent amino acids. The varieties were classified into four groups according to which of these acids predominated. Total free amino acids at early and late fruit maturity ranged from 1.04 to 5.53 and 1.24 to 6.45 nM/100 ml juice, respectively in the various varieties. The eight amino acids analyzed accounted for 74 to 96% of the total free amino acids. The amino acid fraction nitrogen in the juices ranged from 60 to 90% of the total nitrogen. The eight amino acids accounted for 60 to 96% of the amino acid fraction Kjeldahl nitrogen and 37 to 85% of the total Kjeldahl nitrogen. Argining accounted for 15 to 50% of the total nitrogen in the juices of the various fruits.