No abstract

That ascorbic acid may play a significant role in the red color deterioration of fruit juices was first pointed out by Beattie, Wheeler, and Pederson (2) and by Pederson, Beattie, and Stotz (6) who observed parallel losses of ascorbic acid and anthocyanins during storage. The best correlation between ascorbic acid and red color losses was obtained with strawberry juice. Pederson and coworkers postulated that an interaction between ascorbic acid and anthocyanins may occur. Similar observations and conclusions were reported by Nebesky, Esselen, McConnel, and Fellers ( 5 ) .The availability of crystalline pelargonidin 3-monoglucoside isolated from strawberries (10) prompted us to study these interactions in simplified artificial systems as well as in strawberry juice. I n the presence of ascorbic acid, maximum anthocyanin destruction was observed under those conditions which favor the aerobic oxidation of ascorbic acid. EXPERIMENTALPelargonidin 3-monoglucoside chloride was obtained by a previously described procedure (20). The anthocyanin picrate was recrystallized six times from hot dilute picric acid solution before conversion to the chloride. The model systems contained 28 mg. pigment per 100 ml. of Sorensen's disodium citrate-hydrochloric acid buffer of pH 3.40. The strawberry juice used in these experiments was expressed from Dresden strawberries grown a t Geneva, N. Y., during the 1950 season. This juice had a pH of 3.4 and an ascorbic acid and anthocyanin content of 49 mg. and 23 mg. per 100 ml., respectively. All samples were heated to 9O"C., and held for 5 minutes in order to expel most of the dissolved gases. The solutions which were to be held under essentially anaerobic conditions were rapidly poured into 2-dram (7.39 ml.) screw-capped vials, leaving no headspace. They were cooled in a 30°C. constant-temperature bath and sealed with paraffin wax. In experiments where a fairly constant air supply was desired, 50 ml. of solution in a 250-ml. volumetric flask was shaken continuously in an automatic shaker in which the temperature could be controlled. Anthocyanin losses were followed by a previously described method (9) based on the difference in absorption at 500 mp produced by a change in pH from 3.4 to 2.0. Ascorbic acid was determined by the method of Robinson and Stotz (7) which involves oxidation by indophenol under specific conditions. The above authors warn against the possible interference of sulfhydryl compounds in the ascorbic acid determination. We found that thiourea does tend to give high ascorbic acid values but that the error is small if the thiourea content does not exceed 0.1% and the excess indicator is extracted rapidly. RESULTS AND DISCUSSION

A set of 40 adapted homozygous spring wheat (Triticum aestivum L.) genotypes were grown under similar conditions of irrigation and high fertility utilizing large plots and microplots seeded at normal densities, and spaced plants (60 × 60 cm grid). The objective was to see how well spaced plant traits, especially grain weight and harvest index, and microplot yields predicted true yielding ability as measured with the large plots. Phenotypic correlation coefficients were calculated using genotype means.Microplot yield was highly correlated (r = 0.67 at the 1% level) with large plot yield but explained less than half of the variation between the genotypes. Much of the residual was probably related to the highly significant genotype Χ plot type interaction. With spaced planting, yield/plant was correlated (r = 033 at the 5% level) with crop yield. Better correlations with crop yield were obtained with plant and shoot harvest indices (r = 0.56 and 0.66, respectively, at the 1% level). No numerical components of yield measured on spaced plants gave better correlations with crop yield than yield per plant itself.These results emphasize the major effect that the degree of interplant competition, probably primarily for light in this case, has on the performance of a genotype. As the degree of competition declined going from crop plots to spaced plants, genotypes which can more fully occupy the increased space available were favored; thus, the performance of non‐erect genotypes improved noticeably relative to erect ones. We conclude that harvest index measurement offers promise as a predictor of yielding ability where the seed available is limited.