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  • Author or Editor: Suman Singha x
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Fruit of 34 peach (Prunus persica L. Batsch). cultivars were harvested at maturity and visually evaluated by panelists on a 1 to 10 scale, where 10 = excellent color. CIELAB coordinates (L* a* b*) of fruit color were measured at the midpoint between the stem and the calyx end with a Minolta CR-200b calorimeter on the blushed and ground areas of each fruit. Simple linear regressions of color coordinates with panel ratings indicated that blush chroma, blush L*, blush hue angle and E* (total color difference between ground and blush) all influence visual color evaluation. Not only does assessing fruit color with a calorimeter permit color to be reported in internationally accepted units, but the relationships indicate that instrumental values relate well to qualitative ratings.

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Shoots of `Almey' crabapple [Malus baccata (L.) Borkh. × M. pumila var. niedzwetzkyana (Dieck) Schneid.], `Seckel' pear (Pyrus communis L.), and `Mrs. Bradshaw' geum (Geum quellyon Sweet.) were cultured on Murashige and Skoog (MS) medium supplemented with 8.8 μm BA and containing 0.1% to 0.4% Gelrite. Comparative shoot proliferation and vitrification were determined on Phytagar-solidified medium. Shoot proliferation, culture fresh weight, and vitrification declined in crabapple and geum with increasing Gelrite concentration. Pear proliferation and fresh weight increased with increasing Gelrite levels, but all shoots were vitrified. There were differences in the vitrification response between pear and the other two genera. The percent dry weight of vitrified cultures on Gelrite-containing media was generally higher than that of nonvitrified cultures on medium containing Phytagar. Vitrification precludes using low Gelrite concentrations for propagating these plants. Chemical name used: N-(phenylmethyl) -1H-purin-6-amine (BA).

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Variations in the pattern of fall color development in the leaves of Acer rubrum, Acer saccharum, Quercus coccinea, Oxydendrum arboreum and Euonymus alatus were determined. CIELAB coordinates were measured with a Minolta CR-2000b calorimeter at a marked location on 5 tagged leaves from 2 plants of each species. The changes in hue follow similar trends in these species, but the time of onset varies. Onset of red color development increased variability in hue between leaves of the same species. Based on color changes in E. alatus anthocyanin development occurs prior to significant loss of chlorophyll and red coloration remains masked, whereas in A. rubrum anthocyanin development occurs in association with or following the loss of chlorophyll. This results in differences in the pattern of hue and chroma development between these species.

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Flesh color has been proposed as a maturity index for peaches. The objective of the present study was to determine the effectiveness of this parameter in `Loring', `Jersey Dawn', `Madison', and `Raritan Rose' peach (Prunus persica L. Batsch). Fruit were picked at weekly intervals at three or four harvest dates, with five fruit per cultivar being picked from each of three trees. Flesh firmness and soluble solids were measured immediately following harvest, and CIELAB coordinates (L*a*b*) of blush and flesh color were determined with a Minolta CR-200b calorimeter. There was a highly significant correlation (P < 0.001) between firmness and flesh hue angle for all four cultivars and with flesh chroma especially for the white-fleshed `Raritan Rose'. The correlation values between firmness and blush hue angle were consistently lower. Soluble solids did not consistently correlate with flesh or blush color. Even though blush color influences consumer preference, it was not as good an indicator of maturity as flesh color for the cultivars that we tested.

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Abstract

Abscisic acid (ABA) inhibited bud break and shoot elongation in seedling stem explants of apple (Malus domestica Borkh cv. Northern Spy) cultured in vitro. Inhibition was complete in culture medium containing 100 μM ABA. Transfer of buds from ABA-containing medium to basal medium resulted in increases in both bud break and shoot elongation. ABA levels in such buds declined rapidly following transfer, and growth began when ABA concentration in the buds dropped below a threshold value.

Open Access

Chromaticity values (L*, a*, b*) of tomato (Lycopersicon esculentum Mill. `Celebrity', `Early Pick', and `Mountain Delight') were measured using a Minolta CR-200b tristimulus colorimeter. Lycopene concentrations in acetone extracts of skin disks or pericarp plugs were measured spectrophometrically at 503 nm. The L* or a* value was related to lycopene concentration in all the cultivars; however, the ratio of (a*/b*) provided the best R for all cultivars (0.75). These relationships allow the use of a portable colorimeter for rapid, nondestructive estimation of tomato fruit lycopene concentrations in laboratory or in situ studies.

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Chromaticity values (L*, a*, b*) of `Rome Beauty' apples (Malus domestics) were measured at weekly intervals during maturation periods in 1988 and 1989. Chromaticity was measured using a Minolta Chroma Meter CR-200b calorimeter on four quadrants of the fruit at locations midway between the stem and calyx ends. The apples continued to develop red color through the maturation period. After storage, the peel areas where chromaticity was measured were evaluated for scald intensity. The L* value at harvest was correlated positively with scald intensity, while the a* value was correlated negatively. An equation has been developed to describe the relationship between chromaticity values at harvest and scald intensity after storage.

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Lycopene is the predominant carotenoid pigment in tomatoes and primarily responsible for red color. Spectrophotometric procedures for lycopene evaluation although accurate are time consuming and destructive. The objective of this study was to relate chromaticity values (L*,a*,b*) measured using a Minolta Chroma Meter CR-200b portable tristimulus calorimeter with lycopene concentrations in the pericarp of 'Celebrity', 'Mountain Delight' and 'Early Pick' tomatoes. Fruit were selected to encompass varying maturities from green to red ripe and were obtained from a commercial source. Lycopene from individual skin disks or pericarp plugs corresponding to each location of color measurement was extracted in acetone and measured spectrophotometrically at 503 nm. The L* value (a measure of lightness) or a* value (a measure of redness) was determined to be well correlated with lycopene concentration in all 3 cultivars. The linear regression of the lycopene concentration on the ratio of (a*/b*) provided the best R for all cultivars (0.75).

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Abstract

Bacterial contamination can be a serious problem in plant tissue cultures (4, 6). Contaminants occur because bacteria may survive the explant surface-sterilization procedure (5) or are endogenous in the plant tissue (4). In certain instances, the bacteria may remain latent in the explant(s) and fail to exhibit visual symptoms for prolonged periods (5). Furthermore, Monette (7) recently reported on the inability to detect an Aerococcus sp. and Bacillus fastidiosus contamination in kiwifruit shoot-tip cultures initiated on agar-solidified medium. It is, therefore, imperative that bacterial contaminants are not spread through improperly sterilized instruments.

Open Access

Abstract

Shoot tips of ‘Almey’ crabapple [Malus baccata (L.) Borkh. × M. pumila var. Niedzwetzkyana (Dieck) Schneid.] and ‘Seckel’ pear (Pyrus communis L.) were cultured on Murashige and Skoog (MS) medium containing 8.8 µm BA. Media were solidified with either Bacto-agar, Phytagar, or TC agar at concentrations varying from 0.3% to 1.2%. Explant nutrient levels were influenced both by agar brand and concentration. The trends in nutrient composition, although not identical, tended to be similar for both genera. Increasing agar concentrations resulted in increased P, Fe, Zn, and Al in the explant and reduced Ca, Mg, and Mn levels. Although striking variations in many elements occur both in agar brands and in explants cultured on media containing similar concentrations of different agar brands, variations in shoot proliferation and growth of explants cannot be explained on the basis of variations in individual elements. From the nutritional standpoint, the alterations in the elemental composition of the basal medium by the addition of specific agars best explain variations induced by different agar brands. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine (BA).

Open Access