Endogenous ABA, free and conjugated ACC concentrations, ethylene-forming capacity (EFC), and presence of ACC oxidase (ACO) and ACC synthase (ACS) proteins were monitored during the preharvest maturation period of `Granny Smith' apple fruit (Malus sylvestris L. Mill. var. domestica (Borkh.) Mansf. `Granny Smith'). Total proteins from peel and pulp tissues were also extracted at different maturity stages and separated by sodium dodecyl sulphate polyacrylamide gel electrophoresis, providing evidence of differential protein accumulation during fruit development. Endogenous ABA concentration in the peel tissue was higher than in pulp, the highest level occurring ≈2 months before commercial harvest. In the pulp tissue, concomitant increases in ACC and ABA concentrations were observed, preceded by a peak in EFC. However, no ACO or ripening-related ACS proteins were detectable throughout the period considered, suggesting that very low levels of both enzymes are present during the preclimacteric stage of `Granny Smith' apples. A hypothesis on the possible interaction between ABA and ethylene during maturation of `Granny Smith' apples is proposed. Chemical names used: abscisic acid (ABA); 1-aminocyclopropane-1-carboxylic acid (ACC).
The objectives of this study were to characterize the quality and maturity changes of nectarine (Prunus persica var. Nectarina) fruit cvs. Aurelio and Early May during maturation and ripening and to identify harvest maturity indices. After fruit set, 250 fruit of similar diameter and tree position were tagged to follow maturation and ripening on the tree. During commercial harvest, 48 fruit were ramdomly harvested every 2 to 3 days. Ethylene evolution rate (EER) at 20 °C, fresh weight, and peel ground and cover color (L*, a*, b*, C* and Hue value) were measured on all 48 fruit. Flesh color, firmness at several fruit points, soluble solids (SS), pH, titratable acidity (TA) and SS: TA ratio were measured only to 24 fruit, and the rest were held for up to 7 days at 20 °C as a ripening period to measure the same parameters mentioned above. Pearson correlation coefficients were determined between variables to explore possible harvest maturity indices. The most significant changes occurred in EER, fruit firmness, and peel ground color (a* and hue value). For `Aurelio' nectarines the highest correlations (P < 0.001) were obtained between logEER-tip firmness (r = -0.69), tip firmness-a* ground color (r = -0.66) and, tip firmness-hue ground color (r = -0.67). No important correlations (r > 0.60) were found for `Early May' nectarines. It was also found that fruit softening varies according to the point of measurement in the fruit depending on the cultivar.
Hybrid, non-netted, green-fl esh, honeydew muskmelon fruit physiological maturity occurred by 40 days after anthesis (DAA). Fruit maturity was determined by major increases in quality attributes: moisture content, firmness, soluble solids concentration, weight, volume, and qualitative and quantitative changes in glucose, fructose, and sucrose content. Fruit ripening occurred between 40 and 50 DAA as determined by maximized changes in the aforementioned quality attributes, and by fruit abscission at 50 DAA. Fruit senescence begins with decreases in: quality attributes, hypodermal-mesocarp plasma membrane H+-ATPase (E.C. 3.6.1.3) activity, and protein content, and by increases in: the total free sterol: total phospholipid ratio, and hypodermal-mesocarp lipoxygenase (E.C. 1.13.11.12) activity. Delineated growth and maturation physicochemical data of hybrid honeydew muskmelon fruit should be beneficial to the commercial harvest of mature fruits, which is necessary for maximizing honeydew fruit quality, extending shelf-life, and enhancing consumer satisfaction.
Abstract
The changes in ethylene production rates and development of 1-aminocyclopropane-l-carboxylic acid (ACC) synthase and polygalacturonase (PG) activities were studied during the maturation and ripening of tomato fruit (Lycopersicon esculentum Mill, cv. ‘Castlemart’). There was a linear relationship between internal ethylene concentration and ethylene production rate; both increased exponentially as tomato fruit reached more advanced maturity and ripening. Thus, both of them correlate with the maturity and the ripening stages of tomatoes. A small increase in ACC synthase activity was observed at the early mature green stages which was followed by a marked increase at the breaker stage. ACC level followed the same pattern as ACC synthase activity. PG activity was undetectable or low throughout the mature green stages, but increased significantly after reaching the breaker stage. These data indicate that the onset of the development of ACC synthase activity precedes that of PG activity.
Abstract
Succinamic acid 2,2-dimethyl hydrazide (Alar) has many effects on the species Prunus persica L., depending upon concentration, timing, and physiological stage of plant development. Alar hastens ripening, hastens the occurrence of the climacteric, increases internal flesh color, increases red and yellow skin color, slightly decreases the per cent soluble solids, and decreases flesh firmness. Decreases in soluble solids and flesh firmness seem to be as a consequence of early maturation. Increases in red and yellow skin pigmentation and internal flesh color are increased in fruits of the same firmness. Terminal growth is not altered greatly by Alar, even at high concentration, unless applied near the beginning of the pit hardening stage.
Muskmelon [Cucumis melo L. (Reticulatus Group)] fruit sugar content is the single most important consumer preference attribute. During fruit ripening, sucrose accumulates when soluble acid invertase (AI) activity is less then sucrose phosphate synthase (SPS) activity. To genetically heighten fruit sugar content, knowledge of sugar accumulation during fruit development in conjunction with AI and SPS enzyme activities and their peptide immunodetection profiles, is needed. Two netted muskmelon cultivars, Valley Gold a high sugar accumulator, and North Star a low sugar accumulator, with identical maturity indices were assayed for fruit sugars, AI and SPS activity, and immunodetection of AI and SPS polypeptides 2, 5, 10, 15, 20, 25, 30, 35, or 40 (abscission) days after anthesis (DAA). Both cultivars, grown in the Fall, 1998 and Spring, 1999, showed similar total sugar accumulation profiles. Total sugars increased 1.5 fold, from 2 through 5 DAA, then remained unchanged until 30 DAA. From 30 DAA until abscission, total sugar content increased, with `Valley Gold' accumulating significantly more than `North Star'. During both seasons, sucrose was detected at 2 DAA, which coincided with SPS activity higher than AI activity, at 5 through 25 DAA, no sucrose was detected which coincided with SPS activity less than AI activity. At 30 DAA when SPS activity was greater than AI activity, increased sucrose accumulation occurred. `Valley Gold' at abscission had higher total sugar content and SPS activity, and lower AI activity than `North Star'. `North Star' had AI isoforms at 75, 52, 38, and 25 kDa (ku) that generally decreased with maturation, although the isoform at 52 ku remained detectable up to anthesis (40 DAA). `Valley Gold' had the same four AI isoforms, all decreased with maturation and became undetectable by 20 DAA. Both `Valley Gold' and `North Star' had one SPS band at 58 ku that increased with DAA, and coincided with SPS activity. `Valley Gold' had a more intense SPS polypeptide band at abscission than `North Star'. Thus, netted muskmelon fruit sugar accumulation may be increased, either by genetic manipulation or by selecting for cultivars with a specific number of down-regulated AI isoforms, and higher SPS activity during fruit ripening.
Hybrid honey dew muskmelon (Cucumis melo L. var. inodorus Naud.) fruit physiological maturity, the period of maximized or greatest compositional changes, occurs by 40 days after anthesis (DAA). Fruit maturity was determined by major changes in quality attributes: glucose, fructose, sucrose, and moisture content, firmness, mass, volume, and hypodermal-mesocarp plasma membrane specific H+-ATPase (E.C. 3.6.1.3) activity. Fruit ripening occurs by 50 DAA, as determined by additional changes in the mentioned quality attributes, and by fruit abscission at 50 DAA. Fruit senescence begins with decreases in almost all quality attributes, H+-ATPase activity, protein content, by the largest increase in the total free sterol : total phospholipid (FS:PL) ratio, and in hypodermal-mesocarp lipoxygenase (E.C. 1.13.11.12) activity. Physicochemical profiles of hybrid honey dew muskmelon fruit during growth and maturation should be useful to schedule commercial harvest of mature fruit, which is necessary for maximum honey dew fruit quality, extended shelf-life, and enhanced consumer satisfaction.
Abstract
Green seeds from lima bean (Phaseolus lunatus L.) cvs. G 2 and Green Fordhook 861, contain chlorophylls a and b in a ratio of about 2:1. Chlorophyll content per seed increases during development, reaches a max about 5 weeks after pod formation, then declines sharply during maturation. Bleached seeds have less chlorophyll, especially chlorophyll a, and carotene than non-bleached seeds.
In developing and mature lima bean seeds max chlorophyllase activity appears during the stage which corresponds with max chlorophyll content rather than the stage of most rapid loss of chlorophyll. The enzyme is particulate, located in the chloroplast membranes, and has an optimum pH of 8.5 ± 0.2.
The low carotene content of seeds of green-seeded commercial cultivars might contribute to their sensitivity to light. Several cultivars that were obtained from other countries. (Plant Introductions) contain 10 to 20 times as much carotene as the commercial cultivars tested. These “Introductions” provide genetic material for increasing the carotene content of lima bean seeds. High carotenes would improve nutritional value of beans and might reduce or prevent bleaching.
Seasonal fluctuations of carbohydrate levels and compositions and the activities of related enzymes of three cultivated tomato (Lycopersicon esculentum Mill. cv. Lady First, Momotaro, and Minicarol) cultivars were examined at 45-days interval with seven different sowing in the relatively warm climate of Japan. Fruits picked on early winter to spring seasons had higher sugar concentrations compared to hot season. Fructose and glucose in nearly equal amounts were the predominant sugar in all the seasons. Sucrose was present in trace quantities, but cherry cultivar Minicarol accumulated higher levels than the other two large-fruited types.
Acid invertase (EC 3.2.1.26) was highest at red stage during December to April, while fruit matured during May to August had lowest activity. The activity levels of soluble invertase were predominant compared to cell wall-bound fraction. The sucrose synthase (EC 2.4.1.13) showed highest activity in rapidly growing fruits followed by a very low activity with fruit maturation. Sucrose synthase showed the higher activity during November to February, and almost low activity during all the experimental periods. The sucrose phosphate synthase (EC 2.4.1.14) also showed higher activity during October to February, but the activity levels did not change drastically throughout the fruit development. The results substantiate the conclusion that, in all the planting seasons, acid invertase is a principal enzyme in the process of tomato fruit ripening and during early stage of tomato fruit development, sucrose synthase is the dominant enzyme, which, in turn, plays a part in regulating the translocation of sucrose into the fruit.
Abstract
Comparisons were made of the composition of ‘Valencia’ oranges, Citrus sinensis Osbeck, from orchards in 6 major climatic zones used for citrus culture in the U. S. Six orchards, selected in a compact area in each location, were measured and sampled at intervals during 2 crop seasons. The locations were: Orlando, Fla.; Weslaco, Tex.; Tempe, Ariz.; Indio, Calif.; Riverside, Calif.; Santa Paula, Calif. Statistical evaluations showed that the seasonal trends for most measurements differed significantly among locations.
Observations on flowering showed that full-bloom occurred from 1 to 2 months later in the Far-Western locations than in Texas and Florida. The extremes of the interval between an thesis and the beginning of ripening (a 9 to 1 ratio of total soluble solids to acid in juice) varied from 71/2 to 81/2 months in Weslaco, to 14 to 15 months in Santa Paula, but earliness or lateness of maturity could not be relatd in any simple, obvious manner to the characteristic of the seasonal temperature regimes in the 6 locations. In general, rinds were thinner, smoother and slower to color, and fruits larger, and juicier in Orlando and Weslaco than in the Far-Western locations. Total soluble solids and ascorbic acid in juice at comparable stages of maturity were not influenced in a predictable manner by location, although significant differences occurred in a given season. Of the juice constituents, the acids appear to be the most consistently influenced by climatic conditions during the rapid growth and maturation periods of fruit development. The warmer the climate, the more rapid was the rate of decrease of total acid concentration. Seediness of fruit was influenced by both location and season. Measurements of comparable samples of fruit obtained from widely divergent climatic parameters suggest that the numerous growth and metabolic processes involved in ripening of citrus fruits have independent internal controlling mechanisms. Apparently these processes interact in different ways with external environmental factors, and are not dominated by a pervasive, common internal maturity factor.