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  • Author or Editor: Robert E. Paull x
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Abstract

Plant growth and tuberous root development in yam beans (Pachyrrhizus erosus L. Urb) were investigated using a series of 2-week plantings from April to December. Decreasing daylength at time of planting initiated tuberous root development, whereas increasing daylength inhibited tuberous root development and promoted vine and leaf growth. Once tuberous root formation and flowering began, stem and leaf growth ceased. At the time of planting, the critical daylength for tuberous root formation and flowering was 11 to 12 hr. The optimum planting date in Hawaii for maximum tuber yield of 24 t·ha–1 for yam beans was found to be September to October. Tuberous root development was sigmoidal, with dry matter percentage declining from 17.5% to 9%. There was little change in tuberous root acidity or total sugars during growth. Titratable acidity was about 20 meq·g–1 fresh weight if not induced to form tuberous roots, and ≈15 meq·g–1 fresh weight in plants forming tuberous roots. Total sugar was in the range of 30 to 50 mg·g–1 fresh weight during tuberous root growth of induced plants. Total phenols in the tuberous root declined during development, whereas roots from plants uninduced to form tuberous roots had an increased level of total phenols.

Open Access

The optimum fertilizer levels of N, P, and K for flower production of field-grown Anthurium andraeanum Andre in Hawaii were determined. Applications were at 0, 224, and 448 kg·ha-1·year-1 with all combinations of each nutrient level. Optimum flower production was achieved at 312N-448P-375K kg·ha-l·year-1. Increased N and K application resulted in a linear increase in flower size. Flower stem length also increased with increasing N, P, and K rates. Maximum flower yield occurred when leaf-tissue levels were 1.87% N, 0.17% P, and 2.07% K. Flower stem length and flower size were at their maximum with leaf N at 1.59% and 1.67% and K at 2.20% and 1.86%, respectively. No relationship was observed between leaf percent P, flower size, or stem length. A range of leaf-tissue levels associated with optimum anthurium flower production was determined for Ca, Mg, B, Mn, Fe, Zn, Cu, and Mo).

Free access

Papaya (Carica papaya L.) leaves are large, up to 70 cm wide, and frequently deeply lobed, with seven to 13 major veins. The scan width of current handheld digital leaf area instruments is generally less than 15 cm. A rapid method is needed to estimate the total leaf area of a plant in the field with leaves at different stages of growth from the apex. The length of the main and side veins of papaya leaves can be used to estimate the area of a single leaf and the total leaf area of the plant. The relationship between main vein lengths and total leaf area was determined for mature leaves from the cultivars Sunset, Line-8, and Kapoho. A simple relationship exists between leaf area and the length of the two main side midribs (L3 and L4): Leaf area (cm2) = −2280 + 87.7*L3 + 55.6*L4 (P > F = 0.0001; r 2 = 0.969), explaining ≈94% of the variation between estimated leaf area and leaf area. The most recently matured leaf is the third or fourth discernable leaf from the apex, with a positive net photosynthetic CO2 assimilation rate and an average area of 2331 cm2 that could fix up to 1.6 g carbon per 10-hour day under full sun. The rate of photosynthesis declined with leaf age, and the overall net photosynthetic CO2 assimilation rate of the plant can be predicted. Following 80% leaf defoliation of the plant, the net photosynthetic CO2 assimilation rate of the most recently matured leaf increased 30% to 50% on days 11 and 19 after treatment when the photosynthetic active radiation (PAR) was approximately half of that on day 15 under full sun when no difference in net photosynthetic CO2 assimilation rate was seen. Fruit removal did not affect the net photosynthetic CO2 assimilation rate. Papaya adjusts its single-leaf net photosynthetic CO2 assimilation rate under lower light levels to meet plant growth and fruit sink demand.

Open Access

Abstract

Sequential changes in starch, sugars, organic acids, and headspace volatiles were determined on single soursop fruits from harvest to fruit breakdown. Sucrose increased 4-fold; maximum concentration occurred 3 days after harvest, then declined to 40% of the peak value. Fructose and glucose increased slowly to a peak 5 days after harvest. The ratio of sucrose, glucose, and fructose, respectively, at the edible ripe stage was 4.3:3.0:3.2. There was a 7-fold increase in malic acid and a 3-fold increase in citric acid. Both acids peaked 3 to 4 days after harvest, then declined. About half of the organic acids were present as salts. Headspace volatile production paralleled ethylene evolution. Volatile production began to increase 3 days after harvest and peaked 2 days later. This peak corresponded with the peaks in total sugars, organic acids, and the edible ripe stage when individual fruit results were compared on the basis of the start of the climacteric respiratory increase. After the peak in volatile production, there was a dramatic drop over the next 3 days in major fruity esters produced, with a gradual increase in volatiles, which probably imparted the off-odor of the overripe fruit. The activities of amylase, polygalacturonase, and cellulase increased during ripening. Starch breakdown leading to sugar and organic acid production occurred before any rise in ethylene production. This breakdown of starch may be an important initiating event in the ripening of soursop fruit.

Open Access

The sugar-to-acid ratio of pineapple (Ananas comosus L.) contributes toward giving the fruit its unique flavor. This ratio is an important indicator of both commercial and organoleptic ripeness, and it is useful in determining a harvest date. Citric acid is the major acid in pineapple and usually is determined by titration to a specific pH endpoint, while sugars are determined as total soluble solids by refractometry. Both acid and sugar levels vary with the season in the year-round production cycle. Acid titration is slow and difficult to perform in the field. A digital acidity meter based upon diluted juice conductivity was evaluated for potential field use. The readings obtained from the meter varied with clone and fruit potassium concentration. The meter had utility for field use to evaluate fruit quality and harvest date. Because fruit potassium levels can vary between harvests, the meter should be recalibrated on a regular schedule to adjust for potential crop management and seasonal effects.

Open Access

The uptake of Ca by `Sunset' papaya (Carica papaya L.) fruit and its role in ripening was studied. The highest mesocarp Ca uptake rate occurred in fruit that were <40 days postanthesis when fruit transpiration was probably highest. Ca uptake rate by the mesocarp was low, from 60 to 80 days postanthesis when fruit fresh and dry weight increased. Mesocarp Ca uptake rate increased again from 100 to 140 days postanthesis when fruit fresh weight growth rate declined and dry weight growth rate increased. Mesocarp Ca concentration did not significantly differ from the peduncle to the blossom end. although Ca was significantly higher in the outer than inner mesocarp at the fruit equator. Mesocarp Ca concentration fluctuated significantly throughout the year ranging from 68 to 204 μg·g-1 fresh weight (FW). Soil Ca application did not always increase fruit mesocarp Ca concentration, while K and N fertilization decreased mesocarp Ca concentration. Attempts to increase mesocarp Ca concentration by spraying CaCl2 onto papaya fruit during growth and by postharvest vacuum infiltration and dipping of the cut peduncle into CaCl2 were unsuccessful. Mesocarp Ca concentration was positively correlated to the firmness of ripe papaya fruit and the rate of softening of mesocarp plugs. Less correlation was found between fruit firmness and the ratio of Ca concentration to K or Mg concentration, or to Mg plus K concentrations. Mesocarp Ca concentration of 130 μg·g-1 FW or above was associated with slower fruit softening rate than fruit with a lower concentration.

Free access

Abstract

Anthurium flower (Anthurium andraeanum Andre) postharvest life was studied relative to water balance. Rate of water uptake declined to 20% of the harvest rate within 10 days. Silver nitrate pulsing reduced the water uptake rate decline and helped to maintain an increased rate 10 days after harvest. The spadix was the site of 50% to 60% of water loss while 20% to 40% of the loss occurred via the spathe and 10% to 20% via the stem. Water loss can be reduced by waxing with carnauba and other commerical fruit waxes, and this treatment can double postharvest life. The inhibitors Co2+ and amino-ethoxyvinylglycine significantly reduced the peak of ethylene produced, whereas inhibitors of ethylene response (Ag+, nitrogen and carbon dioxide bubbling) reduced autocatalytic ethylene production from cut anthurium flower stem sections. The cut stem ethylene production peaked 10 hr after cutting, then declined. Cytokinin also affected postharvest life, apparently via effects on water balance. Biocides (quaternary ammonium compound, streptomycin, nystatin, chloramphenicol, and a commercial flower preservative) had little effect on vase life. Wound ethylene-induced stem clogging and not microbial clogging of vascular tissue probably was the major factor limiting postharvest life, inducing water stress and senescence.

Open Access

Abstract

Physiological changes accompanying anthurium flower (Anthurium andraenum Andre) senescence were monitored. Silver pulse treatment of flower stems was used to modify the senescence process. Florets on the spadix continued to open for 5-10 days after harvest. In both treated and untreated flowers, respiration rate was low until senescence began 8 days after harvest. The rate of increase in respiration of silver treated flowers was half that of the controls. Ethylene production remained low throughout the postharvest life of the flowers. Ten days from harvest spathe color began to change from red to blue with no significant changes in the ratios of the anthocyanins. There was a simultaneous change in tissue pH, from 5.2 to 5.6. Tissue organic acids remained constant during senescence. There was a significant increase in spathe tissue ammonium ion due, apparently, to protein breakdown which probably caused the increase in tissue pH. The concentration of tissue phenolics increased during senescence and could have intensified the color change by copigmentation. Flower senescence apparently was not due to a shortage of carbohydrates, though tissue starch levels did decline by about 25%. The ratio of free sugars in the stem, spathe and spadix remained constant with a slight decline in concentration during postharvest life. Senescence probably was caused by water stress due to stem plugging of undetermined nature. Silver-pulsing of the stem reduced the amount of plugging and therefore reduced the rate of change of all the senescence processes.

Open Access

Papaya (Carica papaya L.) source size and sink strength were modified by a single defoliation or continual defoliation and fruit thinning. Fruit set, development, weight, total sugar (sum of sucrose, fructose, and glucose), sucrose phosphate synthase (SPS), sucrose synthase (SS), and acid invertase (AI) enzyme activities in response to defoliation and fruit thinning were determined. The effects of defoliation and fruit thinning varied with weather conditions, plant growth conditions, and cultivar. Removal of 75% of the leaves significantly reduced new flower production and fruit set, and decreased ripe fruit total soluble solids (TSS), while 50% defoliation did not reduce new fruit set or ripe fruit TSS. When every third leaf from the oldest leaf was not removed, the number of new flowers was reduced by 47% more than when the same number of leaves was removed from the oldest to younger leaves. Continual removal of old leaves reduced new fruit set, fruit weight, and TSS in the 168 day experimental period. Fruit thinning increased new fruit set and ripe fruit TSS. Larger fruit size, faster fruit development, lower respiration rate, and higher sugar contents and AI activity were observed in immature (young) fruit when old fruit were removed. AI activity was reduced during early fruit development and increased again in mature fruit in plants subjected to defoliation, and suggested a role for AI in mature fruit sugar accumulation, while SS activity declined significantly in fruit 154 and 175 days after anthesis and in mature fruit when plants were subjected to continual defoliation. SPS activity was not affected significantly by defoliation or fruit thinning. Source-sink balance was critical for papaya fruit set, development, and sugar accumulation and each mature leaf was able to provide photoassimilate for about three fruit.

Free access

Avocados cannot be exported from Hawaii to the continental United States without a quarantine treatment to prevent the spread of fruit flies. Research was conducted on the maturity and infestation potential of ‘Sharwil’ avocados to assist in development of a multicomponent systems approach for quarantine security. Changes in fruit dry matter content and oil content were determined throughout the harvest season for ‘Sharwil’ avocados grown at three orchard elevations over two production seasons. Also, the ability to infest fruit with Mediterranean fruit fly and oriental fruit fly was measured throughout the harvest season and during fruit ripening. Fruit quality was consistent from one year to the next, regardless of orchard elevation, however, the time of harvest within a production season impacted avocado quality. Late season fruit had higher dry matter and oil contents, were smaller in size, and had a shorter shelf life than early and midseason fruit, but fruit flavor and texture did not change throughout the season. Mean dry matter content ranged from 32% (30 Jan.) to 38% (24 Apr.) in 2007 and from 29% (8 Jan.) to 40% (29 Apr.) in 2008. Percentage of oil content ranged from 21% to 25% in 2007 and from 18% to 28% in 2008. ‘Sharwil’ fruit with a minimum mean oil content of 18% had 29% dry matter and acceptable sensory quality. The dry matter and oil contents of individual avocados were highly correlated (r = 0.97). Avocado was a poor fruit fly host immediately after harvest but became an increasingly favorable host as fruit ripened. Fruit fly infestation rates were similar among early, mid- and late season fruit. The results could be used to develop a maturity standard for ‘Sharwil’ avocados based on dry matter content at harvest, and to develop guidelines for postharvest practices of a systems approach for quarantine security.

Free access