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early stages of growth and development as the glucose and fructose concentrations increased slightly through 28 DAA. It has been well established that sucrose accumulates massively during the final stages of maturation and is the dominant sugar in most

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ReTain™ is a plant bioregulator containing the active ingredient aminoethoxyvinylglycine (AVG), which inhibits the ethylene biosynthesis pathway. In 1997, the first efficacy studies on `Royal Gala' apple with ReTain™ were conducted under New Zealand conditions in Hawkes Bay. ReTain™ was applied 4 weeks before the anticipated start of harvest on `Royal Gala' at 850 and 1700 g·ha–1 with or without adjuvants. ReTain™ application delayed the onset of `Royal Gala' fruit maturation between 1 and 2 weeks, resulting in enhanced fruit size and fruit flesh firmness at harvest. The optimum response for delaying the onset of fruit maturation was achieved using ReTain™ at 850 g·ha–1 if applied in combination with a wetter. Fruit were also graded for fruit quality and air-stored at 0.5 °C. Fruit after 10 weeks of storage showed no difference in fruit flesh firmness, but all ReTain™ treatments had fruit with less yellow background colour compared with untreated fruit. In 1998, efficacy studies were undertaken in three geographical locations on `Royal Gala'. ReTain™ was applied at a rate of 830 g·ha–1 in combination with Silwet L-77 at 0.1%. All trees with the exception of `Royal Gala' grown in the Hawkes Bay had not received any ReTain™ previously. In all regions, seasonal changes in background color and starch pattern index were delayed by ReTain™ treatment. A concurrent delay of an increase in soluble solids concentration and retention of higher flesh firmness were also induced by ReTain™ treatment.

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Abstract

Leaf samples of Ilex opaca ‘Miss Helen’ were collected over a 2-month period and analyzed on a mg/g basis for total nonstructural carbohydrates (TNSC), individual ethanol soluble sugars (IESS), total ethanol soluble sugars (TESS) and apparent storage carbohydrates (ASC). Samples were preserved for analysis by 4 methods: 1) liquid nitrogen killed freeze-dried (NFD); 2) liquid nitrogen killed oven-dried (NOD); 3) oven-dried (OD) and 4) ambient air-dried (AD). The samples showed significant decreases in TNSC between the NFD and NOD, NOD and OD and OD and AD methods; a significant decrease in TESS with the NOD and OD methods and a further significant decrease in TESS with the AD method. A significant increase in ASC was noted with the AD method. Gas liquid chromatographic analysis of the IESS revealed a significant decrease in D-fructose and D-galactose with the AD method, a significant decrease in α-D and β-D glucose with the OD method and an additional decrease in both sugars with the AD method. Sucrose was undetectable with the NOD method, and was significantly decreased with the OD and AD methods. TNSC, TESS and ASC all decreased significantly with leaf maturation and expansion. Time of day of sampling showed no significant differences in any carbohydrate fraction.

Open Access

Abstract

Maturation and germination of mango (Mangifera indica L.) somatic embryos were achieved by sequential transfer of heart-shaped somatic embryos on a series of media based on the B-5 formulation. Precocious germination and other developmental abnormalities were controlled by incorporating 3 μm abscisic acid (ABA) and 6% (w/v) sucrose in the medium. Other factors, including the substitution of Gelrite (0.175%) for agar, the use of solid rather than liquid medium, and the culture of somatic embryos in darkness until physiological maturity also affected normal growth and development. Coconut water (20%, v/v) was also essential for mango somatic embryogeny. Germinated mango somatic embryos were successfully established in planting medium and they have continued to grow in a greenhouse.

Open Access

Abstract

A single-value estimate of maturity response and an independent estimate of the thinning response to treatment can be determined from detailed harvest records. Thinning index is estimated from the total number of fruit per tree; maturity response is estimated from the weighted-average harvest date.

Open Access

In New Zealand, harvest maturity for kiwifruit is determined by the soluble solids concentration (SSC) of juice (minimum 6.2%). Commercial maturity differs in various regions of the country within each season and between years and may be due to differences in temperatures during growth.

Mature `Hayward' kiwifruit vines were grown in controlled environment temperature treatments of 14/8, 18/8, 22/8, 26/8, 14/12 and 22/12C to determine whether the increase in SSC at low night temperatures recorded in a related study was a result of the mean temperature, the min. daily temperature, or the magnitude of the max./min. temperature difference. Measurement was made of fruit size, firmness, starch and total sugar concentrations in the fruit at 10 day intervals.

SSC increased fastest with the coolest mean temperature irrespective of the min. temperature or max./min. difference. In the coolest treatment the concentration of starch decreased rapidly with a rise in total sugar, in the warmest treatment the change in the carbohydrate components was slower. Data will be used to predict harvest date at commercial orchard sites based on field temperature measurements.

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To understand the relationship between fruit cracking and gene expression patterns, we identified two expansin genes from litchi (Litchi chinensis Sonn.) fruit and then examined their expression profiles in pericarp and aril at different stages of fruit development, using the cracking-resistant cultivar Huaizhi and the cracking-susceptible cultivar Nuomici. Two full-length cDNAs of 1087 and 1010 base pairs encoding expansin, named LcExp1 and LcExp2, were isolated from expanding fruit using RT-PCR and RACE-PCR (rapid amplification of cDNA ends) methods. LcExp1 mRNA could be detected from the early stage of fruit rapid growth (59 days after anthesis). The LcExp1 mRNA increased and reached to the highest level at the end of growth phase (80 days after anthesis) in pericarp of `Huaizhi', while the mRNA could be detected at the stage of rapid fruit growth, then increased slightly and finally kept remained almost constant in the pericarp of `Nuomici'. Similar accumulation of LcExp2 mRNA was observed in fruit aril of `Nuomici' and `Huaizhi', whereas LcExp2 accumulated only in pericarp of `Huaizhi' but did not appear in pericarp of `Nuomici'. The results indicate that expression of two expansin genes in litchi pericarp are closely associated with fruit growth and cracking.

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Abstract

Field experiments were conducted on organic soil for 2 years to evaluate the influence of frequent irrigation and topdressings with N on growth, maturity and storage life of onions (Allium cepa L.). With no irrigation, growth to midseason, maturity, and final yield were not influenced by increasing amounts of N. The growth to midseason, and the final yield increased and maturity was earlier with increasing amounts of N applied to onions receiving 5 cm of rainfall + irrigation per week. Sprouting in storage was earlier with high N and latest with no N or with the low N rates. The effect was greater with irrigation.

Onions did not respond to N topdressing without irrigation even though rainfall was regular. With irrigation, the highest yield and earliest maturity was obtained with 22 or 34 kg of N/ha applied whenever the crop received 10 cm of water. No advantage in yield or maturity was obtained by applying N after mid-July. Maturity was earlier without irrigation regardless of N treatment.

Open Access

Abstract

Pomegranate (Punica granatum L. ‘Wonderful’) fruit reached horticultural maturity for commercial harvest when the soluble solids content (SSC) attained a fairly constant level of 15%. The level of titratable acidity (TA) varied from one location to another and from one year to the next but also generally remained stable at the same time that the SSC reached 15%. After harvest, there was no further change in either SSC or TA at 20°C, but redness of the juice continued to increase in intensity up to and after harvest. The respiration pattern of the mature fruit was of the nonclimacteric type, with only traces of ethylene evolved on occasion. Ethylene treatment of the fruit caused a rapid transient rise in CO2 evolution but no changes in SSC, TA, and fruit or juice color. A pseudo-climacteric pattern of respiration was found in very young immature fruit. The respiration rate of dehisced arils paralleled that of the intact fruit, but there was no response to exogenous ethylene treatment. Ethylene evidently stimulated the CO2 output only of the fruit rind.

Open Access

Softening and liquefaction of `Solar Set' locules was studied by examining cell wall polysaccharides during fruit developmental stages (FDS) of immature green, mature green and breaker. Ethanol insoluble solids (EIS) were sequentially extracted by H2O, CDTA, and Na2CO3 solutions. The chromatograms of gel filtration among the same-solution extracts of EISs from three FDS were similar. Gradient DEAE also yielded similar patterns among FDS in each extraction solvent, even though the patterns of Na2CO3 extracts differed from those of H2O and CDTA extracts. The mole ratio of total polyuronides decreased for Gal, Ara, and Xyl at later FDS in both EIS and in all extracted polymers. Gal had the highest mole percentage of total neutral sugars, followed by Ara, Xyl, and Rha. While the mole percentage of neutral sugars for Gal, Rha, Ara, and Xyl were relatively similar among FDS in H2O extracts, those in CDTA and Na2CO3 extracts either increased or decreased, depending on individual neutral sugar. SDS-PAGE showed increased density in locule-tissue proteins, especially one with a molecular weight of less than 20 kDa, during later FDS. Results indicate that pectin depolymerization was limited and major neutral sugars commonly composing side chains showed a net decrease.

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