Plasma membrane (PM) from hypodermal-mesocarp tissues of muskmelon fruits (Cucumis melo L. var. reticulatus Naud.) were compared to the electrolyte leakage changes of the same tissue during maturation and storage at 4 or 24C. During fruit maturity and storage, leakage of the hypodermal-mesocarp tissue increased, which is coincident with increased total sterol: total phospholipid ratios and increased phospholipid fatty acid saturation index of the PM. ATPase activity, a marker for the PM, indicated that the PM increased in buoyant density from 1.13 g.cm-3 to 1.14 g.cm-3 during maturity and ATPase activity peaked with fruit maturation. ATPase activity decreased with 10 days postharvest storage and was less at 24C vs. 4C, which was coincident with increased hypodermal-mesocarp electrolyte leakage. Biochemical changes within the sterol and phospholipid matrix of the PM are suggested to contain the processes capable of altering fruit membrane permeability and subsequent muskmelon fruit storage life.
Total starch and amylose (AM) concentration and a starch index (SI) were determined in `Fuji' apple (Malus domestica Borkh.) fruit from weekly harvests in 1990 and 1991. As apples matured, SI scores increased and total starch and amylose content decreased. The percentage of AM in the total starch decreased as the apples matured. Because KI solutions interact efficiently only with AM, the SI is less reliable in representing total starch during later stages of `Fuji' apple maturation.
Fig fruits treated with 2-chloroethylphosphonic acid (Ethrel) during Period I (initial rapid growth) ceased growth and abscissed. Treatment during Period II (slow growth) stimulated growth and maturation, but quality equal to that of later maturing control fruits was not attained unless the fruits were treated late in Period II. Although Ethrel-treated fruits matured from two to more than three weeks earlier than control fruits, their ultimate average diameter, fresh and dry weights were not significantly different from the control.
Experiments were conducted in 1989 to determine the heritability of shortened fruit maturation (SFM) period in 871213-1, an inbred cherry tomato line (Lycopersicon esculentum var. cerasiforme (Dunal.) A. Gray), and to determine the relationship between this trait and fruit size. In the first study, a cross was made between 871213-1 and NC 21C-1, an inbred cherry line. NC 21C-1 had a mean maturation period of 40.8 days compared to 32.0 days for 871213-1. A mean maturation period for the F1 hybrid of 32.9 days and 32.2 days was found using 871213-1 as the female and male parent, respectively. Analysis of the data from parental, F1, F2 and backcross generations yielded estimates of broad-sense and narrow-sense heritabilities for SFM as 0.72 and 0.56, respectively. Further analysis indicated that genetic control of SFM was quantitative in nature and highly dominant. A test for epistatic interaction showed significance. In the second study, an F2 population from the cross 871213-1 x NC 309-1, a large-fruited tomato line (Lycopersicon esculentum Mill.), was evaluated to determine if any correlations existed between fruit size and SFM. Two fruit characteristics, locule number and fruit weight, were used as estimates of fruit size. Correlations between SFM and these two characteristics were +0.28 and +0.61, respectively. Broad-sense heritability of SFM was estimated as 0.64.
Cell suspension cultures of four date palm cultivars were established, namely, Niboat Saif, Madjhool, Sukarri, and Berhi. In this study, two factors were tested for their effect on embryo maturation and hyperhydration. The effect of sucrose concentration was assessed by inoculating 0.5 g of embryogenic callus into a liquid MS basal medium supplemented with 10 mg/L inositol, 3 mg/L glycine, 20 mg/L glutamine, and 0, 20, 30, 40, 50 g/L sucrose. Polyethylene glycol (PEG) concentration effect on embryo maturation and hyperhydration was tested. PEG (molecular weight 7000–9000) was added at concentrations of 0, 10, 30, and 60 g/L to the date palm suspension cultures. Cultures were examined and subcultured every 3 weeks for 2 months. Embryos formed were then transferred to a solid MS medium supplemented with 10 mg/L inositol, 3 mg/L glycine, 5 mg/L glutamine, and 30 g/L sucrose. The number of embryos germinated from each treatment was counted to compare cultivar differences. Preliminary data suggests that the medium containing 30 g/L sucrose is most effective for embryo maturation, and those embryos germinated when transferred to a solidified MS medium. The study found that incorporating PEG into the medium reduced the hyperhydration of date palm tissues. The various cultivars reacted differently to the treatments employed.
Of 10 genotypes of bean (Phaseolus vulgaris L.) studied, all produced better quality seeds at low maturation temperatures. Resistance to mechanical injury was also maximal in low temperature matured seeds. In general, the colored seeded genotypes unlike the white seeded genotypes, tolerated a wide range of maturation temperatures. However, ‘Spartan Arrow’, which has colored and large seeds was susceptible to mechanical injury at all maturation temperatures, and the white seeded line 26W showed good tolerance at all temperatures. It appears that it will be possible to breed white-seeded lines showing improved tolerance of high seed maturation temperatures.
Applications of (2-chloroethyl)phosphonic acid (ethephon) to peach trees (Prunus persica(L.) Batsch) prior to the completion of pit hardening (stage II) resulted in the early onset of the final fruit swell (stage III) and hastened fruit maturity. Applications during stage I (initial swell) were ineffective. Succinic acid-2,2-dimethylhydrazide (SADH) applications made prior to the completion of stage II resulted in early fruit maturation. Ethephon and SADH in combination during stage II or in successive applications (SADH in stage I and ethephon in stage II) were more effective in the promotion of early fruit maturity than either material alone.
Changes in the physical and chemical properties of the plasma membrane from hypodermal mesocarp tissue of netted muskmelon (Cucumis melo L. var. reticulatus Naud.) fruit were compared in relation to the permeability changes of the same tissue during fruit maturation and storage at 4 or 24C. As muskmelon fruit progress from immaturity to maturity, and with storage of mature fruit at 4 or 24C, increased permeability of the hypodermal-mesocarp tissue occurs coincident with an increase in the saturation index of the plasma membrane phospholipids. Buoyant density of the plasma membrane from hypodermal mesocarp tissue increased from 1.13 to 1.14 g·cm-3 during fruit maturation. Vanadate-sensitive ATPase (EC 188.8.131.52) activity was highest in mature fruit at harvest. After 10 days of storage, vanadate-sensitive ATPase activity was much lower in fruit kept at 24C than in those kept at 4C. The decrease in vanadate-sensitive ATPase activity in fruit stored at 24C was correlated with increased hypodermal-mesocarp membrane permeability. We suggest that biochemical changes affecting the lipid matrix of the plasma membrane influence fruit membrane permeability and possibly muskmelon storage life.
The coordinate expression of mRNA classes in pecan (Carya illinoensis) zygotic and somatic embryos has been studied. MRNA was isolated from zygotic embryos at early and late maturation stages (12 to 22 weeks post-pollination) and during germination. Additionally, mRNA was isolated from somatic embryos derived from a repetitive embryogenic system prior and after cold (6 weeks at 4°C) and desiccation treatments (5 days). These treatments have been determined to enhance somatic embryo conversion. The abundance of embryogenic mRNA classes was determined using various cloned cotton mRNA probes (Hughes and Galau, 1989). This study is a part of our efforts to elucidate the developmental and physiological differences between zygotic and somatic embryo systems in pecan.
Aminoethoxyvinylglycine (AVG) applied to apple trees (Malus domestica Borkh.) 1 week before harvest suppressed C2H4 production and delayed C2H4 peaks of fruit kept at room temperature. Early season cultivars (‘Early McIntosh’, ‘McIntosh’) were less affected by AVG than were late-season cultivars (‘Cortland’, ‘Royal Red Delicious’). While ripening was significantly delayed, maturation of ‘Puritan’ apples, as judged by changes in firmness, peel chlorophyll concentration, percent soluble solids, flesh starch concentration, and titratable acidity, was unaffected by AVG tree-sprays applied up to 6 weeks before harvest. Addition of C2H4 to the storage atmosphere accelerated ripening of AVG-treated fruit, whereas their ripening was slowed by storage at 0°C rather than at 3.3°.