Abscisic acid (ABA) levels in seeds of tomato (Lycopersicon esculentum Mill.) fell about 10-fold during fermentation to remove mucilaginous tissue. Imbibing seeds in 20 µg/ml ABA prevented germination and increased ABA content of the seed 15-fold. Subsequent germination in water averaged greater than 90%.
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).
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.
Vegetative and fruit responses of ‘Montmorency’ sour cherries to Alar were evaluated from 1966 to 1968. Mature trees were treated with from 1000 to 8000 ppm of Alar at 2 weeks after full bloom. Alar significantly increased fruit color and decreased the force required to separate the fruit from its pedicel early in the harvest season. These differences were sufficient to advance the start of commercial harvesting one week. Fruit firmness was significantly increased in both handpicked and mechanically harvested fruit. Alar treated fruit showed a significant ability to resist softening when mechanically harvested. Fruit color and firmness enhancement was evident in both canned and frozen processed fruit.
Alar altered the fruit growth curve and contributed to a more uniform size. Fruit acidity and respiration were significantly reduced. Alar reduced terminal growth, by reducing internode length, but increased flower bud initiation.
Fruits were collected on weekly intervals in 1980, beginning at fruit set (ovary shatter) and continuing through harvest. Additional samples collected at harvest in 1980 and veraison in 1981 were sorted into preveraison green, postveraison green, and ripening categories. Seed number per berry was directly related to accumulation of 14C-photosynthate, fresh weight, and dry weight. Seed number had little relationship with berry content of indoleacetic acid (IAA), abscisic acid (ABA) or percentage of acidity. Percentage of soluble solids was not affected by seed number prior to veraison, but after veraison, percentage of soluble solids and intensity of juice color were inversely related to seed number. Nonripe fruit at the time of harvest had fewer seeds per berry, and fruit containing an immature seed did not accumulate ABA or enter veraison. IAA levels were similar in ripening and nonripening fruit. IAA declined to basal levels by about 55 days after peak bloom. ABA began to increase after 65 days from peak bloom and berry changes associated with veraison occurred after 72 days.
To clarify the cause of low sucrose accumulation in seedless `Crest Earl's' netted muskmelon [Cucumis melo L. (Reticulatus Group)] fruit induced by CPPU, the activity level of sucrose metabolizing enzymes was compared between seeded and seedless fruit. CPPU promoted growth of the ovary in both pollinated and nonpollinated flowers until 10 days after anthesis (DAA), and thereafter the growth rate of nonpollinated fruit was lower than in the controls. Sucrose accumulation of seedless fruit remained lower than in seeded fruit, but there was no difference in fructose and glucose content between seeded and seedless fruit. Acid invertase activity declined sharply 20 DAA in seeded and seedless fruit, and was hardly detectable at 35 DAA, when sucrose accumulation began. Neutral invertase (NI) activity in both seeded and seedless fruit decreased from 20 DAA until 35 DAA; thereafter, NI activity in seeded fruit remained relatively constant, with a small but insignificant increase in maturity. Sucrose synthase (SS-c: sucrose cleavage direction) activity in seeded fruit decreased from 20 to 30 DAA, and then increased as fruit matured, while SS-c activity in seedless fruit did not change during development. Sucrose phosphate synthase (SPS) activity in seeded fruit increased from 25 to 30 DAA and remained relatively constant until harvest. SPS activity in seedless fruit declined gradually from 30 to 45 DAA, then remained at a low level. Sucrose synthase (SS-s: sucrose synthesis direction) activity in seeded fruit increased rapidly after 30 DAA, concomitant with sucrose accumulation. In contrast, SS-s activity in seedless fruit increased only slightly after 30 DAA indicating levels of SS-s activity are closely related to sucrose accumulation in parthenocarpic seedless muskmelons. Chemical name used: [1-(2-chloro-4-pyridyl)-3-phenylurea] (CPPU).
Separation pull force of thornless blackberries (Rubus spp.) decreased at a rate insufficient to allow adequate mechanical harvest differentiation between the black ripe and red fruit. When a force sufficient to remove 80% of black ripe fruit was applied to floricanes, green and red fruit comprised as much as 50% of detached fruit. Ethephon, applied at 500 and 1000 ppm 4 days prior to harvest, reduced fruit size and total soluble solids, but increased the ripe/unripe harvest ratio more than two-fold. Two shaker models tested were effective in removing black ripe fruit. Of the two, the unit with higher frequency (40 vs. 25 Hz), but with shorter stroke (1.7 vs. 5.0 cm), was more efficient, as it removed fewer unripe fruit. Chemical name used: (2-chloroethyl) phosphonic acid (ethephon).
Flowering occurred over a 5-week period in semi-erect, tetraploid thornless blackberries (Rubus spp.) (cvs. Black Satin, Hull Thornless, and Dirksen Thornless). The harvest durations were slightly longer. The terminal flower bud of the primary axis (A1) of the inflorescence was first to open, followed by the terminal flower bud on one of basal secondary axes (A2). Remaining terminal flower buds on A2 axes opened sequentially in acropetal direction at a constant rate (two flowers/day). However, bloom pattern of flower buds located laterally on A2 axes was less definite. Within a floricane, the bloom on the primary fruiting laterals began at the distal end and progressed basipetally to the cane base. Ripening sequence of berries in a cluster followed that of the bloom. The time difference in anthesis between fruiting laterals and among flower buds within inflorescences was a major factor affecting the range of fruit maturity.
Trans-jasmonic acid (JA), cis-JA, and trans-methyl jasmonate (MeJA) were quantified in pulp and seeds of `Tsugaru' apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] and `Satohnishiki' sweet cherry (Prunus avium L.). Trans-JA and cis-JA showed similar changes during development in both types of fruit. JA concentration was high in the early growth stages of apple pulp development, decreased with days after full bloom (DAFB), and then increased again during maturation. There was an initial decrease in concentration of MeJA in apple pulp, followed by a general increase towards harvest. Concentrations of JA and MeJA in the pulp of sweet cherry were high during early growth stages, then decreased towards harvest. PDJ treatment at 104 DAFB (preclimacteric stage) increased endogenous abscisic acid concentration and anthocyanin concentration at 122 and 131 DAFB (maturation stages) in apple. JA concentration in apple seeds was also high in the early growth stages, then decreased, and finally peaked at harvest. MeJA concentration in apple seeds increased towards harvest. In the seeds of sweet cherry, JA and MeJA concentrations generally increased until harvest. In both types of fruit, concentrations of JA and MeJA in the seeds were higher than those of pulp. On a dry weight basis, changes in concentration in the seeds preceded those in the pulp. These results demonstrate that relatively high amounts of JA and MeJA are associated with young developing fruit. These substances may have a role in regulation of fruit growth at early growth stages, though this has not been demonstrated. Chemical name used: n-propyl dihydrojasmonate (PDJ).
The effects of rootstock on `Delicious' (Malus domestics Borkh.) apple ripening, quality, size, mineral composition, and storability were studied over 4 years. Removal of the effects of crop load by analysis of covariance suggested that M.27 EMLA advanced fruit ripening and that M.7 EMLA delayed fruit ripening. Ott.3, M.9, MAC 9, OAR 1, M.9 EMLA, and M.26 EMLA either were inconsistent in their effects on ripening or consistently-resulted in an intermediate time of ripening. Fruit size consistently was largest from trees on M.9 EMLA and smallest from trees on OAR 1. Fruit from trees on MAC 9 generally had relatively high Ca contents, and fruit from trees on OAR 1 had relatively low Ca concentrations. The effects of rootstock on storability appeared to be related to their effects on maturity arid Ca levels.
