Search Results
Abstract
It is generally agreed that fruit ripening is a biologically active process often involving high metabolic activity, increased activity of some enzyme systems, and ultimately in fleshy fruits, deterioration of the organ. These events occur in nature only at the proper physiological stage indicating that natural control systems operate to prevent premature ripening. Because of the dynamic nature of ripening in many species, it is probable that endogenous control systems also function to initiate ripening at the proper stage of ontogeny. The presence of these natural control mechanisms suggest that ripening may be subject to manipulation by horticultural, physiological or biochemical means and indeed, we are becoming increasingly aware of and conversant with concepts and techniques leading to control of this important plant process.
Abstract
Fruit set on mature spurs and on 1-year-old wood (lateral bloom) was followed as a step in the development of a chemical thinning protocol for ‘Greensleeves’ apple trees. Initial set (fruit firmly attached 15 days after full bloom) was a reasonable predictor of final set on spurs but not on lateral clusters. High initial set values on lateral clusters reduced final set. Likewise, initial and final set values on either spur or lateral clusters were inversely related following a 1000 ppm carbaryl treatment, although lateral clusters were more readily thinned than spur clusters by carbaryl. Without the carbaryl treatment, final set per cluster was comparable on spur and lateral clusters, and final set on lateral clusters was improved by defruiting alternate clusters on these 1-year-old branch sections 15 days after full bloom.
Abstract
In British Columbia, ‘Bartlett’ pears are thinned with naphthaleneacetamide (NAAm) applied by gun application at 10 μg-liter (w/v) or with air-blast sprayers at 44 g a.i.ha-1, between 13 and 21 days after full bloom. Concern has been expressed by packinghouse personnel about the storage quality of these pears. Higher incidences of breakdown have been suggested, and no controlled experiments have been reported to substantiate or refute such claims. Therefore, a study was conducted during 1980-1983 to assess several quality parameters of ‘Bartlett’ pears thinned by hand and with NAAm.
Root and shoot growth of peach seedlings was strongly suppressed when the roots were held at 8 to 10C. Shoot and root dry weights and root volume increased linearly with increasing root-zone temperature (RZT) to 22C. GA3 at 5.7 μm (2 ppm) added to the aerated full nutrient solution reversed the effect of low RZT on shoot elongation but inhibited root growth at all RZTs. Paclobutrazol (PBZ) (6.8 × 10-3μm) (2 ppb) inhibited shoot elongation at all RZTs and shoot dry weight at 16 and 22C. However, PBZ had no effect on root dry weight accumulation at any RZT. The shoot growth-promoting effect of GA3, relative to control plants, disappeared at higher RZTs, but GA3 reversed the growth-inhibiting effect of PBZ at all RZTs. PBZ increased mean root diameter at all RZTs and significantly increased root volume at 22C. These results show that growth of peach seedlings is profoundly influenced by a cool root-zone environment. The plant growth regulator effects suggest that seedling roots play an important role in whole-plant gibberellin physiology. Some possible implications for fruit production are discussed. Chemical names used: gibberellic acid (GA3); β -[(4-chlorophenyl)methyl]- α -(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol(paclobutrazol,PBZ).
Abstract
‘Golden Delicious’ apples (Malus domestiea Borkh.) were subjected to regular air storage, to conventional controlled-atmosphere (CA) storage (O2 reduced to 2.5% within 20–25 days of harvest by fruit respiration), or to several rapid CA procedures in which O2 levels were quickly reduced to 2.5% by N2 flushing. Fruit subjected to rapid CA (rapid reduction of O2) was consistently 1 to 2 kg firmer and substantially higher in titratable acids than those in conventional CA or air storage at the conclusion of a 6- to 8-month storage period. Long delays in air at 0°C or at ambient temperatures before initiation of O2 reduction resulted in softer fruit.
Abstract
One-year old trees of ‘Spartan’ and ‘Delicious’ apple (Malus domestica Borkh.) on 4 clonal rootstocks were cut to 3 scion nodes and transferred to an aerated Long Ashton full nutrient solution containing 45Ca. Treating the axillary buds with 6-benzylamino purine plus gibberellic acid (BA + GA3) resulted in a small increase in number, fresh weight, and total length of new shoots. Total area of new leaves per tree was unaltered. The BA + GA3 treatment significantly reduced the 45Ca content of the “new shoots” fraction and the total amount of 45Ca absorbed by the treated trees. ‘Spartan’ trees absorbed and transported more 45Ca than did ‘Delicious’ and there was no significant interaction with growth regulators. Of the rootstocks, Mailing Merton (MM) 111 was less efficient than Mailing (M) 26, M 7, or MM 106 in transporting 45Ca across the graft union to either scion cultivar. Growth-regulator-treated trees on M 26 roots absorbed significantly less 45Ca than did comparably treated trees on MM 106 or MM 111 roots.
Abstract
Gibberellic acid (GA3) sprays applied approximately 4 weeks before harvest reduced postharvest surface marking of ‘Van’ and ‘Lambert’ sweet cherries (Prunus avium L.). Surface pitting was reduced more consistently than was visible bruising. GA3-treated fruits were larger and firmer when harvested at a prescribed color maturity. Mesocarp tissue of treated fruits was higher in alcohol insoluble solids, higher in dry weight and contained less nitrogen per unit of fresh or dry weight. Ethephon applied a few days before harvest reduced fruit removal force but did not consistently reduce the incidence of bruising or surface pitting. ‘Lambert’ fruits picked without stems developed more surface pitting than stemmed fruits. It is proposed that GA3 improves postharvest fruit condition by more than one mechanism. Increased fruit firmness may reduce the tendency to bruise but pitting appears to be suppressed by some other physiological effect of the GA3 treatment.
Abstract
Dipping or vacuum infiltrating ‘Golden Delicious’ apples (Malus domestica Borkh.) with water before a 10-day 17% CO2 gassing treatment increased the incidence and severity of CO2-associated peel injury. Susceptible fruits receiving a localized water treatment using flannelette rings were injured preferentially in the wet areas. When the flannelette rings were soaked with water, carbonic acid, 0.05 m succinate, 0.05 m oxalacetate and 0.05 m malonate and the fruits held in controlled atmosphere storage, only malonate caused severe surface injury. Dips or vacuum infiltration treatments involving malonate caused a similar type of injury. However, this injury was clearly different in appearance from CO2 injury. Infiltrating fruits with 0.02 n HCl (pH 1.8) caused no injury suggesting that CO2 injury is not simply due to tissue acidification.
Abstract
Regrowth of decapitated seedlings of apple (Malus domestica Borkh.) of a compact phenotype revealed stronger apical dominance and narrower branching angle than normal seedlings. Normal and compact seedlings were also found to differ in their phyllotaxy at lower nodes. Spraying with 2,3,5-triiodobenzoic acid (TIBA) before and/or after decapitation increased apparent apical dominance in compact seedlings; reduced shoot thickness in normal seedlings; and reduced shoot length and increased branching angle of both phenotypes. Gibberellic acid (GA3) increased shoot length and reversed the TIBA effect on branch angle in the compact seedlings. These differing growth regulator effects are thought to relate to differences in endogenous growth substance levels. Shoot tips of normal seedlings were higher in abscisic acid (ABA) but the dwarf pea bioassay indicated the presence of another acidic inhibitor present only in the compact seedlings. Normal seedlings exhibited higher levels of gibberellin-like growth promoters.
Abstract
Both 2-chloroethylphosphonic acid (Ethrel) and succinamic acid 2,2-dimethyl hydrazide (Alar) aided machine harvesting and improved quality of mechanically harvested sour cherries, Prunus cerasus L., cv. ‘Montmorency’ in a two year experiment. Alar applied two weeks after bloom at 2000 ppm reduced fruit acid levels, reduced the force required for fruit removal, and advanced red color development, but when used alone did not reduce fruit removal force enough to make shake and catch harvesting economic. Ethrel at 500 ppm applied one week prior to harvest on trees previously treated with Alar (2000 ppm) proved to be the best treatment each season on trees tested in both years. This combination resulted in adequate fruit removal coupled with better fruit quality than was attainable with Ethrel alone. Ethrel at 250 or 500 ppm specifically and effectively enhanced fruit removal but was phytotoxic at 1000 ppm as evidenced by gumming and leaf removal.