Metabolism and translocation of 1, 2-14C(2-chloroethyl) phosphonic acid in Prunus persica (L.) Batsch

1,2-¹⁴C (2-chloroethyl)phosphonic acid (¹⁴C-CEPA) translocation and metabolism was studied in short-term experiments on ‘Andross’ peach trees at the end of Stage I of fruit development. The chemical was applied to the fruit surface or to the abaxial surface of the basal leaf of a developing shoot. When the tracer was applied to the fruit, no translocation of the chemical occurred. When the ¹⁴C-CEPA was applied to the leaf, translocation was observed. Thin-layer chromatography (TLC) of the radioactivity recovered in acidic methanol extracts of both fruits and one-year shoots, collected 24, 48 and 96 h after ¹⁴C-CEPA application to the leaf, indicated that the translocation occurred in forms different from the original chemical. Treatment of chromatograms with AgNO₃ and FeCl₃ at 100°C showed that the colour reaction of sugars was associated with the radioactive areas. Therefore it seems likely that the translocation of ¹⁴C-CEPA occurred in sugar-conjugated form. Results of the TLC of ¹⁴C-CEPA before spotting or overspotted with sugars or fruit and leaf extracts, showed that the binding of ¹⁴C-CEPA to sugars is not a metabolic reaction, although the complex, being more stable than the original chemical and biologically active, could have physiological significance in determining long-term responses of tissues to treatments with CEPA.     

Preharvest applications of ethephon reduce superficial scald of ‘Fuji’ and ‘Granny Smith’ apples in storage

In 1989 and 1990, preharvest applications of 2-chloroethyl phosphonic acid (ethephon) at dosages from 50–400 mg 1’1 were applied to ‘Fuji’ and ‘Granny Smith’ apples. In 1989, the greatest reduction in scald after storage on both ‘Fuji’ and ‘Granny Smith’, relative to the untreated control resulted from applying 400 mg 1^?1 ethephon five weeks before harvest and was 45% and 55% of controls, respectively. On ‘Granny Smith’ 400 mg 1^? was also effective when applied three weeks before harvest. In 1990, preharvest applications of ethephon at either 200 or 400 mg 1^?1 reduced scald in both cultivars relative to the controls. Ethephon applied six weeks before harvest had no dosage effect on scald reduction after storage. There was no consistent effect on fruit maturity at harvest from any treatment in either year, and no effect on quality of fruit out of storage.     

Low temperature and gibberellic acid stimulation of germination in Sambucus caerulea Raf

Sambucus caerulea (elder) seeds did not germinate after 4°C cool treatments for up to 30 days, when monitored for a further 30 days at 21°C. When seeds were soaked for 24 h in gibberellic acid (GA₃) prior to and during cold treatment, germination percentage depended on GA₃ concentration and duration of cold treatment. The highest germination percentage was 55 (1000 mg l⁻¹ GA₃ for 30 days at 4°C). When seeds were treated with ethephon at 0, 100 or 1000 mg l⁻¹, no germination was recorded after a subsequent 30-day 4°C treatment. Ethephon added to GA₃ gave a strong interaction, leading to further promotion in germination. Optimal germination was obtained after 1000 mg l⁻¹ GA₃ and 100 mg l⁻¹ ethephon for 30 days at 4°C (69%).The addition of ethanol, acetone, dimethyl sulfoxide or polyethylene glycol to the GA₃ soak as infusion agents either reduced or did not change the germination percentage.     

Controlled Environment Cabinets for Experiments with the Cultivated Mushroom

Apparatus for the study of the effects of temperature, relative humidity and rate of ventilation on the initiation and development of sporophores of the cultivated mushroom is described.

At low rates of ventilation the initiation of primordia was delayed, the yield was reduced, and the sporophores were more spindly as compared with those given higher rates of ventilation.

The number and total weight of sporophores were greater at high relative humidities (80-95%) than at low (40-50%).

The number and total weight of sporophores were greater at 65° F. than at 70° F.     

Thinning ‘Red Fuji’ apples with ethephon or NAA

Summary

A series of trials in Tasmania examined the thinning effects of ethephon and NAA on ‘Red Fuji’ apple. In the ethephon trials, concentrations from 25 to 600 ppm were applied at full bloom (FB) or 14 days after full bloom (AFB) to trees on either seedling or M.M.106 rootstocks. The NAA trial involved spraying concentrations of 5, 10 or 15 ppm at FB or 14 days AFB to trees on seedling rootstocks. Ethephon thinning of ‘Red Fuji’ was similar at FB and 14 days AFB. The dependence of fruit thinning on ethephon concentration was described by fitting non-linear response curves. These relationships were stronger and less variable for M.M.106 than seedling trees. Ethephon proved a satisfactory thinner for trees on both rootstocks. At the high spray volume used, the preferred concentrations at both FB and 14 days AFB would be 25 or 50 ppm for seedling and 100 or 200 ppm for M.M.106 rootstocks. NAA under-thinned at 5 ppm and over-thinned at 10 and 15 ppm at both FB and 14 days AFB. No firm recommendation can be given for NAA as a thinner of ‘Fuji’ at this stage.     

Alleviative effects of calcium acetate on defoliation and fruit drop induced by 2-chloroethylphosphonic acid in citrus

Experiments were conducted to evaluate the effects of calcium acetate on defoliation and fruit drop of ponkan (Citrus reticulata Blanco) and Meiwa kumquat (Fortunella crassifolia Swingle) trees treated with 2-chloroethylphosphonic acid (ethephon). Ethephon at 200 or 300 p.p.m. caused about 20% defoliation of ponkan trees, while this defoliation was materially alleviated by an addition of 0.05 M calcium acetate to the ethephon solution. Acceleration effects on fruit color did not differ with ethephon or ethephon + calcium acetate treatments. Ethephon at 400 p.p.m. caused about 30% fruit drop in kumquat trees, and an addition of 0.05 M calcium acetate to the solution almost completely prevented the fruit drop. Fruit color of kumquat was most advanced by the use of ethephon alone, and the addition of calcium acetate decreased the effect slightly.     

Effect of ethephon on bulbing,bull-necking,yield and sprouting during storage of two onion cultivars (Allium cepa L.)

Ethephon at 1 000 and 3 000 mg l^?1 applied either on one occasion or three times at weekly intervals to two onion cultivars reduced average bulb weight and total yield by 14% to 67%. In cv Hygro the percentage of bull-neck bulbs was reduced by ethephon but cv Cepavon was unaffected. The number of bulbs sprouting in store was reduced in both cultivars by all ethephon treatments except the single 1000 mg l^?1 application.     

Storage conditions and ripening of the custard apple Annona squamosa L.

Annona squamosa is a climateric fruit in which maximal carbon dioxide production preceeds that of ethylene during post-harvest storage. Normal ripening occurred at temperatures between 15 and 30° C, although the fruits were susceptible to fungal attack at temperatures above 25° C. Storage temperatures below 15° C caused chilling-injuries. Ripening was enhanced by removal of carbon dioxide and by addition of oxygen to the storage atmosphere, and delayed by the addition of carbon dioxide or removal of oxygen. Ethylene had no apparent effect on ripening. Fruits maintained under low relative humidities ripened faster than those stored under high-humidity conditions. Dipping the fruits in a solution of indole acetic acid at concentrations between 10^?4 and 10^?2 M accelerated ripening. Levels of both ascorbic acid and glucose increased to a maximum at the climacteric, but decreased as the fruits became over ripe. The stage of “eating” ripeness occurred at the climacteric. Recommended conditions for storing custard apple are: temperatures between 15 and 20° C, low oxygen and ethylene tensions coupled with 10% carbon dioxide and a relative humidity of 85%–90% in the storage atmosphere.     

The relationship between yield and assimilate supply in lychee (Litchi chinensis Sonn.)

Summary

Experiments were conducted on lychee (Litchi chinensis Sonn.) in subtropical Australia (lat. 27° –29°S) to evaluate the role of assimilates on fruit retention. All the leaves of the last flush, all the leaves of the previous flush (about eight leaves per terminal shoot), or all the old leaves were removed from trees. Medium (3–5.cm diameter) or large branches (5–10.cm diameter) were girdled and defoliated after fruit set, and fruit retention compared with ungirdled and undefoliated branches. Other branches were girdled and defoliated between anthesis and fruit harvest. Finally, 20, 50 or 80% of the flowering panicles were defruited on large trees. Defoliated trees had 35 to 45% lower yields than the controls. This was despite the treatment with all the old leaves removed having a much lower leaf area index than the other defoliation treatments (1.7 vs. 2.3 and 2.8). Leaves next to the inflorescences are more important for yield than the older leaves. Fruit retention was very low on girdled branches that had been defoliated, especially when the leaves were removed in the first 20.d after anthesis. This suggests that the yields of girdled branches were determined by the availability of assimilates soon after fruit set. In contrast, the number of fruit retained on ungirdled branches was unrelated to the number of leaves, with defoliation having no effect on yield. Fruit on these branches were supported by resources from elsewhere in the tree. Thinned trees had similar yields to those of unthinned plots (65–82.kg tree^–1). Thinning apparently increased fruit retention in the remaining clusters, under a higher leaf:fruit ratio. There were large differences in the concentrations of starch in the tree, and seasonal changes, with starch declining from flowering to fruit harvest. In contrast, there were only small responses to the treatments, suggesting that the fruit were mainly dependent on current photosynthesis. Photosynthesis in the leaves behind the fruit clusters was more important than photosynthesis in the older shaded leaves.     

Ethephon as a fruit thinning agent for ‘Murcott’ mandarins

Ethephon (2-chloroethylphosphonic acid) was tested as a fruit thinning agent in an experiment on the mandarin cultivar ‘Murcott’.Ethephon was effective at 150 and 300 mg l^?1, but 300 mg l^?1 gave the higher yield and larger fruit sizes over a 2-year period, following a single spray application during natural fruit fall in November. The thinning percentage was also higher when ethephon was applied to trees with a heavy crop density than when applied to trees with a light crop density.     

Effect of Different Treatments on Branching of Some Apple Trees in Nursery

This study was conducted to determine effect of different treatments on branching of one-year-old ‘Fuji’, ‘Granny Smith’ and ‘Red Delicious, Red Chief’ trees which grafted on M9 rootstock. Plant growth promoting rhizobacteria (Pseudomonas BA-8) strain, 6?Benzyl Adenin (BA) and pinching were used to promote branching. The BA (300?ppm) and BA-8 (10⁹CFU/ml) were applied to first twenty centimeters of the top part of trees. The BA, BA-8 and Pinching was applied to trees at 75?cm in length. According to our results, BA-8 and pinching increased number of branches compared to control and BA treatments for all cultivars. BA-8 increased number of branches in ‘Fuji’, ‘Red Delicious, Red Chief’ and ‘Granny Smith’ from 2.71, 1.70 to 4.25 branches/tree, respectively while pinching increased 1,95 branches/tree in ‘Red Delicious, Red Chief’ and 4,01 branches/tree. The highest branch’s angle was obtained from BA-8 bacteria in ‘Fuji’ (64.46°), and ‘Red Delicious, Red Chief’ (52.08°) and ‘Granny Smith’ (56.91°). BA-8 bacteria treatment was found alternative practice instead of pinching in terms of branching performance.     

The Influence of Low Oxygen Levels and Relative Humidity on Storage of Green Tomatoes

Green and red tomatoes were stored for 3 weeks at 10° C. in 100% nitrogen or low oxygen levels and at different relative humidities. Rots were controlled by 69–76% relative humidity (R.H.) but at 86–92% R.H. considerable fungal rotting was evident after 20 days of storage. Superficial discoloration of the skin occurred on green tomatoes stored in 1·5% or less O₂ but none occurred on those stored in 4–5% O₂.

Rots caused by Rhizopus spp. were more successfully controlled by lowering the relative humidity than were those caused by Fusarium or Alternaria spp. Rots following chilling were reduced by lowering the relative humidity.     

Isotopically-labelled nitrogen uptake and partitioning in sweet cherry as influenced by timing of fertilizer application

Sweet cherry (Prunus avium L.) is a fruit of increasing economic importance though it is less significant than other stone fruit species such as peach. Cherry has received little attention concerning nitrogen (N) uptake and dynamics in mature trees. The aim of this work was to determine N uptake and partitioning as influenced by the timing of fertilizer application in 7-year-old sweet cherry trees cultivated in a cold region (Los Antiguos, Santa Cruz, Argentina; 71°38′ W, 46°32′ S). Nitrogen (95 kg ha⁻¹) was applied as ammonium nitrate to a soil with ‘Bing’ sweet cherry trees grafted onto Prunusmahaleb rootstocks. Fertilization was split into two equal applications per treatment, involving either the commercial fertilizer ammonium nitrate or the same fertilizer labelled with ¹⁵N isotope (10% atom.). Treatments consisted of one early spring (full bloom, October 2005) or one summer (late January 2006, 15 days after harvest) application of ¹⁵N ammonium nitrate to three replicate trees. Fruit were harvested in early January and leaves were collected at both full canopy and leaf fall. All trees were excavated in winter (August, 2006). Trees were partitioned into their components: trunk, branches (current-season shoots, 1-year-old and over-1-year-old branches), buds of the same age, small roots (less than 1 mm thick), large roots, leaves (sampled in February and April), and fruit (collected at harvest). Those components were dried and analysed for total N and ¹⁵N content. Total N per tree and N content derived from the fertilizer did not differ between treatments. Summer postharvest ¹⁵N application partitioned not only to structural components (trunk and roots) but also to buds and leaves. Uptake efficiency was significantly (p = 0.0113) higher in the spring than in the summer application (65.7% vs. 37.44%). Nevertheless, 52.5% of N applied in spring was lost due to harvest and summer pruning. This emphasizes the importance of the postharvest N fertilization which increases N accumulation in both reserve organs and buds though, according to our data, it is less efficiently used. The extent of nitrogen uptake, efficiency of use and partitioning in the following growing seasons are still open questions that deserve further research.     

Effects of temperature on fruit thinning with ethephon in ‘Golden Delicious’ apples

The effect of temperature on the ability of 2-chloroethylphosphonic acid (ethephon), when applied at 20 mm stage of fruit development, to induce ethylene evolution of fruit and leaves and abscission of fruit and leaves was determined using 9-year-old root-bagged ‘Golden Delicious’/M.27 apple (Malus domestica Borkh.) trees in environment-controlled growth rooms. Ethephon at 400 μL L⁻¹ effectively thinned apples, and its thinning effect was not affected by increasing day/night temperature from 21.1/10 to 32.2/21.1 °C. Fruit ethylene evolution was enhanced by application of ethephon. Peak fruit ethylene evolution occurred 1 day after application of ethephon when day/night temperature was 32.2/21.1 °C whereas it occurred 2 days after application of ethephon at a day/night temperature of 21.1/10 or 26.7/15.6 °C. Ethephon increased leaf ethylene evolution drastically but it did not induce leaf abscission regardless of temperature.     

Laboratory Studies on the Toxicity of Hydrocarbon Oils and Similar Substances to the Eggs of Some Common Orchard Pests III. Experiments on the Eggs of the Green Apple Aphis (Aphis Pomi Deg.)

Four days after placing known amounts of a 20 p.p.m. aqueous solution of 1-naphthaleneacetic acid (NAA) (¹⁴C carboxyl-labelled) on the upper surface of detached apple leaves in a greenhouse, approximately 10% of the applied radioactivity was found within the leaves, 10% was still on the surface, and 80% was lost.

Apple leaves were found not to decarboxylate NAA, and the disappearance of carbon 14 from the leaf surface is attributed to the breakdown of NAA by ultraviolet radiation. The carboxyl group is lost, leaving a neutral compound, inactive in auxin tests, whose ultraviolet absorption spectrum is similar in general form to that of NAA.

When a 50 p.p.m. aqueous solution of NAA containing a non-ionic wetting agent is placed on the surface of an apple leaf held in darkness at 25° C., absorption proceeds at approximately 1% per minute until the surface deposit is dry. Thereafter, absorption continues much more slowly and at a rate depending on the relative humidity of the air and the temperature.

In experiments on translocation a 50 p.p.m. solution of radioactive NAA was applied to the basal leaves of fruiting spurs of Miller's Seedling. Over a period of 4 to 5 days, 17 to 28% of the carbon 14 which entered the leaves was translocated to the bourse and fruits, but between one half and three-quarters of this translocated radioactivity was in a form other than free NAA.

When radioactive NAA was fed into detached apple leaves through the transpiration stream, 80 to 90% was rapidly converted into a watersoluble addition compound (I), neutral in reaction and lacking auxin activity. Over the course of several days this compound was gradually replaced by a second addition compound (II), which is acidic in nature. Compound II built up more rapidly in Cox’s Orange Pippin than in Bramley’s Seedling.

The possible significance of these results is discussed, particularly in relation to the erratic performance of NAA in the field when it is used for the control of fruit drop or as a fruit-thinning agent. 1-NAPHTHALENEACETIC ACID (NAA) is a growth regulator employed in fruit-growing practice for reducing the pre-harvest drop of apples and pears, and as a fruit-thinning agent for apples. One of the chief disadvantages associated with the use of this compound is the variability in response shown by different varieties of apple, and by the same variety when treated under different conditions or in different seasons. These erratic responses make it difficult to predict the results of any particular application of NAA and offer a serious limitation to its use, particularly as a fruitthinning agent.

The aim of the experiments described in this paper was to obtain quantitative data relating to the behaviour of NAA when it is applied in aqueous solution to the surface of an apple leaf. By using NAA labelled with carbon 14 in the carboxyl group, the penetration of this compound into the leaf, its translocation from the spur leaves to the bourse, and its metabolism within the tree were studied. Attention was also devoted to the destruction of NAA by ultraviolet radiation, a discovery that was made during the course of the investigation and which, like the other factors studied, was thought to have a bearing on the variable performance of NAA in the field.     

Studies on Plant Growth-Regulating Substances: I. Field Trials Using Various Synthetic Compounds For the Setting of Outdoor Tomatoes

Blossoming fruit trees in pots, detached blossom spurs and single blossoms were exposed, after various treatments, to low temperature in a cold chamber. Frost damage and supercooling were recorded.

Ability to supercool decrease(j with increasing age of flowers.

Severing of spurs or flowers from a tree favoured supercooling and, the smaller the detached part, the stronger was the tendency to supercool. Removal of wood and leaves from detached spurs increased the proportion of supercooled flowers and decreased the percentage of damaged ones, but spraying with water immediately before exposure to low temperature reduced the effects of these treatments. On the other hand, defoliation of spurs on trees in pots had no effect upon supercooling of flowers but showed a slight tendency to increase the damage.

Varying degrees of competition for water between flowers, leaves and fruits were demonstrated.

Studies of the effect of water supply to flowers before their exposure to low temperature showed that cutting of floral spurs under water suppressed their tendency to supercool as compared with spurs desiccated for 5 minutes, whereas partial desiccation increased the tendency towards supercooling.

Frost damage to flowers wetted before exposure was higher than to dry ones. The degree and method of wetting was important. Wet flowers supercooled for a shorter time, and their supercooling points and “ indicated ” freezing points were higher than those of dry flowers.

Widespread supercooling of blossom occurs in the orchard, but it is usually insufficient to protect from spring frost injury.     

The mode of action of ethephon in increasing health of gladiolus corms

Gladiolus corms and cormels were treated with various combinations of ethephon and the fungicides methylethyl mercury benzoate, benomyl, thiobendazole and methylmercury dicyandiamide either before or after storage at 10 °C and 30 °C for 6 weeks. The treated corms were examined for germination, splitting and rot symptoms caused by Fusarium oxysporum f. sp. gladioli.

Ethephon increased corm splitting in all treatments; it also increased germination in corms stored at 30 °C, and it increased the proportion of corms showing typical Fusarium rot symptoms by stimulating the growth of latent internal Fusarium. The effectiveness of the fungicides tested against F. oxysporum f. sp. gladioli was enhanced by the addition of ethephon. Permeability of corms to methylethyl mercury benzoate was increased by ethephon, and it is concluded that ethephon improves the efficiency of this fungicide, and probably of other fungicides as well, by increasing their penetration into gladiolus corms.     

The Effects of Some Growth Regulators on Peach Flower Bud Abscission

Applications of growth regulators to detached peach laterals in winter had variable effects on flower bud abscission. GA₃ and GA₄₊₇ increased bud abscission while IAA, BA and ABA inhibited abscission. Ethephon had a variable effect. Interactions were obtained between the compounds generally with IAA or GA playing the major role. GA had a peak of activity during a critical period in late winter indicating a variation in responsiveness. Variations in sensitivity to GA were obtained for different cultivars. Field applications of GA₃, GA₄₊₇, and ethephon to Elberta peach trees in winter, alone and in various combinations, promoted bud abscission.     

Potential of ethephon,NAA, NAD and urea for thinning pistachio fruitlets

Alternate bearing, the occurrence of high yield ‘on’ year followed by low yield ‘off’ year, is striking in pistachio (Pistacia vera L.). Floral buds of pistachio are formed a year before bloom, but abscise during the years with heavy crop (‘on’ year). Abscission of floral buds is due to competition between growing seeds on 1-year-old shoots and developing buds on current season growth. We studied the effects of chemical fruit thinning on alternate bearing and nut characteristics in a commercial orchard of ‘Owhadi’ pistachio cultivar during 2003–2004 in Rafsanjan, Iran. In both years, ethephon (100 and 200 mg l⁻¹), naphthaleneacetic acid (NAA) (125 and 250 mg l⁻¹) and urea (2.5 and 5%) were applied to the branch units of each individual ‘on’-year trees. The results showed that ethephon at both concentrations significantly increased fruit thinning and floral bud retention for the subsequent year. Other treatments also increased fruit thinning and floral bud retention but were inferior to ethephon.     

Effects of temperature and plant growth regulators on anthocyanin synthesis and phenylalanine ammonia-lyase activity in chicory (Cichorium intybus L.)

Summary

This study addresses the effects of air temperature and plant growth regulators on anthocyanin synthesis, sugar content and phenylalanine ammonia-lyase (PAL) activity in chicory (Cichorium intybus L.). Anthocyanin in chicory was synthesised at the highest level under 15°/10°C (day/night) temperatures, followed by 20°/15°C, and 25°/20°C; while synthesis was inhibited > 90% at 30°/25°C, resulting in an almost green colour. Sugar contents paralleled anthocyanin development under the same temperatures. The plant growth regulators, abscisic acid (ABA), ethephon and uniconazole all stimulated anthocyanin synthesis, with uniconazole treatment showing the greatest effect. Gibberellic acid (GA₃) inhibited anthocyanin development, while GA₃ in combination with uniconazole alleviated this inhibition.

PAL activity was higher at 15°/10°C or 20°/15°C (day/night) temperatures when plants were treated with ABA, ethephon or GA₃, than at 25°/20°C and 30°/25°C (day/night) temperatures. These results suggest that, under lower temperatures, plant growth regulators may play an important role in anthocyanin synthesis and PAL activity in chicory.