Search Results
Abstract
Observations of pulp and rind tissue of stylar-end breakdown in ‘Tahiti’ lime (Citrus latifolia Tan.) fruit indicate that the disorder is a result of juice invasion of rind tissue at the stylar end causing a tan, watery patch.
Abstract
Black walnut toxicity to crop plants was found to be due to the juglone (5-hydroxy-1, 4-naphthoquinone) in the tree (5). Cook (3) and Massey (9) suggested that toxic material came from the roots of the walnut tree. Bode (2) believed that the toxin came from the leaves. However, the quantity of juglone in the different parts of the walnut tree has not been fully established. Daglish (4) conducted experiments on Juglans regia, in which he suggested that juglone existed in the plant as glucoside of 1,4,5-trihydroxynaphthalene. On hydrolysis it yielded glocose and alpha-hydrojuglone.. This non-toxic hydrojuglone is oxidized to its toxic juglone from exposure to the air or some oxidizing substance from roots of other plants (6). Recent experimental data (Wang, unpublished) showed that 10 ppm commercially purified juglone reduced tomato seedling growth by 50 per cent when roots were immersed in the solution. A 100 ppm application killed the seedlings.
Abstract
The influence of elevated temperature, fruit size, and juice content on the incidence of stylar-end breakdown, a postharvest disorder common to ‘Tahiti’ lime fruit (Citrus latifolia Tan.), was investigated. Freshly picked limes were placed in a water bath maintained at temperatures ranging from 25°C to 50° for 3 hours. The incidence of stylar-end breakdown in these fruit increased exponentially from 0% in those fruit incubated at 25° to 85% in fruit heated at 50°. A standard treatment of heating fruit for 3 hours at 42° was employed to determine the relative susceptibility of fruit varying in size and juice content. Limes less than 3.5 cm in diameter did not break down whereas the incidence of the disorder in fruit 3.5 cm to 7.0 cm in diameter, respectively, ranged from 2% to 63%. Fruit with greater than 50% juice content were more susceptible to the disorder than those with less than 50%, but no strict correlation was found. It is suggested that the incidence of stylar-end breakdown associated with heat is mediated by liquid expansion in juice vesicles giving rise to internal pressure sufficient to rupture these vesicles. Controlling postharvest temperature of limes and maintaining strict picking schedules so that fruit are not allowed to attain maximum size significantly reduces the incidence of the disorder.
An experiment was conducted to determine if gibberellic acid (GA; ProGibb, Abbott Labs) can be mixed with Aliette or Agri-Mek and oil to reduce application costs, without reducing GA efficacy, and if Silwet and Kinetic adjuvants enhance GA efficacy. Five tank mixes were tested along with a nonsprayed control. The tank mixes included: 1) GA, 2) GA + Silwet, 3) GA + Kinetic, 4) GA + Silwet + Aliette, and 5) GA + Silwet + Agri-Mek + oil. All compounds were applied at recommended concentrations. In September, ≈24 L of each tank mix was applied with a hand sprayer to mature `Hamlin' orange trees [Citrus sinensis (L.) Osb.] on sour orange (Citrus aurantium L.) rootstock. Peel puncture resistance (PPR), peel color, and juice yield (percent juice weight) were evaluated monthly between Dec. 1997 and Mar. 1998. On most sampling dates the fruit of treated trees had higher PPR and were less yellow in color than fruit from control trees. However, in Jan., fruit treated with GA + Silwet and GA + Kinetic had greater PPR than other treatments. In Feb., fruit treated with GA + Silwet + Agri-Mek + oil had the lowest PPR. The effect of the different tank mixes on juice yield was usually similar to the effect of the tank mixes on PPR and peel color. On 8 Jan. 1998, fruit from trees treated with GA alone yielded significantly more juice than fruit from control trees. On 24 Feb. 1998, fruit from trees treated with GA alone yielded more juice than fruit from the other treatments. Thus, GA efficacy is generally not reduced by these tank mixes, nor improved by adjuvants.
Gibberellic acid (GA) applied in late summer or fall delays subsequent loss of peel puncture resistance (PPR) and development of yellow peel color in many citrus cultivars. Our objective was to determine the optimal time to apply GA for increasing juice yield of `Hamlin' sweet orange [Citrus sinensis (L.) Osb.]. Mature trees on sour orange (Citrus aurantium L.) rootstock were sprayed with ≈24 L of a solution of GA (45 g a.i./ha) and organo-silicone surfactant (Silwet, 0.05%). Trees were sprayed on 26 Aug., 9 Sept., 2 Oct. (colorbreak), or 13 Oct. 1997, or nonsprayed (control). Peel puncture resistance, peel color, and juice yield were evaluated monthly between Dec. 1997 and Mar. 1998. Fruit from trees sprayed with GA had peels with higher PPR and less yellow color than fruit of control trees for most of the harvest season. The effect of GA on PPR and peel color lasted about 5 months. Juice yield was usually numerically greater for GA-treated fruit than for nontreated fruit. Fruit treated with GA at color break had significantly greater juice yield when harvested in late February than fruit from control trees. Thus, GA applied at color break appears to be the most effective time for enhancing peel quality and juice yield of `Hamlin' oranges.
Abstract
Effects of boric, indole-3-acetic, gibberellic, succinic and fumaric acids, and water extract from onion bulbs on onion pollen germination and tube growth were studied. Boric acid stimulated pollen germination and tube growth at 100 mg/liter but was toxic at 200 mg/liter. Indole-3-acetic acid slightly increased pollen germination and tube elongation at 0.05 mg/liter, but inhibited pollen tube growth at 200 mg/liter. Gibberellic acid not only enhanced germination percentage, but the higher concentrations also increased the pollen tube lengths. Succinic and fumaric acids stimulated germination, but pollen tubes burst at the higher concentrations. At 200 mg/liter of fumaric acid no germination of pollen grains was observed, but with 25 ml of bulb extract in the culture medium, germination and tube growth were stimulated. Pollen tubes developed abnormally at higher concentrations.
Abstract
Freshly dehisced pollen of Allium cepa L. was stored under various conditions of temperature and relative humidity for up to 198 days. One series of treatments was freeze dried before storage. The degree of viability was determined by germination percentages at periodic intervals. Germination of approximately 60% of the initial germination was maintained in pollen samples freeze dried and stored at −18° and 5% relative humidity. Without freeze drying, approximately 38% of initial germination was maintained in samples of onion pollen stored 198 days at −18° and 10% relative humidity. Pollen stored at −18° and 80% relative humidity germinated 34% of initial germination after 56 days of storage and gradually declined to 4% by 170 days.
Freezing tolerance and the lethal freezing temperature were determined for detached leaves of avocado (Persea americana Mill.) by either electrolyte leakage or visual appearance of browning. Leaves from field-grown trees of `Gainesville', `Booth8', and `Winter Mexican' in both Gainesville and Homestead, Fla., were evaluated. All cultivars in both locations survived ice formation in their tissue. Leaf tissue had a temperature limit (lethal freeze temperature) at and below which the tissue died. The lethal freezing temperature varied from -5.1 to -9.3C, depending on time of year and location. The lethal freeze temperature for a cultivar decreased over the fall and winter as temperatures decreased. Leaves of `Booth-8' and Winter Mexican' decreased 2.5 and 1.5C, respectively, in Homestead from 13 Nov. 1982 to 5 Feb. 1983. The plants growing at the lower temperature location (Gainesville) had lower lethal freeze temperatures. Leaves of `Gainesville' had a lethal freeze temperature of - 9.3C from trees at Gainesville and - 7.8C from trees at Homestead.
Abstract
Menazon (S-(4,6 diamino-s-triazin-2-methyl) o,o-dimethyl phosphorodithioate) an organophosphate insecticide, and usnic acid, an allergen present in lichens, inhibited germination of mung bean (Phaseolus mungo L.). On the third day of germination, cotyledons were examined histochemically and ultrastructurally and the resultant photomicrographs showed abundant starch grains and protein bodies in the treated seeds compared to the controls. Electron microscopic examination showed extensive endoplasmic reticulum and ribosomes along with vacuoles and normal mitochondria in control tissue. In contrast, the presence of protein bodies and disruption of the cytoplasmic organization were conspicuous in the menazon- and usnic acid-treated mung beans. This suggests impaired utilization of food reserves during germination.
Abstract
‘Tahiti’ (Citrus latifolia Tan.) lime fruit varying in turgor, estimated by fruit water potential and rind oil release pressure, were collected and assayed for susceptibility to stylar-end breakdown. Susceptibility was determined by heating fruit for 3 hours at 42°C in a constant temperature water bath. Incidence of stylar-end breakdown was about 40% in the most turgid fruit, water potential ≥–4 bars and rind oil release pressure ≤2.0 kg. Decreasing turgor resulted in a linear decrease in susceptibility. Minimum susceptibility of from 0% to 2% was found in limes with water potential ≤–11 bars and rind oil release pressure ≥4.5 kg. Stylar-end breakdown can be controlled by maintaining strict picking schedules so that fruit are not allowed to get too large, controlling postharvest field heat, and harvesting fruit with reduced turgor pressure.