Abstract
Evapotranspiration and transpiration were determined for Aphalandra squarrosa Nees. ‘Dania’, Maranta leuconeura Kerchoviana E. Morr., Philodendron scandens subsp. oxycardium (Schott) Bunt., and Brassaia actinophylla Endl. Aphelandra transpiration was 1.5 to 2 times more per unit leaf area than other species. The hypostomatous leaves of Aphelandra and Brassaia had 151 and 131 stomata per mm2; stomatal density per mm2 was 66 for Maranta and 29 for Philodendron on abaxial surface, and 12 and 9, respectively, on adaxial surface. Midday abaxial water vapor conductance was 0.46, 0.26, 0.16, and 0.06 cm sec−1 for Aphelandra, Brassaia, Maranta, and Philodendron, respectively.
Abstract
Volatile extracts were isolated from pods of southernpea by vapor-phase ether extraction. In bioassays conducted with freshly emerged adult curculios Chalcodermus aeneus (Boh.), the insects were significantly more attracted to extracts of the susceptible ‘California Blackeye No. 5’ than to air with no extracts. Extracts of the breeding lines Ala. 963.8 and CR 22-2-21 were repellent to the insects as evidenced by directed travel away from the extracts towards air alone. Gas chromatographic profiles of the 3 extracts showed obvious qualitative and quantitative differences.
Abstract
Increasing water stress situations were imposed on Schefflera arboricola Hayata ‘Compacta’ for up to 7 days under controlled growth chamber conditions. Net CO2 exchange and transpiration rates, stomatal conductance to water vapor and xylem water potential were measured at constant temperature, photosynthetic photon flux density (PPFD), and atmospheric humidity. A strong relationship was found for transpiration and CO2 exchange process. When the water content of the substrate decreased as a result of transpiration and soil surface evaporation, both transpiration and CO2 exchange rates decreased drastically. Xylem water potential remained fairly constant during this soil moisture deficit. Following the drying cycle, efficient and fast recovery of the plants was observed.
Abstract
The chloroform test is a good measure of fermentation, a vital step in the manufacture of black tea. Time of harvest, temperature and duration of exposure to chloroform were variables on two-leaf-and-a-bud samples to assist in selection of Chinese tea clones grown under Florida conditions. Change in color from green to deep golden brown to brown, indicative of good fermentation, took place faster and more uniformly among samples plucked in the morning. Best color development occurred at 27° to 30° C and with 150 to 180 minutes exposure to chloroform vapor.
Abstract
Chilling injury (CI) of ‘Marsh Seedless’ grapefruit was reduced by a preharvest spray of benomyl (Benlate) but not of Vapor Gard (VG) pinolene antitranspirant Postharvest treatments with benomyl and thiabendazole (TBZ) also reduced CI. The effect of high CO2 atmospheres (up to 20%) induced under 0.0254 mm (1 mil) PVC film varied sharply with picking date. CI was almost eliminated in such atmospheres in early and midseason pickings but accentuated in the late (postbloom) picking. Modified atmospheres tended to increase decay regardless of picking date.
Some plant-derived natural volatile compounds exhibit antifungal properties and may offer an opportunity to control the causes of postharvest spoilage without affecting quality of, or leaving a residue on, fresh produce. The natural wound volatile (E)-2-hexenal has exhibited significant antifungal activity in earlier studies, but effects on spore germination and mycelial growth have not been separated, nor has the inhibitory mode of action been determined. To determine the efficacy of (E)-2-hexenal for control of Botrytis cinerea Pers. ex Fr. spore germination and mycelial growth, and to examine the mode of action, in vitro and in vivo studies were performed. Under in vitro bioassay conditions, spore germination was more sensitive to the compound than was mycelial growth. Vapor from 10.3 μmol of (E)-2-hexenal in a 120-mL petri dish completely inhibited spore germination. However, 85.6 μmol of (E)-2-hexenal was required to completely inhibit mycelial growth. Lower concentrations of the compound (5.4 and 10.3 μmol) significantly stimulated mycelial growth, especially when the volatile was added 2 days following inoculation. Mycelial growth did not occur as long as the vapor-phase concentration was 0.48 μmol·L-1 or greater. Light microscopy analysis indicated that a high concentration of volatile compound dehydrated fungal hyphae and disrupted their cell walls and membranes. Exposure of B. cinerea-inoculated and non-inoculated strawberry (Fragaria ×ananassa Duch.) fruit in 1.1-L low-density polyethylene film-wrapped containers to vapor of (E)-2-hexenal at 85.6 or 856 μmol (10 or 100 mL, respectively) per container for durations of 1, 4, or 7 days during 7 days of storage at 2 °C promoted the incidence of B. cinerea during subsequent shelf storage at 20 to 22 °C. Loss of fruit fresh mass and fruit firmness during storage at 22 °C was increased by (E)-2-hexenal treatment, but fruit total soluble solids, pH, titratable acidity, and color (L, C, and H values) were not affected. Thus, maintenance of a high vapor-phasel level of (E)-hexenal, perhaps >0.48 μmol·L-1, may be necessary to inhibit mycelial growth and avoid enhancing postharvest mold problems, while significantly higher levels may be necessary to completely eliminate the pathogen.
Abstract
A technique to measure intercellular air volume was developed, based on the relationship between pressure reduction and air expansion, with correction for water vapor pressure. This technique yields air efflux curves, and the extracted air can be used to measure the gas composition of internal atmospheres. ‘Grevenstein’ apple (Malus domestica Borkh.), ‘Bartlett’ pear (Pyrus communis L.), ‘Hayward’ kiwifruit (Actinidia chinensis Planchon), ‘Independence’ nectarine [Prunus persica (L.) Batsch], and ‘Russet’ potato (Solanum tuberosum L.) had intercellular volumes of 16.6%, 5.14%, 3.64%, 5.76%, and 1.64%, respectively.
Abstract
The comparative analysis of leaf-oil components separated by vapor phase chromatography was tested on stubborn infected and non-infected sweet orange leaves as a possible new technique for detection of stubborn disease of citrus. Three leaf-oil components: citronellol, nerol, and geraniol were found reduced in the stubborn infected leaves, but the reduction was shown to be related to the smaller leaf size and not due to the stubborn pathogen. However, one component, linalool, showed an increase in stubborn or stunt infected leaves relative to respective controls. This increase was not related to leaf size, but probably due to the presence of the pathogen.
Several processes including controlled atmosphere, hypobaric storage and the application of protective films have been developed to extend shelf-life of fruits and vegetables. Recently, the application of edible coatings that can simulate controlled atmosphere storage to prolong product freshness is becoming a popular concept. The ability of these coatings to extend postharvest storage life depends on their differential permeability to CO2, O2 and water vapor.
This talk will describe the developmental aspect and specific applications of edible coatings on various fresh and minimally processed fruits and vegetables.
Of 18 commonly used adjuvants evaluated on pecan [Carya illinoinensis (Wangenh) K. Koch], a few exhibited potential for substantially suppressing net photosynthesis (A) and the conductance of foliage to water vapor (g sw ) when used within their recommended concentration range; however, most provided no evidence of adversely influencing A or g sw . Suppression of gas exchange by certain adjuvants persisted at least 14 days after a single application. The recently developed organosilicone-based surfactants generally exhibited the greatest potential for suppression. These data indicate that orchard managers should consider the potential adverse influence of certain adjuvants when developing orchard management strategies.