The production of CO2 by apple and pear fruit was measured during and after alternating 12-hr exposures to air and N2 atmospheres. Typical stimulation of CO2 evolution in the absence of O2 was observed. Five or more anaerobic cycles imparted a permanent reduction on the subsequent aerobic respiration rate. The differences between control respiration and aerobic CO2 evolution by fruit exposed to cyclic anaerobiosis indicated that the capacity for aerobic respiration was reduced by the early anaerobic cycles. Suppression of the anaerobic stimulation of CO2 production was observed after several cycles suggesting that the capacity for fermentation was accumulatively impaired. Subsequent measurements of physical characteristics showed that flesh softening and chlorophyll degradation, processes which generally coincide during ripening, were differentially affected by cyclic anaerobiosis. Apple scald was induced by anaerobiosis. Pear fruits subjected to anaerobic cycles or continuous anaerobiosis did not ripen during the 14-day poststorage period at 21°C.
The effects of root anaerobiosis on root respiration and leaf conductance (kl) were determined in solution culture experiments. Respiration of feeder roots (<2 mm diameter) in air (21% O2) of Pyrus betulaefolia Bunge, Pyrus calleryana Decne, Pyrus communis L. (‘Old Home’ × ‘Farmingdale 97’) and Cydonia oblonga Mill. ‘Provence BA 29’ was reduced by no more than 50% after 21 days of anaerobiosis. In contrast, root respiration of Prunus persica (L.) Batsch ‘Lovell’ was reduced by 80% with anaerobiosis, whereas that of Salix discolor Muhl. increased. Reductions in kl with anaerobiosis generally were more pronounced than reduction in root respiration when measured in air. Respiration rates of aerobically or anaerobically treated pear roots were inhibited by 25% to 50% when incubated in 0.5% O2 compared to rates in air. More work is required in order to delineate the relationship of root respiration and kl with anaerobiosis.
The effect of anaerobiosis, imposed during germination of ‘Calypso’ cucumber (Cucumis sativas L.) seeds, was studied. Anaerobic conditions inhibited reserve mobilization from the cotyledons and dry weight gain by the embryonic axis. Within the embryonic axis, lipid degradation was stopped and use of all readily metabolizable carbohydrate reserves was strongly stimulated. By 48 hr of exposure to an anaerobic environment, the axis was nearly depleted of endogenous carbohydrate reserves. Aerobically germinating seeds accumulated a massive concentration of hexose sugars within the axis during the same time period. Thus, growth inhibition within cucumber seeds during anaerobiosis may result in part from carbohydrate deprivation of the embryonic axis.
The effect of rootzone salinity (0 to 90 mM NaCl) on shoot growth of 6 grape cultivars [‘Sultana’ (syn. ‘Thompson Seedless’), ‘Carbernet Sauvignon’, ‘Crouchen’, ‘Shiraz’, ‘Doradillo’ and ‘Palomino’] grown as rooted cuttings was determined in sand cultures. Relative shoot growth values over 23 days with salt were ‘Palomino’ 100, ‘Sultana’ 94, ‘Shiraz’ 87, ‘Crouchen’ 83, ‘Cabernet Sauvignon’ 63, and ‘Doradillo’ 59. Application of concurrent waterlogging (anaerobiosis) stress on the root system depressed shoot growth more than salt stress alone and changed the ranking for shoot growth. Waterlogging increased total uptake of Na and Cl, increased the amount of Na and Cl transported into the shoots, and resulted in visible leaf damage within 5 days of the onset of the waterlogging.
Seedlings of Juglans hindsii Jeps. and J. regia L. reacted similarly and were much more sensitive to waterlogging at root temperatures of 33°C than those of Pterocarya stenoptera DC. At 23°C,J. regia expressed symptoms of waterlogging earlier than J. hindsii. Paradox plants, hybrids between the 2 walnut species, were more tolerant than J. hindsii but are still considered highly sensitive to anaerobiosis. These results support the contention that use of J. regia seedlings as rootstocks to avoid blackline introduces greater potential for damage if soils become saturated. Some plants of each type which demonstrated increased tolerance have been selected. Levels of abscisic acid, or changes therein did not appear to be useful parameters in screening walnut seedlings for tolerance to waterlogging. Phenolic compounds decreased in roots of waterlogged plants. Although the magnitude of change in phenols was the same in Juglans and Pterocarya plants, it occurred over a much longer period with the latter. Phenols lost from roots may be a secondary phenomenon but contribute to hypersensitivity of Juglans to waterlogging.
A mathematical model was developed to characterize the interaction of fruit O2 uptake, steady-state O2 partial pressures in modified-atmosphere (MA) packages ([O2]pkg), and film permeability to O2 (Po
2) from previously published data for highbush blueberry (Vaccinium corymbosum L. `Bluecrop') fruit held between 0 and 25C. O2 uptake in nonlimiting O2 (Ro
max,T) and the [O2]pkg at which O2 uptake was half-maximal (K½
T) were both exponentially related to temperature. The activation energy of 02 uptake was less at lower [O2]pkg and temperature. The predicted activation energy for permeation of O2 through the film (
Biological production of sulfide (S2-) in soil has been reported to depend on system redox potential and on the concentrations of available sulfate (
Photosynthesis and transpiration rates of seedlings of 4 citrus rootstocks under flooded conditions were measured over a 10-day period. For all rootstocks photosynthesis and transpiration decreased, but photosynthesis decreased relatively less than transpiration. Stomatal closure is inferred to account in part for the reductions observed.
Flooding did not increase ethanol concentration in either tops or roots, suggesting that ethanol is not an end-product of. anaerobic respiration in citrus seedlings. Only in the neutral soil was rough lemon (Citrus limon L. Burm. f.) found to be more tolerant to short-term flooding than ‘Cleopatra’ mandarin (Citrus reticulata Blanco) and trifoliate orange (Poncirus trifoliata L. Raf.). Tolerance to flood injury was greater at a soil pH of 7 than 4.5.
Tomato fruit were given a short-term (24 h) high CO2 (80%) or N2 (100%) treatment and then transferred to air storage at 20 °C. The CO2 treatment stimulated ACC oxidase activity and ethylene production, whereas the N2 treatment increased ACC content but did not increase ethylene production. Both CO2, and N2 treatments delayed ripening for one day, but fruit ripened normally. Although short-term 80% CO2, had a stimulating effect, and 100 % N2 had no effect on ethylene production, ripening was delayed slightly by both treatments. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).
Highbush blueberry (Vaccinium corymbosum L. `Bluecrop') fruit sealed in low-density polyethylene packages were incubated at 0, 5, 10, 15, 20, or 25C until O2 and CO2 levels in the package reached a steady state. A range of steady-state O2 partial pressures (1 to 18 kPa) was created by placing a range of fruit weights within packages having a constant surface area and film thickness. The steady-state O2 partial pressure in packages containing the same weight of fruit decreased as temperature increased, indicating the respiratory rate rose more rapidly (i.e., had a greater sensitivity to temperature) than O2 transmission through the film. Steady-state O2 and CO2 partial pressures were used to calculate rates of O2 uptake. CO2 Production. and the respiratory quotient (RO). The effects of temperature and 02 partial pressure on O2 uptake and CO2 production and the RQ were characte∼zed. The steady-state O, partial pressure at which the fruit began to exhibit anaerobic CO2 production (the RQ breakpoint) increased with increasing temperature, which implies that blueberry fruit can be stored at lower O2 partial pressures when stored at lower temperatures.