It is known that pure O2 enhances in sweet potato roots the respiratory increment produced by C2H4 (Theologis and Laties, 1982, Plant Physiol.). Our experimental results indicates that the decrease in respiration with decreasing O2 concentration is due to the restriction of an “oxidase” whose apparent Km for O2 is 5-6 fold higher than that of cytochrome oxidase. The magnitude of the apparent Km for O2 is affected by the diffusion of O2 and experiment conditions. The effect of O2 on respiratory rise produced by C2H4 is due to the curtailment of C2H4 action rather than to respiration as such. The apparent Km for O2 of this system is larger than that of respiration.
Abstract
The storage performance of kiwifruit (Actinidia chinensis Planch. ‘Hayward’) was evaluated during and after storage for up to 24 weeks in 2% O2 and 0%, 3%, 5%, and 7% CO2 at 0°C. In addition, the influence of exposure to 0.5 or 1 μl·-liter−1 C2H4 on fruit performance was evaluated. The rate of softening during storage was reduced in proportion to the CO2 level and was accelerated by C2H4. The presence of white core inclusions under controlled atmospheres (CA) plus C2H4 was dependent upon the CO2 concentration. Two other physiological disorders were observed, and their severity was influenced by the combination of elevated CO2 and C2H4. The results suggest that there are 2 types of interactions between CO2 and C2H4, competition and synergism, which occur in kiwifruit during storage.
We have investigated the effects of different O2 concentrations on the onset of the climacteric rise in C2H4 evolution and subsequent ripening of `Gala' apples. The data show that the effect of low O2 on the timing of the onset of the C2H4 climacteric is saturable in that for low O2 to retard the onset of the rise in C2H4 evolution its concentration must be decreased below 8%. Further, the results suggest that the retarding effects of low O2 on the onset of ripening cannot be ascribed to the inhibitory effects of low O2 on the action of the low levels of C2H4 evolution by preclimacteric apples. The results concerning the rate of C2H4 evolution and accumulation of the ACC-oxidase protein show that application of low O2 after the initiation of the climacteric rise in C2H4 is not as effective in delaying senescence as when it is imposed early, i.e., at the preclimacteric stage.
et al., 2012 , 2014 ). Owing to its longevity, stability, and ability to cross biological membranes, H 2 O 2 is the most ubiquitous intracellular messenger ( Rhee et al., 2017 ). H 2 O 2 oxidizes cysteine thiol groups of phosphatases, which are
peroxide (H 2 O 2 ), which decomposes rapidly into harmless products water and oxygen ( Randhawa et al., 2012 ). Hydrogen peroxide is generated via superoxide, presumably in a noncontrolled manner, during electron transport processes such as photosynthesis
Seed materials and priming. Seeds of I. indigotica Fort. were provided by Mashan TCM base in Jinan City, Shandong Province, China. Seeds were soaked in CaCl 2 (5, 10, 15 g/L), GA 3 (0.2, 0.4, 0.6 g/L), and H 2 O 2 (20, 40, 60 m m ) for 12 h using a
The mechanism of C2H4 action on plant respiration is not well understood. In the present work we treated peeled sweet potato roots (Ipomea batatas cv. MD715) with 10 ppm C2H4 in air and 3% O2 Analytical data showed a close relationship between respiration and activity of phosphofructokinase while the activity of pyrophosphate fructose-6-phosphate phosphotransferase remained constant under all experimental treatments. At the respiratory peak there was an increase in both pyruvate and fructose-2,6-diphosphate. The change in the levels of pyruvate, followed closely that of the respiration drift, while those of fructose-2,6-diphosphate did not correlated so closely. The data indicate that the stimulation of respiration by C2H4 in sweet potato roots is closely associated with an enhancement of glycolysis. The levels of ATP also increased with the rise in respiration and reflected the magnitude of the respiratory increment.
Plant responses to drought stress involve multiple mechanisms at molecular, biochemical, physiological, and metabolic levels ( Bhargava and Sawant, 2013 ; Shanker et al., 2014 ; Todaka et al., 2015 ). Many small molecules, such as Ca and H 2 O 2
Abstract
Clonal plants of four olive (Olea europaea L.) cultivars that originated in cool, moderately hot, and hot climates were examined for their photosynthetic potentials. Within 3 to 4 weeks, plants had fully expanded leaves; by 3 months the apparent photosynthesis, A, increased to a maximum of 5.4 µmol CO2/m2 per sec, while the water use efficiency (WUE) was 2.6 mmol CO2/mol H2O. The mean chloropohyll content was 0.564 mmol/chlorophyll (a + b)/m2. Mean assimilation rate was negatively correlated to leaf area. The values of A were three to four times less than those reported for apple and almond, whereas WUE was 22% greater. A values were proportional to stomatal conductance. Mesophyll resistance was higher than several C3 plants and the optimum temperature for photosynthesis varied among cultivars, seemingly according to the climate where they originated. Stomata opened and closed within 10 min in response to changes in humidity. Gas exchange properties were not affected by peltate removal.
The response of different doses of calcium sulfate or phosphogypsum (PG) on several postharvest quality parameters of `Laguna' cantaloupe hybrid were analyzed in the semi-arid San Francisco experiment station (UCLA), located in the Lara state, Venezuela. The experimental design was a completely randomized block with four treatments (0, 300, 600, and 1200 kg/ha, PG) with five replications. The PG was surface-spread on the irrigation furrows, 1 day before sowing. The fruits were harvested at maturity and stored under an average temperature of 28°C for posterior quality analysis. The PG treatments did not have any effect on the studied parameters: total soluble solids (°Brix), consistency (kg/cm2), diameter, and cavity of the fruit, pulp thickness, and dry and fresh matter. All of the parameters evaluated decreased during the 6 days of storage. These results could be because of the low doses of PG used or because the supply of calcium was not a limitation in these soils.