The effect of varied anaerobic atmospheres on the metabolism of sweet potato (Ipomoea batatas IL.1 Lam.) roots was studied. The internal gas atmospheres of storage roots changed rapidly when the roots were submerged under water. 02 and N2 gases disappeared quickly and were replaced by CO2. There were no appreciable differences in gas composition among the four cultivars that were studied. Under different anaerobic conditions, ethanol concentration in the roots was highest in a CO2 environment, followed by submergence and a N2 environment in all the cultivars except one. A positive relationship was found between ethanol production and pyruvate decarboxylase activity from both 100% CO2-treated and 100% N2-treated roots. CO2 atmospheres also resulted in higher pyruvate decarboxylase activity than did N2 atmospheres. Concentrations of CO2 were higher within anaerobic roots than those in the ambient anaerobic atmosphere. The level of pyruvate decarboxylase and ethanol in anaerobic roots was proportional to the ambient CO2 concentration. The measurable activity of pyruvate decarboxylase that was present in the roots was about 100 times less than that of alcohol dehydrogenase. Considering these observations, it is suggested that the rate-limiting enzyme for ethanol biosynthesis in sweet potato storage roots under anoxia is likely to be pyruvate decarboxylase rather than alcohol dehydrogenase.If excessive soil moisture occurs prior to harvest of sweet potato storage roots, it will cause roots to decay in the field as well as adversely affect the quality and storage life of the roots (10, 15). In flooded soil, 02 exchange between the soil and the air is reduced about 10,000 times compared to diffusion in gas-filled pores (6).02, within flooded soils, may be depleted within 24 h (14). N2 gas concentrations remain fairly constant in the soil with some fluctuation throughout the flooded period (14). CO2, the byproduct of respiration, accumulates in flooded soils. The partial pressure of CO2 in flooded soils ranges from 0.2 to 0.8 atm within 1 to 3 weeks of flooding depending on soil properties and temperatures (3). Likewise, the internal gas atmospheres of sweet potato roots displayed a similar pattern, except that N2 was replaced gradually by CO2 during a 72-h submergence period (1
‘Jewel’ sweet potatoes [Ipomoea batatas (L.) Lam] were grown for 2 seasons on an Orangeburg loamy sand soil with 3 N sources, 3 K rates, and 2 N rates. NH4NO3 and Ca(NO3)2 were equivalent in influence on root quality at harvest and storage, but NaNO3 significantly reduced root dry matter content. With an increase in N rate from 101 to 202 kgN/ha, weight loss during storage increased and carbohydrate levels, dry matter content, and root intercellular space values decreased. An increase in K applications from 70 to 280 kg/ha reduced root dry matter content.
Fruit pH, inflection point pH, % acid content at inflection point pH, and % acid content at pH 8.1 were unpredictable based on days from full bloom and were not useful as maturity indices for 3 red strains of ‘Delicious’ or ‘Law Rome’ apple (Malus domestica Borkh.). Soluble solids content of the red strains of ‘Delicious’ could not be predicted consistently. Soluble solids/% acid (SS/A) at pH 8.1 values were the most predictable for all red strains of ‘Delicious’ with apparent optimum fruit quality within the 40 to 50 range index. None of these parameters were reliable for ‘Law Rome’ fruits.
Flood-damage was simulated by submerging freshly harvested storage roots of 4 cultivars of sweet potato (lpomoea batatas (L.) Lam) under water for 48 hours. Root ethanol accumulation (μmoles/g fresh weight) for each cultivar was: ‘Centennial’, 38.6; ‘Jasper’, 42.9; ‘Jewel’, 48.8; and ‘Caromex’, 74.4. Storage losses due to rotting and accelerated weight loss were highest in ‘Caromex’ and second highest in ‘Jewel’. The amount of ethanol formed was not correlated with the apparent activity of either pyruvate decarboxylase or alcohol dehydrogenase. Cultivars differed upon removal from anaerobic conditions in their ability to metabolize accumulated ethanol. Cured roots of the 2 tolerant cultivars eliminated ethanol earlier than those of the 2 susceptible cultivars after anaerobic treatment. Thus, flood-damage to sweet potato storage roots may involve at least 2 factors, the rate of ethanol accumulation due to anaerobic treatment and the subsequent lag period and extent of metabolism of accumulated ethanol upon removal of anaerobic conditions.
‘Jewel’ sweet potatoes [Ipomoea batatas (L.) Lam.] were grown during 2 seasons to evaluate 3 N sources, 3 K rates, and 2 N rates on a sandy loam soil. Nitrogen source did not influence yield; however, NaNO3 significantly increased foliar and root Na concentrations over those obtained with NH4NO3 or Ca(NO3)2. Higher yields were obtained with 140 kg K/ha than with 70 or 280 kg K/ha and 101 kg N/ha than with 202 kg N/ha. No foliar or root mineral concentrations were deficient. Nitrogen, P, Ca, and Mg concentrations were lower in root than foliar tissues.
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