Response to mid-day wilting (dehydration avoidance) among sweet potato [Ipomoea batatas L. (Lam)] genotypes is a consistent trait within and among years. This response is significantly related to storage root dry weight and net photosynthesis in most years. The relationship is more obvious among relatively high-yielding clones or when data are obtained over several years. Reduced mid-day wilting increases yield in high-yielding genotypes through increased net photosynthesis and increased partitioning of assimilates to storage roots. Increased storage root dry weight is also related to the percentage of water in the vines at near full-turgor through increased partitioning to roots and reduced mid-day wilting. Wilting response and vine moisture together account for nearly 25% of the variation in yield of high-yielding clones tested over 5 years with irrigation.
Calcium is the fifth most abundant element in the earth’s crust, accounting for more than 3% of its composition. The exchangeable Ca content of a “normal” soil ranges from 65 to 85% of its total exchange capacity (12). Leaves of dicotyledonous plants generally contain from 0.5 to 5.5% Ca on a dry weight basis (44). The aboveground woody portions of trees in a 36-year-old apple orchard (35 trees per acre) contain about 200 lb. of Ca/acre as compared to about 175 lb. of all other nutrient elements combined (98). Recognizable foliar symptoms of Ca deficiency are seldom observed on field-grown fruit or vegetable crops. Despite these facts, serious economic losses occur annually from physiological disorders resulting from an inadequate level of Ca in the fruits, storage roots, or tubers of many plants or to the heart leaves of cabbage, lettuce, and other compact leafy vegetables.
Phloem cross-sectional areas (PCSA) in main stems and storage root stalks were determined for 3 cultivars of sweet potato [Ipomoea batatas (L.) Lam] for 98 days, starting 14 days after transplanting at 10-day intervals. As the number of storage roots increased, the total amount of phloem in the storage root stalks available for translocation was greater than that in the main stem. For the last 3 harvest periods, ‘Jasper’ was the only cultivar with less phloem in the storage root stalks than in the main stem. The correlation between PCSA of the storage root stalks and storage root weight was nonsignificant for ‘Jasper’ and ‘ Porto Rico’ but significant for ‘Centennial’, which suggested that the amount of phloem tissue is not critical for storage root development.
Yield, quality, and respiration studies were conducted with 23 mutations of the ‘Centennial’ sweet potato (Ipomoea batatas (L.) Lam). None of the mutant selections produced significantly higher yields than the original cultivar. Total carotenoid pigments of mutant clones ranged between 1 and 14 mg per 100 g of fresh tissue, with 10 mutants not different from the original cultivar and 13 with less pigments. Dry matter content varied from 26 to 34% in the fleshy roots with 4 selections significantly higher than the ‘Centennial’ roots. Dark skin color (rose or purple) was accompanied by orange flesh color in all samples tested. There was a large variation in respiration rates of storage roots between mutant clones and ‘Centennial’ roots.
The effect of inoculation with Azospirillum brasilense strain Cd on mineral concentration in sweetpotato, [Ipomeo batatas (L) Lam cv. TI-155] tissue and ionic composition of plant nutrient solution was investigated in a greenhouse study. In the field, inoculation of sweetpotato with Azospirillum spp. has been reported to enhance. sweetpotato yield. In this study, 48-h old broth cultures were used as inoculum at a population density of approx. 1 × 108 cfu/ml. The inoculum (0.20 L) was added to the reservoirs containing 30.4 L of a modified half Hoagland's plant nutrient solution at 28 days after the start of the experiment Results indicate that percent total nitrogen in sweetpotato foliage tended to be higher for the inoculated fibrous mat than in the fibrous mat for non-inoculated plants. The percent total nitrogen in storage roots for the non-inoculated treatment tended to be higher than in storage roots for inoculated plants. Inoculation resulted in a slight increase in foliar phosphorus concentration but had no effect on phosphorus concentration in sweetpotato storage and fibrous root samples. Inoculation tended to reduce foliar calcium concentration. Magnesium concentration in leaf tissue was not influenced by inoculation. Foliar potassium concentration tended to increase slightly. The effect of inoculation on potassium concentration in sweetpotato root tissue was not well-defined; potassium concentration tended to be higher in fibrous root tissue for the inoculated treatment. But in storage root tissue, potassium concentration was higher for the non-inoculated treatment than for the inoculated treatment. Inoculation did not affect foliar concentrations of any of the micronutrients measured. This study indicates no effect of inoculation on ionic strength of nutrients in solution reservoirs.
Consumer Services, Raleigh. Once plants had been established, plant stands were recorded at 2–3 weeks after planting. Sweetpotato storage roots were harvested on 11–12 Oct. (114 DAP) and 18 Oct. (123 DAP) in 2012 and 2013, respectively. Storage roots from
photoassimilates down to form and/or grow storage roots, resulting in increased yield. This study examined the influence of Pro-Ca on sweetpotato vegetative growth and storage root yield among four cultivars. Materials and Methods Two experiments were conducted in
Alstroemeria `Regina' and A. `Orchid' Linn. plants were grown in rhizotrons to facilitate non-destructive observation of shoot, rhizome, and storage root growth. In plants grown at 21/11 C or 21/21 C day/night temperatures under either 8 hr night interruption or an 8 hour short days, storage root growth was favored by cool (11 C) night temperatures and long days. The seasonal patterns of storage root and rhizome growth were inversely related to the seasonal pattern of shoot growth. Growth of shoots and rhizomes followed a cyclic pattern. The cycles of shoot and rhizome growth were in phase with each other until the plants resumed vegetative growth due to high soil temperature. At this point, the cycles of shoot and rhizome growth were shifted out of phase with each other. Thinning shoots by 60% resulted in delay and damping out of the peak of storage root growth; the cyclic growth of storage roots was disrupted when plants were thinned by 60% such that the cycles of active storage root growth were delayed by 1 week.
`Red Jewel' sweetpotato [Ipomoea batatas (L.)] roots were cured [32 ± 1C, 85% ± 5% relative humidity (RH)] for 7 days immediately after harvest and cured for O. or 8 additional days before being stored (16 ± 1C, 85% ± 5% RH). Midway through storage, roots were heated (32 ± 1C, 85% ± 5% RH) for 0, 2, 4, 6, 8, 10, 12, or 14 days and placed back into storage. Before being bedded, roots were presprouted (32 ± 1C, 85% ± 5% RH) for O or 8 days. Plant emergence was accelerated with extended curing or presprouting and with increased midstorage heating duration. Early plant production increased with increasing duration of midstorage heating of roots not subjected to extended curing or presprouting. Eight days of extended curing eliminated response to midstorage heating; but, with 8 days of presprouting, a quadratic response to midstorage heating peaked at ≈ 8 days. However, when combined with midstorage heating, presprouting had more of an effect than extended curing on early plant production. Briefly extending curing, midstorage heating, and presprouting each independently increased the cumulative number of midseason plants, but only presprouting influenced total plant production. Treatments did not influence deterioration of bedded roots or number of sprouts <20 cm produced during 10 weeks of harvest.
Boron has been used to overcome the disorder blister in varieties such as `Jewel'. `Hernandez' is an attractive, good-yielding variety with uniform shape that will consistently pack out at 80% to 90%. Over time in storage, however, roots develop blister-like symptoms, rendering roots unmarketable for fresh market. Our objective was to evaluate the effect of different B rates and application times on the yield and quality of `Hernandez' roots. Rates were varied up to 2.24 kg actual B/ha 6 days after planting, while various soil and foliar application times (6, 34, and 69 days after planting) were evaluated at 1.12 kg·ha–1. In 1994, three row plots were arranged in a randomized complete block design and replicated four times. Planting was on a deep sand to maximize the effect of the B carrier Solubor. Roots were harvested, graded, and weighed 120 days after planting and storage roots evaluated for blister-like symptoms in Mar. 1995. No significant differences in yield were attributed to B rate or application method. Blister-like symptoms were more severe when no B was applied; however, application of B did not eliminate symptoms, as most roots had the blister-like appearance. Boron application did not solve the problem, but symptoms were less apparent when some B was applied.