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- Author or Editor: James O. Garner Jr. x
Ten day old potted rooted cutting of sweetpotato genotypes `Travis' and MS 21-1 were exposed for seven days to cold (12°C) or 21°C (control) temperatures. Chemical changes that may accompany tolerance or susceptibility to chilling were monitored. No consistent differences in total fatty acid composition were found between the two genotypes. There was an increase in peroxidase (POD) activity of the crude enzyme extract for MS 21-1, the chilling tolerant genotype, when exposed to 12°C for seven days. No differnces were found in POD activity for `Travis', the chilling sensitive genotype. Superoxide dismutase (SOD) and catalase (CA) activity for crude enzyme extracts did not differ between genotypes and was not influenced by storage temperature.
Responses of four sweetpotato genotypes (`Centennial', `Travis', `Vardaman' and `MS 21-2') to water stress were studied. Two irrigation regimes (irrigation vs non-irrigation) were imposed on five-week old cuttings grown in a greenhouse environment. Transpiration and leaf diffusive resistance (LDR) were measured with a steady state porometer and mid-day total leaf water potentials were determined with a thermocouple psychrometer. Leaf growth was inhibited earlier than root growth. Water stress caused a reduction of leaf size in Centennial and in leaf number in the other three. Storage root number of Vardaman was not inhibited by limited soil moisture but development of storage roots was retarded by water stress. Total growth under non-irrigation of MS 21-2 was inhibited more than Vardaman. Mid-day leaf water potential did not show promise as a good indicator of water status. Genotypic differences in the water stress sensitivity as measured by LDR, were observed.
Selected physiological and anatomical characteristics of four chilling-tolerant sweetpotato genotypes were evaluated. Although the genotypes were considered highly tolerant to chilling, it was proposed that differences in their mechanism for tolerance existed. A genotype temperature interaction for chlorophyll fluorescence ratio was observed when the plants were exposed to 5 °C. Genotype differences were found for electrolyte leakage and peroxidase activity. There were no differences found for fatty acid percentage composition of the glycolipid or the phospholipid fraction from leaf samples. There were no differences in diffusive resistance and transpiration rate among the genotypes; however, stomata density, leaf shrinkage, and specific leaf weight differed among the genotypes. Differences were also found among the genotypes for percent leaf dry weight, leaf thickness, and cellular structure of the leaf. It was concluded that the basis or mechanism for chilling tolerance was not the same for the four genotypes tested; therefore, combining traits for tolerance could lead to higher tolerance levels.
In two experiments, 16 sweetpotato genotypes (Ipomoea batatas L.) were evaluated for drought tolerance using the detached-leaf water loss method. Dry weight loss was also determined. Difference in the rate of leaf water loss over a 48 hour period were found. `Vardaman' had the greatest amount of dry weight loss and the least amount of water loss. No relationship between dry weight loss and water loss was found.
When measuring chlorophyll fluorescence using two sweetpotato genotypes, `Vardaman' had a higher rate of photosynthetic transport activity.
In two experiments, 16 sweet potato genotypes (Ipomoea batatas L.) were evaluated for drought tolerance using the detached - leaf water loss method as reported by Walker and Miller (1986). Dry weight loss was also determined. Differences in the rate of leaf water loss over a 48 hour period were found.
Vardaman had the greatest amount of dry matter loss and the lowest level of water loss. However, no relationship between dry matter loss and water loss was found.
Physico-chemical characteristics of purple and yellow passion fruit (Passiflora edulis Sims.) were compared with those of maypop (Passiflora incarnata L.). Fruit diameter of maypop and purple passion fruit followed a typical sigmoidal growth curve. There were no differences in growth rate between the two species during the exponential phase. Growth differences, occurred after the exponential phase (10 and 20 days after anthesis). Fruits of the commercial types were heavier than greenhouse and wild grown maypop. Wild grown maypop produced heavier fruit compared to greenhouse grown maypop. Commercial passion fruit produced heavier rinds and greater pulp weight. Yellow passion fruit had the lowest percentage pulp and the most soluble solids. Greenhouse grown maypop had the lowest soluble solids. No differences in juice pH were found between the two species. Wild maypop fruits had the highest sucrose and greenhouse grown purple passion fruit had the lowest. Yellow and purple passion fruit had higher fructose than maypop. Glucose was significantly different between the two species, but not within species.
Fruit growth (diameter) of purple passion fruit (Passiflora edulis Sims.) and maypop (P. incarnata L.) followed a sigmoidal growth curve. Passion fruit were larger than either greenhouse-grown or wild maypop fruit. Wild maypop produced larger fruit than greenhouse-grown maypop. Yellow passion fruit had the lowest percentage of pulp and the highest soluble solids concentration (SSC) and greenhouse-grown maypop had the lowest SSC among the four groups tested. Purple and yellow passion fruit had lower juice pH than maypop. Wild maypop fruit had the highest sucrose content and purple passion fruit had the lowest. Yellow and purple passion fruit juice had higher fructose and glucose contents than did maypop juice.
Vine-ripened yellow passion fruit (Passiflora edulis f. flavicarpa Deg.) were placed in styrofoam trays and wrapped with VF-60 plastic film and stored for 15 and 30 days. Wrapping prevented fruit weight loss while maintaining external appearance. Storage time contributed to quality loss of external appearance. Wrapping maintained fruit glucose and fructose content at 43 and 40 mg·ml-1 up to 15 days, respectively, and did not influence juice pH. Initial sucrose content of wrapped fruit declined 62% after 15 days in storage. Plastic film did not effectively modify O2 or CO2.
Fruit growth and composition of commercial passion fruit types and maypop were compared. Fruit growth (diameter) of purple passion fruit (Passiflora edulis Sims.) and maypop (P. incarnata L.) followed a sigmoidal growth curve. Passion fruit were larger than both greenhouse-grown and wild maypop fruit. Wild maypop produced larger fruit compared to greenhouse grown maypop. Yellow passion fruit had the lowest percentage pulp and the highest soluble solids. Greenhouse-grown maypop had the lowest soluble solids. Purple and yellow passion fruit had lower juice pH than maypop. Wild maypop fruit had the highest sucrose and purple passion fruit had the lowest. Yellow and purple passion fruit juice had higher fructose and glucose than did maypop juice.
Vine-ripened yellow passion fruit (Passiflora edulis f. flavicarpa Deg.) packed and shipped from Homestead, Fla., were stored for 15, 30, or 45 days at 5, 10, or 15C. Fruit analyzed immediately on arrival had the best external appearance and highest fruit weight. Fruit weight loss increased with storage time at all temperatures and the response was linear. Fruit external appearance deteriorated rapidly at 5 and 15C. Pulp percentage at 5C increased linearly with storage duration and did not change at 10C. Pulp percentage at 15C changed quadratically with storage time, increasing up to 30 days and then decreasing by 45 days. Soluble solids concentration did not change at 5 or 10C, but decreased linearly at 15C. Sucrose content decreased quadratically at 5C, linearly at 15C, but increased linearly at 10C. Fructose and glucose content decreased quadratically with storage time at 15C. Glucose content increased linearly at 5 and 10C and fructose content did not change at these temperatures.