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Zhengke Zhang, Yu Zhang, Donald J. Huber, Jingping Rao, Yunjing Sun and Shanshan Li

‘Fuyu’ perisimmon fruit were treated with 500 nL·L−1 1-methylcyclopropene (1-MCP) for 24 h at 20 °C and then stored at 4 °C for 45 days to investigate the effects of 1-MCP on chilling injury (CI) during storage at 4 °C. Persimmon fruit developed CI, manifested as rapid softening and external and internal browning. Injury symptoms were reduced by 1-MCP treatment. 1-MCP also delayed increases in respiration and ethylene production. Compared with control fruit, 1-MCP-treated fruit exhibited increased superoxide dismutase and catalase activities within the initial storage period and lower membrane permeability, malondialdehyde content, and peroxidase and polyphenol oxidase activities throughout the entire storage period. These results suggest that reduction of CI symptoms in persimmon fruit in response to 1-MCP treatment may be attributed to altered oxidative status.

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Henry Taber, Penelope Perkins-Veazie, Shanshan Li, Wendy White, Steven Rodermel and Yang Xu

The purpose of this experiment was to determine the response of tomato (Solanum lycopersicum L.) cultivars with fruit of average and high lycopene to increased K fertilization. The field experiment was designed as a factorial, split-plot, randomized complete block with four replications. The main plot consisted of K rates ranging from 0 to 372 kg·ha−1 K as KCl, and the subplot was cultivar (‘Mountain Spring’ or the high-lycopene Florida hybrid, ‘Fla. 8153’). The soil type was a well-drained, central Iowa loam with a soil test level considered low. The soil K application effect on total marketable fruit yield was linear (P < 0.001, Y = 53 Mg·ha−1 + 0.084x, r2 = 0.51) with both cultivars responding similarly. Fruit K analysis indicated a linear response to fertilization across four harvest dates, from 1236 to 1991 mg·kg−1, fresh weight basis. Harvest date had no effect on fruit lycopene concentration, but there was a significant (P = 0.006) interaction of K fertilization rate and cultivar. Overall, ‘Fla. 8153’ contained 9.5 mg·kg−1 more lycopene in fruit tissue than ‘Mountain Spring’. ‘Mountain Spring’ lycopene concentration was not enhanced by higher K fertilization (44.2 mg·kg−1). ‘Fla. 8153’ lycopene concentration increased 21.7% at the highest K rate compared with lower rates (62.9 vs. 51.7 mg·kg−1, respectively). A controlled greenhouse study in the fall of 2005 with the same cultivars indicated similar results. Fruit K concentration for ‘Fla. 8153’ was significantly (P < 0.01) correlated to the fruit carotenoids, phytoene and phytofluene, indicating a possible role for K in one of the enzymes that synthesize phytoene. In the field and greenhouse studies, increasing fruit K concentration in the high-lycopene ‘Fla. 8153’ depressed fruit β-carotene by 53%. These results indicate that K fertilization can affect carotenoid biosynthesis, and the response of tomato to a high K rate is genotype dependent.