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  • Author or Editor: J.K.C. Rose x
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Tomato fruit (Solanum lycopersicon L.) can develop mealiness and enhanced softening when exposed to chilling temperatures during storage, but the involvement of cell wall-associated enzymes in chilling injury development is not well understood. To study this aspect of injury development, we have exposed breaker stage tomato cv. Trust fruit to a chilling temperature of 3 °C for 0, 7, 14, and 21 days followed by storage at 20 °C for 12 days. Ethylene production was not affected by storage except after 21 days, where production was greater at 20 °C. Exposure of fruit to chilling temperatures delayed the ripening-related color change (chroma and hue) and initially increased compression values, but percentage of extractable juice was not affected consistently. Increased polygalacturonase activity during ripening was reduced by about 50% after 7 days at 3 °C, and further inhibited with increasing storage periods. In contrast, the activities of pectin methylesterase and α-galactosidase were not significantly affected by the cold treatments. β-Galactosidase activity was greater in all chilled fruit compared with fruit ripened at harvest, whereas endo-β-1,4-glucanase activity was lower after 21 days at 3 °C. These results will be compared with equivalent changes in the activities of cell wall enzymes that are associated with wooliness development in chilling-injured peach fruit.

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The aim of the present work was to establish appropriate conditions for the in vitro micropropagation of Eremanthus erythropappus (DC.) MacLeish through shoot multiplication on apical and nodal bud explants. Explants were excised from in vitro-grown seedlings and incubated on Murashige and Skoog medium containing different combinations of 6-benzylaminopurine (BAP) and 1-naphthalene acetic acid (NAA) (for apical buds) and gibberellic acid and NAA (for nodal segments). Proliferation of apical shoots was successfully achieved in the presence of BAP and NAA, each at 1.0 mg L−1, while the elongation of apical shoots could only be attained on medium containing NAA at 1.0 mg L−1. Elongation of nodal shoots was induced in the presence of NAA at 2.0 mg L−1. The most suitable medium for inducing root proliferation on explants of E. erythropappus was NAA at 1.0 mg L−1.

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