Difference in Flower Longevity and Endogenous Ethylene Production of Portulaca umbraticola Cultivars

Abstract

Portulaca umbraticola Kunth, with ephemeral flowers, has become an important summer bedding plant in Japan. A lot of new cultivars have recently been bred with different flowering characteristics, but there is little information about P. umbraticola cultivars. In this study, we investigated the differences in flower longevity, endogenous ethylene production and ethylene sensitivity between a conventional cultivar, ‘Single Red’ (SR), and a newly released cultivar, ‘Sanchuraka Cherry Red’ (SCR). The flowers of SR opened and closed earlier than those of SCR and the flower longevity of SCR was significantly longer than that of SR. The effects of pollination, filament wounding and pistil removal on flower longevity were also investigated in both cultivars. Pollination, filament wounding and pistil removal significantly accelerated senescence in both cultivars, but filament wounding was much more significant in accelerating senescence. Endogenous ethylene production from flower opening to closure was significantly higher in SR than in SCR. The peak ethylene production in SR occurred 2 h earlier than that in SCR. Exogenous ethylene treatments of 0.5, 1, and 2 μL·L⁻¹ significantly accelerated the rate of senescence in both SR and SCR. The use of ethylene action inhibitor 1-methylcyclopropene (1-MCP) and ethylene biosynthesis inhibitor aminoethoxyvinylglycine (AVG) significantly improved flower longevity in both cultivars, with the latter being much more effective. The better flower longevity of SCR seems to be related to lower endogenous ethylene production. The senescence of P. umbraticola cultivars seems to be ethylene-dependent.