1-methylcyclopropene improves ethylene tolerance of unrooted herbaceous cuttings but delays adventitious root development in Angelonia, Calibrachoa, impatiens, portulaca, sutera, and verbena cultivars

Abstract

Knowing which herbaceous taxa are ethylene sensitive and managing exposure of unrooted terminal stem cuttings to ethylene in those taxa are critical for maintaining high-quality propagules that root readily. Of 59 taxa surveyed, freshly harvested terminal cuttings of Begonia hybrid ‘Snowcap’, Lantana camara L. ‘Patriot Sunbeam’, and Portulaca oleracea L. ‘Fairytales Sleeping Beauty’ were sensitive to exogenous application of 1 μL·L-1 ethylene, as demonstrated by leaf abscission within 24 hours of treatment. Exposure to 1-methylcyclopropene (1-MCP) at 700 μL·L-1 for 4 hours before ethylene treatment prevented ethylene injury in these species/cultivars. Exposing unrooted cuttings to 700 μL·L-1 1-MCP induced significant endogenous ethylene biosynthesis in terminal cuttings of the five taxa tested: Euphorbia pulcherrima Willd. ex Klotzsch ‘Visions of Grandeur’, Impatiens hawkeri W. Bull ‘Sonic Red’, Pelargonium peltatum (L.) L’Herit. ‘Mandarin’, Pelargonium × hortorum Bailey (pro sp.) [inquinans × zonale] ‘Rocky Mountain White’, and Petunia×hybrida Vilm. ‘Suncatcher Coral Prism’. Exogenous 1 μL·L-1 ethylene improved adventitious rooting in two cultivars: Begonia hybrid Anita Louise and Fuchsia triphylla L. Honeysuckle. Other trials showed that 1-MCP exposure reduced root number and length of P. ×hortorum ‘Kardino’ and delayed adventitious rooting in all six cultivars tested: Angelonia angustifolia Benth. ‘Carita Lavender’, Calibrachoa ×hybrida Llave & Lex. ‘Terra Cotta’, I. hawkeri ‘Sonic Red’, P. oleracea ‘Fairytales Sleeping Beauty’, Sutera cordata Kuntze ‘Abunda Blue Improved’, and Verbena ×hybrida Groenl. & Ruempl. ‘Aztec Wild Rose’. Subsequent exposure to 1 μL·L-1 ethylene partially mitigated the negative effects on rooting from exposing cuttings to 1-MCP.