2017 ASHS Annual Conference

Unrooted cuttings are prone to environmental stress during shipping and storage. During these periods, dehydration and carbohydrate depletion can occur, potentially delaying rooting and extending crop schedules. Unrooted cuttings of poinsettia ‘Prestige Red’ (PR) and ‘White Star’ (WS) were stored at 10°C for 8 days. Twelve cuttings of each cultivar were sampled every 2 days. Six were used for rooting and six for carbohydrate analysis. Fresh weight loss averaged across cultivars was 8% when cuttings were stored for 8 days. Shoot turgidity, rated on a scale of 1 - 5 with 5 being fully turgid, decreased an average of 1.7 points after 8 days in storage. After 24 hours in propagation under mist, all cuttings returned to a turgidity rating of 5. After 4 weeks, the propagated cuttings were scored on a scale of 1 – 5 with 1 having no roots and 5 having >10 roots, 2.5 cm or longer. Root ratings for PR decreased from 2.2 with no storage to 1.2 after 8 days in storage. WS root ratings increased from 2.1 with no storage to 2.7 after 2 days in storage, but decreased to 1.9 after 8 days in storage. Overall, WS had significantly higher root ratings than PR. Initial fructose and glucose concentrations were not significantly different between cultivars, while sucrose content was greater in PR (4.48 mg·g^-1 dry weight) than WS (3.27 mg·g^-1 dry weight). As storage duration increased, concentrations of fructose, glucose, and sucrose in WS decreased by 13, 29, and 38%, respectively, and in PR by 22, 54, and 63%, respectively. Multivariate correlation analysis showed glucose (r = 0.4824, P ≤ 0.01) followed by reducible sugars, fructose + glucose, (r = 0.4222, P ≤ 0.05), to be good predictors of root rating. While white cultivars have often been thought to be less durable than red cultivars in postharvest environments, PR was more negatively impacted by storage than WS, which may have been caused by its loss of carbohydrates over the 8-day storage duration.