(38) Carbohydrate Content in Leaves of Three Poinsettia Cultivars (Euphorbia pulcherrima) Grown at Two Locations

Abstract

In Mexico, poinsettia plants are grown under very different and changing environments, thus influencing their metabolism and changing the sugar content that is important in leaf and bract longevity. In the present study, the content of total soluble and reducing sugars and starch was evaluated in leaves of three cultivars, `Marmol', `Supjibi', and V-17 `Angelika', in two contrasting environments: Cuautla, Morelos [24.6 °C, 74% relative humidity (RH), lat. 18°49'N; 1300 msl], and Texcoco, Mexico (14.6 °C, 61.6% RH, lat. 19°31'N; 2310 msl). Plants were grown under greenhouse conditions in 6-inch pots; the substrate and cultural practices were similar in both locations. In Texcoco, plants were covered with black plastic for 12 hours at night to control growth and flowering initiation (15 Sept. to 12 Nov.). In Cuautla, this was not necessary. Leaf samples were taken 8 days after initial covering of plants in Texcoco (84 days after transplant) and 155 days after transplant, when plants were ready for sale. Total soluble sugars were reduced between 84 and 110 days after transplant in leaves of `Supjibi' and `V-17' cultivars independently of the location, while changes in `Marmol' were minimal between days 84 and 155. Significant statistical differences were found for leaf total soluble sugars between locations, being higher in Cuautla, Morelos. For reducing sugars, no differences were detected among cultivars and for the two locations.