Response of poinsettia cultivars to aluminum exposure for postharvest disorders
Bernard Bible and Richard McAvoy
Presentations (Papers) XXVIth International Horticultural Congress. August 15, 2002, Toronto Canada
2002
บทคัดย่อ
Poinsettia (Euphorbia pulcherrima Willd. Ex Klotzch) bracts are susceptible to postharvest disorders like the pathogenic fungus, Botrytis cinerea, and the abiotic disordr, bract necrosis. Aluminum is a known antagonist of calcium uptake and Ca activities in plant membrane and cell walls. Alminum exposure damages root tips, which are the sites of much Ca uptake and cytokinin synthesis. Therefore, Al exposure to poinsettia may aggravate the incidence ofeither or both of these disorder. Rooted cutting of Supjibi and Maren were transplanted into a closed water culture system and later pinched leaving 4-5 nodes per shoot. The plants were grown in the standard Ca (4mM) solution intially. At bract coloration, all plants were placed in the low, 0.5 mM Ca solution with three levels of Al bract coloration, all plants were placed in the low, 0.5 mM Ca solution with three levels of Al (0, 61 or 120 μM added). For the Al treatments, initial pH was adjusted to 4.8 with sulfuric acid. After all plants of both cultivars were harvested their bracts were subdivided into transitional-bracts and truebracts and the number of necrotic and healthy bracts recorded. Mineral nutrients in bracts were determined. Botrytis incidence was higher on transitional-bracts than on true-bracts for Supjibi at all Al levels while for Maren, Botrytis was higher on transitional-bracts than on true-bracts only at the highest Al exposure. Bract necrosis was not evident on Maren plants at any Al treatment level.The incidence of bract necrosis on Supjibi was the same on true-bracts and transitional-bracts in each Al solution. For supjibi, exposure to diffferent AI levels had no consistent effect on the incidence of bract necrosis.