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Title: Thidiazuron, a non-metablized cytokinin, shows promise in extending the life of potted plants

Author
item Jiang, Cai-Zhong
item WU, LANFANG - UC DAVIS, PLANT SCIENCES
item MACNISH, ANDREW - UC DAVIS, PLANT SCIENCES
item KING, ANN - UC DAVIS, PLANT SCIENCES
item YI, MINGFANG - UC DAVIS, PLANT SCIENCES
item REID, MICHAEL - UC DAVIS, PLANT SCIENCES

Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2009
Publication Date: 12/1/2009
Citation: Jiang, C., Wu, L., Macnish, A., King, A., Yi, M., Reid, M.S. 2009. Thidiazuron, a non-metablized cytokinin, shows promise in extending the life of potted plants. Acta Horticulturae. 847: 59-65.

Interpretive Summary: Leaf yellowing, senescence, and abscission are significant problems that reduce the marketability and longevity of many cut flowers and potted flowering plants, including alstroemeria, lilies and chrysanthemums. In addition to the visual quality implications of leaf yellowing, it may have a physiological effect in reducing the photosynthesis that is crucial for normal flower development and longevity. Thidiazuron (TDZ), an inexpensive and non-metabolized phenyl-urea compound, has been shown to have a potent cytokinin-like activity at 50-100 times lower concentrations than the synthetic cytokinin benzylaminopurine (BAP). TDZ is commonly used at high concentrations as a defoliant in cotton production (‘Dropp’) and at low concentrations for tissue regeneration in culture. Ferrante et al. have demonstrated that TDZ dramatically retards chlorophyll degradation in leaves of cut flowers of alstroemeria, tulips and chrysanthemums. TDZ also was reported to markedly delay the onset of leaf senescence in Pelargonium and to reduce flower abscission and the senescence of leaves and flowers in cut inflorescences of phlox and lupins. Although the exact mode of action of TDZ is not well known, evidence suggests that TDZ can modulate cytokinin biosynthesis and/or metabolism, and may mimic the activity of auxin. It has been hypothesized that the long-lived cytokinin effect provided by TDZ treatment not only prevents leaf yellowing, but also reduces ethylene sensitivity. Here we report the effects of spray-application of TDZ on leaf yellowing and display quality of potted plants. We examined the possible use of TDZ for delaying leaf yellowing in a range of potted plants, including geranium, freesia, Ornithogalum, and Euphorbia fulgens. Spray treatments with 2 to 10 µM TDZ at the end of the production cycle had significant, sometimes spectacular effects on the postharvest performance of most species studied. In addition to a considerable delay in leaf yellowing and/or abscission in most species tested, TDZ application improved display performance in a number of species. In geranium, for example, the individual florets on TDZ-treated plants had a significantly longer life than those on control plants. In E. fulgens, flowers lasted longer, and more flowers opened on the TDZ-treated plants. Our results indicate significant potential for TDZ as a tool to improve the postharvest life of potted flowering and foliage plants.

Technical Abstract: Application of low concentrations of thidiazuron (N-phenyl-N’-1,2,3-thiadiazol-5-yl urea, TDZ) has been shown to be a very effective means of delaying leaf yellowing in cut flowers such as alstroemeria, stock, lilies and tulips. We examined the possible use of this compound for delaying leaf yellowing in a range of potted plants, including geranium, freesia, Ornithogalum, and Euphorbia fulgens. Spray treatments with 2 to 10 µM TDZ at the end of the production cycle had significant, sometimes spectacular effects on the postharvest performance of most species studied. In addition to a considerable delay in leaf yellowing and/or abscission in most species tested, TDZ application improved display performance in a number of species. In geranium, for example, the individual florets on TDZ-treated plants had a significantly longer life than those on control plants. In E. fulgens, flowers lasted longer, and more flowers opened on the TDZ-treated plants. Our results indicate significant potential for TDZ as a tool to improve the postharvest life of potted flowering and foliage plants.