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Title:   Author  item
                                            MACNISH, ANDREW - University Of Californiaitem
                                            Jiang, Cai-Zhongitem
                                            REID, MICHAEL - University Of California
  Submitted to: Postharvest Biology and Technology
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 11/24/2009
                                    Publication  Date: 1/12/2010
                                    Citation: Macnish, A.J., Jiang, C., Reid, M.S. 2010. TREATMENT WITH THIDIAZURON IMPROVES OPENING AND VASE LIFE OF IRIS FLOWERS. Postharvest Biology and Technology. 56:77-84.Interpretive Summary: Dutch iris (Iris × hollandica) is a commercially important cut flower species, although their marketability is limited by their short vase life of 2-5 d.  The failure of iris flowers to open fully after dry transport and storage is also a major postharvest problem.  Thidiazuron (TDZ) is a non-metabolizable phenyl-urea compound with strong cytokinin-like activity.  TDZ is commonly used at either high or low concentrations as a defoliant or for regeneration in plant tissue culture, respectively.  Treatment with TDZ has also been reported to prevent leaf senescence in a range of cut flower species including alstroemeria, chrysanthemum, lupin, phlox and tulip.  In addition, inclusion of 5-45 μM TDZ in vase water was found to reduce ethylene-mediated flower abscission and senescence on phlox and lupin stems, respectively.  This treatment also stimulated opening of additional flower buds on cut lupin and tuberose stems.  
Given the positive response of iris flowers to BA application, we hypothesized that a pulse treatment with the non-metabolizable TDZ would prevent leaf yellowing and also improve the opening and longevity of cut iris flowers.  In this study, we tested the ability of TDZ to improve iris flower opening and longevity.  A postharvest pulse extended the vase life of flowers by up to 1.5 d relative to control stems (4 d).  TDZ treatment also stimulated growth of the pedicel and ovary by up to 2.5 cm that, in turn, led to more complete opening of flowers.  Inclusion of gibberellic acid (GA3) in the TDZ pulsing solution did not extend vase life further but did increase flower shoot elongation by an additional 1.0 cm.  Provision of sucrose with the TDZ plus GA3 treatment had an additive effect, increasing vase life and shoot growth by a further 0.8 d and 1 cm, respectively.  Pulsing stems with this combined treatment prior to storing flowers dry for 14 d at 0 °C provided maximum flower opening and display life after storage.  
In conclusion, pulsing with TDZ in combination with GA and sucrose is a simple and practical postharvest treatment for improving the opening and longevity of fresh and dry-stored iris flowers.  This treatment provides an opportunity to transport iris flowers to more distant markets and/or dry store stems for special holidays such as Mother’s Day.
                                Technical Abstract: The marketability of Dutch iris (Iris × hollandica) cut flowers is limited by their short display life and frequent failure to open fully.  We tested the ability of thidiazuron (TDZ), a phenyl urea compound with cytokinin-like activity, to improve iris flower opening and longevity.  A postharvest pulse with 200-1000 μM TDZ for 6-24 h at 0 or 20 °C extended the vase life of flowers by up to 1.5 d relative to control (0 μM TDZ) stems.  TDZ treatment also stimulated growth of the pedicel and ovary by up to 2.5 cm that, in turn, led to more complete opening of flowers.  Inclusion of 350 mg L-1 gibberellic acid (GA3) in the TDZ pulsing solution did not extend vase life further but did increase flower shoot elongation by an additional 1.0 cm.  Provision of 20% sucrose with the TDZ plus GA3 treatment had an additive effect, increasing vase life and shoot growth by a further 0.8 d and 1 cm, respectively.  Pulsing stems with this combined treatment prior to storing flowers dry for 14 d at 0 °C provided maximum flower opening and display life after storage.  Treatment with 500 μM TDZ stimulated a significant increase in ethylene production by flowers during their opening.


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