The
              Report

No. 73: Using clones to establish 
tea tree plantations

The full report
This is a summary of a full report of the same name published by RIRDC (Pub no 99/155, UQ-63A) by Assoc. Prof. David H. Simons, University of Queensland. Phone: 07 5460 1231, fax: 07 5460 1455, email: David.Simons@mailbox.uq.edu.au 
The report is available in hardcopy under (Wildflowers & Native Plants Program )or downloadable from this site.

Researchers from Queensland University have developed dosing and application systems for an alternative agent – known as 1-MCP – to combat ethylene-induced postharvest wilting in wildflowers. Premature flower fall or abscission and fl ower senescence (e.g., wilting) are ethylene-related postharvest problems for various cut flowers.

Unintentional exposure of these flowers to ethylene, a plant hormone, reduces their longevity and marketability. Treatments that inhibit ethylene biosynthesis or action can be used to protect sensitive Australian wildflowers against exposure to ethylene.

This is essential in capitalising on the increasing international demand for Australian wildflowers as an exotic alternative to traditional cut flowers such as carnations, roses and chrysanthemums.

There has been limited research into the postharvest physiology and horticulture of wildflowers, particularly relating to their unintended exposure to ethylene in commercial situations.

To date, the most successful commercial treatment for preventing ethylene-induced wilting has been by pulsing flower stems with silver thiosulfate (STS).

But as the active ingredient of STS is silver, a heavy metal, it may soon be withdrawn from commercial use due to possible environmental hazards.

Associate Professor David Simons, Andrew Macnish, Daryl Joyce, and Peter Hofman of the University's Gatton College School of Land and Food, carried out the work which was funded partly by the Rural Industries Research and Development Corporation (RIRDC).

The Study

As part of RIRDC's Wildflower and Native Plant Program, the research aimed to:

• develop dosing (concentration, duration and temperature) relationships for 1-MCP treatment of native cut flowers;

• extend the postharvest longevity of various ethylene-sensitive native cut flowers through treatment with 1-MCP; and

• devise and test practical application systems for 1-MCP treatment.

Experiments were conducted to determine an effective 1-MCP pre-treatment protocol for protecting native Australian cut flowers against unintentional exposure to ethylene.

A species of grevillea was given 1-MCP treatments with different concentrations of the agent, treatment duration and treatment at various temperatures.

Experiments were then carried out on a number of other native Australian cut flowers to screen their response to 1-MCP and other ethylene treatments. Included were Dorrigo waratah, red boronia, Asteraceae, NSW Christmas bush, Geraldton waxfl ower, Rutaceae, Grevillea hybrids, Lemon-scented tea tree, rice flower, Apiaceae, NSW waratah, Grampian's thryptomene, and yellow Morrison.

The research also involved a detailed investigation into the effects of temperature on 1-MCP treatments of native flowers. Several practical application systems for using 1-MCP were also developed and tested.

The Results

The research showed that 11 ethylene-sensitive native Australian cut flowers can be protected against exogenous ethylene by pre-treatment with 1-MCP.

Pre-treatment of flowers in the laboratory with 10 nL 1-MCP/L for 12 hours at 20°C was effective in preventing the ethylene-induced loss in vase life.

Also, pre-treatment of flowers with low 1-MCP concentration of 10 nL 1-MCP/L was not effective when applied at the low temperature of 2°C.

But pre-treatment of C. uncinatum flowers on a commercial scale with the high 1-MCP concentration of 150-200 nL 1-MCP/L for 14-15 hours at 2°C was highly effective in reducing ethylene-induced wilting.

A 1-MCP pre-treatment did not afford long-term protection against ethylene to cut G. 'Sylvia' and C. uncinatum flowers.

Application of 1-MCP inside sealed polyethylene tents or coolrooms were practical treatments for reducing ethylene-induced flower fall from C. uncinatum.

Sustained release of 1-MCP gas by forced air movements from tubes placed into fl ower cartons also afforded C. uncinatum with protection against ethylene. This treatment should on refi nement, be the most viable system for providing long term protection against ethylene.

Based on the findings of this study, it is recommended that pre-treatment of native cut flowers inside sealed polyethylene tents or through bunches standing in buckets of water in coolrooms with 150-200 nL 1-MCP/L for 3 to 15 hours duration at 2 or 20°C can provide short-term protection against ethylene.

The use of 1-MCP as a practical alternative to STS for anti-ethylene treatment of cut flowers will still depend in part upon optimisation of 1-MCP pre-treatment protocols which provide long term protection against ethylene.

In particular, refi nement of sustained delivery of 1-MCP into fl ower cartons warrants further attention.

Optimisation of sustained delivery of 1-MCP is being followed up in ongoing work as part of a PhD study by Andrew Macnish, one of the researchers involved in the project.

Nevertheless, the 1-MCP treatments developed in this RIRDC-sponsored work have been shown to provide complete short-term protection of cut flowers against ethylene, and are appropriate to cover the relatively short period of unrefrigerated export by air.

Summary

In summary, 1-MCP treatments developed in this RIRDC sponsored work have potential as postharvest anti-ethylene treatments for sensitive native Australian cut flowers.

Application of 150-200 nL 1-MCP/L for 3-15 hours duration at 2 or 20°C to native cut flowers inside enclosed coolrooms or tents was completely effective in reducing ethylene-induced fl ower fall.

However, compared to STS pulsing, 1-MCP pre-treatment provides native cut flowers with relatively short-term protection against ethylene. Sustained release of 1-MCP from inside cartons has potential, following refi nement, to provide cut flowers with longer term protection against ethylene by remaining available to bind to newly formed ethylene receptors.

This treatment would be easy to use and allow rapid dispatch of cut flowers to markets by eliminating the need to pre-treat flowers.

Additionally, it may appeal to growers without suitable enclosed treatment structures and those concerned about handling chemicals such as 1-MCP and STS.

Treatments with 1-MCP developed in this study are comparatively easy to apply and can provide protection to sensitive cut flowers where the period of postharvest handling is brief.

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