The Effects of Stress on the Quality of Pelargonium Propagules during Shipment as Measured Using Chlorophyll Fluorescence

The potential of slow phase chlorophyll fluorescence (CF) to predict the physiological status of Pelargonium propagules (seven varieties in 28 different batches) post shipment or post simulated shipment was evaluated. The rooting ability of the cuttings was recorded and used to confirm the results from the CF data. The use of cardboard versus polystyrene packaging and the inclusion of two treatments (ethylene binding agents included in the packaging or spraying with foliar nutrients) for the alleviation of stress were also evaluated. Chlorophyll fluorescence curves reflecting healthy and stressed Pelargonium material were identified and curve shapes were interpreted in conjunction with the ratio Fss:Fmax values which correlated with rooting potential of each batch. The results from the evaluation of the packaging parameters (through varying the amount of 0 2 and using different forms of binding agents) demonstrated that the physiological status of the cuttings improved when stored with AgNO 3 and with KMnO 4. Cuttings which were stored under anaerobic conditions senesced whereas cuttings stored under normal or reduced 0 2 showed no apparent ill effects. All batches of cuttings showed significant variation in response to various foliar treatments. From the results there was a relationship between CF data and rooting potential of the pro-pagules. Curve types suggest that some batches had exceeded a 'threshold stress level' for certain varieties and consequently would not respond to treatment. The results showed a seasonality effect in the mother stock (reflecting rooting potential) which may have contributed to the variation detected between batches and between different varieties. Overall, the inclusion of ethylene binding agents and O 2 absorbers in the packaging appeared to be 274 beneficial to the physiological status of the propagules. The application of chlorophyll fluorescence to the prediction of the physiological status and rooting ability of propagules post shipment is discussed.