A Temperature Management Model For Controlling Flowering Date And External Quality Of Dendrobium In Greenhouse

Crop model is a useful tool for the optimization of greenhouse crop and climate management. Because of the novel extra quality and ornamental value, Dendrobium(Dendrobium nobile Upin King'Serenadei') is the top product of pot planted flowers in china. In order to optimize the climate management for Dendrobium grown in a greenhouse, a pot planted Dendrobium development and flowering model was developed, and on the base of this model, a temperature management model for controlling flowering date and external quality of Dendrobium in greenhouse was developed. Experiments with different planting dates,different densities and different times of vernalization during vernalization period were conducted in heating greenhouse in Nanjing(E118.83°, N31.04°) from September 2008 to March 2009. The temperature effects on the vernalization,devernalization,development and flowering of Dendrobium were quantitatively analyzed using the experimental data, a model for predicting the development stages of Dendrobium was developed using thermal index relative thermal effectiveness, RTE. Independent experimental data were used to validate the model. Combined with the external quality, a temperature management analyzed by the effect of environment, a temperature management model for controlling flowering date and external quality of Dendrobium in greenhouse was developed. The results as follows:(1) Development and flowering model:The effect of vernalization temperature on the development and flowering of Dendrobium was quantitatively analyzed. On the base of discussing Physiological vernalization days and devernalization effects, a model was developed using RTE(Relative Thermal Effectiveness). The results show that the PVT (Physiological vernalization days) of Dendrobium nobile is 36 days, DVE is 0.275, it means that Dendrobium nobile finished Vernalization is 36 days in the optimum vernalization temperature, when the vernalization temperature rises 1℃, the days of finishing Vernalization will increase 0.275 day, the TRVE for the duration from beginning of vernalization to flower bud initiation was 36.03, the RTE for the duration from flower bud initiation to bud break, from bud break to flowering data, from flowering data to harvest date were, respectively,26.51,16.50,10.34. The model based on temperature can give predictions of the development stages and flowering data of Dendrobium satisfactory.The determination coefficient between the predicted and observed development stages is 0.97, with RMSE is 1,1.58,4and 6.52days, respectively. The model developed in this study gives more accurate predictions than the Growing Degree Days (GDD) based model (with RMSE of 3.16,6.36,14.09 and 18.7 days, respectively).(2)Temperature management model:A greenhouse flowering model and external quality were integration to develop a temperature management model for controlling flowering date and external quality of Dendrobium in greenhouse. According the minimum, optimum, and the maximum temperature, the control set point ranges between 6 to 15℃for the nighttime temperature, and the control set point to 28℃for daytime temperature, Dendrobium needs the shortest time to finish vernalization, reach harvest date and has the best external quality (the number of flower node and bud) were calculated by using a model for predicting flowering date and external quality of Dendrobium. According to saving more energy and keeping the invariably average temperature, the control set point ranges in±0.5℃,±1℃,±1.5℃,±2℃,±2.5℃,±3℃, then Dendrobium needs the shortest time to finish vernalization, reach harvest date and has the best external quality(the number of flower node and bud) were calculated. Simulation analysis shows that Dendrobium needs the shortest time to reach harvest date and has the best external quality when the control set point ranges between 9-14℃for nighttime temperature, and 18-28℃for daytime temperature, also the set point temperature could fluctuated in the optimal range of 0.5℃,±1℃,±1.5℃,±2℃,±2.5℃,±3℃, respectively.Our model which connects different temperatures and times of vernalization during vernalization period, the flowering date, the external quality and the harvest date, not only can predict the flowering date, the external quality of Dendrobium and the harvest date based on the temperatures and times of vernalization during vernalization, but also can predict the he temperatures and times of vernalization during vernalization based on the flowering date, the external quality of Dendrobium and the harvest date. The model developed in this study can be used for temperature management decision support for greenhouse Dendrobium production.