A Photo-Thermal Model For Predicting Growth And External Quality Of Dendrobium Nobile In Greenhouse

Radiation and temperature are the important factors that effects growth, flowering date and external quality of the ornamental plants. A photo-thermal model for predicting growth and external quality is a useful tool for the optimization of greenhouse climate management since it can quantitatively predict growth and external quality of the ornamental plants planted under different temperature and radiation conditions. Dendrobium nobile not only is one of the four tropic orchids, but also is the important festival flower in China. It's important to qualify the effects of radiaton and temperature on growth and external quality of Dendrobium nobile and then to develop a photo-thermal model for predicting growth and external quality of Dendrobium nobile in greenhouse for planting management and environment optimization of Dendrobium nobile. Experiments of Dendrobium nobile (Dendrobium nobile Upin King cv'Serenadei) with different planting dates, vernalization (dates and persisting days) and densities (75 pl/m2,60 pl/m2,45 pl/m2) were conducted in greenhouses located at Nanjing from the October in 2008 to the March in 2009. In this research, firstly based on the quantitative analysis, a model for predicting growth of Dendrobium nobile was developed using the accumulated photo-thermal index per plant (PTI). Secondly the effects of radiation and temperature on external quality of greenhouse Dendrobium nobile Upin King cv'Serenadei are studied. Then a model for predicting the number of flower buds nodes and flower buds per plant when harvest of Dendrobium nobile was developed using vernalization persisting days and another model for predicting length and the maximum diameter of the first flower bud of Dendrobium nobile was also developed using the accumulated photo-thermal index per plant (PTI). Independent experimental data were used to validate these models. The main research results are as follows:(1) The photo-thermal model for predicting growth of Dendrobium nobileThe biomass production and dry matter partitioning is the foundation of growth and formation of external quality. Based on the response of Dendrobium nobile growth to temperature and photo-synthetically active radiation, PTI was used as an index to develop a model for predicting growth. Independent experiment data were used to validate the model. The results show that the model can give predictions of the growth of Dendrobium nobile satisfactorily. Based on the 1:1 line, the determination coefficient (R2) between the predicted and the measured value for total dry weight per plant, shoot dry weight per plant, root dry weight per plant, stem dry weight per plant, leaf dry weight per plant, flower dry weight per plant are 0.93,0.90,0.92,0.91,0.90,0.91, respectively; the root mean squared error (RMSE) are 0.19g-pl-1,0.21g-pl-1,0.26g-pl-1,0.24g-pl-1,0.25g-pl-1,0.23g-pl-1, respectively.(2) The photo-thermal model for predicting external quality of Dendrobium nobileThe qualitative analysis about the effects of vernalization and densities on external quality of greenhouse Dendrobium nobile Upin King cv'Serenadei shows that the number of flower buds nodes and flower buds per plant when harvest were decreased with difference between actual vernalization time (AVT) and physiological vernalization time (PVT) (AVT-PVT), the length and maximum diameter of the first flower bud were reduced slightly while the density increased. Then a model for predicting the number of flower buds nodes and flower buds per plant when harvest of Dendrobium nobile was developed using vernalization persisting days and another model for predicting length and the maximum diameter of the first flower bud of Dendrobium nobile was also developed using the accumulated photo-thermal index per plant (PTI). Independent experimental data were used to validate these models. The results show that the model can give predictions of the external quality of Dendrobium nobile satisfactorily. Based on the 1:1 line, the r2 and RMSE are 0.98 and 0.10 nodes-pl-1, for the number of flower buds nodes per plant; 0.96 and 0.32 buds-pl-1, for the number of flower buds per plant; 0.97 and 0.17cm, for the length of the first flower bud;0.99 and 0.10cm, respectively for the maximum diameter of the first flower bud.The prediction model developed in this study gives significantly higher prediction accuracies for growth and external quality of Dendrobium nobile. Based on the results obtained in this study, it can be concluded that the model developed in this study can give a satisfactory predictions of Dendrobium nobile, hence, can be used for decision making for precision control of light and temperature in greenhouse Dendrobium nobile production. Dendrobium nobile is Orchidaceae pant with crassulacean acid metabolism(CAM), whose seedling stage is too long, so in this research we used mature plants of Dendrobium nobile as experimental material. Therefore,this model can't be used to predict growth and external quality of Dendrobium nobile base on seeding stage. In the future, more researches should be made to improve the model.