Predicting The Effects Of Substrate Water Potential On Growth And External Quality Of Cut Lilium

Water is an essential factor which affects the crop growth and the formation of the growth and external quality. The aim of this study is to quantitatively investigate the effects of water on crop growth and external quality of cut Lilium. Experiments of Lilium ’Sorbonne’with different planting dates (2009.3.26,2009.4.26,2009.9.27) and different levels of water treatment (-4～-10kPa,-10～-15kPa,-15～25kPa,-25～40kPa) were conducted in a flower greenhouse in Naijing from March2009to January2010. Based on the model describing the effect of photo-thermal index (PTI) on greenhouse flower growth and external quality, we analyzed the effect of substrate water potential on the leaf area index (LAI), the maximal photosynthesis rate, dry matter production and partitioning of cut Lilium, meantime, collected the data of external quality including plant height, the number of leaf unfolding, flower length and flower diameter under different treatments, then developed a model to predict the growth, external quality, relative yield and validated the model with independent experimental data. The results showed a well predicted conclusion of LAI, dry weight and various external quality indices. This study provided the theoretical basis and decision making to water management during cut Lilium production. The main research results are follows:(1) Determination of the critical value for substrate potential. According to our experiment and result analysis, all the growth and external quality indices linearly decrease along with the decreasing substrate water potential when its value is below-15kPa, but remain constant above-15kPa. Thus we deem-15kPa as the threshold value for cut Lilium growth.(2) Predicting the effects of water on LAI of cut Lilium.The study quantitatively analyzed the maximum leaf length (Lmax), increasing rate of LAI (rLAI) and LAI under different water treatments. The results showed that Imax,rLAI and LAImax increased along with the increasing of substrate water potential, the two indexes were stable when the water potential attended-15kPa, but linearly decreased accompanied the decrease of water potential below-15kPa. Independent data acquired to validate the model, the result showed that the coefficient of determination (r2) and the relative root mean square error (rRMSE) between the measured and predicted number of leaf unfolding, leaf length and LAI were0.96,0.82,0.97and6.32%,8.78%,7.12%, respectively.(3) Predicting the effect of water on maximal photosynthesis rate and dry matter production of cut Lilium. The study quantitatively analyzed the maximum leaf gross photosynthesis rate (Pg,max) and initial photo-energy utilization ratio (ε) under different water treatments. The results showed that Pg,max and ε were almost the same when the water potential was above-15kPa, but linearly decreased accompanied the decrease of water potential below-15kPa. Independent data acquired to validate the model, the result showed that the coefficient of determination (r2) and the relative root mean square error (rRMSE) between the measured and predicted for Pg,max and biomass were0.96,0.81and4.37%,10.54%, respectively.(4) Predicting the effect of water on dry matter partitioning of cut Lilium. The study quantitatively analyzed the indexes of organs aboveground and underground under different water treatments. The results showed that the indexes for flower, stem, leaf, root (PIF, PIST, PIL, PIR) increased but bulb(PIB) decreased along with the increasing when the water potential was above-15kPa, respectively. And all the increasing rate of these indexes (rPIF, rPIST. rPIL.rPIR,rPIB) linearly increased accompanied the increase of water potential below-15kPa. Independent data acquired to validate the model, the result showed that the coefficient of determination (r2) and the relative root mean square error (rRMSE) between the measured and predicted for the dry weight of organs (DMF, DMST, DML, DMB, DMR) were0.96,0.95,0.86,0.95,0.85and19.18%,12.35%,19.42%,12.23%,31.73%, respectively.(5) Predicting the effect of water on external quality (plant height, leaf number, flower length, flower diameter) of cut Lilium. The study quantitatively analyzed the external quality under different water treatments. The results showed that the effect of water on cut Lilium total leaf number was not significant. The external quality showed no difference when the substrate water potential was above-15kPa, but the increasing rate of plant height, flower length and flower diameter (rH, rFL,rFD) linearly decreased along with the decrease of water potential below-15kPa, which resulted in the decrease of harvesting plant height (HH), flower length (FL) and flower diameter (FD). Independent data acquired to validate the model, the result showed that the coefficient of determination (r2) and the relative root mean square error (rRMSE) between the measured and predicted for the HH, N, FL and FD were0.97,0.96,0.97,0.89and7.54%,6.32%,9.56%,1.15%, respectively.(6) Predicting the effect of water on relative yield of cut Lilium. The study quantitatively added up the different ranks (rank A, B, C and D) of relative yield under different water treatments. The results showed that the rank A and B increased along with the increasing substrate water potential above-15kPa, but opposite to the rank C and D. when the substrate water potential was below-15kPa, the ratio of (RA+RB)/(RC-RD) decreased, which led to bad external quality. Independent data acquired to validate the model, the result showed that the coefficient of determination (r2) and the relative root mean square error (rRMSE) between the measured and predicted for the relative yield were0.87and6.41%, respectively.This model is capacity for dynamicly predicting the cut Lilium growth, external quality and relative yield according to the date of planting, substrate water potential, PAR and temperature in greenhouse. In the model, we used substrate water potential to replace the subatrate water content and comprehensively considered the effect of temperature, light and water on cut Lilum which could be used in various types of soil or substrate, and provided the theoretical basis and decision making to water management during cut Lilium production.