Prediction of Phenology, Phyllochron and Leaf Area in Wheat (cv. Sardari)

and objectives Prediction of development periods of crops by mathematical models, especially, time to growth ending is so important in every area. So, as impotence of prediction of phenology, leaf area and time to leaf growth ending, this research performed to introduce and test of Phenology MMS model in environmental conditions of saqez, prediction of leaf appearance rate, phyllochron in stress condition of drought and to correct coefficient of allometric equations of predicting of leaf area of wheat(cv. Sardari). In this research, Phenology MMS evaluated using field data for wheat . Then time and thermal time needed to leaf growth ending and phyllochron (degree day per leaf) obtained using segmented model in every stress level. So, the best algometric model selected for describing of relation between leaf area and leaf number. Results Results showed that the model predicted wheat development periods well and was capable to estimate day and thermal time needed to every special development period in three state: day after sowing, day after emergence and day after vernalization. Also, results released that time to leaf growth ending will occur after reception of 1716 degree day which equal to 238.8 day after emergence. On other hands, a leaf will include to plant 16.6 day after emergence. By increasing in tension, the slope of regression line of leaf number versus thermal time, decreased and reached to 0.0029 leaf per degree day in sever tension. Vice versa, phyllochron upgraded by increasing in tension and it changed from 133.3(medium tension) to 339.1 degree day per leaf (sever tension). Results of predicting of leaf area using exponential segmented models showed that segmented model was better than exponential models in predicting of leaf area. As for being acceptable of results of phonological model for prediction of thermal time, leaf number and phyllochron, we advise using of this model in modeling and agronomical studies. So, drought stress can effect on leaf appearance rate and phyllochron value. The best model to estimate leaf area was segmented model. Because this model was simple and capable to develop based on physiological meanings that can indicate clear introducing of leaf area variations.So, drought stress can effect on leaf appearance rate and phyllochron value. The best model to estimate leaf area was segmented model. Because this model was simple and capable to develop based on physiological meanings that can indicate clear introducing of leaf area variations.