Investigation of leaf area index, dry matter and crop growth rate on theyield and yield components of soybean cultivars

Yield in most crops is resulted from a number of physiological processes which occurred during plant growth and development. These processes are realized at morphological، pheonological and physiological levels and often are controllded by many genes. In order to determine the effective of physiological traits onseed yield of soybean (Glycine max L.) cultivars and their relationship with yield components، a field study was conducted in 2010. In this study، six cultivars (Gorgan3، Sahar، Sari، DPX، Hill and Telar) and two Genotypes of soybean (032 and 033) were used in a completely randomized block design with four replications. leaf area index، dry matter and crop growth rate revealed that cultivars have the same trend. The analysis of aforementioned traits in R1 (flowering) and R5 (seed filling onset) stages indicated that cultivars had significant differences. But correlation coefficients did not confirm significant relation among traits with seed yield. Analyzed data showed yield enhancement in high- yield cultivars is stemed from high harvesting index which inturn resulted from more pod and seed number. Recorded weather data in the growing period showed the tempratuers higher than 38 to 410C in flowering stage. Results showed that extended vegetative period faced the plants by high temperatures through delayed flowering، as thise cultivars with lower pod and seed number، had lower yield.