Abstract: Lycium ruthenicum Murr.was grown under field conditions in the middle reaches of Shiyang River in China in the presence and absence of irrigation and fertilization,and stem and leaf growth at different stages and ecostoichiometric characteristics of the species were measured.Associations between organ growth rates and ecostoichiometric characteristics were analyzed,and the growth rate hypothesis of the ecostoichiometric theory was tested.Irrigation and fertilization significantly increased stem length,basal diameter,leaf length,leaf width,and leaf dry weight of L.ruthenicum (P<0.05);however,there were no significant differences in stem length,basal diameter,leaf area,and leaf dry weight between treated plants and controls.During the growth period,new L.ruthenicum shoots showed increased C content and C∶N and C∶P ratios and decreased N and P contents and N∶P ratio.Furthermore,stems of treated plants showed lower C content and C∶N,C∶P,and N∶P ratios but higher N and P contents than those of controls.During the growth period,leaves showed decreased C,N,and P contents and increased C∶N,C∶P,and N∶P ratios.Leaves of treated plants showed lower C content and C∶N,C∶P,and N∶P ratios but higher N and P contents than those of controls.Stems showed significantly higher C content and C∶N and C∶P ratios (P <0.05) but significantly lower N and P contents and N∶P ratio (P <0.05) than leaves.The growth rate hypothesis states that the individual growth rate is negatively correlated to N∶P and C∶P ratios and positively correlated to N and P contents in vivo.In the present study,there were no significant correlations of stem and leaf growth rates of L.ruthenicum with N and P contents and C∶P and N∶P ratios,indicating that stem and leaf growth rates and ecostoichiometric characteristics of L.ruthenicum did not support the growth rate hypothesis under irrigation and fertilization.

Key words: Lycium ruthenicum Murr., ecological stem and leaf growth, ecological stoichiometry, growth rate hypothesis