The Physiological Mechanism of Plant Growth and Senescence Characteristics in Wheat Regulated by Exogenous Cytokinin

Compared to control(CK),the plant heights,leaf areas per plant,fresh weights and dry weights per plant of the tested cultivars in exogenous 6-BA treatment(10 mg/L)were all decreased.The fresh weights and dry weights per plant at 35 d after treatment were much lower than CK.Meanwhile,the chlorophyll a and chlorophyll b contents at late phase after 6-BA treatment showed an increase tendency compared to CK.It is found that the decrease of photosynthetic rate(Pn)in tested varieties in 6-BA treatment was the main reason of the reduction of dry matter production per plant.The tested 6-BA treatment had little adverse effects on chlorophyll synthesis and photosynthetic dark reaction in photosynthesis,and Pn showed same change pattern with stomatal conductance(Gs)in the measurement points.It was suggested that the decrease of CO2 transportation capacity by 6-BA was the main reason of lower in Pn and dry matter production per plant than CK.The 6-BA treatment increased the leaf catalase(CAT)activity at the late phase after treatment.There was a significant negative correlation between CAT activities and MDA concentration(r=-0.738 1*),indicating that the decrease of over-oxidization degree of cell membrane system in 6-BA treatment was due to largely by the increase of CAT activity.In this study,it is found that the inhibition effect on photosynthesis by overdose exogenous 6-BA was much more than that on cell division.In wheat production,the concentration and amount of exogenous cytokinin materials applied should be carefully determined depending on the maturation properties and leaf senescence characteristics of the cultivars in future.