Effects Of Brassinolide And Uridine On Growth And Nutrient Uptake Of Young Tress And Rootstocks Of Apple Under Potassium Chloride Treatment

Potassium chloride（KCl）fertilizer has high potassium content and low price,but it contains chlorine.Most fruiter are sensitive to chlorine and are vulnerable to damage due to improper application.In this study,apple rootstock Malus hupenensis Rhed seedlings and 1-year-old’Fuji’apple saplings（rootstock Malus hupenensis Rhed）were used as experimental materials to investigate the effects of brassinolide（EBR）and uridine on root growth and nutrient absorption of apple under 50 mmol·L^-1potassium chloride treatment.The results are as follows:（1）Spraying appropriate concentrations of brassinolide and uridine could promote the growth and nutrient absorption of Malus hupehensis Rehd seedlings.Foliar application of 0.1mg·L^-1～0.5 mg·L^-1brassinolide and 0.05μmol·L^-1～0.5μmol·L^-1uridine significantly increased the dry and fresh weight,total root length,surface area,volume,average diameter,bifurcation number and root activity of Malus hupehensis Rehd seedlings,and also significantly increased the nutrient contents of N,P,K,Ca,Mg in roots and aboveground.（2）The hydroponic solution contained 25-200 mmol·L^-1three types of potassium salts（KCl,KNO₃,K₂SO₄）,which inhibited the growth and nutrient absorption of Malus hupehensis Rehd seedlings.The higher the concentration,the greater the degree of inhibition.At the same concentration of 25 and 50 mmol·L^-1,the degree of inhibition of KCl on the fresh weight,root activity,surface area,volume,average diameter and nutrient content of Malus hupehensis Rehd seedlings was the highest among the three potassium salts.（3）Foliar sprays of 0.05 mg·L^-1～1.0 mg·L^-1EBR and 0.05μmol·L^-1～50μmol·L^-1uridine under the treatment of culture solution containing 50 mmol·L^-1of KCl reduced the inhibitory effect of KCl on young growth and nutrient absorption of Malus hupehensis Rehd to different degrees,and reduced the malondialdehyde content of Malus hupehensis Rehd under KCl treatment.Among them,the best effect was achieved at 0.1 mg·L^-1for brassinolide and 0.05μmol·L^-1for uridine.（4）Foliar sprays of 0.5 mg·L^-1brassinolide and 0.5μmol·L^-1uridine,separately and in combination,both promoted the growth and nutrient uptake of young apple trees,and significantly reduced the inhibitory effects of potassium chloride watering treatment on growth,root development and nutrient uptake of young apple trees,with brassinolide alone having the best effect.