Effect Of Iron And Potassium Nutrition On Growth And Physiological Characteristics Of Blueberry Plantlets

Iron and potassium are essential nutrition elements and have vital physiological function for plants. In China, the cultivation of blueberry started relatively late and there is a lack of research on the characteristic of mineral nutrition for it. It is a fact that fertilization managed blindly, often by experience, to limit blueberry production to some extent. A cultivated species of blueberry plantlet was used to study the effect of iron levels (0μmol/L, 10μmol/L, 50μmol/L and 200μmol/L) on growth and physiological characteristics with aggregate culture. By measured physiological parameters as biomass, chlorophyll content, photosynthetic parameters and iron content, the relationship between Fe level and growth and physiological characteristics in plantlets of blueberry was verified, and the optimal concentration of iron was determined. On this basis, two blueberry cultivars:"Coville" and "Northsky" was used to study the differences in responses to iron deficiency between them. Besides, we designed six different potassium levels (0,2,6,18mmol/L) to explore the effects on growth and physiological characteristics of blueberry plantlets and to determine the optimal concentration range of potassium. The results of experiments were as follows.(1) Different iron levels dramatically affected the growth and physiological characteristics of blueberry plantlets. Iron deficiency symptoms occurred when its concentration in culture medium was 0μmol/L and 10μmol/L. These two treatments inhibited photosynthetic activity, leaf chlorophyll content, photosynthetic rate stomatal conductance while increased substomatal CO2 concentration; 50μmol/L resulted in a higher content of dry biomass and fresh biomass, and it also presented certain advantages in increment of plant height, chlorophyll, photosynthetic parameters and iron content in leaves; 200μmol/L didn't result in the symptoms of iron toxicity, but led to a lower growth index than 50μmol/L. The optimal concentration of iron was 50μmol/L.(2) The research of different blueberry cultivars in response to the same degree of iron stress showed that:after 22 days and 30 days of iron starvation, it led to a severe yellowing of young leaves of "Coville" and "Northsky" respectively. Also, iron deficiency resulted in a large decrease in chlorophyll and carotenoid content, an increasing ratio of chlorophyll a/chlorophyll b, a drop of photosynthetic rate, and a significant decline of plant biomass. In addition, iron deficiency elevated malonaldehyde (MDA) content while reduced sugar content and iron concentration in leaves; compared with "Coville", "Northsky" was more sensitive to iron deficiency.(3) Different potassium levels dramatically affected the growth and physiological characteristics of blueberry plantlets. The results showed that 2mmol/L and 6mmol/L presented certain advantages in plant biomass, chlorophyll, photosynthetic rate, and the appropriate potassium concentration range was 2mmol/L-6mmol/L; Ommol/L inhibited plant biomass, leaf chlorophyll content, photosynthetic rate; 18mmol/L resulted in a lower plant biomass and photosynthetic rate, it reached the significant level (P<0.05) compared with 2mmol/L and 6mmol/L.