Effects of potassium on plant growth, potassium cycle and distribution in different maize genotypes

Potassium (K) cycling and recycling are important for maintaining plant growth and enhancing K use efficiency. Two maize (Zea Mays L.) hybrids,yuyu 23 and xingnong 998, were used as the testing materials. Two K levels, high (1.85 mmol/L) and low (0.1 mmol/L) were set up under the conditions of sand and nutrient culture. Dry weight, K accumulation and distribution in each organ of maize, K cycling and flowing between xylem and phloem, K uptake and use efficiency were studied. The results show that during the ten days after the high and low K applications, compare with the high K treatment, the dry weight, K concentration and accumulation in each plant organ, K uptake efficiency and transported amount in the xylem under the low K treatment are decreased, while the K use efficiency and retranslocated amount from leaves by phloem are increased. At the same time, the K recycling from lower leaves to roots through phloem is activated under the low K condition, and then transported to the upper leaves via xylem. The upper leaves of two maize cultivars are the K sink in the low K treatment, 38.5% and 70.3% of K are provided by phloem of the middle and lower leaves, but their assimilation is not synchronized with K transportation to the upper leaves. In the low K treatment, the dry weight increment of yuyu23 is higher than that of xingnong 998, because the cultivar of yuyu23 has larger root dry weight, greater K uptake efficiency and accumulation, more proportion K from xylem transported into the upper leaves, and the K uptake capacity of yuyu23 is stronger than the K use in whole plant. High K nutrient genotype of maize should have greater K uptake and use capacities.