Effect of Nitrogen Level on Growth, and Relationships between Petiole Nitrate Level, Leaf Chlorophyll Index, and Hypocotyl Nitrate Level of Radish

The aim of this study was measuring nitrate and leaf chlorophyll content in aerial parts of plant, from which we can predict the hypocotyl nitrate content of radish. A factorial experiment in a completely randomized design with five replicates was carried out on two varieties of radish (Cherry Belle and Sparker). Plants were grown in perlite containing pots and were treated with five levels of N (0, 25, 50, 100 and 200 mg/l). Vegetative traits including leaf area, leaf and hypocotyl fresh and dry weight, hypocotyl length and diameter, and hypocotyl and petiole nitrate levels in fresh and dry matter, soluble solids in hypocotyl and petioles, and leaf chlorophyll index were measured. A positive correlation between leaf chlorophyll index and nitrate level in hypocotyl dry matter was observed at harvest time (r2 sparkler = 0.841, r2 cherry belle = 0.869). Significant positive correlations were also found between hypocotyl and petiole nitrate level in fresh matter, and between leaf and nitrate level in hypocotyl dry matter. Based on equations obtained from this study, we can claim that increase per unit in petiole nitrate content could result in the increase of 0.212 and 0.266 units in hypocotyl nitrate content, respectively, in Cherry belle and Sparkler varieties. Results showed that petiole sap test is a rapid and valid technique for describing nitrate status of radish plants