Abstract: The biological characteristics and physiological indices of “Liangyoupeijiu” (“LYP9”) and its parents were studied in hydroponic experiments under different nitrogen levels. The results showed significant differences in biological characteristics of both “LYP9” and its parents under different levels of nitrogen supply. Biological response of “LYP9” and its parents affected by variety, nitrogen level and their interaction with the effects order of variety factor > nitrogen level factor > interaction of the two factors. With the exception of the maximum root length, the biological characteristics and physiological indices such as aboveground (shoot) and belowground (root) dry weight, nitrogen accumulation, chlorophyll content and photosynthetic rate increased with increasing nitrogen level. In the study, “LYP9” showed the highest level and significant transgressive heterosis in plant height, root volume, dry matter weight, nitrogen accumulation, chlorophyll content and photosynthetic rate. Whereas total nitrogen uptake increased, nitrogen use efficiency decreased with increasing nitrogen level. Physiological response to nitrogen nutrient of “LYP9” and the parents at seedling stage was similar. Intervarietal differences existed in the response of aboveground (shoot) and belowground (root) systems to nitrogen.