Please outline the composition principles for ascertaining a nutrient solution formula. 请简要说明在确定营养液配方时的组成原则。
Physiological responses of Solanum nigrum L and Solanum melongena L seedlings to Cadmium stress were investigated by nutrient solution culture. 采用营养液培养法研究了镉胁迫条件下龙葵和茄子幼苗的生长及生理响应。