Absorption of Mineral Elements: Mostly mineral elements absorbed by root hairs in their water soluble state. These minerals diffuse freely into the epiblema, cortex and then they reach into the endodermal cells. In the endodermis, casparian strips are found which retard such type of movement. According to Butler (1953) and Epstein (1955) no metabolic energy is required for the movement of minerals across the living cells of the cortex. Suppose the part of cytoplasm has free space, the ions will be translocated passively through the wet cell walls and plasmodesmata of the cells of the cortex and will go to endodermis.
From the endodermis the ion will reach to the xylem through the living cortical cells. Such process is called “symplast theory” of ion uptake. By this active process the ions move from endodermis to non - living elements of xylem. It requires energy which is supplied through respiration. Some special cells called transfer cells take part in the movement of mineral into the xylem. Though in the xylem upward translocation of the nutrients takes place, through the cells of the cambium, these nutrients are radially translocated in the phloem also.
