Mechanism of Absorption of Elements

Two Stages of Mineral Uptake

Most of what is understood about how plants absorb minerals comes from experiments on isolated cells, tissues and organs, and this work shows that absorption happens in two distinct stages.

• Stage one — into the apoplast: ions move quickly into the 'free space' or 'outer space' of the cell, called the apoplast, by a passive process that needs no metabolic energy. This movement happens mainly through ion channels — trans-membrane proteins that act as selective pores, letting particular ions pass through the cell membrane down their concentration gradient.
• Stage two — into the symplast: ions then move more slowly into the 'inner space' of the cell, the symplast. This step does require the plant to spend metabolic energy — it is an active transport process, working against a concentration gradient where needed.

Flux, Influx and Efflux …