Plants only uptake ions.
http://en.wikipedia.org/wiki/Mineral_uptake
"
In plants,
mineral uptake is the process in which minerals enter the cellular material, typically following the same pathway as
water. The most normal entrance portal for mineral uptake is through plant roots.(Roots, 2005) Some
mineral ions diffuse in-between the
cells. In contrast to water, some minerals are actively taken up by plant cells. Mineral
nutrient concentration in roots may be 10,000 times more than in surrounding soil. During transport throughout a plant, minerals can exit
xylem and enter cells that require them. Mineral ions cross plasma membranes by a chemiosmotic mechanism. Plants absorb minerals in
ionic form:
nitrate (NO3−),
phosphate (HPO4−) and
potassium ions (K+); all have difficulty crossing a charged
plasma membrane.
It has long been known plants expend
energy to actively take up and concentrate mineral ions. Proton pump hydrolyzes
ATP to transport H+ ions out of cell; this sets up an electrochemical gradient that causes positive ions to flow into cells. Negative ions are carried across the plasma membrane in conjunction with H+ ions as H+ ions diffuse down their concentration gradient."