Plants need to build the complex molecules they need from minerals (elements and simple compounds), which they get from the soil. Animals on the other hand get their complex molecules
ready made from their food в they need very few minerals to supplement their diet. If a plant shows poor growth it may be due to a lack of one or more minerals in the soil. It\’s possible to do chemical tests to find out which minerals are deficient, but it\’s often more convenient to add a general fertiliser. This is sometimes called NPK fertiliser because it contains the elements nitrogen (N), phosphorus (P) and potassium (K).
These elements, plus magnesium (Mg), are the minerals that plants need in the greatest quantities. The concentration of minerals in the soil is very low. They dissolve in water and move around the soil in solution. Root hair cells are adapted to absorb the water out of soil by osmosis в they have a large surface area, thin walls and are close to the xylem cells used for transporting water up the plant. Minerals cannot be absorbed by osmosis (which is the movement of water only) or diffusion (because the minerals are in very low concentration). The root hair cells have carrier molecules on their surface that pick up the minerals and move them into the cell against the concentration gradient.
This requires energy, and is called active transport. Now try a. Amino acids have various prominent functions in plants. Besides their usage during protein biosynthesis, they also represent building blocks for several other biosynthesis pathways and play pivotal roles during signaling processes as well as in plant stress response. In general, pool sizes of the 20 amino acids differ strongly and change dynamically depending on the developmental and physiological state of the plant cell.
Besides amino acid biosynthesis, which has already been investigated in great detail, the catabolism of amino acids is of central importance for adjusting their pool sizes but so far has drawn much less attention. The degradation of amino acids can also contribute substantially to the energy state of plant cells under certain physiological conditions, e. g. carbon starvation. In this review, we discuss the biological role of amino acid catabolism and summarize current knowledge on amino acid degradation pathways and their regulation in the context of plant cell physiology.