Education Zone

Transport across the plasma membrane is the most important part of nutrient accumilation. Factors that effect the an ions transport across the membrane will determine the rate of uptake to a large extent.

Ion Diameter- For ions of the same valency and similar membrane transport systems, size determines its rate of uptake. Smaller the faster.

Valency- as increases the rate of uptake decreases. partly to do with the increase in size, mainly to do with the interaction with the ion and membrane. Ions that have different forms (different valancies) are taken up faster at a certain pH because these conditions produce a greater concentration of the lower valency ion.

Respiration- because the vast majority of ion transport requires energy, respiration levels are closely linked to uptake. Factors include, level of oxygen, carbohydrate availability, and temperature. Oxygen levels decrease, so does respiration levels, reducing rate of uptake. Damage to the respiratory system by toxic oxygen spieces also will have an effect. Temperature affects uptake as it would any enzymatic reaction, increasing the rate in many reactions as temperature increases. Temperature effect is less pronounced on cold tolerant spieces.

Competition of ions of the same valency and size- this happens even between required ions and those that are unwanted. shows that the binding sites on the transporter protiens and ion channels recognise ions by their physical properties, not specific to their nutrtional use. Toxic substances that resemble useful ions could accumalate in the cell. magnesium ions are often low in plants that are sprayed with fertilizers high in potassium and calcium (more effective competitors).

Concentration of an ion in external solution- over long and short periods of time can effect the rate of uptake of that particular ion. The availability of transporter protiens will be affected over longer periods of time by the availability of ions. luxury uptake is allowed over short periods of time when an increase in concentration of certain minerals, Causes the induction of a faster uptake system allowing nutrients to be stored in the vacuole for leaner times, until a maximum value is reached. The second faster system, channel protien, allows faster uptake as well. Both systems are less specific with the minerals taken up. These systems are proceeded by increased protien synthesis.

Internal concentrations- effect uptake rate. low concentrations of a particular ion in the vacuole leads to synthesis of more protien carriers, producing more rapid uptake. this will subside after a short period.

cations and anions often associate as a method of crossing the plasma membrane, the rate of this is effected by the concentration and rate of uptake of the least abundant or slower absorbed ion. rate of uptake of the faster ion is slowed by the slower ion. This has little effect in times of low ion concentration, but becomes important as th ions increase in concentration.

Root morphology also effects uptake of different ions. basal cells in general take up fewer nutrients than apical root zones. Depends on factors such as nutritional status, species, and other enviromental factors.

• Effects nutrients have on the development of plants

• Effects nutrients have on yield

• Factors that effect the rate of mineral uptake

• Explanation of the mineral uptake into the cells of plants

• Uptake of mineral nutrients in the apoplasm

• Transport of nutrients throughout the plant

• Nitrogen nutrition