30 December 2011

Plant Nutrition: Mineral Absorption (Part One)

This video looks at how soybean plants affect their soil environment to increase mineral availability, specifically in respect to iron.

you

you yellow soybeans are not healthy soybeans why because soybeans turn yellow when they lack a critical mineral iron plants require a balance of minerals for healthy growth without the proper balance of minerals the plant will not grow normally and eventually crop yields will decrease this in turn affects humans because a substandard food crop will be less nutritious minerals such as iron come from the soil depending on soil conditions mainly pH the mineral can be bound to a soil particle or soluble in the soil this animation will focus on the reactions required to free a mineral from the soil which makes the mineral soluble and available for uptake by the plant in this example we will follow the mineral iron as it makes its way into a soybean plant to grow properly plants extract iron from the soil for this process to be successful iron must be available in a soluble form it cannot be absorbed by the plant without first being made soluble but under certain conditions such as high pH most of the iron is bound to oil particles and only a small amount is soluble and available to the plant to

make more iron available the soil conditions must change especially near the root surface here we see iron bound to soil particles unless this iron is released from the particles the plant will exhibit iron deficiency stress soybeans are sensitive to low iron levels which causes the plants to exhibit yellow leaves this yellowing of the young leaves slows plant growth and reduces yield because of its chemical properties iron is bound to soil particles when the soil pH is too high the mineral remains bound until the pH is lowered how can the plant lower the pH pH is a function of the concentration of hydrogen ions the more hydrogen ions the lower the pH hydrogen ions can be produced by the action of the hydrogen ATPase family of proteins when these are active hydrogen ions are released into the soil and the pH drops as the pH drops iron is released from the soil particles and becomes available a soluble iron minerals have additional features that need to be considered for proper mineral absorption in the case of iron it exists in the soil primarily in the F III or ferric state but it must be

changed to the ferrous or fe 2 state before it can move into bean or soybean plants these plants have evolved a system that facilitates this conversion embedded in the cell membrane is a protein called f ro f ro reduces ferric iron to ferrous iron at the root surface by transporting an electron from NADPH here we have seen that the plant is capable of modifying its soil environment to increase mineral availability this has a direct effect on the soil by decreasing the pH thereby providing soluble ferric iron to the F ro protein while this protein can convert ferric iron into ferrous iron additional help is required to move the iron into the plant another protein a ferrous iron transporter also found in the root cell membrane is needed to move the FE 2 into the root cortex part 2 of this animation will describe the action of this protein as well as the mechanisms used by the plant to distribute the mineral two leaves and seeds you