Food from Photosynthesis

     In contrast to animals, fungi and other heterotrophic organisms that rely on organic materials for nutrition, plants synthesize their own food through the use of inorganic substances. This synthesis is the chemical process of photosynthesis. Photosynthesis, complimented with the uptake of nutrients from the soil makes up the method of food acquisition of Achillea millefolium.


     Photosynthesis requires light energy, water, and carbon dioxide to complete the process of converting sunlight to a usable food source.  

Light Energy
    The process of photosynthesis takes place in the plant’s chloroplast, using the pigment chlorophyll to absorb the energy from the sun. Chloroplast and chlorophyll are found in all green parts of the plant, for example, the leaves and stem.

Water Acquisition and Transport
     Next, water in the soil is pulled up throughout the plant via a structure known as xylem. Water begins its journey by being absorbed through Achillea millefolium’s horizontal underground fibrous root system. Water is absorbed by the roots because of its water potential. Water moves into the cells of the Yarrow root via osmosis. This is because there is a higher concentration of solutes inside the cell, and water always moves from an area of low concentration to an area of high concentration.
     Once the water enters the root cells it moves toward the xylem through pathways known as the apoplast which are connections between cell walls, and pathways known as symplast, connections in the interior of the cell. After reaching the xylem, the water continues to the upper parts of the plant due to transpiration, adhesion, and cohesion. 
     As water begins to transpire through the leaves, it creates a reduced water potential, or increased solute concentration, of the cells in the leaves.  As previously stated, water will always move from an area of low concentration to a high concentration; thus, water molecules will be pulled along to the regions of high concentration. Adhesion and cohesion now assist in the pulling up of additional water molecules. Adhesion gives the polar water molecules a high affinity for other polar molecules, for instance, the cellulose of the Yarrow cell walls. Cohesion is the property that allows water molecules to stick to one another. As you can see, all three processes (transpiration, adhesion, and cohesion) work together to transport water through Achillea millefolium.

Carbon Dioxide
      Finally, Carbon Dioxide is needed to complete photosynthesis. To allow for the entrance of CO₂, leaves contain small pores called stomata.  Stomata include two guard cells, and when the guard cells have adequate water they bow outward causing an opening for gas exchange (CO₂ entrance).

Sugar Creation and Transport
      Although the previous steps are vital in the process of photosynthesis, the most important factor is that all of those ingredients combine to create sugar! These sugars commonly are found as glucose and sucrose. These sugars act as the primary source of energy for Achillea millefolium. This calls for sugar transport to all parts of the plant.
After production, the sugars travel through a cell via the apoplast or symplast toward the phloem. Although similar to xylem in its ability to transport nutrients, phloem transfers nutrients to all areas in need of nutrition in all directions.   
      The transport of sugars and other nutrients begins because of the high sucrose concentration in the phloem. Then, water flows in from nearby xylem by osmosis which, in turn, creates pressure within the phloem. This pressure build-up causes the concentrated and pressurized sucrose solution to flow to areas of lower sucrose concentration (areas in need of nutrients).
     Lastly, in order to keep the flow of sugars and nutrients going, high concentrations of sugar must be maintained so that osmosis of water and pressure build-up continues. In order to add a concentrated solution (more sugar) to an already concentrated solution, active transport is necessary. Any excess of sugars that are not usable at the time of dispersal are stored as starch.

    Here completes the ongoing cycle of nutrient acquisition, transport, and storage for Achillea millefolium.               Other species within the Multiple Organisms Web Page such as the Sugar Maple and Tamarack also use photosynthesis as a means of nutrition acquisition. Discover more about these organisms as well!

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To explore the reproductive cylce of Yarrow, continue to Reproduction.