Nutrition

If you have already checked out the Classification page you would know that Chenopodium a. is a member of the angiosperms, meaning it is a flowering plant. With the exception of a very limited number of plants nearly all of plants receive the energy they use for growth and all other processes necessary for the sustenance of life from the conversion of light energy to usable energy in the form of sugars. This process is more commonly known as photosynthesis. Photosynthesis is detailed in the diagram to the right, but just as an overview I will briefly go over some of the main points of the photosynthetic pathway. Photosynthesis is a process that occurs within the chloroplasts which are mostly located in the leaf region of the plant. The chloroplasts contain chlorophyll, the green pigment of the plant responsible for both the coloration of the leaves and absorption of light. Within the chlorophyll, water, gas, and light energy go through a reaction process that ends up producing sugar (glucose) and oxygen gas. The overall reaction is shown below. This is known as the light dependent step in the photosynthetic pathway, because without light this initial part of the reaction would not be able to occur. The glucose that is produced through this complex pathway is the primary nutrient source of the plant.

Overall reaction of photosynthesis; 6CO2 + 6H2O + (light energy)----> Glucose + 6O2.

The above is just an explanation of how the majority of plants get their energy, and better yet it is an overview of the basics of photosynthesis; however, many plants have unique adaptations that help them grow better or withstand many diverse environments. Members of the Caryophyllales utilize a unique photosynthetic pathway that is slightly different than what the C3 or CAM plants undergo. Chenopodium ambrosioides is actually considered a C4 plant which refers to the fact that carbon dioxide is first incorporated into a four carbon chain. See Adaptation for more detail.

Photosynthesis is the process by which plants go about acquiring energy for themselves, but how do plants take in water?  Water is critical to life for plants, without which there would be no processes of photosynthesis. Is water 'sucked' in by the roots and actively transported to the tops of the trees where the water is most crucial? Does water magically reach the tops of plants with no understanding of this process by humans? Of course not, but the process is much more elaborate than one might expect, in fact water transport by plants completely blows my mind. The mechanism of water transport is somewhat complex so I will not describe this process in gory detail, but a basic understanding of this natural 'mystery' will be quite enough for now.

There are two major transport tissues in plants. The first, phloem (indicated by number 4 in the photo below), carries the nutrients produced in the leaves via photosynthesis down to the rest of the plant and the second transport tissue, xylem (indicated by number 1 in the photo below), is responsible for the transport of water from the roots to the rest of the plant. These processes are driven by pressure differences. In nutrient transport of sugars they move from areas of high concentration (where they are being produced) to areas of low concentration (areas that are consuming sugars for metabolism). Movement goes from the top of the plant to the root system and nutrients are 'dropped' off along the way. Getting water from the roots to the leaves and stems is not a simple process, but in its most condensed form this process relies on concentration differences, similar to the transport of water. When a plant is undergoing photosynthesis there are special cells in these areas known as stomata that are open to the external environment. The stomata allow the plant to take in the carbon dioxide they need to go through the photosynthetic pathway and produce usable energy for themselves. Because these stomata are open, some evaporation will take place in the cells adjacent to the stomata therefore increasing the solute concentration in these cells and decreasing their water potential. This sets up a pressure difference between the cells. The cells closest to the stomata now have a high solute concentration and the cells closest to the roots have a low solute concentration. Water passively flows from the soil into the plants and up the xylem to the points of highest solute concentration. There are many intermediate steps to this process that I have left out, but in its simplest form this is how nutrients and water are transported in cells. If you can keep in mind the pressure differences it is easy to track the net flow of the nutrients and water.   

 Next: Adaptation
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