The Life of PlantsBy Aditya Singh 8B

Background Information

We all know that for a plant to grow it needs: sunlight, water, carbon dioxide and nutrients. But the process that helps convert these raw materials into sugars (such as glucose) and chloroplast that the plant needs to live is complex. This presentation intends to investigate the transfer of water molecules from the soil to the highest leaves of a plant. There are 3 major stages: transfer from soil to roots; transfer from roots to leaves through the stem; and of course transfer of water from the stems to the leaves.

From Soil to Roots

Each root contains 3 major parts that contribute to the intake of water. These are:

1. Root hairs: these help absorb the water through osmosis. This is when water moves from where it is in high concentration to where it is in low concentration i.e., osmosis occurs across a concentration gradient. Water concentration inside the root is always lower than outside as this water is immediately transferred through the stem.

2. Phloem: helps create new cells at the root this for better absorption. The phloem is responsible for the absorption of nutrients that later on help develop roots.

3. Xylem: this part of the root extends into the stem. It helps carry the water up the stem. This is done due to the difference in pressure between the top of the stem and the bottom. Since the pressure at the bottom is higher, the water is pushed upwards.

From Roots to Stem

As explained earlier, the water is transferred up the stem due to the difference in pressure (this difference is caused due to transpiration, explained later on in this presentation.). There are 3 major parts to the stem:

1. Cambium: These are responsible for the production of new vessels of xylem and phloem (which help transfer the water).

1. Epidermis: this is the outer layer of the stem. It is made up of only a single layer of cells and it responsible for protecting the stem. Also, it cuts down the loss of water.

2. Vascular bundle this is the long ‘pipe’ that water flows through. It is made up of several vessels of xylem and phloem.

From Stem to Leaves

After the water is pulled up from the roots, through the stem, it has to reach the leaves as it is needed for the plant to survive and produce its food.

Transpiration is the method by which water evaporates from the leaves to the air (water evaporates from the spongy cells, into the air spaces, and out of the leaves). This process is responsible for the difference in pressure caused in the stem (which enables water to move up). This continuous flow of water is referred to as the cohesion and adhesion method: as water molecules leave the leaf, other water molecules take their place. sTo avoid excess loss of water, leaves often have a wax cuticle on their outer layer. This slows down the rate of evaporation of water.

It is important that water continues to leave the plant through evaporation as without this, there would be no pressure difference created for water to move up the stem or even into the roots (the concentration of water will be higher inside the roots as water will be trapped there). This will not allow the plant to produce food and eventually, the plant will die. Also, the roots will die as they will be water logged.

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