Transport in Plants

Like all living organisms, plants require a system to transport minerals, food and water throughout their structures. Transportation in plants is carried out by two different tubes:

  • Xylem
  • Phloem

Xylem vessels transport water and mineral ions from the roots to the leaves. Phloem vessels transport food substances, such as sucrose and amino acids, from the leaves to other parts of the plant.

  • Therefore, the veins in a leaf consist of xylem tubes, which transport water to the leaf, and phloem tubes, which transport sugars away from it.

The diagram below shows the process of water and mineral ions taken up by plants.

A detailed diagram of a plant, showcasing the xylem and phloem transport systems. On the left, the xylem, coloured in orange, is labelled to have a one-way flow for transporting water and minerals, no end walls between cells, and is stiffened with lignin. The plant's green stem contains the xylem and phloem structures. On the right, the phloem, shown in blue, facilitates a two-way flow and carries both water and food. It has distinct end walls with perforations. The base of the plant has brown roots embedded in soil. Arrows point upwards indicating the uptake of "Water and minerals" from the soil, and there's also a label indicating "Photosynthesis products" moving within the plant. Above the stem, bright yellow flowers bloom.

  • The process that transports substances in the xylem is called transpiration
  • The process that transports substances in the phloem is called translocation

Root Hair Cells

Root hair cells have a small, thin extension. It pokes out into the soil to absorb water by osmosis. The purpose of these root hair cells is to increase the surface area of the root that is in contact with the soil. This allows the plant to absorb more water and minerals.

They also contain a lot of mitochondria, which release energy from glucose during respiration. This provides the energy needed for the active transport of mineral ions.

  • As root cells are located underground in the dark, they dont have chloroplasts.

The diagram below shows the absorption of water and minerals from the soil by root hair cells.

A zoomed-in view of a plant's root hair cell interacting with its surrounding environment. On the left, the green root hair cell is shown in detail with labels identifying the cytoplasm, cell wall, nucleus, vacuole, and the protruding root hair. Arrows depict the movement of water and minerals from the surrounding brown soil particles into the root hair cell. On the right, there's a depiction of a plant with vibrant green leaves planted in brown soil. Below the plant, a label reads "PLANT" and an arrow points downwards to a brown circle representing the root system, labelled "ROOTS". From the roots, another arrow completes a cycle back to the plant, emphasising the continuous movement and absorption of nutrients.

Water passes into the root hair cells by osmosis due to the higher water potential of the soil compared to the cytoplasm of the root hair cell. Once the water is absorbed by the plant through the root, it is transported by the xylem to the leaves, entering the mesophyll cells.

The water absorbed from the soil by the plant is used for:

  • Photosynthesis
  • Supporting leaves by keeping the cells rigid
  • Cooling the leaves by evaporation
  • Transporting dissolved minerals around the plant

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