Chapter Six: Plant Nutrition

Tissues and Cells Inside Plant

The position and location of xylem / phloem in sections of roots, stems, and leaves.

• Remember XYLEM is always on the inside and on top.

Phloem

Part of vascular bundles. Basically the tube that transports Sucrose and Amino Acid to rest of plant from leaves to the entire plant.

Xylem

Part of vascular bundles; also the tube that transports water and mineral ions such as magnesium or nitrate from roots to leaves.

Adaptation of Xylem: (a) Thick walls with lignin; waterproof cell wall. (b) No cell contents, allow free passage of water. As cells are essentially dead. (c) Cells joined end to end with no cross walls to form a long continuous tube; provide support.

Root Hair Cells

Single-celled extensions of epidermis cells in the root. Grow between soil particles and absorb water & minerals from the soil. Water enters the root hair cells by osmosis, because soil water has a higher water potential than the cytoplasm of the RHC.

Root Hair increases the surface area of the cells significantly. As it increases the rate of absoption of water by osmosis and mineral ions by active transport.

Chapter Three: The Movement Into and Out of Cells

Experiments

Pathway Taken by Water

Root Hair Cells → Root Cortex Cells → Xylem → Leaf Mesophyll Cells

The pathway can be investigated by placing a plant like celery into a beaker of water that has eosin stain added to it. After few hours, you can see leaves of the celery turning the same colour as the dyed water, proving that water is being taken up by the celery. If a cross-section of the celery is cut, only certain areas of the stalk is stained the colour of the water, showing that the water is being carried in specific vessels through the stem. These are xylem vessels.

• Describe the process of Water from Root Hair Cells to Xylem.

Investigating Factors of Transpiration

A shoot is cut underwater, placed in a tube, and dried. A capillary tube is removed, allowing a single air bubble to form. The plant adapts to the new environment, recording its starting and ending locations. The wind speed or temperature is adjusted, and the bubble is reset. The faster the bubble travels, faster transpiration occurs.

https://youtu.be/FWxh28CTEcM

• Temperature: Temperature of room (cold room and warm room)
  • As temperature increases, the rate of transpiration also increases.
  • Particles have more kinetic energy so transpiration occurs as a faster rate as water molecules evaporate from mesophyll and diffuse away faster at lower temperature.
• Wind speed: Use an electric fan to mimic different wind speeds
  • As wind speed increases, the rate of transpiration also increases.
  • Good airflow removes water vapour from the air surrounding the leaf which sets up a concentration gradient between the leaf and the air, increasing water loss.
• Humidity: Create a more humid environment using a sealed container or covering.
  • As humidity increases, the rate of transpiration also decreases.
  • Humidity is a measure of moisture (water vapour) in the air; when the air is saturated with water vapour, the concentration gradient is weaker, so less water is lost.