Topic Summaries
Transpiration and translocation
Transport Systems
Blood and heart disease
Stem cells, microscopy, and microorganisms
Transport in cells
Human health and enzymes
Plant transport systems
Pathogens and non-specific immunity
The immune system and drugs
Plant disease and monoclonal antibodies
Photosynthesis and respiration
The nervous system and homeostasis
The brain and the eye
Hormone regulation and waste excretion
Reproductive hormones and plant hormones
Cell division, reproduction, and DNA structure
DNA synthesis and inheritance
Genetic engineering and modification
Evolution and natural selection
Species and classification
Resource cycles and environmental change
Biodiversity and environmental management
Biomass and trophic levels
Food supply and biotechnology
Science skills: Experimental procedures
Science skills: Presenting and using data
Science skills: Measuring results
Transport Systems
Blood and heart disease
Stem cells, microscopy, and microorganisms
Transport in cells
Human health and enzymes
Plant transport systems
Pathogens and non-specific immunity
The immune system and drugs
Plant disease and monoclonal antibodies
Photosynthesis and respiration
The nervous system and homeostasis
The brain and the eye
Hormone regulation and waste excretion
Reproductive hormones and plant hormones
Cell division, reproduction, and DNA structure
DNA synthesis and inheritance
Genetic engineering and modification
Evolution and natural selection
Species and classification
Resource cycles and environmental change
Biodiversity and environmental management
Biomass and trophic levels
Food supply and biotechnology
Science skills: Experimental procedures
Science skills: Presenting and using data
Science skills: Measuring results
- The movement of water through a plant occurs through transpiration, where water is pulled through the plant as it is continuously released from the leaves through stomata. Water enters the root hair cells by osmosis and travels through them to the xylem.
- Water travels up the xylem in the stem into the spongy mesophyll of the leaf by osmosis.
- Water evaporates out of spongy mesophyll cells, forming water vapour in the air spaces of the spongy mesophyll.
- Water vapour diffuses out of the leaf through stomata.
- Stomata control gas exchange and water loss by opening and closing, which is controlled by guard cells.
- When guard cells are turgid, the stomata are open, allowing water vapour to leave the leaf and carbon dioxide to enter for photosynthesis.
- When dehydrated, guard cells are flaccid and the stomata are closed, preventing further water loss.
- Transpiration rate equal to the decrease in mass or volume of water absorbed divided by time. This rate is affected by various factors:
| Factor | Effect on transpiration rate |
| Temperature | Transpiration rate increases as temperature increases because molecules have greater kinetic energy, speeding up the rate of evaporation and diffusion. |
| Humidity | Transpiration rate decreases as humidity increases as the atmosphere has a higher concentration of water vapour, decreasing the diffusion of water vapour out of the leaf. |
| Air movement | Transpiration rate increases as wind increases as it carries water vapour from the leaf. |
| Light intensity | Transpiration rate increases as light intensity increases as the stomata open wider to allow carbon dioxide in for photosynthesis, allowing water vapour to escape. |
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