Summary of "¿QUÉ ES LA TRANSPIRACIÓN VEGETAL?"

Transpiration — main scientific concepts and phenomena

Definition

Transpiration: movement of water from inside the plant to the atmosphere through stomata (microscopic leaf pores). Higher (terrestrial) plants absorb water through roots and transport it via the vascular system to leaf tissues.

Water balance and usage

Plants use less than 10% of absorbed water for tissues and metabolic processes; they transpire more than 90% of the water they absorb. This means plants consume/transpire much more water than animals.
Functions of water in plants:
- Carries mineral salts (e.g., magnesium for chlorophyll).
- Supplies hydrogen for synthesis of carbohydrates (combines with CO2).
- Is partially stored as a reserve in tissues (mainly leaves).
Photolysis during photosynthesis splits water and releases oxygen to the atmosphere.

Biological functions and effects of transpiration

(As listed in the video)

Supplies mineral nutrients and hydrogen for biosynthesis.
Releases oxygen via stomata (from photolysis).
Acts as a water reserve in tissues (mainly leaves).
Maintains cell turgor and mechanical support; lack of water leads to plasmolysis and wilting.
Regulates leaf and local temperature (the source states transpiration can cool leaves by ~10°C relative to surrounding air).
Cools the atmosphere by releasing water vapor that absorbs heat.
Generates the suction (transpirational pull) enabling water uptake even when soil water is limited.
Contributes to cloud formation and larger-scale water/regional climate regulation.

Variation between species and climates

Arid-adapted plants:
- Tend to have fewer or smaller leaves (or none) and therefore low transpiration.
Humid-warm ecosystem plants (e.g., Amazon rainforest):
- Often have abundant large leaves, high stomatal densities (reported up to ~40,000 stomata per cm²), and high transpiration, strongly influencing the local water cycle.
Urban vegetation loss reduces transpiration and contributes to urban warming. Introducing green roofs, vertical gardens, and street vegetation can help restore evapotranspirative cooling and environmental balance.

Measurement methods and methodology

Potted plant / sealed substrate method

Stop irrigation and seal the soil/substrate surface to prevent soil evaporation.
Weigh the whole potted plant (pot + substrate + plant) at regular intervals until weight stabilizes.
Calculate transpired water as: initial weight − final constant weight (express in g or mL per time period).
Optional/Recommended:
- Estimate leaf area to express transpiration per unit leaf area.
- Record environmental conditions (air temperature and humidity) to relate transpiration to the environment.
Note: If the soil surface is not sealed, measured loss is evapotranspiration (soil evaporation + plant transpiration).

Leaf / branch sampling for field (tree) estimates

Excise a leaf or branch and weigh it in situ over time until weight stabilizes.
Seal the cut scar (e.g., with wax) to prevent transpiration from the wound so that water loss occurs only through intact stomata.
Calculate transpired water per sample as: initial weight − final constant weight.
Extrapolate to whole-tree values by counting total leaves/branches and multiplying; multiply per-tree values by the number of trees to estimate stand or crop transpiration.

Additional recommended measurements

Record rainfall, air temperature, relative humidity, and reservoir/supplemental water availability for irrigation planning and interpretation of transpiration data.

Related concepts

Evapotranspiration: the combined loss of water from soil evaporation and plant transpiration — an important measure for estimating crop water needs and planning irrigation.
Transpiration plays key roles in:
- Plant physiology (water/nutrient transport, turgor maintenance).
- Ecosystem water cycling and cloud formation.
- Local and regional climate moderation and urban heat mitigation.