The movement of water and solutes in plants

Explain the quantitative importance of evapotranspiration in plants

• Evapotranspiration is a significant process for plants as it accounts for a large portion of the water cycle, contributing to the movement of water from the soil to the atmosphere.

• It plays a crucial role in regulating the temperature of plants and the surrounding environment through the cooling effect of water vapor release.

• Quantitatively, evapotranspiration is a major factor in determining the water requirements of crops and natural vegetation, influencing agricultural practices and ecosystem dynamics.

• The process of evapotranspiration also affects regional and global climate patterns, making it an important component of Earth's hydrological cycle.

List and explain three functions of evapotranspiration in plants.

• Gas exchange

  • Evapotranspiration facilitates the exchange of CO2 and O2 for photosynthesis and respiration in plants

• Cooling

  • Evapotranspiration plays a crucial role in regulating the temperature of plants and the surrounding environment through the cooling effect of water vapor release

• Transport of photosynthates and nutrients

  • Evapotranspiration is essential for the transport of photosynthates and nutrients from leaves to other organs through the phloem

Explain the quantitative importance of evapotranspiration in plants

• Evapotranspiration is a significant process for plants as it accounts for a large portion of the water cycle, contributing to the movement of water from the soil to the atmosphere.

• It plays a crucial role in regulating the temperature of plants and the surrounding environment through the cooling effect of water vapor release.

• Quantitatively, evapotranspiration is a major factor in determining the water requirements of crops and natural vegetation, influencing agricultural practices and ecosystem dynamics.

• The process of evapotranspiration also affects regional and global climate patterns, making it an important component of Earth's hydrological cycle.

List and explain three functions of evapotranspiration in plants.

• Gas exchange

  • Evapotranspiration facilitates the exchange of CO2 and O2 for photosynthesis and respiration in plants

• Cooling

  • Evapotranspiration plays a crucial role in regulating the temperature of plants and the surrounding environment through the cooling effect of water vapor release

• Transport of photosynthates and nutrients

  • Evapotranspiration is essential for the transport of photosynthates and nutrients from leaves to other organs through the phloem

List and explain two mechanisms by which plants uptake water, and identify the one that is predominant

Cohesion-tension theory

• This mechanism involves the evapotranspiration of water from the leaves, creating a negative pressure that pulls water up through the xylem.

• The tension created by evapotranspiration is the predominant mechanism for water uptake in plants

Osmotic root pressure

• In the absence of transpiration, roots can generate positive osmotic pressure, facilitating water absorption.

• However, this mechanism typically represents less than 1% of the cohesion-tension mechanism and is not the predominant method of water uptake in plants

Make a drawing illustrating the anatomical features of a leaf that contribute at minimizing/controlling evapotranspiration

Anatomical adaptations

• Waterproof cuticle coating the

  epiderm

• No intercellular space among epidermal cells

• Disposal of stomata at the lower face

• The substomatal space (air saturated with water vapor) prevents direct flowing of water through the stomatal aperture (only vapor can escape)

Physiological adaptations

• Regulatory control of stomata opening and closing

Identify and explain two physiological adaptations to control evapotranspiration in plants

Regulatory control of stomata

• Plants have developed physiological adaptations to regulate the opening and closing of stomata, such as the arrangement of cellulose microfibrils in guard cells and the presence of aquaporins

  • which control the movement of water and ions to adjust the turgor pressure and volume of guard cells, ultimately influencing stomatal aperture

Anatomical adaptations

• Plants exhibit anatomical adaptations to minimize evapotranspiration, including the presence of a waterproof cuticle coating the epidermis, the absence of intercellular space among epidermal cells, and the disposal of stomata at the lower face of leaves. These adaptations help reduce water loss through transpiration