Temperature and water relation patterns in subalpine understory plants.

Area of Science:

• Plant Ecology
• Physiological Ecology
• Subalpine Flora

Background:

• Subalpine understory species face fluctuating environmental conditions.
• Understanding plant adaptations to sun and shade is crucial for ecosystem dynamics.

Purpose of the Study:

• To compare daily temperature and water relations of 7 perennial subalpine understory species.
• To investigate the effects of natural sun and shade exposure on these species.
• To evaluate potential adaptive patterns in response to water and photosynthetic stress.

Main Methods:

• Field measurements of rainfall, leaf, air, and soil temperatures.
• Assessed stomatal conductance to water vapor diffusion and plant/soil water potentials.
• Included leaf and root morphological measurements.

Main Results:

• Sunlit herbaceous plants experienced severe wilting (xylem water potential < -2.0 MPa) with increased leaf temperatures and conductance.
• Shrubby species showed higher leaf temperatures (>30°C) and consistently lower xylem water potentials without wilting.
• Stomatal conductance was greater on abaxial leaf surfaces, with closure occurring when either side faced direct sun.

Conclusions:

• Midday wilting in herbaceous species may be an adaptive strategy.
• Leaf hypostomy and bicoloration, along with specific stomatal behaviors, appear significant for water and photosynthetic relations.
• Shrubby species demonstrate distinct adaptations to high temperatures and water stress in subalpine environments.