Drought, thermal response, and climate-patterning in cuticular conductance of the widespread C4 grass Themeda triandra.

In Themeda triandra, minimum cuticular conductance after stomatal closure (gmin) is thermally stable with no distinct phase transition temperature (30–55°C) across six Australian accessions.

• Why it matters: Grasslands face rising temperatures and water scarcity, yet it is unclear how drought and heat shape within-species variation in leaf water-loss traits.
• What they did: Six Australian accessions spanning a climatic gradient were grown well-watered, then exposed to short-term drought; gmin was measured in control and droughted plants, and gmin responses were tested across 30–55°C using fresh, fully hydrated leaves.
• The result: Under well-watered conditions, gmin was unrelated to climate-at-origin, but under drought gmin was lower in accessions from cooler and wetter regions, with drought effects varying strongly among accessions.