- 1 Drought-deciduous leaves are common in habitats with predictable, seasonal drought, and a reduction in transpirational surface area is generally considered an important drought-response strategy. Yet leaf demographic responses to unpredictable drought events that can occur at any time during the growing season have been little studied in ecological systems.
- 2 We created drought in a natural population of the herbaceous desert perennial Cryptantha flava (A. Nels.) Payson (Boraginaceae) in north-eastern Utah, USA, by installing rainout shelters just before and during the early part of the growing season, from 1 March until mid-June in 1998, and from 1 March until mid-May in 1999.
- 3Droughted plants exhibited water stress through lower rates of midday photosynthesis and conductance, and by producing leaves with a smaller surface area and greater specific mass than plants exposed to ambient precipitation.
- 4 Under drought, leaf life span increased on flowering stalks and vegetative rosettes and new leaf production decreased, reducing leaf turnover and increasing standing leaf crop in droughted plants.
- 5 A larger number of leaves under drought conditions compensated in area for their smaller size, which means that transpirational surface area was not reduced.
- 6 The reduction in photosynthetic rate and the increase in leaf life span are consistent with a more general pattern in response to other low resource conditions, paralleling leaf-level responses to shortages of nutrients and light.
- 7 Plants in the drought and ambient precipitation treatments responded to late-season rainfall with increased leaf production, providing an additional example of developmental plasticity in response to temporal heterogeneity in water availability.