Stomatal Response to Water Stress and its Relationship to Bulk Leaf Water Status and Osmotic Adjustment in Pearl Millet (Pennisetum americanum[L.] Leeke) uri icon

abstract

  • The water potential (?) at which stomata completed closure (?8Lmin) was determined for pearl millet (Pennisetum americanum (L.) Leeke) at two growth stages by monitoring changes in leaf conductance (gL) and ? following shoot detachment. Leaf water status was evaluated concurrently using a pressure-volume (P-V) technique.In a pot experiment with young vegetative plants, ?8Lmin closely approximated to the estimated ? at zero turgor (?u) both for control and for drought-conditioned plants which had osmotically adjusted. However, for penultimate leaves of field-grown flowering plants, ?8Lmin was found to be 0.61 (irrigated plants) and 0.87 (droughted plants) MPa below ?u. In drought-stressed field-grown plants, osmotic adjustment (characterized by a decrease in solute (osmotic) potential (?s ) at both full hydration and zero turgor) was insufficient to maintain a positive bulk leaf turgor potential (?p) once ? had declined to below about -1.5 MPa. It is suggested that localized adjustment by the stomatal complex in response to environmental differences, leaf ageing and/or ontogenetic change, is responsible for the uncoupling of stomatal from bulk leaf water status

publication date

  • 1983