Physiologia Plantarum 133: 354–362. 2008 Copyright ª Physiologia Plantarum 2008, ISSN 0031-9317 Light-induced transpiration alters cell water relations in figleaf gourd (Cucurbita ficifolia) seedlings exposed to low root temperatures Seong Hee Leea, Janusz J. Zwiazeka and Gap Chae Chungb,* aDepartment of Renewable Resources, 4-42 Earth Sciences Building, University of Alberta, Alberta, Canada T6G 2E3 bDivision of Plant Biotechnology, Agricultural Plant Stress Research Center, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 500-757, Korea Correspondence Water relation parameters including elastic modulus (e), half-times of water *Corresponding author, w exchange (T 1/2), hydraulic conductivity and turgor pressure (P) were e-mail:
[email protected] measured in individual root cortical and cotyledon midrib cells in intact figleaf gourd (Cucurbita ficifolia) seedlings, using a cell pressure probe. Received 4 December 2007; revised 7 January 2008 Transpiration rates (E) of cotyledons were also measured using a steady-state porometer. The seedlings were exposed to low ambient (approximately 22 21 doi: 10.1111/j.1399-3054.2008.01082.x 10 mmol m s ) or high supplemental irradiance (approximately 300 mmol m22 s21 PPF density) at low (8°C) or warm (22°C) root temperatures. When exposed to low irradiance, all the water relation parameters of cortical cells remained similar at both root temperatures. The exposure of cotyledons to supplemental light at warm root temperatures, however, resulted in a two- to w three-fold increase in T 1/2 values accompanied with the reduced hydraulic conductivity in both root cortical (Lp) and cotyledon midrib cells (Lpc). Low root temperature (LRT) further reduced Lpc and E, whether it was measured under low or high irradiance levels.