Pressure-volume curves: revisiting the impact of negative turgor during cell collapse by literature review and simulations of cell micromechanics.
The Scholander-Hammel pressure chamber has been used in thousands of papers to measure osmotic pressure, πc , turgor pressure, Pt , and bulk modulus of elasticity, ε, of leaf cells by pressure-volume (PV) curve analysis. PV analysis has been questioned in the past. In this paper we use micromechanical analysis of leaf cells to examine the impact on PV curve analysis of negative turgor in living cells (Pt ). Models predict negative Pt (-0.1 to -1.8 MPa) depending on leaf cell size and shape in agreement with experimental values reported by J. J. Oertli. Modeled PV curves have linear regions even when Pt is quite negative, contrary to the arguments of M.T. Tyree. Negative Pt is totally missed by PV curve analysis and results in large errors in derived πc and Pt but smaller errors in ε. A survey of leaf cell sizes vs habitat (arid, temperate, and rainforest), suggests that the majority of published PV curves result in errors of 0.1-1.8 MPa in derived πc and Pt , whereby the error increases with decreasing cell size. We propose that small cell size in leaves is an ecological adaptation that permits plants to endure negative values of water potential with relatively little water loss.
Department of Engineering Mechanics, Tsinghua University, Beijing, 100084, China.|Center for Nano and Micro Mechanics, Tsinghua University, Beijing, 100084, China.
Yiting
Y
Ding
Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, T6G 2G8, Canada.
Yanxiang
Y
Zhang
Department of Engineering Mechanics, Tsinghua University, Beijing, 100084, China.|Center for Nano and Micro Mechanics, Tsinghua University, Beijing, 100084, China.
Quan-Shui
QS
Zheng
Center for Nano and Micro Mechanics, Tsinghua University, Beijing, 100084, China.|College of Forestry, Northwest A&F University, Yangling, 712100, China.
Melvin T
MT
Tyree
D000490:Allium / Q000166:cytology; D048429:Cell Size; D003198:Computer Simulation; D020342:Finite Element Analysis; D059828:Plant Cells / Q000502:physiology*; D018515:Plant Leaves / Q000166:cytology / Q000502:physiology*; D011312:Pressure; D031301:Robinia / Q000166:cytology
Finite element method (FEM); cell size; collapse; negative turgor; osmotic pressure; pressure chamber; pressure-volume curves