Experimental evidence for negative turgor pressure in small leaf cells of Robinia pseudoacacia L versus large cells of Metasequoia glyptostroboides Hu et W.C. Cheng. 2. Höfler diagrams below the volume of zero turgor and the theoretical implication for pressure‐volume curves of living cells. (23rd January 2017)

• Record Type: Journal Article
• Authors: Yang, Dongmei; Li, Junhui; Ding, Yiting; Tyree, Melvin T.
• Is Part Of: Plant, cell and environment. Volume 40:Number 3(2017)
• Page Start: 340
• Page End: 350
• Publication Date: 2017-01-23
• Subjects: pressure volume curves -- osmotic pressure -- bulk modulus of elasticity -- thermocouple psychrometer -- micromechanical models -- apoplastic water -- negative turgor -- Höfler diagram -- leaf water relations; Plant physiology -- Periodicals; Plant cells and tissues -- Periodicals; Plant communities -- Periodicals; 581.105
• DOI: 10.1111/pce.12860
• Languages: English
• ISSNs: 0140-7791

Abstract

Abstract: The physiological advantages of negative turgor pressure, Pt, in leaf cells are water saving and homeostasis of reactants. This paper advances methods for detecting the occurrence of negative Pt in leaves. Biomechanical models of pressure‐volume (PV) curves predict that negative Pt does not change the linearity of PV curve plots of inverse balance pressure, PB, versus relative water loss, but it does predict changes in either the y ‐intercept or the x ‐intercept of the plots depending on where cell collapse occurs in the PB domain because of negative Pt . PV curve analysis of Robinia leaves revealed a shift in the x ‐intercept ( x ‐axis is relative water loss) of PV curves, caused by negative Pt of palisade cells. The low x ‐intercept of the PV curve was explained by the non‐collapse of palisade cells in Robinia in the PB domain. Non‐collapse means that Pt smoothly falls from positive to negative values with decreasing cell volume without a dramatic change in slope. The magnitude of negative turgor in non‐collapsing living cells was as low as −1.3 MPa and the relative volume of the non‐collapsing cell equaled 58% of the total leaf cell volume. This study adds to the growing evidence for negative Pt . Abstract : It is well known that water in xylem conduits is normally under negative pressure, but the concept of negative pressure in living cells (negative turgor) has rarely been addressed experimentally except for microscope studies of J. Oertli. This study verifies negative turgor in the small palisade cells of Robinia pseudoacacia L through pressure chamber analysis, models and quantitative anatomical studies. We demonstrate negative turgor of up to −0.7 MPa in the common range of balance pressure and water content of pressure‐volume curves: 0 to 3.3 MPa balance pressure and 0 to 0.35 in relative water content loss of leaves. We conclude that negative turgor needs to be invoked in explain the water balance of leaves with small cells (<10 µm diameter).