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. 1. Evidence from pressure‐volume curve analysis of dead tissue.

Abstract

This paper provides a mini-review of evidence for negative turgor pressure in leaf cells starting with experimental evidence in the late 1950s and ending with biomechanical models published in 2014. In the present study, biomechanical models were used to predict how negative turgor pressure might be manifested in dead tissue, and experiments were conducted to test the predictions. The main findings were as follows: (i) Tissues killed by heating to 60 or 80 °C or by freezing in liquid nitrogen all became equally leaky to cell sap solutes and all seemed to pass freely through the cell walls. (ii) Once cell sap solutes could freely pass the cell walls, the shape of pressure-volume curves was dramatically altered between living and dead cells. (iii) Pressure-volume curves of dead tissue seem to measure negative turgor defined as negative when inside minus outside pressure is negative. (iv) Robinia pseudoacacia leaves with small palisade cells had more negative turgor than Metasequoia glyptostroboides with large cells. (v) The absolute difference in negative turgor between R. pseudoacacia and M. glyptostroboides approached as much as 1.0 MPa in some cases. The differences in the manifestation of negative turgor in living versus dead tissue are discussed.

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

“…The first paper in this series (Yang et al . , companion paper) and Yang et al . explained how pressure volume curve analysis has been used in the past to estimate the water relations components to quantify Höfler diagrams.…”

“…Sample sizes, transportation methods and rehydration methods were identical to Yang et al . (, companion paper)…”

“…Yang et al . (, companion paper) also provided evidence for negative turgor pressure through an examination of PV curves of dead tissue. The primary conclusion was that species with small leaf cells have more negative P t than species with large leaf cells.…”

“…() and Yang et al . (, companion paper), (2) Independently measure π using thermocouple psychrometers, (3) independently estimate apoplastic water content by quantitative anatomical analysis, and (4) use the decision Table to make conclusions about negative P t .…”

“…The y ‐intercept was discussed in Yang et al . (, companion paper). The second and most important objective was to calculate a modern version of the Höfler diagram based on the negative turgor confirmed in the x ‐intercepts and y ‐intercepts of PV curves of Robinia augmented by a few simple assumptions.…”