Rp. Beckett, PRESSURE-VOLUME ANALYSIS OF A RANGE OF POIKILOHYDRIC PLANTS IMPLIES THE EXISTENCE OF NEGATIVE TURGOR IN VEGETATIVE CELLS, Annals of botany, 79(2), 1997, pp. 145-152
Pressure-volume (PV) isotherms were determined for a range of poikiloh
ydric plants. The plants included a lichen, a filmy fern, three bryoph
ytes and two angiosperms. Graphs of turgor potential (psi(p)) as a fun
ction of relative water content (RWC) derived from the PV curves sugge
sted that most of the cryptogams, but not the angiosperms, contained s
ignificant amounts of intercellular water when fully hydrated. In seve
ral species part of the PV curve fell below the extrapolated linear po
rtion of graph, implying that over this range of RWCs the plant's cell
s have negative turgor; values as low as -0.3 MPa were recorded. Negat
ive turgor occurred in those species with a high bulk modulus of elast
icity, implying that it develops only in plants that have cells with r
igid walls. Plants that can display negative turgor will undergo cytor
rhysis at lower RWCs than plants in which negative turgor does not occ
ur. The significance of these findings for the water relations of poik
ilohydric plants is discussed. (C) 1997 Annals of Botany Company.