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Pressure‐volume analyses on shoots of Picea abies and leaves of Coffea liberica at various temperatures
Author(s) -
Gross K.,
PliantNguyen T.
Publication year - 1987
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1987.tb06130.x
Subject(s) - coffea , botany , turgor pressure , picea abies , horticulture , shoot , chemistry , biology
Shoots from two ecologically different evergreen tree species, Picea abies (L.) Karst and Coffea liberica Hiern, were used to carry out pressure volume (PV) measurements at 5–35°C. For this purpose a pressure chamber was equipped with thermoelectric temperature regulation. The non‐linear sections of the resultant PV curves were sigmoidal for both species, with recognizable points of inflexion. These points, at around ψ= 1.12 MPa and relative water content (RWC) = 88.5% for Picea and at ψ= 0.92 MPa and RWC = 95.5% for Coffea , were characterised by a temporary increase in the resistance to water flow of the entire shoot (R 5 ). The maximum value of the bulk modulus of elasticity (ɛ max) was also in the region of the point of inflexion. This value was considerably higher in Coffea than in Picea . The osmotic pressures at full water saturation (π 0 ) and at turgor loss point (π p ) showed a clear temperature dependence between 15 and 35°C differing only slightly from the theoretically expected situation. At 25°C these values were 1.72 and 2.48 MPa. respectively, for Picea and 1.58 and 1.87 MPa. respectively, for Coffea . The turgor loss point occurred at 76–77% RWC in Picea and at 86% RWC in Coffea , the proportion of apoplastic water varied between 22 and 25% in Picea but was only 9–10% in Coffea . The ecological differences between the two species are reflected in their temperature dependence for R 5 , which was much steeper for Coffea than for Picea . The energy of activation for the water conductance of the whole shoots was 13.0–14.4 kJ mol −1 in Picea and about 23 kJ mol −1 in Coffea .