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H. WALTER AND E. STADELMANN
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Fig. 16. Suction tension (5), osmotic value (W), and turgor pressure (P) in
Triticum sp. and Hordeum vulgäre plants cultivated in pots during drought and
watering ( □ ) periods. R is the refractometric value of the expressed sap indicated
as percent sugar content; S is the suction potential (— water potential φ); W is the
potential osmotic pressure (—osmotic potential φ 8 ). The values of R parallel
approximately the osmotic values (after Kreeb, 1964, p. 79).
Simultaneous determinations of water potential and osmotic potential
in the same experiment have been made occasionally (e.g., Boyer, 1965,
p. 231; Weatherley, 1965, p. 165). Kreeb (1964, p. 79) measured both
osmotic quantities for Triticum sp. and Hordeum vulgäre plants cultivated
in pots subjected to periods of drought and watering (Fig. 16). The
change in water balance affects strongly the suction tension S (—water
potential ψ). The potential osmotic pressure ?r* (—osmotic potential ψ 8 )