Plant water status. Leaf water potential was
measured with a pressure chamber using the technique
described by Barrs and Weatherley (1962) and Turner
(1982). Water potential was measured in four different
positions of the same plant; the leaf tip (5–8 cm), leaf base
(1 cm from leaf junction), leaf sheath (middle position
between base of leaf sheath at stem and leaf junction) and
stem base (first visible internode from the base of the
plant). A small plastic bag was placed over the tip of the
fully expanded youngest leaf and the leaf was cut about
5–8 cm below the tip. The leaf base was covered with a
small plastic bag immediately after removing the leaf tip
from the base, and leaf base water potential determined.
Leaf sheath water potential was measured following the
same procedure. Leaf tip, leaf base and leaf sheathWP was
measured on the same leaf. Stem water potential (SWP)
was measured on the same tiller of the plant. After
measurement of the leaf sheath WP, the stem base was put
through the pressure chamber using a circular orifice. The
piece of stem was put immediately in the plastic bag and
water potential was measured in the same manner as for
leaf water potential. Midday WP (12:00–14:00 h) was
measured five times during the stress cycle