Conversely, FH-901, FH-634, and FH-2000 were high
yielding under W1 regime; however, exhibited a sharp decline in yield under W2 regime. A positive correlation between
SCY and BY under water stress (r ¼ 0.44 in 2003; r ¼ 0.69 in 2004) indicates that BY is also a primary determinant of
SCY under water stress and genetic improvement of BY under water-limited environment may also improve SCY. Pn,
gs, and E were significantly reduced by water stress. Substantial genotypic variation for gas exchange attributes existed
among the cotton cultivars.