Fc. Meinzer et al., CARBON-ISOTOPE DISCRIMINATION, GAS-EXCHANGE, AND GROWTH OF SUGARCANE CULTIVARS UNDER SALINITY, Plant physiology, 104(2), 1994, pp. 521-526
Physiological features associated with differential resistance to sali
nity were evaluated in two sugarcane (Saccharum spp. hybrid) cultivars
over an 8-week period during which greenhouse-grown plants were drip-
irrigated with water or with NaCl solutions of 2, 4, 8, or 12 decisiem
ens (dS) m(-1) electrical conductivity (EC). The CO2 assimilation rate
(A), stomatal conductance (g), and shoot growth rate (SGR) began to d
ecline as EC of the irrigation solution increased above 2 dS m(-1). A,
g, and SCR of a salinity-resistant cultivar (H69-8235) were consisten
tly higher than those of a salinity-susceptible cultivar (H65-7052) at
all levels of salinity and declined less sharply with increasing sali
nity. Carbon isotope discrimination (Delta) in tissue obtained from th
e uppermost fully expanded leaf increased with salinity and with time
elapsed from the beginning of the experiment, but Delta was consistent
ly lower in the resistant than in the susceptible cultivar at all leve
ls of salinity. Gas-exchange measurements suggested that variation in
Delta was attributable largely to variation in bundle sheath leakiness
to CO2 (Phi). Salinity-induced increases in Phi appeared to be caused
by a reduction in C-3 pathway activity relative to C-4 pathway activi
ty rather than by physical changes in the permeability of the bundle s
heath to CO2. A strong correlation between Delta and A, g, and SCR per
mitted these to be predicted from Delta regardless of the cultivar and
salinity level. Delta thus provided an integrated measure of several
components of physicological performance and response.