Ce. Wilson et al., Differentiation between osmotic injury and chloride toxicity of rice seedlings grown under saline conditions, COMM SOIL S, 30(15-16), 1999, pp. 2101-2112
Rice (Oryza sativa, L.) is most sensitive to salinity injury as a seedling.
Information describing-the effects of salinity on the seedling rice plant
is limited. Therefore, the current study was conducted to determine if sali
nity injury to rice seedlings is the result of toxic levels of chloride, or
if a change in osmotic potential interferes with the plant's ability to ab
sorb water and nutrients. Rice was grown in controlled environmental condit
ions through the seedling growth stage. In hydroponic culture with a 50% Ho
agland's solution, the rice was exposed to osmotic tensions of 0, 50, 100,
200, 400, 800, or 1,600 kPa imposed by either CaCl2 or polyethylene glycol
(PEG). The rice was grown for 1 wk following imposition of the osmotic trea
tments. Visual ratings were then obtained and plants were harvested for dry
matter determination and Cl- concentration. Shoot weights were lowered for
PEG treatments compared to CaCl2. Root weights differed little between CaC
l2 and PEG treatments. Root weights decreased with increasing osmotic tensi
on whether decreased by CaCl2 or PEG. Salinity related damage to leaves and
roots was worse for PEG than for CaCl2 treatments. Not surprisingly, uptak
e of Cl- tended to increase with increasing rates of CaCl2, but not with PE
G. These data suggest that rice sensitivity to salinity is the result of ch
anges in the osmotic potential gradient rather than to chloride toxicity.