Variations in salt tolerance of reed canarygrass (Phalaris arundinacea L.) plants grown at sites with different degrees of cattle urine contamination

Variations in the silt tolerance of reed canarygrass (RCG) plants grown at sites with different degrees of cattle urine contamination were investigated. Cattle urine overflowed the urine reservoir and invaded the grassland. Soils and RCG plants were collected from sampling spots selected along the urine flowing line from 0 (contaminated site beside the urine reservoir) to 100 m. With increasing distance from the reservoir, the contents of K, Na, Ca, Mg and NO3-N in the soil and Na, K and NO3-N in the collected RCG plants decreased. The RCG plants were grown in a standard solution to obtain a large number of clones and seeds for the next generation. After the RCG clones and their next generation were subjected to water culture to the fifth leaf stage, NaCl was applied to the solution to investigate their salt tolerance. The salt tolerance, which was the highest in the RCG clones and their next generation for the plants collected from the site beside the reservoir, decreased with increasing distance from the reservoir. Under saline water culture conditions, Na and free-proline contents in shoots, K content in shoots and roots, water potential of leaves and plasmalernina ATPase activity of roots increased in the RCG clones and their next generation along with a higher salt tolerance. In conclusion, responses to saline conditions were similar between the RCG clones and the next generation that were cross-pollinated. It was considered that, even within a confined range of the grassland, salt-tolerant RCG plants that had adapted to the urine-contarninated soils were selected, and that high salt: tolerance was genetically controlled. It appears likely that the maintenance of the water potential and K-absorbing function under NaCl stress contributed to the high salt tolerance.