EFFECT OF SALICYLIC ACID ON THE DRY MATTER AND NITROGEN ACCUMULATION, PARTITIONING AND TRANSLOCATION IN TWO CONTRASTING RICE GENOTYPES UNDER SALT STRESS

Salt stress is one of the important abiotic stresses that affect agricultural production. Salicylic acid (SA) plays an important role in plant growth and development as well as against stress. The purpose of this work was to analyze the short-term and long-term effect of SA on the dry matter (DM) and nitrogen (N) accumulation, partitioning, and translocation in two contrasting rice genotypes (salt-tolerant LD5, salt-susceptible MDJ30) under salt stress. Forty two-day-old rice plants were exposed to salinity stress (0, 4.6 dS m(-1)) for two weeks and then the salt group was sprayed with 60 ml SA (0, 0.5 mmol L-1) per pot for two days. The short-term and long-term effects of SA were analyzed by sampling at 6 and 12 days after the SA treatment, and at heading and maturity stage, respectively. The results showed that salt stress significantly reduced the DM and N accumulation of each above-ground organ, changed allocation pattern and reduced their translocation to panicles. Genotypes showed differences in DM and N distribution and translocation under salt stress. Compared with MDJ30, LD5 accumulated more DM under salt stress, had a higher proportion of stem-sheath DM and maintained the DM translocation to panicle. The response of N accumulation to salt stress in LD5 was higher than that in MDJ30 at tillering stage but was less than that at heading and maturity stage, reflecting that salt tolerant variety gradually adapted to the restriction of N acquisition due to salinization. Exogenous SA promoted the accumulation of DM and N in stem + sheath at short-term and in above-ground organs of rice under salt stress at long-term. SA increased the partitioning ratio of DM and N in panicles of MDJ30 under salt stress but decreased that in LD5. This was mainly due to the fact that SA increased the translocation of assimilates from vegetative organs to panicles of MDJ30, but decreased that of LD5 as its short-term promotion effect resulted in an excessive accumulation in stem + sheath. These results suggested that SA promoted assimilates accumulation in the above-ground organs of rice under salt stress, changed the distribution pattern of nutrients, and its effect on the translocation of assimilates was related to the salt tolerance of genotypes.