The Physiological Response Study Of Helianthus Tuberosus Seedings To Salicylic Acid And Nitrogen Under Salt Stress

In order to provide a possible theoretical basis for the promoting of Helianthus tuberosus growth and production under saline envrionment, the sand cultural study was carried out to study the effects of salicylic acid and nitrate on the growth, morphology and physiological indexs of Helianthus tuberosus under salt stress, which was conductive to investigate the link of Helianthus tuberosus physiological with the use of salicylic acid and nitrate.The major findings are as follows.(1) Application of0.1mmol·L-1salicylic acid could not only protmote the growth of Helianthus tuberosus under non-salt stress, but also reduced the inhibition of salt stress on the growth of Helianthus tuberosus relatively, promoted the matter accumulation and the moisture absorption of Helianthus tuberosus. At the same time, application of salicylic acid alleviated the damage of salt stress on PS II system, increased the various chlorophyll fluorescence parameters and promoted the transformation of light energy to chemical energy and the increasing of energy efficiency. Application of salicylic acid could also be conductive to increase soluble sugar, soluble protein and proline contents, and decrease MDA content and electrolyte leakage. Compared with salt-tolerant "NY-1", the relief effect of salicylic acid on salt-sensitive"QY-2"was more effective under the same salt stress.(2) Under the treatment with different salt concentrations, application of0.1mmol·L-1salicylic acid effectively alleviated the inhibition of NaCl stress on the photosynthesis of Helianthus tuberosus, then promoted the increasing of the chlorophyll content, photosynthetic rate, transpiration rate, stomatal conductance and water use efficiency, while the intercellular CO2concentration was significantly decreased. At the same time, application of0.1mmol-L"1salicylic acid not only effectively decreased Na+accumulation, but also promoted K+, Ca2+uptake and upward transport., then maintained the balance of mineral nutrients effectively. The relief effect of salicylic acid was also more significant in the range of0-100mmol·L-1NaCl concentration. (3) The application of nitrogen (the ratio of NH4+/NO3-as1/4) could be relatively good for the increasing of Helianthus tuberosus seeding growth, morphology and physiological indexs. while the response level of "QY-2" was better to the proportions of NO3--N augment. For example, with the proportions of NO3--N augment., the increase of the biomass accumulation, osmotic adjustment matter content and nitrogen use efficiency and the decrease of MDA on the treatment with "QY-2" were higher than the treatment with "NY-1".(4) The treatment of low concentration of salt stress had a little effect on the inhibition of plant growth, but high concentration of salt stress remarkably inhibited Helianthus tuberosus growth, with respect to NH4+-N, the proportions of NO3--N augment not only contributed to the dry matter and water accumulation under the same salt concentrations, but also maintained the stability of photosynthetic system. For example, it promoted the increase of the chlorophyll content, photosynthetic rate, transpiration rate, stomatal conductance and water use efficiency significantly, while the intercellular CO2concentration was significantly decreased. The increasing of the proportions of NO3--N was also good for the reducing of Na+accumulation and the protomtion of K+, Ca2+selective uptake and upward transport. At the same time, the SOD, POD, CATå'ŒAPX activity were also promoted, which had a function of eliminating reactive oxygen species, thus enhanced the resistance of Helianthus tuberosus to salt stress.To sum up, promotion of salt adaptation of Helianthus tuberosus with proper salicylic acid and nitrogen was mainly attributed to the enhancement of the photosynthesis, the osmotic adjustment ability and the antioxidation ability.