Studies On Physiological And Biochemical Characteristics Of Leymus Chinensis Seedlings In Salt And Drought Stress

Rhizomes in clonal plants play a key role in storage and transport of nutrients as well as production of tillers; at the same time, the growth of rhizomes reserving carbohydrates affects not only the growth and development of forage but also the adaptability of forage in response to environment. However, up to now physiological functions of rhizomes in response to abiotic stress are poorly known. Investigated physiological responses of rhizomes of Leymus chinensis---perennial rhizome gramineous plant---to salt and drought stress, an experiment was conducted to measure physiological parameters after three treatments, namely RHS(only rhizome was stressed), ROS(only root was stressed) and RHSS(rhizome and root were all stressed) together to NaCl or PEG in auto-rain-shelter greenhouse, and were used to investigate the physiological and ecological adaptability of these rhizomes and roots.The results obtained were listed as follows:1. Under salt stress, RHS, ROS and RHSS treatments decreased dry biomass of different tissues of Leymus chinensis with them changed in the order of RHS >ROS >RHSS approximately relative to CK. But no significant differences were found between RHS and ROS treatments except root dry biomass, and had same find between ROS and RHSS treatments except rhizome dry biomass. Drought stress changed no rhizomes dry biomass significantly under RHS treatment while all tissues dry biomass were lower than CK. Compared ROS with RHS, significant differences were only found in root and total dry biomass; However, compared ROS with RHSS, there was no significant difference in all tissues dry biomass.2. Under salt or drought stress, three treatments increased or decreased SOD, POD and CAT activities to different extents compared with control and no significant rule was found in these changes, however, three antioxidazed enzymes changed in harmony ways and thus the reactive oxygen species in the plants can be maintained to a low level. From comparing three(RHS, ROS, RHSS) treatments, it was found that, under salt stress there were significant differences only CAT activities in leaves and highest under RHS treatment; SOD activities were in the order of RHSS >RHS, ROS and CAT activities RHS, ROS >RHSS in rhizomes respectively; SOD and POD activities were highest under ROS treatment in roots while CAT activities changed same in rhizomes. Under drought stress, among three treatments SOD activities were in the order of RHSS >ROS >RHS and POD, CAT activities in orders of RHSS >ROS, RHS in leaves; SOD activities were in the order of RHS, ROS >RHSS in rhizomes while CAT activities highest under ROS treatment; It was found that, there were highest SOD activities under RHS treatment, and POD activities were in the order of RHSS, ROS >RHS while CAT activities ROS >RHS >RHSS.3. Under salt stress, MDA contents were significantly higher than CK in rhizomes and roots of Leymus chinensis while no significant differences among three treatments; However, MDA contents in leaves were in the order of RHSS >ROS, RHS. From comparing three(RHS, ROS, RHSS) treatments, it was found that, under drought stress MDA contents were in orders of RHSS, ROS >RHS in rhizomes and roots but the order of RHSS >ROS >RHS in leaves.4. Compared with CK, under salt stress, it was found that, only soluble protein(SP) contents in leaf and rhizomes decreased significantly by RHSS treatment; under drought stress, only soluble protein(SP) contents in leaves and rhizomes increased by RHSS treatment and also only soluble protein(SP) contents in roots decreased by ROS treatment.5. Salt stress with three treatments(RHS, ROS and RHSS) made soluble sugar (SS) contents were highest in the shoots and roots under RHS treatment, but in the rhizomes were found under RHSS treatment. However, under drought stress, it was found that there were hightest soluble sugar(SS) contents in shoots and rhizomes under RHSS treatment, while in roots under ROS treatment.6. Salt stresses on different organs of Leymus chinensis made the proline (Pro) contents in shoots, rhizomes and roots all increased with them in shoots, and in shoots they were approximately in the order of RHSS >ROS >RHS and in roots RHSS, ROS >RHS, and there was higher contents in rhizomes under RHS treatment than the others. Drought stresses on different organs of Leymus chinensis made the proline (Pro) contents in shoots, rhizomes and roots changed variably. Comparatively, Proline(Pro) contents in shoots were in the order of RHSS >ROS >RHS and roots ROS >RHS > RHSS, but in rhizomes highest proline(Pro) contents were found under ROS treatment.