Study On The Effects Of Water Retaining Agent On Iris Lactea Var. Chinensis And Iris Tectorum Under Drought Stress

The morphology and physiological and biochemical characteristics of two-year-oldindividual seedlings of Iris lactea var. chinensis and Iris tectorum which were grown in potswere studied under indoor natural drought stress. According to the added amount of waterretaining agent and air-dried soil weight of the pot ratio were0%(control),0.05%,0.1%,0.3%,0.6%, the study set five treatment level. The purposes of the study were to research theirmechanisms of drought resistance and choose the best concentration of water retaining agentfor Iris lactea var. chinensis and Iris tectorum. This paper found out that:(1) Under drought stress, the leaves of Iris lactea var. chinensis and Iris tectorum appearthe phenomenon of wilting, yellowing, dead. Their biomass was inhibited to varying degrees.And the treatment added water retaining agent was inhibited less than the control. Applicationof water retaining agent can alleviate their symptoms and delay the onset of symptoms.(2) Under drought stress, the soil moisture, the relative water content and tissue water contentof Iris lactea var. chinensis and Iris tectorum decreased; the treatments of Iris lactea var. chine-nsis and Iris tectorum showed smaller decline than the control. A certain amount of water retai-ning agent can slow down the decreasing degree of the soil and plant leaves' water,and it can re-duce the damage caused by drought stress on Iris lactea var. chinensis and Iris tectorum.(3) The chlorophyll content of all the treatments of Iris lactea var. chinensis and Iristectorum overall decreased. And the chlorophyll content of the treatment added water retainingagent was higher than the control. The application of a certain amount of water retaining agentcan reduce the chlorophyll destruction and decomposition rate under drought stress. Thechlorophyll a/b of Iris lactea var. chinensis was increased first and then decreased, chlorophylla/b of Iris tectorum was overall upward trend. And chlorophyll a/b of the two plant control wasat a low level.(4) Under drought stress, cell membrane permeability and MDA content of Iris lactea var.chinensis and Iris tectorum was overall increased. The relative conductivity of0.05%,0.1%concentration of Iris lactea var. chinensis and other treatment except the contol of Iris tectorumhas declined in the later. MDA content of Iris lactea var. chinensis and Iris tectorum hasdecreased to some extent in the later. The treatments of Iris lactea var. chinensis and Iristectorum showed smaller increase than the control. Applying a certain amount of waterretaining agent, can reduce the relative conductivity and MDA content of the two kinds of plantleaves, and reduce the damage degree of their membrane system.(5) With the extension of drought stress, SOD and POD activity, SP and Pro content of Irislactea var. chinensis and Iris tectorum increased at first, then decreased. And SOD and PODactivity, SP content rebounded in the late. Compared with the control, water retaining agent processing can make the leaves SOD and POD activity, SP and Pro content remain at a highlevel under drought stress, be able to remove excess free radicals and maintain the osmoticpotential of cells in the lower, thereby reduce the degree of harm they are coerced.(6) Through principal component analysis and subordination function analysis, we got theconclusions: The best water retaining agent concentration for Iris lactea var. chinensis was0.1%. The best water retaining agent concentration for Iris tectorum was0.3%.