Study To Effects Of Cu²⁺ And Cd²⁺ On Pakchoi At Different Growing Stages

Wastewater irrigation and its impact on environment have been important subjects concerned in many fields including water resource utilization, wastewater treatment in small towns and agricultural ecological environment in recent years. The wastewater is the water quality on physical properties, chemical properties and biological properties has been changed after human activities. Wastewater often contains one or several kinds of heavy metal with different concentration. The soil and vegetable irrigated by wastewater will have heavy metal residue, which will brings direct or indirect harm to the vegetable growth and people health by the food chain. The extent of harm is different from the combination concentration and heavy metal ions. The research investigated the effects of different concentration of Cu²⁺,Cd²⁺ with single treatment and combined on leaf dry matter accumulation, chlorophyll, Cu²⁺,Cd²⁺ accumulation concentration in root and leaf, based on potted plant pakchoi. The main results and conclusions are showed as below:(1) Single treatment of different concentrations of Cu²⁺ or Cd²⁺ demonstrated negative effects on dry matter accumulation of pakchoi in two growing stages. With the increase of concentration, the dry matter accumulation significantly increased. But the extent of inhibition on pakchoi dry matter accumulation was different from concentrations, crop, growing stages and parts (root or leaf). From the effects that single treatment of different concentrations of Cu²⁺, Cd²⁺ on the dry matter accumulation of two growing stages of pakchoi root and leaf, early stage of pakchoi growing less affected by Cu²⁺, Cd²⁺.In the latter stage of growing the influence increased, in other words pakchoi at this time is more sensitive to Cu²⁺ and Cd²⁺. Pakchoi dry matter accumulation will be influenced serious if irrigated with water containing the ion at this time.(2) Different concentrations of Cu²⁺, Cd²⁺ all have negative effects on pakchoi dry matter accumulation, but the combination of different concentrations, different stages of crop growth inhibition have different degrees. High concentrations of Cu²⁺, Cd²⁺ performed synergistic with the dry matter accumulation of cabbage root and leaf. Summer crop of cabbage root dry matter were not sensitive to accumulation of high concentrations of Cu²⁺ in the stress of low concentration of Cd²⁺. (3) The results showed that different concentrations of Cu²⁺, Cd²⁺ had some effects on chlorophyll of two different growing stages of pakchoi. The inhibition of Cd²⁺ high concentration of a single treatment (AH) on the synthesis of chlorophyll concentration was less than low single Cd²⁺ treatment (AL). From the view of Cd²⁺ on the impact of chlorophyll, the late pakchoi growing more sensitive to Cd²⁺.The inhibition increased with the increase of the Cu²⁺concentration. The statistical analysis showed that the low concentrations of Cu²⁺ on the growing of two pakchoi first two stages of growth chlorophyll synthesis was small, high concentrations of Cu²⁺ treatment was relatively larger.(4) The treatment of Different density Cu²⁺and Cd²⁺ all had inhibitory action to the chlorophyll on different growing stages. With the increasing of the Cu²⁺and Cd²⁺, the chlorophyll content reduces obviously. Under the highly concentrated Cd²⁺, we irrigated with highly concentrated Cu²⁺ at the same time, the results showed that it will aggravate the destruction or inhibitory to the chlorophyll content of pakchoi at the entire period of growing, the low concentrated Cu²⁺ and Cd²⁺ had low effect to it.(5) Compared to water control CK treatment, the concentration of Cu²⁺and Cd²⁺ in roots and leaves of pakchoi under the treatments different concentrations of Cu²⁺, Cd²⁺ were increased significantly. The concentration of Cd²⁺ under low single treatment (AL) was about 2.1 times and 1.7 times of CK in the two growing stages, under high single treatment(AH)was about 7.4～11.9 times and 5.7～8.6 times of CK. Under the treatment of low concentration Cu²⁺, the Cu²⁺ accumulation in roots and leaves of pakchoi were all about 2.1 times of CK, but under the treatment of high concentration Cu²⁺, the Cu²⁺ accumulation in leaves was about 4.2～5.0 times, and in roots it was 5.1～5.7 times, which showed that with the increasing of Cu²⁺, the Cu²⁺ concentration decreased from the roots to leaves.(6) Under the combined treatments of different concentrations of Cu²⁺, Cd²⁺ , the concentrations of Cu²⁺, Cd²⁺ in the pakchoi were all higher than CK treatment. The concentration of Cu²⁺, Cd²⁺ in the roots and leaves varies from the concentration of Cu²⁺, Cd²⁺, the growing season and the growing stages.