Synergistic Inhibitory Effect Of Polypeptides And Dense Planting On Cadmium Absorption Of Rice

According to the biological characteristics of polypeptides,including containing carboxyl groups,sulfhydryl groups,and making the leaves of rice smaller and straighter during growing period of rice,the researches were carried out on whether combination of polypeptides with dense planting(increasing root density)can synergistically inhibit the absorption of cadmium by rice,at the same time,the biochemical mechanism relationships were researched among the cadmium content in rice,the changes of soil available cadmium,soil microbial population changes and root density changes.All works is to provide a technical reference for rice safe planting in moderate and light cadmium pollution soil(0.37-2.0 mg/kg),as follows:1.Design of the small-scale experiment,taking the conventional special fertilizer for rice as the control and Xiangliangyou 900 as the research variety,the soil containing different cadmium concentrations(1 mg/kg,2 mg/kg,5 mg/kg)was artificially prepared,and 1,2,4and 6 rice seedlings were planted in the soil of different cadmium contents respectively to study the synergistic inhibition effect of combination of polypeptides with dense planting on cadmium absorption by rice.(1)The synergistic inhibition effect of combination of polypeptides with dense planting on cadmium absorption by rice plants.The results showed that combination of polypeptides with dense planting could significantly reduce the cadmium content in rice roots,stems and leaves,and the maximum of reduction could reach 79%(stems).With the increase of the number of planting plants,the cadmium content of polypeptides groups and special fertilizer groups gradually decreases in the range of 1-4 plants.For the research groups of 6 plants,the cadmium content of some plants increases slightly,it may be the reason that the plant density is too high and affects the plant growth(small plant).(2)The synergistic inhibition effect of combination of polypeptides with dense planting on cadmium absorption of rice.The results showed that the cadmium content of rice in the combination of polypeptides with dense planting all reached standard(GB 2762-2017,less than 0.2 mg/kg),and with the increase of the plants number(1 mg/kg soil),the cadmium content in rice gradually decreased from 1 to 4 plants(the lowest was 0.04 mg/kg).Although the rice cadmium content of 6 plants slightly increased,it was still qualified(0.05 mg/kg),The cadmium content of rice about special fertilizer combination gradually decreased with the increase of the number of plants,but all of them were unqualified(the lowest cadmium content was 0.24 mg/kg),so combination of polypeptides with dense planting had a synergistic inhibition effect on the cadmium absorption of rice.(3)Research on the effect of combination of polypeptides with dense planting on soil and on the inhibition mechanism of cadmium absorption by rice.The results showed that combination of polypeptides with dense planting could increase soil p H(higher than 0.2),and reduce available cadmium content of soil(the maximum of reduction is 0.48 mg/kg),at the same time,combination of polypeptides with dense planting increased the population richness and diversity of soil microorganisms,and increased the relative abundance of beneficial bacteria such as desulfurization bacteria and myxococcus.The groups could also increase significantly the root density per unit soil volume(the maximum can be increased by2-3 times)to reduce relatively the cadmium absorption of rice per plant.In summary,the synergistic effect of the above factors realized the cadmium absorption inhibition of rice.2.Simple scale-up experiment,soil with cadmium content of 2 mg/kg and 5 mg/kg were prepared and put into a large container(67 cm×50 cm×50 cm)for simple scale-up experiment.The results showed that the inhibition effect of combination of polypeptides with dense planting on cadmium absorption by rice plants was greater than that of conventional special fertilizer for rice,and the maximum of reduction reached 62%.As for the cadmium content of rice,the brown rice of polypeptides group was qualified to the standard(containing 0.189mg/kg cadmium)under the condition of 2 mg/kg cadmium in the soil,but it was not up to the standard(0.203 mg/kg cadmium)under the condition of 5 mg/kg cadmium,which indicated that combination of polypeptides with dense planting had a range requirement for cadmium content in the soil(within 2 mg/kg).The rice of special fertilizer combination for rice did not meet the standard.3.Simple field verification and exploration experiment,based on the paddy field with soil cadmium content of 0.37 mg/kg(Lichuan City,Hubei Province),taking special fertilizer for rice as control(treatment 1,conventional density),dense planting(vertical row)+polypeptides as treatment 2(encryption 1 times),dense planting(vertical row)+polypeptides+cadmium-reducing rice varieties as treatment 3(encryption 1 times).The results showed that the cadmium content of rice in treatment 2 was similar to that in treatment 3(containing 0.186 mg/kg cadmium),both of which were qualified to standard,while rice in treatment 1(0.214 mg/kg)was not up to standard.The above results indicated that combination of polypeptides with dense planting had a synergistic effect on the cadmium absorption of rice and had a certain application prospect.