Study On The Physiological Mechanism Of Potato Continuous Cropping Obstacle And Its Regulation

Potato (Solanum tuberosum L.), as a high-yielding grain crop and an important economiccrop, has its remarkable economic benefits and a long industrial chain. It is predicted that thecultivation area of potato is increasing year by year; however, because of factors such as potatogrowing in large quantities, continuous cropping obstacles have been arisen, which seriouslylimits the healthy development of potato industry. At present, little information was availableabout the mechanism of preventing continuous potato cropping obstacles and concrete measures.This paper attempts to make up for the weaknesses of the researches mentioned above by detailedanalysis.The first part of this study aimed at the relationship between potato continuous croppingobstacle and the changes in soil environmental factors. Those in the study were the soil of potatogrown in different continuous cropping years. Combined with the growing and development ofpotato, this part explored the phenoliacids allelochemical accumulation, change of soil enzyme,change of edaphon flora composition, seedling resistant physiology, plant growing anddevelopment of potato grown in different continuous cropping years and the Influences of potatocontinuous cropping soil on germination of seeds of Lolium multiflorum and Festuca arundinacea.The results indicated that as the continuous cropping prolonged, soil salinity, alkaline hydrolysisnitrogen content and bulk density increased, but pH value and the content of available phosphorus,available potassium and organic matter decreased. The activities of urease, catalase, alkalinephosphatase and invertin decreased when the continuous cropping lasted5and7years, thenumbers of soil bacteria and actinomycetes decreased, the number of fungus increased with theextension of the continuous cropping. As a whole, in comparison with contrast, potato continuouscropping obstacles for3years were not obvious, but when the continuous cropping lasted5and7years, the continuous cropping obstacle was significant, and the growth and development of theseedlings were dramatically inhibited, and it was corresponded to the changes in the biotic andabiotic environmental factors of the soil. The content of chlorophyll, activities of CAT and SOD,root activity of seedlings leaves decreased significantly when the continuous cropping lasted5and7years, yet MDA content and the producing rate of active oxygen increased. Along with theincreased years of continuous cropping, especially the continuous cropping lasted5and7years, the seed germination of Lolium multiflorum and Festuca arundinacea were inhibited significantly.From the analysis above, it can be concluded that when the potato continuously cropped for5and7years, a series of biotic and abiotic stresses from the soil were produced, and resulted in thecontinuous cropping obstacle of the seedlings.The second part of this study aimed at the improvement of fulvic acid on the growth andresistance in continuous cropping potato. The results indicated that the continuous croppingpotato seedlings endured stress from the soil, and the growth and development were inhibitedsignificantly; however, fulvic acid irrigation mitigated the harmful influences caused by thecontinuous cropping, so as to stimulate the growth and development of the continuous croppingpotato seedlings. The treatment of fulvic acid also significantly alleviated the decline in thecontents of chlorophyll, proline and soluble sugar, promoted the activity of SOD and CATrelatively, and even reduced the content of MDA and the level of reactive oxygen species. Theseabove results suggested that the fulvic acid treatment alleviated the obstacles of the continuouscropping in some way, and thus improved the overall resistance of potato plants. The fulvic acidtreatment also improved the content of starch, vitamin C and soluble protein in potato tuberssignificantly. So it can be concluded that the treatment of fulvic acid not only improved thegrowth and development of potato seedlings, but also enhanced its resistance to the continuouscropping, therefore fulvic acid do have some function in overcoming the continuous croppingobstacles in potato.The third part studies the effect of exogenous salicylic acid on the growth and resistancephysiology of continuous cropping potato. In the study, continuous and not continuous croppingpotato seedlings are treated with different concentrations of exogenous salicylic acid, and thegrowth, the ability of stress tolerance and antioxidant, tuber nutrition are discussed. The resultsindicate that5years of continuous cropping leads to the significant decrease of chlorophyllcontent, net photosynthetic rate, cell membrane stability index, osmoregulation substance content,antioxidant content, and autioxidant enzyme activities; tuber yield and hardness decrease; tuberstarch, Vc, soluble protein content also decrease. Meanwhile, the content of MDA, the levels ofreactive oxygen species leaves significantly increase, and the growth of plants is evidentlyinhibited. After the treatment of exogenous salicylic acid, the relative water content of potatoseedlings increases, and chlorophyll content, net photosynthetic rate, root activity and cell membrane stability index increase; growth is promoted, and the leaf osmoregulation substancecontent, antioxidant content, and autioxidant enzyme activities are improved; tuber yield,hardness, starch, Vc, soluble protein content, MDA content, and reactive oxygen species aredecreased significantly. From what is mentioned above, after the treatment of a certainconcentration of exogenous salicylic acid, the stress resistance of potato seedlings is improved,and the damage caused by continuous cropping obstacles is reduced. Thus potato plant growthand development is promoted, and potato tuber yield is improved, and the tuber nutrition andquality are also improved.To sum up, the continuous cropping of potato to a certain year could result in deterioration ofsoil biotic and abiotic environmental factors, thus changing the soil physical chemical properties,microbial flora structural composition, and soil enzyme activity, which leads to the decrease ofsoil porosity, increase of unit weight and degree of salinity, accumulation of phenolic acidsallelochemicals; potato growth is inhibited, and continuous cropping obstacles are significant.After the treatment of a certain concentration of exogenous fulvic acid and salicylic acid, thedamage to potato caused by continuous cropping could be reduced, and plant resistance isimproved, which not only do some help in relieving the physiological barrier of potato caused bycontinuous cropping, but also work positively in potato plant growth and tuber yield and quality,thus providing theoretical support for the healthy and sustainable development of potato and theillustration of potato continuous cropping obstacle physiological mechanism and its regulationapproach.