Development Process And Calcium Regulation Of Vegetable Seedling Root System

Root is an important organ to absorb nutrients and water,and the vigorous and healthy root system is the vital component and the symbol of the quality seedlings.In the process of seedling,there are many factors affecting root development,among which mineral nutrients in the substrate are particularly important.To improve our understanding for the root growth and development in vegetable seedlings and the regulation role of calcium in the process,the extraction method of mineral nutrients in substrate,the characteristics of root development and growth in cucumber,watermelon,eggplant,pepper,cabbage and cauliflower,and the regulation role of calcium on the root development in cucumber were analyzed.The main results were as follows:1.Eighteen treatments were designed with three factors:solid-liquid ratio?1:5,1:10,1:20?,extraction temperature?25?,50??and oscillation time?2,5,10 h?.The 13 mineral nutrient contents of vegetable seedling substrate were determined.The results showed that the treatment with the highest NO₃^--N and K extraction content was obtained under solid-liquid ratio of 1:20,extraction temperature of50°C,oscillation time of 5 h,and the treatment with the highest extraction content of NH₄⁺-N,P,Ca,Mg,S,Fe,Mn,Cu,Zn,Na,and Cl was solid-liquid ratio of 1:20,extraction temperature of 50°C and oscillation time of 10 h.Furthermore,we analyzed the data by TOPSIS modeling.This model comprehensively evaluated the 13 mineral nutrient extraction content of the seedling substrate,and the optimal treatment for the extraction content was a solid-liquid ratio of 1:20,an extraction temperature of50°C,and an oscillation time of 10 h.2.The root development and growth of six vegetables was observed,the results indicated that their differences reached significant level?P<0.01?.The root growth rate and total growth of cucurbit vegetables seedlings were significantly higher than that of solanaceous and cabbage vegetables seedlings.The order of root-shoot ratio of three vegetable types was as follows:solanaceous vegetables>cucurbit vegetables>cabbage vegetables;Significant differences were also found between different vegetables of the same type?P<0.05?.The primary root length,total root length,first-order lateral root number,and root surface area of watermelon seedlings are significantly higher than that in cucumber seedlings.Except for root-shoot ratio and root dry mass,the other indexes of pepper seedlings were significantly higher than those of eggplant seedlings.The root indexes of broccoli seedlings except for the average diameter were significantly higher than those of cabbage seedlings.3.The regulation of calcium on the root development and growth in cucumber seedlings was studied by applying calcium chloride in gradient of 0,1.25,2.5,5,and 10 mmol/L.The results showed that the primary root length increased as calcium concentration improved.Total root length,first-order lateral root number,root volume,root surface area,root activity,and root dry mass increased as exogenous calcium concentration ranged between 0 to 5 mmol/L.While the increase in growth was inhibited when calcium concentration was higher than 5 mmol/L;In addition,calcium and IBA combined application promoted total root length,first-order lateral root number,root volume,and root surface area,which are larger than calcium or IBA alone.The total root length,first-order lateral root number,the root volume,and the root surface area of calcium and NPA combined application were inhibited compared with the application of calcium or the application of NPA.In conclusion,regulation of calcium on root development and growth of cucumber seedlings maybe depend on IAA.