| Optimization of microtuber propogation technique in potato is the key to heighten the propagating index of microtuber and lower the cost. And aeroponic culture in potato could realize the goal, which is of distinct dominance of tuberization. But the pHysiological mechanism related to the dominance has not been researched. Therefore in order to probe into the mechanism of potato microtuber in aeroponic culture, two type of planting modes were designed with nutrition solution and varieties in two factors and three levels in crack test. At the same time the mechanism of organ establishment, glucide and nitrogen metabolism, related protective enzymes and hormones changing was researched in the experiment. The results were as follows.1. The growth characteristic, correlation relationship among root, stem and leaf and tuberizing potentialAfter planting 10 days, 9 items, including leaf area, stem height and diameter, roots volume, stolon and tuber number, roots activity, chloropHyll content and dry matter, began to be mensurated. The results showed that the flourishing time of stolon formation was earlier 30-day than that of tuberization, and the time was 20-day and 56-day respectively. At the same time the flourishing time of tuberization was the time of the most stolons while the the time of the most tubers was that after planting 92 days. With regard to root volume, it added up to the maximum after planting 56 days in substrate culture while it did after 80 days in aeroponic culture. That is to say, the maximum in substrate culture was earlier 24 days than that in aeroponic. The stem height and diameter and dry matter weight of overground section per potato plant were all reaching the maximum after planting 68 days in substrate culture while those did after 80 days in aeroponic culture. Namely the maximum in substrate culture was earlier 12 days than that in aeroponic. Through curve estimation, we found that the stolons were changing with time cubic curve in substrate culture while those did with time quadratic curve in aeroponic culture. And tubers, root volume, stem height and diameter, and dry matter weight per plant were all changing with time cubic curve in substrate or aeroponic culture.The findings also suggested that root activity reached the maximum after planting 56 days in substrate culture while it did after 68 days in aeroponic culture. Namely the maximum of root activity in substrate culture was earlier 12 days than that in aeroponic. The LAI reached the maximum after planting 68 days in substrate culture while it did after 80 days in aeroponic culture and the maximum of LA1 in substrate culture was earlier 12 days than that in aeroponic. In addition chloropHyll content reached the maximum after planting 44 days in substrate culture while it did after 68 days in aeroponic culture. As a result the maximum of chloropHyll content in substrate culture was earlier 24 days than that in aeroponic. Through curve estimation, we knew that root activity and chloropHyll content were changing with time cubic curve in substrate or aeroponic culture, and LAI were changing with time cubic curve in substrate culture while those did with time quadratic curve in aeroponic culture.Correlation analysis indicated that there were of distinct correlating relationships between indexes and yield, which had something to do with planting mode. In substrate culture there was distinct positive correlation between leaf and root development and stolons increasing, and the amount of leaf and root influenced dry matter accumulating overground plant. In aeroponic culture there were positive correlations among root, stem and leaf as well as between those and stolon and tuber. And the relationships between every index in aeroponic culture were root activity with chloropHyll content and stolons, and root volume with stolons and dry matter weight. There was no direct correlation between LAI and other indexes, and there was only directly positive correlation between dry matter weight and root volume.Through analysis of variance between harvesting tubers amount, the result suggested that in substrate and aeroponic culture there was difference between combinations in tuber amount. But in substrate culture there was not evident difference among varieties or nutrition solution while in aeroponic culture there was significant difference among combinations and nutrition solutions. And in substrate culture the amount of tubers was the most with A2 and Eshu-3 among combinations and as for tuber amount Gaoyuan-7 was the optimum, while in aeroponic culture the amount of tubers was the most with A1 and Eshu-3 among combinations and as for tuber amount Shepody was the optimum.Through analysis of variance between harvesting tubers weight, the result suggested that in substrate and aeroponic culture there was significant difference between combinations in tubers weight. But in substrate culture there was not evident difference among varieties or nutrition solution while in aeroponic culture there was distinct or awfully significant difference among combinations and nutrition solutions concerning tuber weight. And in substrate culture the amount of tubers was the most with A2 and Shepody among combinations and as for tuber amount Gaoyuan-7 was theoptimum, while in aeroponic culture the amount of tubers was the most with Al and Eshu-3 among combinations and as for both tuber amount and weight Shepody was the optimum.2. Characteristic of glucide and nitrogen metabolism and relationship between those and tuberizationAfter planting 20 days of and 56 days respectively, namely the flourishing time of stolon formation and the flourishing time of tuberization, we mensurated soluble glucide, sucrose, glucose and total nitroten content. The results indicated that in aeroponic culture the contents of soluble glucide and sucrose increased, which were higher than that in substrate culture. The content of soluble glucide of Eshu-3 was the lowest in substrate or aeroponic culture, and it was the most in potato plant cultured by Al. Furthermore Al could promote the soluble glucide content of Shepody in aeroponic culture. From high to low the order of sucrose content was Shepody, Gaoyuan-7 and Eshu-3 in substrate or aeroponic culture. Either Al or A3 could improve the glucrose content of potato plant, which of Shepody could incease with A1 or A3 in aeroponic culture. The glucrose content in substrate culture was less than that in aeroponic. A2 could increase the glucose content at the flourishing time of stolon formation and Al could increase that at the flourishing time of tuberization in substrate culture. The total nitrogen content at the flourishing time of tuberization was more than that at the flourishing time of stolon formation and it was higher in aeroponic culture evidently compared with substrate culture. Furthermore the total nitrogen content at every phase could be improved with Eshu-3 and A2 in both aeroponic and substrate culture. At the same time there was awfully distinct positive difference between soluble content and minituber weight or amount at the flourishing time of tuberization3. Characteristic of enzymes metabolism and tuberizing potentialAfter planting 20 days of and 56 days respectively, namely the flourishing time of stolon formation and the flourishing time of tuberization, we mensurated the content or activity of sucrase, nitrate reductase, superoxide dismutase (SOD), and peroxidase (POD). The result suggested that the SOD activity would decrease with potato plant growing but at the flourishing time of tuberization the SOD activity was the far more in tubers than that in stems or leaves. On the circumstance of aeroponic culture SOD activity was higher than that in substrate to illustrate that aeroponic culture had evident effect on improving the SOD activity. The difference of SOD activity between varieties was very small, and A2 could promote the SOD activity of tuber. The POD activity of stems and leaves would fall to large extent with potato growing. But at the flourishing time of tuberization the POD activity was the far more in tubers than that in stems or leaves. In aeroponic culture POD activity of every combination at different pHases was higher than that in substrate culture. In addition, POD activity in substrate culture was the highest transacted by combination of A3 andGaoyuan-7 or A2 and Eshu-3, while it in aeroponic culture did by combination of A3 and Shepody or Eshu-3. Furthermore there was lots of POD in stems and leaves or tubers of Eshu-3, and A3 could increase POD in early stems and leaves or at the flourishing time of tuberization. At the same time the POD content would increase in Eshu-3 plant transacted by A3, especially in stems and leaves at the flourishing time of stolon and in tubers at the flourishing time of tuberization.Sucrase activity would increase with plant growing, and it was higher in aeroponic culture than in substrate culture. Especially aeroponic culture could distinctly or awfully remarkably promote sucrase activity at the flourishing time of tuberization. Sucrase activity was the highest with A2 and Gaoyuan-7 in substrate culture while it did with Shepody and A2 or Al in aeroponic culture. Nitrate reductase in stems and leaves was higher at the flourishing time of tuberization than that at the flourishing time of stolon. Furthermore that of tubers was higher than that of stems and leaves, and that of aeroponic culture was higher that of substrate culture. The maximum of different combination all was the combination of A3 and Shepody at the flourishing time of tuberization and it was A2 and Shepody at the flourishing time of stolon. Shepody was of high nitrate reductase activity both in substrate and aeroponic culture, nutrition solution had different effects on nitrate reductase activity at different pHases. A2 was the optimum in aeroponic culture.There were awfully remarkable negative correlation between tuber weitht or amount and glucose content, remarkable or awfully remarkable positive correlation between tuber weitht or amount and soluble glucide or sucrose at the flourishing time of tuberization, remarkable or awfully remarkable positive correlation between tuber weitht or amount and SOD activity or POD activity at the flourishing time of tuberization and at the flourishing time of stolon. In addition there was remarkable correlation between tuber weight and SOD activity at the flourishing time of tuberization, remarkable or awfully remarkable correlation between tuber weight or amount and sucrase or nitrate reductase in stems and leaves at the flourishing time of tuberization.4. Characteristic hormones metabolism and tuberizationAfter planting 20 days of and 56 days respectively, namely the flourishing time of stolon formation and the flourishing time of tuberization, we mensurated the content of GA3, JA, IAA, ABA and ZR. The result indicated that GA3 content would increase a little in substrate culture and decrease in aeroponic culture with growth. And it in aeroponic culture was much higher than it in substrate culture at the flourishing time of stolon. There was no evident difference at the flourishing time of tuberization. IAA content would decrease with growth. And it in aeroponic culture was higher than it in substrate culture, especially at the flourishing time of tuberization. Varieties did not influence IAA content. Al could influence IAA content at the flourishing time of stolon. A2 and A3 could increase IAA content at the flourishing time of tuberization in aeroponic culture. ZR content...
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