Research On Nutrition Regulation Mechanism Of Potato Production By Aeroponic Culture

The influences of virus in seed potato is an important reason for production decline. At present, culture with virus-free seed potato is the most effective techniques of increasing crop yield. As a result, how to produce virus-free seed potato is concerned particularly. Seed potato production by aeroponic culture is a technology developed in recent years. This technology has improved the growth environment, solved the oxygen deficit difficulty of root system and avoided the obstacles of continuous cropping. Because of the advantages of high yield and efficiency, it has broad application prospects, however, this method is not mature enough, especially the part of nutrient solution regulation needs to be further improved.The research was conducted according to several problems existing in the process of seed potato production by aproponic culture, the main contents and conclusions in this research were as follows:(1) Suitable proportion of nitrogen,phosphorus and potassium in the nutrient solution for seed potato production by aproponic cultureThere are complex coupling effects between nitrogen, phosphorus and potassium in nutrient solution, which are closely related to the growth of potato crops. The test indexes were different between different treatments due to the different proportion of nitrogen, phosphorus and potassium in nutrient solution. Eexcept plant height and stem diameter, the differences of other test indexes between different treatments were not obvious at both early and late growth stage, however, the differences were greater during the middle growth stage. Among the five groups nutrient solution designed in this experiment, the chlorophyll a,chlorophyll b,PSâ…¡photochemistry efficiency and root activity of the plants with T3 treatment were higher than others, because of these advantages the tuber number and tuber formation rate rised, especially for the tuber formation rate of second order stolon branch. The results show T3 nutrient solution was more suitable for the growth of potato, the tuberization performance of plants was improved, the contents of nitrogen,phosphorus and potassium in T3 nutrient solution were 273,77.5,351mg/L respectively, and the proportion was 1:0.28:1.3. (2) Effects analysis of calcium treatment on cold resistance of potato seedlings in aeroponic cultureThe experimental results of low-temperature stress showed that the electrolyte leakage and MDA content in leaves of potato seedlings with calcium treatment were decreased, compared with the control, the activities of anti-oxidant enzymes (POD,CAT and SOD) in leaves were improved and the contents of osmotic adjustment substances (soluble sugar and soluble protein) in seedlings leaves were increased, however, the effect of calcium application on praline content in leaves is not obvious. Furthermore, calcium treatment could efficiently restrain the root activity drop of potato seedlings. The results above indicate that the calcium signaling is closely related to the physiological regulation of aeroponic potato seedlings in the low temperature condition, calcium application with appropriate concentration could improve the cold resistance of seedlings. After low temperature stress relief, the enzymatic and nonenzymatic protection systems has continued to work in order to resist and repair the damage caused by stress. As the exogenous Ca2+ treatment concentrations were different, the results were different. The damage of the seedlings lacking calcium was the most serious, theoretically, this group seedlings need more anti-oxidant enzymes to remove reactive oxygen species and lipid peroxidation products in the process of adaptive regulation, while the experimental results showed that the activities of anti-oxidant enzyme did not increase substantially, even after the stress relief, the anti-oxidant system of seedlings has not been repaired rapidly. May be not only the enzymes synthesis function was damaged but also the other associated physiological metabolism, thus the adaptive regulation ability of seedlings was affected. Besides, the variational trends and variational extents of the membrane permeability, membrane lipid peroxidation product content, osmotic adjustment substances content, anti-oxidant enzymes activity and root activity showed that the exogenous Ca2+ treatment concentrations were different, the sensitivities and adaptive ability of seedlings to low temperature condition were different. During the low temperature stress, both the treatmentâ…¡(exogenous Ca2+ concentration is 7.0 mmol/L) and treatmentâ…¢(exogenous Ca2+ concentration is 10.5 mmol/L) could improve the cold resistance to some extent, and the difference between treatmentâ…¡and treatmentâ…¢was not obvious, however, after low temperature stress relief, the treatment effect of the latter was worse than the former. By comparing the indexes differences of membrane permeability, membrane lipid peroxidation level and root absorption activity between the two treatments, it can be found that the treatment time was longer, the differences were greater. May be due to the Ca2+ concentration of treatment III was too high and the treatment time was too long, the seedlings were subjected to calcium ion toxicity or the root absorptions on other ions were affected. Thus, the physiological metabolism and the repair for damage caused by environmental stress would be affected.(3) Response characteristic of photosynthetic apparatus of potato plants under low-potassium stressThe response mechanism of photosynthetic apparatus of potato plant under low-potassium stress was analyzed and the internal relations among the photosynthetic parameters were investigated. The results showed that the contents of chlorophyll a. chlorophyll b and carotenoids in leaves were decreased under low-potassium stress, however, the effect on the content ratio of chlorophyll a/b was not obvious, there was no significant difference during treatment period (P>0.05); Variable fluorescence (Fv),PSII photochemical efficiency and potential activity in leaves with the low-potassium treatment were lower than those in the control group, the drop of variable fluorescence was due to the increase of initial fluorescence (Fo) and the decrease of maximal fluorescence (Fm); In the early stages of low-potassium stress, the decrease of net photosynthetic rate (Pn) was mainly due to stomatal limitation, as further extension of stress time, non-stomatal limitation had gradually become an important factor which caused the photosynthetic rate to drop; The response characteristic of photosynthesis to light of leaves under low-potassium stress could well be described by non-orthogonal hyperbola Farquhar model, the coefficient of determination of Pn-PAR response curve in each stage was higher than 0.92 and the analysis results indicated that both the values of apparent quantum yield (AQY) and maximum apparent photosynthetic rate (Pmax) were decreased obviously, however, the effects of potassium concentration on light compensation point (LCP) and dark respiration rate (Rd) were not significant.