The Research On The Physiological Adapting Responses Of The Root Of Camellia Oleifera To Phosphorus Deficiency

Oil tea (Camellia oleifera Abel) is the main woody edible oil tree species in south of China. The phosphorus of Southern soil is generally deficiency, so phosphate fertilizer need fertilize in the soil to meet the needs of the growth of camellia, but the phosphate fertilizer can be easily fixed by soil, and turn to be ineffective phosphorus which can’t be absorbed by oil tea. Therefore, making full use of the genetic diversity of camellia, taping potential of the utilization of phosphate, screening and breeding of P-efficient oil tea varieties could be a mean to solve the contradiction between the phosphorus oil tea needed and soil supplied. In this thesis,taking one year old oil tea grafting seedling and seeding as experimental material and culturing them in sand under four levels of phosphorus, the shoot growth characteristics, root morphology configurations, root physiological characteristics, components of root exudates and organic acid content of root exudates under different levels of phosphorus were studied; a simple and efficient method for the determination of10kinds of organic acids in Camellia oleifera root tissue and exudation by HPLC was established; the capability of root exudates and organic acids in mobilization of soil phosphorus and sparingly soluble phosphate were verified; the root responsing mechanism that the oil tea adapt to low phosphorus was explored. The main results were as follows:1. The different phosphorus levels had a significant influences on the shoot-, root-related traits of oil-tea seedlings. With the decline of phosphorus level, the oil-tea seedlings height, ground diameter, the overground and underground biomass all decreased significantly, while the lateral root weight increased within a certain range (P1to P3); Oil-tea root-shoot ratio, root volume, number of lateral root, average length of lateral root and total length of lateral root showed the increasing trend, and the taproot long showed a decreasing trend. Under different phosphorus levels, the number of lateral root from different parts of the plant root systems ranked as lower> middle> upper,and lateral root length of upper and lower were longer than middle.2. The different phosphorus levels had a significant impact on the phosphatase activity and root activity of the oil-tea seedlings. With phosphorus levels declined, the APase activity of the root exudates, root tissue and leaf decreased significantly; while the root volume, root active absorption area, root active absorption area ratio increased significantly.3. Chemical components of root exudate samples of the four phosphorus levels were analyzed and identified by GC-MS.The main components of root exudates were ester and alkane,and the relative content of the two categories compounds were within88.66%-96.36%. With phosphorus levels declined, the ratio of ester compounds showed a trend of increasing, while alkane ratio showed a trend of decline. Among the ester compounds, the relative content of triethyl citrate was highest, and increased as the phosphorus level declined. The carboxyl of ester compounds may come from the citric acid, oxalic acid, oxalic acid,2,5-furan2formic acid, phthalic acid and palmitic acid. The number of the organic acids under no phosphorus (P0,3) and low phosphorus (P1,6) level were more than that under normal phosphorus (P2,2) and high phosphorus (P3,2) level.4. A simple and efficient method was developed for the determination of organic acids in Camellia oleifera root tissue and exudation by high performance liquid chromatography and the samples cultured in sand with different phosphorus concentration was determined. The results showed that collecting root exudation by the solution culture and extracting the organic acids from the dry root powder with ultraso-nic extraction on a water bath had good effect.With the decline of phosphorus level, the organic acids content in root tissue increased significantly, of which the lactic acid,malonic acid, citric acid, succinic acid, oxalic acid and acetic acid had bigger rate of increase amplitude; The organic acids content of root exudates under no phosphorus (PO) and low phosphorus (P1) level were higher than normal phosphorus (P2)level, but the no phosphorus level(PO) was lower than low phosphorus (PI) level. Among the10kinds of organic acids in the root root tissue and root exudates, the content of lactic acid and malonic acid were higher than any else.5. The experiment to investigate the mobilization of phosphorus (P) in red soils and sparingly soluble phosphate compounds with root exudates and organic acids compounds were carried out. The main results were as follows:the root exudates of oil-tea can signally promote the activity of P in soil, the activation efficiency were different between the soil from different places; the root exudates also can dissolved the sparingly soluble phosphate compounds, and the solubility of the sparingly soluble phosphate in root exudates were different, the solubility ranked as Al-P>Ca-P>Fe-P.The activation efficiency of the main organic acids on soil phosphorus and sparingly soluble phosphate were different. The activation efficiency on soil ranked as the order:citric acid> malic acid> oxalic acid> succinic acid> acetic acid> formic acid; Among the organic acids, oxalic acid, citric acid and malic acid had a higher activation efficiency on the three kinds of sparingly soluble phosphate compounds, which activation efficiency ranked as the order:oxalic acid> citric acid> malic acid.