| Oiltea(Camellia oleifera Abel.) is mainly distributed in South China where acidic red soils are predominant, and available phosphorus (P) is one of main ecological factor limiting the increase of oiltea’s yield. Camellia oleifera ’Huashuo’and some common cultivars were selected as research materials and theories and technologies of molecular biology, plant physiology and root biology was applied in the study. The adaptive mechanism of oiltea to low phosphorus was discussed in terms of the expression of genes induced by low phosphorus, secretion of organic acids by roots, photosynthesis physiology and utilization of sparing soluble phosphates. The information obtained is valuable to further understand P utilization of oiltea in acidic red soil, cultivate varieties of P effective and increase efficiency of P fertilizer application in oiltea production. The results are as follows:(1) Phosphate transporter named CoPhtl;3and CoPhtl;4were isolated from oiltea with the method of RT-PCR and RACE. The CDS of CoPhtl;4is1629bp in length and it codes a predicted protein of543amino acids. The amino acid identity compared with other phosphate transporters is highly conserved and the similarities were all above70%. Eleven transmembrane domains and one suspect were predicated in CoPhtl;4and feature sequence(GGDYPLSATIMSE) located at the4th domain. Putative secondary and tertiary structure shows the protein is rich in alpha helix (66.97%) and possesses the main feature of transmembrane protein. The real-time RT-PCR results showed that expression of CoPhtl;3and CoPhtl;4in root, CoPhtl;3in leave of oiltea camellia were induced by P-deficiency and the expression of CoPhtl;3increased as the contenctration of phosphorus supplied.(2) Sand culture, solution collection, GC-MS and HPLC were employed to cultivate oiltea seedlings, collect and determine the kinds and concentration of root exudates. The results showed that oiltea’s seedling height, stem diameter, dried weight and P contents decreased, while the numbers and total length of lateral roots and root/shoot ratios increased when treated by low phosphorus. Root exudates enhanced the mobilization of plant-unavailable phosphorus in red soil, Al-P and Fe-P. The main ingredients of root exudates were esters. Acetic acid was the main acid secreted by oiltea root followed by succinic acid, and APase, oxalic, formic, malic and citric acids increased significantly in response to phosphorus deficiencies. It was confirmed that the greatest extraction capability of P from red soil was obtained by citric acids and there were significant difference in mobilization of Ca-P, Al-P and Fe-P by organic acids and no difference of activation P value of Al-P by oxalic, malic and citric acids were found.(3) Photosynthetic pigments, activities of RUBP and PEPC and photosynthesis was measured by spectrophotometry, portable photosynthesis system and chlorophyll fiuorometer. Content of chlorophyll and photosynthesis was increased by suitable P concentration, and photosynthesis was restricted by low or high P concentration though non-stomatal factors. The highest net photosynthetic rate (Pn) of C. oleifera ’Huashuo’ was observed in0.1mmolL-1P treatment and that of C. oleifera’XCL15’ was observed in1.0mmol-L-1. Fv/Fm and Yield first increased and then decreased as increase of P in culture solution. RUBP activates was highest in proper P concentration while PEPC activities rose in other P concentration, which made up for the decrease of RUBP. C. oleifera’Huashuo’is more resistant to low P than C. oleifera ’XCL15’.(4) The effect of sparing soluble phosphates (Ca-P, Al-P, Fe-P) and organic phosphate (O-P) on nutrients content of acid soil, seedlings growth, nutrients content and photosynthesis of oiltea was studied by pot experiment. Nutrients content of acidic soil was distinct affected by application of sparingly soluble and organic phosphates. Fe-P accumulated the total phosphorus while Ca-P and Al-P increased the content of available phosphorus significantly. Meanwhile, the content of nutrients between rhizosphere and non-rhizosphere soil had significant differences. The seedling height, ground diameter and weight of oiltea increased and root/shoot ration decreased significantly by Ca-P and Al-P treatment, and P content of plant was improved and the contents of N and K affected by exogenous phosphates. Pn was increased for all P treated seedlings, and P treatments except for Fe-P increased SPAD values. Ca-P, Al-P and Fe-P treatment increased Fv/Fm, Fv’/Fm’, Yield and qP.In conclusion, under P deficience, oiltea camellia satisfy their requirements for growth by starting high affinity inorganic phosphate transport system, promoting the excessive secretion of organic acids by root and expanding the roots to the increased phosphorus acquisition capability. At the same time, the photosynthetic protection system is started and the growth of shoots slowed. Characteristers such as expression of Phtl, parameters of fluorescence chlorophyll and secretion of organic acids can be used as the index of breeding P efficiency varities and level of P supplied. |
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