| With a long cultivation history in China, oil-tea camellia is a general reference to a section of species that are relatively high in oil content in genus Camellia. Research on Camellia was mainly concentrated in the fields of conventional breeding and cultivation measures for a long time, yet few studies were conducted on photosynthetic physiology in China and overseas. For the purpose of providing theoretical basis for compound cultivation, based on the photosynthetic properties of six camellia species (C. oleifera, C. vietnamensis, C. gigantocarpa, C. japonica, C. semiserrata, and C. osmantha) and six clones selected from C. oleifera (Cenruan2, Cenruan3, Cenruan24, Xianglin86, Changlin4and Gan190), investigation was carried out on photosynthetic and growth properties during seedling stage of five camellia species (C. oleifera, C. vietnamensis, C. gigantocarpa, C. semiserrata, C. osmantha) and five superior clones (Cenruan2, Cenruan3, Cenruan24, Xianglin86and Gan190) under three levels of light intensity treatments (60%,75%and90%), and studies were done on photosynthetic and growth properties of selected superior clones from Guangxi (Cenruan3), Hunan (Xianglin86) and Jiangxi (Gan190) at adult stage under the condition of low-light stress by simulating a natural shading environment under high arbor trees. Research results are as follows:(1) There were differences in photosynthetic properties among different camellia species and different clones of C. oleifera. The order of daily average net photosynthetic efficiency of different camellia species was C. oleifera>C. osmantha-> C. gigantocarpa> C. vietnamensis> C. japonica> C. polyodonta. The daily average net photosynthetic efficiency of C.oleifera was the highest, at7.24μmol·m-2·s-1, and C.polyodonta was the lowest, at3.72μmol·m-2·s-1, merely taking up51.52%of C. oleifera. Among the tested C. oleifera clones, photosynthetic properties of Xianglin86was the highest, at6.86μmol·m-2·s-1, Cenruan2was the lowest at3.97μmol·m-2·s-1, only taking up57.87%of Xianglin86. The daily average net photosynthetic efficiency followed this order:Xianglin86> Cenruan24> Changlin4> Cenruan3> Gan190> Cenruan2, respectively.(2) By simulating the light radiation condition, the maximum net photosynthetic efficiency of different camellia species ranged between8.4and10.5μmol·m-2·s-1, with C.oleifera the highest and C. polyodonta the lowest. Light compensation point of C.oleifera was merely15.50μmol·m-2·s-1, with the high capacity to utilize low light, followed by C. osmantha and C.japonica. C. polyodonta, C. vietnamensis and C. gigantocarpa had weak capacity to utilize low light. Light saturation point of C. osmantha which was distributed in areas of low latitude, showed high tolerance against strong light, while C.japonica which was distributed at high latitude showed the opposite. Among the tested clones, the maximum net photosynthetic efficiency ranged between5.8and11.4μmol·m-2·s-1, Cenruan3the highest and Cenruan2the lowest. The light compensation point of Gan190was16.36μmol·m-2·s-1,with the strongest capacity to utilize low light, while Cenruan2and Changlin4showed the weak capacity to utilize low light. Light saturation point of Cenruan3was537.86μmol·m-2·s-1, with the highest capacity to utilize strong light, while Gan190had the weakest capacity to utilize low light, with the light saturation point at383.55μmol·m-2·s-1.(3) In late September and early October, under the shading-free condition, the curve of diurnal variation of net photosynthetic rate of the tested camellia species during seedling stage as well as C. oleifera clones during seedling and adult stage demonstrated single and double apexes. C. gigantocarpa of camellia species and Cenruan24of C. oleifera clone during seedling stage and Xianglin86during adult stage showed single apexes. The remaining camellia species, Sect. Paracamellia, C. vietnamensis and C. polyodonta during the seedling stage, and Cenruan2, Cenruan3, Xianglin86and Gan190of C. oleifera clones during the seedling stage, as well as Cenruan3and Gan190during the adult stage showed double apexes. Along with the increase of shading intensity, the curve of diurnal variation of net photosynthetic rate of all the camellia species during seedling stage and C. oleifera clones during seedling and adult stage showed single apexes. Under the condition of60%-90%shading, the curve of diurnal variation of net photosynthetic rate of all tested camellia species during seedling stage and C. oleifera clones during seedling and adult stage was lower than the control. Ratio of daily average net photosynthetic efficiency against that of control was higher than the ratio of photosynthetic active radiation against that of control under the same shading condition, indicating that under the condition of60%-90%shading, capacity of leaves of all tested camellia species and C.oleifera clones to capture low light was increased.(4) Content of chlorophyll a, b and carotenoid in leaves of C. vietnamensis, C. oleifera, C. polyodonta, C. osmantha, Cenruan2, Cenruan3and Xianglin86during seedling stage and Cenruan3, Xianglin86and Gan190during adult stage under60%-90%shading condition increased obviously. Content of chlorophyll a, b and carotenoid in leaves of C. gigantocarpa, Cenruan24and Gan190under75%-90%shading condition was obviously higher than that of control. The synthesis of leaves chlorophyll and carotenoid under low light was enhanced in consistency with the increased capacity to utilize low light under shading condition for photosynthesis. Under low-light condition, increase of Qchlb/Qchla in the tested camellia species and C. oleifera clones during seedling stage was not obvious. During the process of chlorophyll synthesis, chlorophyll b was not synthesized in priority. Except C. oleifera, Qchlb/Qchla of remaining camellia species and C. oleifera was obviously higher than that of control, the increase extent of chlorophyll was higher than that of carotenoid, and chlorophyll was synthesized in priority. Among the C. oleifera clones during adult stage, except Qchlb/Qchla of Gan190under90%shading condition was obviously higher than that of control, Qchlb/Qchla of the remaining shading treatments was not increased significantly, and tendency to synthesize chlorophyll in priority was not obvious. However, Qchlb/Qchla in leaves of three tested clones under75%and90%shading treatments as well as Xianglin86and Gan190under60%shading treatment was increased significantly, chlorophyll b was synthesized in priority to better capture scattered light.(5) During seedling stage, among the tested camellia species, the tolerance ability against low light of C. gigantocarpa and C. vietnamensis was the highest that there was no inhibiting to the growth of root, stem and leaves under90%shading treatment condition, and the growth of root was enhanced under the situation of60%shading intensity. C. oleifera and C. osmantha had relatively strong ability of low-light tolerance; there was no significant impact of each shading treatment on the growth of root, stem and leaves. C.polyodonta had relatively weak ability of low-light tolerance during seedling stage, and the growth of root system was inhibited obviously under60%shading treatment. Among the different clones of C. oleifera, Cenruan2and Gan190had the strongest ability of low-light tolerance, there was no inhibiting effects of each treatment on the growth of root, stem and leaves, and partial shading treatment enhanced the vegetative growth of the plant. Cenruan24had a relatively strong ability of low-light tolerance, although root growth was inhibited under90%shading condition, the growth of stem and leaves was enhanced under partial shading condition. Cenruan3and Xianglin86during seedling stage had a relatively weak ability of low-light tolerance, and75%shading would obviously inhibit the growth of root.(6) Twenty-two months after shading treatment was applied on the tested C. oleifera clones during adult stage, it was found out that growth of Cenruan3and Xianglin86under90%shading condition and Gan190under60%-90%shading condition was prone to capturing light. Meanwhile,90%shading treatment also enhanced the growth of Xianglin86and Gan190towards capturing light. However, there was no significant difference in the content of N, P and K between three clones and control under each shading treatment. Under60%shading condition, Cenruan3had normal bud initiation and fruits, and there was no significant difference in fruit quality and oil composition compared with control. Though Gan190had similar bud quantity, fruit quantity and oil composition compared with control, fruit enlargement was inhibited. Bud initiation and fruits of Xianglin86were significantly lower than that of control. Although oil composition of fruits of Cenruan3, Xianglin86and Gan190under75%and90%shading condition was similar with that of control, bud initiation and fruits were obviously inhibited. At the adult stage, ability of low-light tolerance of three clones followed this order:Cenruan3>Gan190>Xianglin86.(7) At seedling stage, camellia species and C. oleifera clones all had relatively strong ability of low-light tolerance. C. gigantocarpa, C. vietnamensis, C. oleifera, C. osmantha, Cenruan2and Gan190of C. oleifera could grow normally under90%shading condition (in early October photosynthetic active radiation was61.83μmol·m-2·s-1). Cenruan24could grow normally under75%shading condition (in early October photosynthetic active radiation was178.87μmol·m-2·s-1). Cenruan3and Xianglin86could also grow normally under60%shading condition (in early October photosynthetic active radiation was311.91μmol·m-2·s-1). C. oleifera clones at adult stage had relatively weak ability of low-light tolerance. Bud initiation and fruits of Cenruan3, Xianglin86and Gan190under75%shading condition (on September30th the diurnal average synthetic active radiation was193.25μmol·m-2·s-1) were inhibited. However, Cenruan3could grow normally under60%shading condition (on September30th the diurnal average synthetic active radiation was280.72μmol·m-2·s-1), and Gan190could also flower and have fruits normally.
|
PDF Full Text Request