| Camellia oleifera is a unique species of southern woody oil plant in China,with a high economic,social and ecological benefits.It has been planted since the southern song Dynasty with a history of more than 2300 years.Moreover,Camellia.oleifera is mainly distributed in the south of China,and the extreme low temperature in the South has a certain effect on the growth and development of Camellia.oleifera.In this study low temperature stress tests were carried out at four different temperatures at-5,0,5 and 10 degrees.The main study was to analyze the critical temperature of cold injury of Camellia.oleifera seedlings under the conditions of different low temperature stress,according to the growth and development of Camellia.oleifera seedlings and the changes of biochemical indexes of seedling leaves.At last according to the critical temperature and the meteorological data of nearly 30 years in Jiangxi Province,the suitable planting grade regionalization of Camellia.oleifera in Jiangxi province is analyzed.It will provide reference for reasonable planting and layout of Camellia.oleifera in Jiangxi province.The main results are follows:(1)The changes of leaves of Camellia.oleifera seedlings under the low temperature stress were investigated.Although it is a relatively low temperature resistant oil crop,it will adversely affect its growth and development at low temperature.Under the low temperature stress at-5 ?,the color of leaves of Camellia.oleifera seedlings gradually changed yellow with time,the number of dark green leaves and the number of green leaves decreased gradually.The number of leaves of the two kinds of leaves was 84.41% from the initial total leaf number,to the final 51.37%,which decreased by 33.04%.Under the low temperature stress of 10 degrees,the number of deep green and green leaves of Camellia.oleifera seedlings accounted for 84.62% of the total leaves at the beginning,accounting for 80.07% and 4.55%.Under low temperature stress at-5 ?,chlorophyll content in leaves of Camellia.oleifera seedlings decreased significantly under low temperature stress at 10 ?,indicating that the damage to leaves was more obvious at-5 ? under low temperature stress,but the change of leaf color was more stable under low temperature stress at 10 ?,indicating that the effect on leaf was slight.(2)The changes of biochemical indexes in leaves of Camellia.oleifera seedlings under low temperature stress were analyzed.The biochemical indexes of leaves increased with time.Excessive accumulation of malondialdehyde(MDA)has a damaging effect on plant cells,indicating that the damage to plant cells will increase as time goes on.The content of soluble protein increased with the increase of time,indicating that the plant cells can enhance the cold resistance,increase the soluble protein content and increase the intracellular permeability under the low temperature stress.The relative conductivity of the leaves increased because the plant cells were threatened under continuous low temperature stress,and the membrane system was destroyed,resulting in the exudation of the intracellular liquid,resulting in the increase of the relative electrical conductivity.It is suggested that Camellia.oleifera seedlings under normal low temperature stress conditions are harmful to their normal growth and development.The biochemical indexes of the leaves of Camellia.oleifera seedlings were analyzed with the temperature change of low temperature stress.The changes of biochemical indexes in leaves of Camellia.oleifera seedlings increased with the increase of time under low temperature stress at 0 ?,and the relative conductivity value of leaves increased with the increase of time at the beginning of low temperature stress at 5 ?.After the time,the relative conductivity is worth to be stabilized.Under the low temperature stress of lower or equal to 0 ?,seedlings will be destroyed by the threat of low temperature stress,and under the low temperature stress at or equal to 5 ?,the cell membrane of seedlings will be damaged by the initial threat of low temperature stress,but after a period of time,it can be self-regulating and recovering.It indicated that the critical temperature for the freezing injury of Camellia.oleifera seedlings ranged from 0 ? to 5 ?.The changes of biochemical indexes in leaves of C.oleifera seedlings under different temperatures were compared with the time.The changes of biochemical indexes in leaves were obvious at a temperature below 2 ?,while the changes of biochemical indexes in the leaves were relatively slow when the temperature was higher than 2 ?.Combined with the above analysis,the critical temperature of seedlings to freeze injury is 2? Celsius.(3)According to the influence of climate factors on the growth and development of Camellia.oleifera,the key climatic indexes were selected,and the climatic index data of 87 meteorological observation stations in Jiangxi(1981-2010 years)were rearranged,then the suitability for planting of Camellia.oleifera in Jiangxi province was represented. |
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