Introduction The Camellia oleifera (C. oleifera) cultivars 'Huashuo' (HS) and 'Huaxin' (HX) are new high-yielding and economically valuable cultivars that frequently encounter prolonged cold weather during the flowering period, resulting in decreased yields and quality. The flower buds of HS sometimes fail to open or open incompletely under cold stress, whereas the flower buds of HX exhibit delayed opening but the flowers and fruits rarely drop. Methods In this study, flower buds at the same development stage of two C. oleifera cultivars were used as test materials for a combination of physiological, transcriptomic and metabolomic analyses, to unravel the different cold regulatory mechanisms between two cultivars of C. oleifera. Results and discussion Key differentially expressed genes (DEGs) and differentially expressed metabolites (DEMs) involved in sugar metabolism, phenylpropanoid biosynthesis, and hormone signal transduction were significantly higher in HX than in HS, which is consistent with phenotypic observations from a previous study. The results indicate that the flower buds of HX are less affected by long-term cold stress than those of HS, and that cold resistance in C. oleifera cultivars varies among tissues or organs.This study will provide a basis for molecular markers and molecular breeding of C. oleifera.

Camellia oleifera is a typical subtropical evergreen tree species. It blooms in autumn and winter and often suffers from cold damage during its flowering period. The symptoms of injury are petals, young fruits falling off, ovary browning, etc., which seriously affect the normal development of flowers and fruits.In this experiment, the four-year-old C. oleifera seedlings ‘Huashuo’ were used as experimental materials.Before low temperature stress, exogenous substances of 10 mg·L -1 ABA, 0.1 mg·L -1 brassinosteroid（BL）and 10 mmol·L -1 calcium chloride（CaCl 2 ） aqueous solution and clear water as control（CK） were sprayed on the bracts were applied to study the alleviating effects of different exogenous substances on C. oleifera under low temperature stress. The results showed that exogenous substances increased the pollen germination rate and filament length of C. oleifera under low temperature stress, and the relative electrical conductivity, malondialdehyde and starch contents of flower organs（petals, anthers and filaments） decreased compared with the control. In addition, the contents of glucose, fructose, sucrose, soluble sugar and soluble protein were significantly increased. The observation of petal anatomical structure revealed that the petals treated with exogenous substances were more intact than the control. According to correlation analysis and membership function analysis, the carbohydrate substances such as fructose and sucrose in the organ of C. oleifera are cold resistant protective substances, which can be used as key indexes of cold resistance of C. oleifera floral organs. Spraying the above three kinds of exogenous substances can improve the cold resistance of C. oleifera floral organs（petals, anthers and filaments）, among which the treatment with 0.1 mg·L -1 BL aqueous solution has the most significant effect on the mitigation of cold injury.

为了筛选油茶近缘种高光效种质资源,从而为培育油茶新品种提供优质材料,以2个普通油茶品种('湘林1'与'湘林97')和6个近缘种(博白大果油茶、越南油茶、浙江红山茶、溆浦大红山茶、攸县油茶、滇山茶)为试验材料,对其叶片的净光合速率、蒸腾速率、胞间CO2浓度、气孔导度、水分利用效率等光合参数进行了测定和分析.观测结果表明:滇山茶、攸县油茶、越南油茶、博白大果油茶和'湘林1'与'湘林97'叶片的净光合速率均呈"单峰"曲线的变化趋势,其气孔导度和蒸腾速率亦均呈"单峰"曲线的变化趋势,而其胞间CO2浓度却呈"V"型曲线的变化趋势;浙江红山茶和溆浦大红山茶的净光合速率均呈"双峰"曲线的变化趋势,其气孔导度呈"平稳"型曲线的变化趋势,胞间CO2浓度呈"W"型曲线的变化趋势,蒸腾速率呈"单峰"曲线的变化趋势,说明其均存在光合"午休现象".相关性分析结果表明:净光合速率与气孔导度呈极显著正相关(P<0.01),与水分利用效率呈显著正相关(P<0.05);气孔导度与水分利用效率呈极显著正相关(P<0.01).主成分分析结果表明:从5个光合参数中提取了特征根>1的主成分2个,其累计贡献率为83.545％;主成分1(F1)中净光合速率、气孔导度和水分利用效率的累计正向贡献率最多,主成分(F2)中蒸腾速率的累计正向贡献率最多;根据综合评价结果可知,2个普通油茶品种及6个近缘种的光合效率由高到低依次为:油茶'湘林1'>滇山茶>油茶'湘林97'>攸县油茶>博白大果油茶>越南油茶>溆浦大红山茶>浙江红山茶.