Effects Of Temperature And Light On Volatile And Non-volatile Quality Of Fresh Tea Leaves

With the pursuit of green development and the continuous improvement of consumers’environmental awareness,high-quality ecological tea is increasingly favored by people.Therefore,the construction of ecological tea garden has become a necessary measure for the development of tea industry in the new century.Tea quality is closely related to the ecological environment in which the tea plant（Camellia sinensis）,the results showed that temperature and light change affected the synthesis and accumulation of tea metabolites,and thus affected the quality of tea.However,the effect mechanism of temperature and light on the volatile and non-volatile quality of fresh tea leaves remains unclear.Hence,it is ecologically significant to study the influence of temperature and light variation on the volatile and non-volatile quality of tea leaves.In this study,‘Fuyun No.6’and‘Huangguanyin’,common tea cultivars in Fujian Province,were selected as the research objects.Effects of the difference between day and night temperature（DIF）（15℃/15℃,20℃/15℃,25℃/15℃,and 30℃/15℃）,photosynthetically active radiation（PAR）(200μmol·m^-2·s^-1,400μmol·m^-2·s^-1and 600μmol·m^-2·s^-1)and diffused light on volatile and non-volatile quality components and related physiological indexes of fresh tea leaves were simulated by the artificial climate chamber.The main results are as follows:（1）Volatile and non-volatile quality components of‘Fuyun No.6’and‘Huangguanyin’have different responses to DIF.At PAR=200μmol·m^-2·s^-1,the increase of DIF reduced the relative content of cis-3-hexenol and increased the content of caffeine in‘Fuyun No.6’and‘Huangguanyin’.For‘Fuyun No.6’,free amino acids increased with increasing DIF and reached a maximum of 3.39±0.07%at 15℃,while the ratio of tea polyphenols to amino acids decreased and the opposite was true for‘Huangguanyin’.Increasing DIF significantly increased the net photosynthetic rate,relative content of trans-2-hexenal and hexanal,while the relative content of 2-ethylhexanol and total flavonoids content decreased in‘Fuyun No.6’.At PAR=400μmol·m^-2·s^-1,the increase of DIF increased the caffeine content and the ratio of tea polyphenols to amino acids of‘Fuyun No.6’and‘Huangguanyin’,and decreased the relative content of 2-ethylhexanol in‘Huangguanyin’.For‘Fuyun No.6’,the free amino acids content decreased and the net photosynthetic rate increased with increasing DIF.Under the condition of PAR=600μmol·m^-2·s^-1,the increase in DIF increased the net photosynthetic rate and caffeine content and decreased the total flavonoids content of‘Fuyun No.6’and‘Huangguanyin’.For‘Fuyun No.6’,the relative content of trans-2-hexenal and hexanal increased with increasing DIF,while the content of 2-ethylhexanol and cis-3-hexenol decreased.And there was a correlation between photosynthetic parameters and the relative content of non-volatile quality components of tea leaves under the temperature treatments.（2）Volatile and non-volatile quality components of‘Fuyun No.6’and‘Huangguanyin’have different responses to PAR.Theβ-glucosidase activity of‘Fuyun No.6’and‘Huangguanyin’increased with increasing PAR under the treatment with DIF=0℃.The net photosynthetic rate and lipoxygenase activity increased with increasing PAR for‘Fuyun No.6’,while‘Huangguanyin’showed the opposite trend.Under the treatment of DIF=5℃,the increase of PAR increased the net photosynthetic rate of‘Fuyun No.6’,and for‘Huangguanyin’,the content of free amino acid and caffeine decreased by 29.90%and 45.56%respectively with the increase of PAR,while the ratio of tea polyphenols to amino acids increased.Under the treatment of DIF=10℃,the ratio of tea polyphenols to amino acids of‘Huangguanyin’increased with the increase of PAR.Under the treatment with DIF=15℃,the content of soluble sugar and the ratio of tea polyphenols to amino acids of‘Fuyun No.6’and‘Huangguanyin’increased with increasing PAR,while the free amino acids content decreased by 52.93%and 31.59%,respectively.Under diffused light treatment,the content of free amino acids increased by1.92%,and the content of total flavonoids decreased by 5.26%and there were no significant differences in photosynthetic parameters,photosynthetic pigments and related enzyme activities.In addition,there was a correlation between photosynthetic parameters and the relative content of non-volatile quality components of tea leaves under the light treatments.In summary,the changes of temperature and light have significant effects on volatile and non-volatile quality and related physiological indexes of fresh tea leaves.The response of the relative physiological indexes of different varieties to temperature and light was inconsistent,which affected the volatile and non-volatile quality of fresh tea leaves.The results of this study provide a new perspective for the site selection and cultivation management of tea gardens in the future.