Lifeng Ma

Accumulation and distribution of arsenic and cadmium by tea plants.

It is important to research the rules about accumulation and distribution of arsenic and cadmium by tea plants, which will give us some scientific ideas about how to control the contents of arsenic and cadmium in tea. In this study, by field investigation and pot trial, we found that mobility of arsenic and cadmium in tea plants was low. Most arsenic and cadmium absorbed were fixed in feeding roots and only small amount was transported to the above-ground parts. Distribution of arsenic and cadmium, based on their concentrations of unit dry matter, in tea plants grown on un-contaminated soil was in the order: feeding roots>stems≈main roots>old leaves>young leaves. When tea plants were grown on polluted soils simulated by adding salts of these two metals, feeding roots possibly acted as a buffer and defense, and arsenic and cadmium were transported less to the above-ground parts. The concentration of cadmium in soil significantly and negatively correlated with chlorophyll content, photosynthetic rate, transpiration rate and biomass production of tea plants.

Metabolomic analysis using ultra-performance liquid chromatography-quadrupole-time of flight mass spectrometry (UPLC-Q-TOF MS) uncovers the effects of light intensity and temperature under shading treatments on the metabolites in tea.

To investigate the effect of light intensity and temperature on the biosynthesis and accumulation of quality-related metabolites, field grown tea plants were shaded by Black Net and Nano-insulating Film (with additional 2–4°C cooling effect) with un-shaded plants as a control. Young shoots were subjected to UPLC-Q-TOF MS followed by multivariate statistical analysis. Most flavonoid metabolites (mainly flavan-3-ols, flavonols and their glycosides) decreased significantly in the shading treatments, while the contents of chlorophyll, β-carotene, neoxanthin and free amino acids, caffeine, benzoic acid derivatives and phenylpropanoids increased. Comparison between two shading treatments indicated that the lower temperature under Nano shading decreased flavonols and their glycosides but increased accumulation of flavan-3-ols and proanthocyanidins. The comparison also showed a greater effect of temperature on galloylation of catechins than light intensity. Taken together, there might be competition for substrates between the up- and down-stream branches of the phenylpropanoid/flavonoid pathway, which was influenced by light intensity and temperature.

Metabolomic Analyses Reveal Distinct Change of Metabolites and Quality of Green Tea during the Short Duration of a Single Spring Season

The sensory quality of green tea changes greatly within a single spring season, but the mechanism is not clearly elucidated. Young shoots of the early, middle, and late spring season were subjected to metabolite profiling using gas chromatography-time-of-flight mass spectrometry (TOF/MS) and ultraperformance liquid chromatography-quadrupole-TOF/MS. Multivariate analyses revealed largely different metabolite phenotypes in young shoots among different periods. The contents of amino acids decreased, whereas carbohydrates, flavonoids and their glycosides, tricarboxylic acid cycle, and photorespiration pathways were strongly reinforced in the late spring season, which were well reflected in the sensory quality of made teas. Metabolomic analyses further demonstrated distinct variations of metabolite phenotypes in mature leaves. The results suggested that the fluctuation of green tea quality in the spring season was caused by changes of metabolite phenotypes in young shoots, which was likely related to the remobilization of carbon and nitrogen reserves from mature leaves.

Estimation of N2O emission from tea garden soils, their adjacent vegetable garden and forest soils in eastern China

The objective of this study was to investigate nitrous oxide (N2O) emissions from different land-use types in eastern China. The dynamic changes of N2O emissions were investigated in tea gardens with different nitrogen application rates, their adjacent vegetable garden and forest soils from June 2009 to May 2010. The results showed that high nitrogen application in a tea garden significantly increased soil N2O emissions. Lower N2O emission and percentage of N2O–N to the applied N were observed in a tea garden with low N application than that from vegetable garden, indicating reasonable control of N application can efficiently decrease N2O pollution in tea gardens. Both air and soil temperature had significant and positive impact on N2O emissions, but little effect of precipitation was observed. Therefore, N application rate and environmental temperature are the most essential factors in influencing N2O emission and should be taken into consideration in the field management of tea production.

Soil carbon sequestration, plant nutrients and biological activities affected by organic farming system in tea (Camellia sinensis (L.) O. Kuntze) fields

Abstract There is growing interest in investigations into soil carbon (C) sequestration, plant nutrients and biological activities in organic farming since it is regarded as a farming system that could contribute to climate mitigation and sustainable agriculture. However, most comparative studies have focused on annual crops or farming systems with crop rotations, and only a few on perennial crops without rotations, e.g. tea (Camellia sinensis (L.) O. Kuntze). In this study, we selected five pairs of tea fields under organic and conventional farming systems in eastern China to study the effect of organic farming on soil C sequestration, plant nutrients and biological activities in tea fields. Soil organic C, total nitrogen (N), phosphorus (P), potassium (K) and magnesium (Mg), available nutrients, microbial biomass, N mineralization and nitrification were compared. Soil pH, organic C and total N contents were higher in organic tea fields. Soil microbial biomass C, N and P, and their ratios in organic C, total N and P, respectively, net N mineralization and nitrification rates were significantly higher in organic fields in most of the comparative pairs of fields. Concentrations of soil organic C and microbial biomass C were higher in the soils with longer periods under organic management. However, inorganic N, available P and K concentrations were generally lower in the organic fields. No significant differences were found in available calcium (Ca), Mg, sodium (Na), iron (Fe), manganese (Mn), copper (Cu) and zinc (Zn) concentrations between the two farming systems. These findings suggest that organic farming could promote soil C sequestration and microbial biomass size and activities in tea fields, but more N-rich organic fertilizers, and natural P and K fertilizers, will be required for sustainable organic tea production in the long term.