Inter-comparison studies of levels of aluminium, calcium, magnesium and iron in tea and other plants

Abstract

The tea plant Camellia sinensis has been found to accumulate a lot of aluminium. Tea being a very common beverage and considering the world wide concern over the toxicity of aluminium to both human beings and plants, it was necessary to carry out a more extensive study on aluminium levels in tea. Thus the study has been carried out to determine levels of aluminium in different parts of the tea plant i.e. in leaves, stem and roots and compare to that accumulated in other plants grown in the same locality. The effects of calcium, magnesium and iron on the accumulation of aluminium was also investigated.

The results showed that the tea plant camellia sinensis accumulates large amounts of aluminium in the older leaves. The young leaves i.e. two leaves and a bud were found to accumulate relatively low amounts of aluminium. The shoot had the lowest.

The results indicated that although the amount accumulated in tea leaves varied from one place to another, the tea plant was found to accumulate more aluminium than all the other plants that were considered in this study, i.e. plants that were growing in the same locality with tea.

In all the plants considered in this study accumulation of aluminium in the plants i.e. in the leaves, stem and roots was found to be in the order of;- aluminium in leaves aluminium in roots aluminium stem. Grains were found to accumulate very little aluminium and in some cases it was not detectable. (See pp78-80 tables 3.15, 3.16 and 3.17).

Although tea leaves accumulate very high levels of aluminium as compared to most other plants, the results showed that only 34% is extracted during tea making.

Organic solvents were found to extract very little aluminium as compared to inorganic solvents like water. For example hexane extracts only 3% while acetone which is slightly polar extracts 13%.

For all the plants considered in this study, accumulation of calcium in the leaves, stem and roots is in the order of calcium in leaves > calcium in stem > calcium in roots. In case of magnesium, the order of distribution varies from one plant to the other. For iron the order is similar to that of Aluminum i.e. iron in leaves > iron in roots iron > in stem.

For all the plants considered in this study no effect of calcium, magnesium and iron was noted on the amount of aluminium accumulated.

All the soil samples from the six different regions where the plant samples were obtained were found to contain a lot of aluminium and iron but very low amounts of calcium and magnesium. Aluminium was found to be in the range of 55000-98000mg/kg while iron was in the range of 68750mg/kg-115000mg/kg. Although the soils were found to be deficient in calcium and magnesium most plants were found to accumulate very high levels of these elements.

The results indicated that the soil pH of all the soil samples was in the range of 4.0 - 5.2, which means that all soils were acidic.