It contains the prepared leaves and leaf buds of Thea sinensis (Linne) kuntz., belonging to family Theaceae.
TEA
Biological Source
It contains the prepared leaves and leaf buds of Thea sinensis (Linne) kuntz., belonging
to family Theaceae.
Geographical Source
It is mainly cultivated in India (Assam), Ceylon, Japan and
Java.
Cultivation and Collection
It is an evergreen shrub growing to 4 m by 2.5 m at a slow
rate. The plant prefers light (sandy) and medium (loamy) soils and requires
well-drained soil. The plant prefers acid and neutral soils and can grow in
very acid soil. It can grow in semishade (light woodland). It requires moist
soil and prefers a pH between 5 and 7. Prefers the partial shade of light
woodland or a woodland clearing. It is reported to tolerate an annual rainfall
of 70–310 cm, an average annual temperature range of 14–27°C and a pH in the
range of 4.5–7.3. It prefers a wet summer and a cool but not very frosty dry
winter. Seed can be sown as soon as it is ripe in a green house. Stored seed
should be presoaked for 24 h in warm water and the hard covering around the
micropyle should be filed down to leave a thin covering. It usually germinates
in one to three months. Prick out the seedlings into individual pots when they
are large enough to handle and grow them on in light shade in the green house
for at least their first winter. Plant them out into their permanent positions when
they are more than 15 cm tall and give them some protection from winter cold
for their first year or three outdoors. Seedlings take 4–12 years before they
start to produce seed.
Characteristics
Twig of tea plant
Leaves are dark green in colour, lanceolate or elliptical,
on short stalks, blunt at apex, base tapering, margins shortly serrate, young
leaves hairy, older leaves glabrous.
Microscopy
The epidermal cells are made of polygonal cells which are
slightly wavy walls. It consist on itself stomata and trichomes. The trichomes
are thick walled, uni-cellular, conical (covering) which arise on the lower
surface and in large number in young leaves. The mesophyll region consist of
two rows of palisade parenchyma cells and large lignified sclereids which arise
at some intervals and are extended across the mesophyll from one epidermis to
the other. Cluster crystals of calcium oxalate are scattered in phloem and in
parenchyma. In the midrib area a prominent ridge is present both above and
below. Vascular bundle consisting of xylem and phloem are present; the entire
region being covered by slightly lignified band of pericyclic fibres. The
pericyclic fibres are up to four fibres in width at the widest region. The
remaining portion is covered with spongy parenchyma with scattered lignified
sclereids.
Chemical Constituents
The leaves are a rich source of caffeine (1–5%). It also
contains theobromine and theophylline in minor quantities. The colour of tea
leaves is due to tannin (10–20% gallotannic acid). The agreeable odour is due
to presence of a yellow volatile oil. Tea leaves also contain protein, wax,
resin and ash.
Chemical Tests
1. Caffeine and other purine alkaloids,
gives murexide colour reaction. Caffeine is taken in a petridish to which
hydrochloric acid and potassium chlorate are added and heated to dryness. A
purple colour is obtained by exposing the residue to vapours of dilute ammonia.
In addition of fixed alkali the purple colour disappears.
2. Caffeine also produces white
precipitate with tannic acid solution.
Uses
It is used as stimulant, astringent and also as diuretic.
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