Protective Effects Of
Tea On Human Health
- Flavonoids,
the most prominent of which is catechins and their derivative polyphenols,
are the most abundant and most biologically active molecules that are
responsible for most of the health-giving properties of tea.
- Tea
contains theanine, (which is a unique amino acid in tea), proteins,
caffeine, vitamin C, carbohydrates, polysaccharides, and lipids.
- Inappropriate
diets and smoking generates high levels of reactive oxygen species, like
peroxides in humans, which are the basic cause of heart disease. Tea
polyphenols have strong scavenging properties for free oxygen radicals,
thus lowering the risk of heart ailment.
-
Cancer
is as a result of uncontrolled proliferation of cells mutated by oxidative
stress or carcinogens in foods and environment.
Tea polyphenols induce enzymes that detoxify carcinogens, thus
inhibiting cancer initiation or carcinogenesis of cancer tumours.
- Catechins, (particularly,
epigallocatechin) interact with an enzyme in human intestines to suppress
glucose uptake, by inhibiting sodium-dependent glucose transporter mechanism,
thus preventing diabetes.
- Kidney
diseases are the results of free radical-induced oxidative
stress, tea catechins relieve high oxidative stress, improve renal
blood circulation and are effective in easing the pains caused by renal
diseases.
- Osteoarthritis
is
also prevented by tea polyphenols through inhibition of the production
of catabolic mediators implicated in the progression of arthritis.
-
Theanine
and catechin which are the component of green tea has
neuro-protective effects, thereby preventing cerebral stroke.
- L-Theanine
in tea has been reported to effectively control flu-like symptoms of the
common cold.
- Anti-viral
and anti-bacterial properties of tea reduce influenza,
infections of respiratory tract, and lungs as well as preventing pulmonary
diseases.
- Tea
also raises basic metabolic rate, so that at equal food intake and
exercise levels, body weight is reduced for those who drink 8 – 10 cups of
tea a day. This explains why fewer Japanese are obese.
- Black
tea polyphenols prevent tooth-removing diseases and dental
plaque formation.
- Tea
contains 20 – 30 mg of caffeine per 100 ml and daily caffeine intake
must not exceed 600 mg/day which is equivalent of 2 – 3 litres of tea/day. Even
fruit-flavoured teas contain normal caffeine as green / black tea.
- Normal
green / black tea does not provide any calorie / energy, but
fruit-flavoured teas may contain traces of sugars, thereby providing few
calories. Herbal infusions do not contain calories.
Introduction
- Tea
plant (Camellia sinensis (L) O. Kuntze) (family: Theaceae) was
discovered by Chinese around 2700 BC in South-east Asia, in the high valley of
the Brahmaputra, the Irrawaddy, the Salween and the Mekong rivers of the
borders separating India, China and Burma.
- In
its wild state, it forms an evergreen bush which on cultivation, is kept at a
low level (Tea Table) (Plate 1) to enable the young shoots, from which
tea is made, to be plucked.
- Today,
tea is cultivated in China, Japan, India, Sri Lanka, Indonesia, South American
Countries, High altitude regions of Africa, Middle East, Australia and
Russia.
- Depending
on weather the tea harvests (leaves) undergo fermentation or not, respectively,
makes tea to be black or green.
- The
black tea is orange to dark-red in colour which sometimes gives scented
infusion. It contains low level of Catechins (4.0 g/100g) and high level of
Theaflavins (0.94 g/100g).
- The
green tea, on the other hand, gives insipid beverage with yellowish colour and
it contains highest level of Catechins (14.2 g/100g) and zero Theaflavins.
Botany
- Tea
was formerly named Thea japonenense. Later Linnaeus renamed it Thea
sinensis. In 1959, the generic name was changed to Camellia. The
plant is a diploid with 2n = 2x = 30. A number of triploids and tetraploids
have been found or created by research efforts.
- There
are 2 main varieties of tea – the sinensis (the China
plant with small leaves C. sinensis var. sinensis) and the
assamica (the Assam plant with large leaves C.
sinensis var. assamica) varieties.
- The
assam tea plant is a shrub which grows up to 15 m high with straight trunk.
- The
China tea is also a shrub which grows up to 6 m high with several stems.
- Other
minor varieties include Cambodian tea, of which the following varieties
are being cultivated – Manipuri, Lushai and Betjan which
are stable ecotypes.
Ecology Of Tea
Climate
and soil characteristics are the most important ecological factors for
growing Tea:
CLIMATE:
- Tea
thrives under equatorial, humid and temperate climatic types. Generally, tea
thrives within latitude 430 north and 270 south.
- Assam
tea is less hardy than the China variety which tolerates dry season and lower
temperatures.
- The
plant performs under 1500 – 4000 mm of rainfall, with a dry season of not more
than 3 months. Around the Equator, tea thrives under 1800 mm rainfall but, with
altitude of between 1800 – 2000 m asl. The dry season must not be less than 3
months.
- The
ideal average annual temperature is between 180C and 200C.
The growth of tea plant is seriously affected at 300C and 120C
and tea plant dies at 50C. It does not tolerate frost.
- Sunshine
hours of 5 hours per day, on the average, is required by tea. In cloudy
conditions and heavy and continuous rainfall, the yield drops.
- The
tea plant thrives under high relative humidity of between 70% – 90%. This is
favoured by permanent shade, windbreaks or irrigation by spraying. In dry air,
the bud becomes dormant and the plant stops growing.
Soil
requirements:
- Geological
origin does not greatly affect the development of tea plant.
- Generally,
the best plantations of tea are found on deep soils with a good structure,
well-drained with a well-developed humus-bearing layer and high mineral
reserves.
- Quaternary
soils, recent alluvial soils, soils on granite or gneiss and soils derived from
eruptive rocks or volcanic ash are suitable for tea growing .
- The
tea plant requires acid soils with pH of between 4.5 – 5.5, if the pH is not up
to 5.5, it is better.
- The
tea plant performs badly on alkaline or compact soils.
- Tea
is generally grown on well-drained sloping terrain, but the slope must not be
more than 25% - 30%,unless land improvement carried out effectively checks soil
erosion.
Tea
Agro-Techniques
- Tea
production technology involves various agro-techniques which may be broadly put
under two management componants;
- Nursery management- the methods of
propagation of tea seeds, cuttings, saplings etc. are included under the
nursery management.
- Crop management- embraces various
field-techniques of brining up tea and ancillary crops that are intended
to exploit the highest possible productivity from a tea plantation.
Tea is propagated
either by vegetative parts or seeds; where tea is propagated through vegetative
parts is called VP nursery and where tea seeds from a general seed bariers are
germinated to tea saplings in called seed nursery.
VP nursery: The purpose
of the vegetative propagation is to strike the nodal leaf cuttings from the
desired tea plant and put in a suitable rooting medium for raising individual
plants having similar genetic constitution of the parents. For a successful
nursery management through vegetative propagation, it is essential to maintain
a ready-stock of mother tea bushes from which the nodal leaf cuttings are
supplied to the VP nursery. The mother tea bushes are selected either from the
existing tea plantation or a separate Nucleus Clone Plot (NCP)
A.
Selection of mother tea bush
Mother tea bushes are
preliminary selected from an existing tea planatation on the basis of same
selection criteria of morpho-physiological characteristics of the plant
viz-bush-frame, vigour and growth, leaf-pubescence, the density of
plucking-points on plucking table etc.
Field Techniques:
A high yielding mature
plantation of good seed source is selected. A few bushes are marked with tall
bamboo stakes and screening of bushes is made on basis of the following
morphological characters of plant.
i)
Bush frame and growth
ii)
Flowering habit
iii)
Chloroform test
iv)
Rooting trail
v)
Quality test
vi)
Yield performance test
B. Nucleus clone plot
(NCP)
The selection of mother
bushes from existing tea plantation is time consuming and laborious. For a continuous
supply of tea cutting of highly productive and quality clones, a separate area
is planted with recognized clones that known as Nucleus Clone Plot (NCP). It is
the source of mother bushes of known genetic constitution which may be
propagated in the VP nursery with little time and effort. It is estimated that
NCP consisting of 400 mother bushes may supply as much as nodal leaf cuttings
to plant out about 10 acres of land. Spacing of plants are generally used at
1.80 m X 1.20 m. NCP may be established in three ways.
i)
By using the existing clonal plantation
ii)
By converting a portion of mature
seedling tea plantation through grafting of the desired clone and
iii)
By planting a separate area with desired
clone
Tea Nursery
A nursery unit of a tea
estate is composed of VP nursery and seed nursery . VP nursery is composed of
two units viz primary beds and secondary beds. In the primary nursery bed, the
fresh tea cuttings are planted for the purpose of rooting/callusing the cuttings
to grow the rooted new saplings. The rooted plants are then transferred to the
polythene sleeves which are kept in the secondary nursery bed till the planting
out in the field.
Tea Agro-Techniques
Nursery and plantation
technique of tea
As we have discussed
about seed nursery and vegetative propagation nursery (VP). According to the
purpose, VP nursery is categorized into two units. Viz. primary nursery bed and
secondary nursery bed.
Primary nursery bed;
the fresh tea cuttings are planted for the purpose of rooting the cuttings to
grow the rooted new saplings.
Secondary nursery bed;
the rooted plants are then transferred to the polythene sleeves which are kept
in the secondary nursery bed till the planting out in the field. Following plan
is executed to build a nursery unit for a tea estate.
Planning; what to
plant? How to plant? Where to plant?
- Nursery site selection: the site is
selected in an open area and in the close proximity to accessible roads,
tea plantation and a perennial water-source steam, pond lake etc.
generally a well-drained flat area without any concretion/hardpan
underneath is suitable.
- Land prepararion: the site is clear
off of jungles and ploughed to a depth of 15 cm. all stumps stubbles,
roots etc. are removed from the site, and leveled properly according to
the topo-sequence, soil texture, the paths and drains. Main drains
surrounding the site are dug up to a depth of 60cm
Nursery and plantation
technique of tea
While the sub-drains
are 30 cm wide and 15 cm deep for the removal of excess water during rainy
season.
3. Nursery
bed preparation: The bed is prepared usually oval shaped during rainy season
and slanting in dry season, 1.5 m wide and 10 m long is size. The shade is
provided with lathe frame 1.5 X 1.2 m and fenced with bamboo split at a height
of 14-22 cm. the nursery beds are designed with proper drains, paths and roads.
Agronomy Of Tea
Propagation of tea: Generative
and Vegetative.
Generative propagation:
- Tea
plantations from seeds result in heterogeneous vegetable materials,
which result in great variations in production, quality and suitability for
fermentation.
- The
seed-bearing tea bushes are left to grow freely for seed production.
- Alternatively,
the young and vigorous tea plants, in the nursery, are selected for the
purpose. After a number of selections upon generations in the garden, high
producers are selected while poor producers are eliminated.
- This
method is used to obtain varieties best suited to ecological conditions of each
region (high yield and superior organoleptic qualities being traits of
interest)
Vegetative Propagation:
- Tea
plant is widely propagated by layering, grafting, stem cuttings and root
cuttings.
- Tea
clones are widely produced by stem cuttings which is simplest and widespread.
- Selection
of best tea bush for cloning is based on 2 primary characters: the yield and
quality of liquor. Secondary characters include sprouting rate of
cuttings, fermentation suitability and tolerance to dry conditions.
- Selection
is generally done on the field, but at times it may be carried out in the
nursery.
Tea Nursery:
The following
principles should be adhered to in setting up cuttings nursery of tea:
- Siting:
It must be sited very close to perennial source of water source of substrate
and well-sheltered from wind.
- Shading:
Tea nursery must be shaded and the shade covering should be 2 m above the
ground which must allow 20% - 30% light penetration.
- Substrate:
The
substrate should be of clay sand composition with little organic matter and
crumbly structure. It must have a pH of between 4.5 - 5.0.
- Containers:
The
substrate is placed in transparent polythene bags perforated at the base.
Transparent bags are preferable to black bags because, they are not expensive,
absorb less heat, dry slowly and enable root development to be monitored.
Preparation of tea
Cuttings:
Ø Cuttings
are taken from semi-hard stems, preferably when the weather is overcast.
Ø They
are packed in plastic bags and moistened. Cutting are prepared, at an angle of
450, in a well-ventilated place sheltered from sun, using a budding
knife.
Ø The
cuttings consist of a leaf, a bud and a stem of 3 – 4 cm long. At times,
multinodal cuttings are used because they are more vigorous and easily root,
but, they involve more vegetative parts.
Ø The
cuttings are placed inside a bucket of water and transported to destinations. The stems are planted upright or
slightly bent.
Ø Maintaining
humidity levels: After planting, the materials are
sprayed with water droplets and covered with polythene sheet of 150 – 400
microns thick to form an humidity chamber.
Ø Preventive
measures: The humidity chamber must be continually checked for
constant humidity levels and the outbreak of disease and insect pests.
Ø Fertilizer
application: This starts when most of the cuttings
have successfully rooted and when hardening-off begins. The recommended
fertilizers are ammonium sulphate, urea or compound fertilizers (2 – 30g/m2)
Ø Hardening-off:
This begins as soon as cuttings have rooted (2 – 4 months after setting). The
polythene sheet is gradually removed over a period of 2 – 3 weeks and the
shading is slowly removed, according to climatic conditions.
Ø Pruning:
This is not recommended in the nursery because it slows down root development.
Rapidly-developing clones are sometimes pruned.
Guide towards
successful establishment of Tea plantation:
Ø Sit
selection
Ø land clearance
Ø Drainage
Ø Anti-erosion
measures
Ø Eradication
of self-propagation weeds
Ø Tilling
Tea plantation:
Planting out:
Ø Only
sturdy seedlings / ramets with stem diameter of 8 – 10 mm are selected for
transplanting into the field.
Ø The
weak and less vigorous seedlings are destroyed and on no account will they be
replanted the following seasons.
Planting density /
spacing:
Ø The
optimum planting spacing of tea plant depends on its vigour, canopy, width of
its plucking table, and soil fertility.
Ø Planting
density in determining factor in calculating the yield of tea plant.
Temporary shading:
Ø When
young, tea plants have to be protected from sun, drying winds and hail by
hedges of leguminous plants (Crotalaria, Tephrosia, etc).
Ø The
hedgerows are retained for 1 – 2 years before tea starts giving harvests, but
hedgerows are regularly pruned and pruned vegetation supplies organic matter to
the soil.
Mulching:
Ø Mulching
is of great importance to development of young tea plants.
Ø It
protects the soil from sun’s rays, drying winds, reduces evaporation and
affords adequate moisture retention during the dry season.
Ø It
checks run-off, muddy situation in heavy rains, temperature extremes and
improves soil organic matter.
Ø 20
– 40 tonnes/ha of grasses (Pennisetum purpureum, Digitaria spp. and
triosacum laxum) are recommended for tea cultivation.
Windbreaks:
Ø Windbreaks
are essential, particularly in exposed regions at high altitudes. The species
normally used include Hakea saligna, Grevillea robusta, Accacia spp.,
Cupressus spp., Eucalyptus spp. and even tea itself.
Bringing Tea into
bearing / yield:
Ø The
main aim of bringing tea plant into bearing is to shape the plant into a
permanent frame which is low, broad, heavily branched and capable of producing
a large number of shoots (Tea Table), culminating in a high leaf yield.
Ø Formative
pruning is mostly used in tea culture. The axillary buds are stimulated by
cutting-off the main stem to a certain height, thereby forming a wide frame /
canopy.
Ø In
formative pruning, the first operations come up in the nursery. The main stem
is cut-off at an height of 10 – 20 cm from the ground, with secateurs. The
second pruning is done, on the field, at an height of 30 cm while the third is
carried out when the young tea plant attains 40 cm without any plucking being
made. These operations form the tea table.
Plucking:
Ø This
is the periodic harvesting. The pluckers are equipped with an apron or
waterproof against damp conditions and rains.
Ø Plucking
may be carried out manually (by hand) or mechanically (tea harvesters)
Ø The
young shoots that appear above the plucking (tea) table is plucked
Ø The
harvests in tea consist of a bud and 2 – 3 leaves
Ø Harvests
in tea is to strike a balance between yield and quality.
Ø The
chemical elements that determine quality in tea are found in greater quantity
in the young shoots.
Ø Never
pluck non-adult shoots (buds and buds + 1 leaf) in order to obtain a short
plucking round and a high yield.
Ø Plucking
round depends on climatic conditions. The average plucking round is 10 days.
Ø The
plucking extremes are 6 – 14 day. Never adopt a fixed plucking round.
Ø Never
pluck shoots under the plucking table
Ø Pluck
the dormant bud in order to encourage the axillary buds to open
Ø Pluck
an minimum of 75% of good leaves (bud + 2 leaves, bud + 3 leaves and dormant
buds + 1 young leaf).
Ø Only
pluck shoots recommended by the factory head who is responsible for the quality
of the commercial product.
Ø Keep
the plucking table horizontal and parallel to the ground.
Productivity pruning:
Ø Productivity
pruning is carried out when the plucking table rises so high and plucking
becomes practically difficult and thus, yield falls.
Ø The
period of the operation of productivity pruning varies from 2 – 6 years
depending on climatic conditions and clonal materials planted.
Ø This
pruning operation comes up at the end or beginning of rains and is done with a
pruning knife.
Ø The
level of pruning is parallel to the ground and at a predetermined height.
Ø All
branches above the height are cut-off while the frame under this height limit
are left intact.
Regenerative pruning:
Ø When
plucking table becomes to high to perform productivity pruning, regenerative
pruning becomes inevitable.
Ø Regenerative
pruning is carried out at 0.35 m from the ground and tipping is done at
an height of 0.60 m.
Skiffing (cutting into
green wood):
Ø This
is carried out when plucking table rises quickly, becomes very irregular or
damaged by hail or frost.
Ø The
plant is slightly cut back in order to maintain a good yield.
Ø This
type of cutting is rarely required.
Fertilizer requirements
of tea:
Ø Annually
and for a yield of 1000 kg/ha of commercial-grade tea, the plant takes up an
average of 40 – 50 kgN, 7 – 9 kgP and 20 – 25 kgK from the soil.
Ø Leaching
is another avenue of nutrient loss in tea plantations, especially in
mountainous regions.
Ø The
quantity of fertilizer to be applied should be calculated accordingly.
Weeding:
Ø The
young tea plant is very sensitive to weed competition. Regular weeding
(manually or
Ø chemically) becomes compulsory.
Disease and Insect
pests of Tea
Diseases:
- Root
rot (Armillariella mellea, Rosellinia arcuata). Common in forested land.
Ø It
slows down growth of young tea plant
Ø Leaf
chlorosis
Ø Excessive
flowering
Ø Leaf
wilting
Ø Eventual
death of tea plant
- Blister
blight (Exobasidium vexans):
Ø Very
dangerous leaf infection
Ø Translucent
to light brown spots, with pink or red spots at the centre.
Ø Blisters
at the underside of leaves
Ø When
the blisters burst, infection continues.
Ø The
affected shoots later die.
- The
leaf insect pest of tea include:
Ø Homona
coffearia
Ø Urticating
caterpillars
Ø Helopeltis
spp.
Ø Aphids
- The
branch insects pest are:
Ø Xyleborus
fornicatus
Ø Zeuxera
coffeae
Ø Termites
(Neotermes, Glytotermes, Coptotermes)
Ø Mites
(Oligonichus coffeae or red spider)
Tea
Pest Management
• Pest-
Pest is a collective term for a wide range of organisms like insects, mites,
virus, bacteria, algae, fungi, bird and rodent etc. which are noxious,
troublesome and destructive to crops food –supply and human property. In any farming system, insects and mites may
suck out plant juice; bacteria, algae, fungi etc. may invade its tissues and
produce various symptoms; rodent and birds may eat and disappropriate
crop-yield and quality.
• Some
animals and plants like Penicillium fungus, silkworm, honey bee,
predatory insect/animals etc. are directly or indirectly beneficial to human
welfare and are collectively called benefactor.
• Tea
crop protection is an essential component of tea husbandry to safeguard tea
plants from the ravages of a multitude of pest, diseases and other maladies.
About 600 million kg of tea is estimated to be lost annually due to ravages of
multitude of pest, diseases and weeds in the World tea. Had there been no pest
and diseases, the annual production of Bangladesh tea could have been increased
at least 10-15 %.
Bangladesh
Tea Spectrum
• In
Bangladesh tea, so far 29 pest, 12 nematode pests, 1 algal and 19 fungal
diseases and 37 kinds of weeds are fund to be associated. Of these, 2 mite
pests, 6 insect pests, 1 algal diseases and 6 stem and root fungal diseases are
found to be most common.
• Pest
management:
• Pest
management implies the regulation of pest activity by adopting suitable methods
so as to minimize their effects and maximize the activity of benefactors. It is
however a long term process and its success may be obtained through an
effective pest surveillance and efficient monitoring system.
• Today,
the concept of pest management has, considering the pest problem as a past of
whole ecosystem, become a multidimentional system, called Integrated Pest
Management(IPM). The IPM is a cohesive system of selection, integration and
implementation of pest control strategies/methods based on the predicted
economic and socio-ecological consequences.
• Different
pest of tea plant infested by different pest in the world wide
Plant pests % of total number
of pest
Foliage 59%
Stem 24%
Root 13%
Flower 2%
Fruit 1%
Seedlin g 1%
Common
pests in tea culture
v Mite
pest
i)
Red spide mite (Oligonychus coffeae N.
Acarina)
Plants parts attracted:
upper surface of the mature leaves
Nature of damage:
sucking
ii) Scarlet mite (Brevipalpus phoenisis Acarina)
Plants parts attracted:
upper surface of the mature leaves
Nature of damage:
sucking
v Insect
Pests
- Mature and young tea attacking
insects
i) Tea mosquito bug (Helopeltis
theivora W. Hemiplera)
Plants parts attracted:
young leaves and shoots
Nature of damage:
sucking
ii) Termite (Microcerotermes
spp.)
Plants parts attracted:
destruction of hard wood and mature bush
Nature of damage:
feeding
2. Nursery attacking insects
i) Field Cricket (Brachypterypes portensus Orthoptera)
Plants parts attracted:
stems, roots
Nature of damage:
cutting
ii) Tea Jassids (Empocsca
flavescenus F. Hemiptera)
Plants parts attracted:
young leaves and shoots
Nature of damage:
sucking
iii) Tea aphids (Toxophera
aurantii F. Hemiptera)
Plants parts attracted:
young leaves and shoots
Nature of damage:
sucking
3. Seed attacking pests
i) Tea seed bug ( Poecilocoris
latus)
Plants parts attracted:
flowers, seeds, bud
Nature of damage:
sucking
a. Stem and leaf
disease i) Red rust Cephaleuros parasiticus
ii) Branch canker Macrophoma
theicola
iii) Black rot Corticium
theae
b. Root disease i)
violet root rot Sphaerostible repens
c. Seedling
disease i) damping off Pythium spp.
Pest
control strategies
Pest management in any
crop is a long term process and its success is dependent upon the selection,
integration and continued consolidation of both adaptive and technological
strategies of pest control. Pest surveillance and monitoring of pest-invasion are
the prerequisites for successful crop protection.
- Adaptive strategies
- Eco-management: since any
manipulation of the ecosystem may aggravate pest problems, a through
understanding of actions and interactions of the various components of tea
ecosystem is necessary to control pests at an acceptable level.
- Maximizing the natural control
agents: the complete destruction of both injurious and non-injurious
pests, parasites predators is likely to upset the natural balance. Many
weeds and non-injurious pests may provide food and shelter for natarul
enemies of injurious pests. When they will be eradicated minor pests may
be encouraged and provide adverse effects on the ecosystem.
Under the perspective
of adaptive strategy most proven methods of pest control are:
i)
Cultural control method: Many
conventional strategies, such as sanitation, destruction of wild/alternate host
plants, soil tillage and water management, crop rotation and the use of pest
free seed/ planting stocks can be employed to repel or reduce the pest-invation.
ii)
Biological control method: This method
involves the use of beneficial organism (benefactor) such as parasites,
predator, pathogenic fungi, virus for the reduction of injurious pests. The
successful utilization of these method depends on a through understanding of
biology and ecology of the pested benefactor.
iii)
Pest resistant varieties:
B. Technological
strategies:
i)
Mechanical control method: This method
includes capturing, destroying the insect pest by manual operations.
ii)
Chemical control method: This method
includes the use of pesticides to kill or deny the pest’s access to their food.