Introduction
Cultivation of plants to get medicinal benefits from it requires intensive care and management. The condition and duration of cultivation is depending on quality of medicinal plant required. Cultivation involves precise control of various factors like rainfall, irrigation, fertilizers, pests, humidity, light and temperature. Proper cultivation helps to get better quality and purity of crude drugs. The properly cultivated plants have good morphological characters and appropriate quantity of chemical constituents.
Advantages of cultivation
- Production of good quality plants
- Better morphological characteristics
- Appropriate content of active chemical constituents
- Have better therapeutic activity
- Good cultivation practices can minimize accidental adulteration
- Regular supply of crude drug is possible
- It helps to use modern technologies like mutation and hybridization
Disadvantages of cultivation
- High cost
- Cultivation is difficult for wild source plants
- Difficult to tackle ecological imbalances which leads to loss
Factors affecting cultivation
Cultivated medicinal plant have advantages over the plant obtained from wild sources. There are various factors which affect the plant growth, development, nature and quantity of secondary metabolites. The factors affecting cultivation are Altitude, Temperature, Rainfall, Day length and day light, Soil, Soil fertility, Fertilizers and manures, Pests and pest control and Plant hormones effect.
Altitude
Altitude is an important factor in cultivation of medicinal plants. For example, tea, cinchona cultivated favourably at an altitude of 1000 to 2000 meters. Cinnamon and cardamom grow favourably at altitude of 500 to 1000 meters.
| Plants | Altitude (meters) |
| Clove | Up to 900 |
| Cardamom | 600 to 1600 |
| Camphor | 1500 to 2000 |
| Cinchona | 1000 to 2000 |
| Tea | 1000 to 2000 |
| Coffee | 1000 to 2000 |
| Saffron | Up to 1250 |
Temperature
Temperature is a crucial factor to enhance the cultivation of medicinal plants. Excess temperature or frost can affect medicinal plants adversely. Every species has adopted their own natural environment to grow. The yield of secondary metabolites could be increased or decreased by change in temperature. For example, camphor can not grow in cold temperature but saffron needs only cold temperature to grow.
| Plants | Optimum Temperature (0F) |
| Cardamom | 50 to 100 |
| Cinchona | 60 to 75 |
| Coffee | 55 to 70 |
| Tea | 70 to 90 |
Rainfall
Proper rainfall is required for proper development of plant. Variations in rainfall results in variable production of medicinal plant. Excessive rainfall can cause reduction in secondary metabolites due to leaching of water soluble substances from plant. Most of the plants require proper irrigation or sufficient rainfall for desirable development. Only xerophytic plants do not require proper irrigation for their development.
Day length and day light
The concentration of active chemical constituent depends on the day length. For example, peppermint produce menthone, menthol and traces of menthofuran in long day condition but if plant grown in short day, it contains only menthofuran. The intensity of light also affects the metabolites of plant. For example, the daylight can increase the amount of alkaloids in belladonna, cinchona, etc.
Soil
Soil is the most important factor as it supports growth of all plants. Every plant species has its own soil and nutritive requirements. Soil provides mechanical support, water and essential food for the development of plants. There are three important characteristics of soils namely physical, chemical and microbiological. Soil contains air, water, mineral matters and organic matters.
Good quality of soil for plant growth should have half of the pore spaces filled with water and half of the pore spaces with air. The soil containing less than 0.5% of organic matter is described as poor soil. The soil containing 0.5 to 1.5% organic matter considered as intermediate soil. The soil containing organic matter between 1.5 to 5.0% describe as rich soil. The pH of soil ranging from 6.5 to 7.5 considered as favourable for plant growth.
Particle size influence the water holding capacity of soil. The type and amount of minerals in soil plays an important role in plant growth. Depending upon particle size of mineral matters there are various types of soils.
| Type of soil | Particle size (diameter in mm) |
| Fine clay | Less than 0.002 |
| Coarse clay or slit | 0.002 to 0.02 |
| Fine sand | 0.02 to 0.2 |
| Coarse sand | 0.2 to 2.0 |
| Stone | More than 2.0 |
Depending upon percentage of clay soil is classified as follows,
| Type of soil | Percentage of clay |
| Clay | More than 50% of clay |
| Loamy | 30 to 50% of clay |
| Slit loam | 20 to 30% of clay |
| Sandy loam | 10 to 20% of clay |
| Sandy soil | More than 70% sand |
| Calcareous soil | More than 20% of lime |
Soil fertility
The capacity of soil to provide nutrients in adequate quantity and in balanced proportion and provides suitable medium for plant growth is known as soil fertility. If cropping is done without fortification of soil with plant nutrients, soil fertility gets lost. Soil fertility can be maintained by adequate use of animal manures, nitrogen fixing bacteria or chemical fertilizers.
Fertilizers and manures
Plant needs food for their growth and development. They basically require carbon dioxide, sunrays, water and mineral matter from the soil for their growth. Plants need 16 nutrients for growth and metabolism. Depending on the quantity required nutrients are classified as micronutrients and macronutrients. Carbon, hydrogen, nitrogen, sulphur, oxygen, calcium, phosphorus, potassium and magnesium are the macronutrients. Copper, zinc, boron, molybdenum, iron, manganese, and chlorine are the micronutrients. Plant gets carbon, hydrogen, oxygen from air and water. Every element performs specific role in growth and development of plant. Deficiency of these nutrients may cause disease in plants.
These elements can be supplied to the plant with the help of chemical fertilizers and manures. Commonly used chemical fertilizers are diammonium phosphate, urea, NPK. Manures are mixed with soil which enhances its nutritional value, thus it results in increase in crop yield. There are three types of manures, farm yard manure (FYM), composite manure, green manure.
Pests and pest control
Pests are the undesired plant or animal species which causes damage to the plant. Pesticides are the chemical substances derived from natural or synthetic sources. There are different types of pests, microbes, insects, non-insects and weeds. These pests affect plant growth and development and cause disease which results in poor quality and yield of crude drugs. Hence pest control is important for proper growth and development of plant.
| Pests | Controlling techniques |
| Microbes: · Fungi: Armil-laria mellea · Bacteria: Xylella fastidiosa · Virus: Mosaic virus | Chemical fumigation of soil, fungicide, bactericide, pruning, etc. |
| Insects: Ants, twig borer, cut worms, leaf hoppers, etc. | Tilling of soil, collection and destruction of eggs, insecticides, etc. |
| Non-insect pests: Monkeys, rats, birds, spider, nematodes, etc. | Construction of concrete warehouses, traps, rodenticides, etc. |
| Weeds: Bermuda grass, runners, American squawroot, etc. | Use of herbicides. |
Methods of pest control
There are different types of methods used to control the pest.
| Methods | Techniques |
| Agriculture | Crop rotation, deep ploughing, plant breeding, etc. |
| Mechanical | It involves manual labour along with different devices for collection and destruction of pests, hand picking and trapping of insects, destruction of eggs and larva, pruning, burning, etc. |
| Chemical | Insecticides: to control insect (DDT), malathione |
| Fungicides | To control fungus (chlorophenols) |
| Herbicides | To control weeds (sulphuric acid) |
| Rodenticides | To control rodents (warfarin) |
| Biological control | Use of another living organism to reduce the activity of pests and other pathogens. |
| Natural pest control | Tobacco, nux vomica, pyrethrum, neem and citronella. |
Plant growth hormones
Plant growth hormones modify the plant growth and development either by promoting or inhibiting the growth. Phytohormones are mainly classified under five classes,
- Auxins (cell elongation)
- Gibberellins (cell elongation + cell division- translated into growth)
- Cytokinins (cell division)
- Abscisic acid (abscission of leaves and fruit)
- Ethylene (fruit ripening)
Types of cultivation
There are two methods of cultivation of medicinal plants, sexual cultivation and asexual cultivation.
Sexual cultivation (seed propagation)
This is the traditional method of plant cultivation. The seeds used in this type of cultivation should be capable of high germination rate, free from diseases and insect. The seeds to be stored in a cool and dry place to maintain their germinating power. A chemical treatment is given to enhance the germination. Commonly used chemicals are gibberellins, cytokinins, ethylene, thiourea, potassium nitrate or sodium hypochlorite.
Asexual method (vegetative propagation)
In this method, instead of seed a vegetative part of plant like stem or root is used. Asexual method further contains three types as follows.
Natural method
In this method vegetative part of the plant is directly used to grow the plant. For example,
- Bulb: squill, garlic
- Tubers: jalap, potato
- Rhizomes: ginger, turmeric
- Stolons: liquorice
Artificial methods
In this method plant is grown by using vegetative part but with some modifications. The techniques used are,
Aseptic method of micropropagation (tissue culture)
In this method, plants are developed in an artificial medium under aseptic conditions from fine pieces of plants like single cells, callus, seeds, seeds, embryos, root tips, shoot tips, pollen grains, etc.
Methods of irrigation
Different types of plants have different requirement of water. By studying the availability and requirement of water for a plant, method of irrigation is to be choosen. Such methods are given below.
- Hand watering: economical and easy
- Flood watering: easy to operate, more wastage of water
- Boom watering: easy to operate, restricted use
- Drip irrigation: scientific, easy but costly
- Sprinkler irrigation: costly, good results
Conclusion
Plants contain higher concentration of active chemical component when they are cultivated scientifically. There are various factors that affect the cultivation drugs from natural origin. Using the scientific approach one can get best quality drugs from the plant.
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