Factors Affecting Cultivation

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Chapter: Pharmacognosy and Phytochemistry : Cultivation, Collection and Processing of Herbal Drugs

Cultivation of medicinal plants offers wide range of advan-tages over the plants obtained from wild sources. There are few factors to concern which have a real effect on plant growth and development, nature and quantity of secondary metabolites. The factors affecting cultivation are altitude, temperature, rainfall, length of day, day light, soil and soil fertility, fertilizers and pests.


FACTORS AFFECTING CULTIVATION

 

 

Cultivation of medicinal plants offers wide range of advantages over the plants obtained from wild sources. There are few factors to concern which have a real effect on plant growth and development, nature and quantity of secondary metabolites. The factors affecting cultivation are altitude, temperature, rainfall, length of day, day light, soil and soil fertility, fertilizers and pests. The effects of these factors have been studied by growing particular plants in different environmental conditions and observing variations. For example, a plant which is subjected to a particular environment may develop as a small plant which, when analysed shows high proportion of metabolite than the plants attained the required growth. Nutrients have the ability to enhance the production of secondary metabolites, at the same time they may reduce the metabolites as well.

 

Altitude

 

Altitude is a very important factor in cultivation of medicinal plants. Tea, cinchona and eucalyptus are cultivated favour-ably at an altitude of 1,000–2,000 metres. Cinnamon and cardamom are grown at a height of 500–1000 metres, while senna can be cultivated at sea level. The following are the examples of medicinal and aromatic plants indicating the altitude for their successful cultivation (Table below).

 


 

Temperature

 

Temperature is a crucial factor controlling the growth, metabolism and there by the yield of secondary metabolites of plants. Even though each species has become adapted to its own natural environment, they are able to exist in a considerable range of temperature. Many plants will grow better in temperate regions during summer, but they lack in resistance to withstand frost in winter.

 

Table: Optimum Temperature for Drug Cultivation

 


 

Rainfall

 

For the proper development of plant, rainfall is required in proper measurements. Xerophytic plants like aloes do not require irrigation or rainfall. The effects of rainfall on plants must be considered in relation to the annual rainfall throughout the year with the water holding properties of the soil. Variable results have been reported for the production of constituents under different conditions of rainfall. Excessive rainfall could cause a reduction in the secondary metabolites due to leaching of water soluble substances from the plants.

 

Day Length and Day Light

 

It has been proved that even the length of the day has an effect over the metabolites production. The plants that are kept in long day conditions may contain more or less amount of constituents when compared to the plants kept in short day. For example peppermint has produced menthone, menthol and traces of menthofuran in long day conditions and only menthofuran in short day condition.

 

The developments of plants vary much in both the amount and intensity of the light they require. The wild grown plants would meet the required conditions and so they grow but during cultivation we have to fulfill the requirements of plants. The day light was found to increase the amount of alkaloids in belladonna, stramonium, cinchona, etc. Even the type of radiation too has an effect over the development and metabolites of plants.

 

Soil

 

Each and every plant species have its own soil and nutritive requirements. The three important basic characteristics of soils are their physical, chemical and microbiological properties. Soil provides mechanical support, water and essential foods for the development of plants. Soil consists of air, water, mineral matters and organic matters. Variations in particle size result in different soils ranging from clay, sand and gravel. Particle size influences the water holding capacity of soil. The type and amount of minerals plays a vital role in plant cultivation. Calcium favours the growth of certain plants whereas with some plants it does not produce any effects. The plants are able to determine their own soil pH range for their growth; microbes should be taken in to consideration which grows well in certain pH. Nitrogen containing soil has a great momentum in raising the production of alkaloids in some plants.

 

Depending upon the size of the mineral matter, the following names are given to the soil (Table 6.3).

 

Table : Type of soil on the basis of particle size.

 


 

 

Depending upon the percentage covered by clay, soils are classified as under (Table below.).

 

Table : Type of soil on the basis of percentage covered by clay.

 


 

Soil Fertility

 

It is the capacity of soil to provide nutrients in adequate amounts and in balanced proportion to plants. If cropping is done without fortification of soil with plant nutrients, soil fertility gets lost. It is also diminished through leaching and erosion. Soil fertility can be maintained by addition of animal manures, nitrogen-fixing bacteria or by application of chemical fertilizers. The latter is time saving and surest of all above techniques.

 

Fertilizers and Manures

 

Plant also needs food for their growth and development. What plants need basically for their growth are the carbon dioxide, sun-rays, water and mineral matter from the soil. Thus, it is seen that with limited number of chemical elements, plants build up fruits, grains, fibres, etc. and synthesize fixed and volatile oils, glycosides, alkaloids, sugar and many more chemicals.

 

(a) Chemical fertilizers

 

Animals are in need of vitamins, plants are in need of sixteen nutrient elements for synthesizing various com-pounds. Some of them are known as primary nutrients like nitrogen, phosphorus and potassium. Magnesium, calcium and sulphur are required in small quantities and hence, they are known as secondary nutrients. Trace elements like copper, manganese, iron, boron, molybdenum, zinc are also necessary for plant growths are known as micronutrients. Carbon, hydrogen, oxygen and chlorine are provided from water and air. Every element has to perform some specific function in growth and development of plants. Its deficiency is also characterized by certain symptoms.

 

(b) Manures

 

Farm yard manure (FYM/compost), castor seed cake, poultry manures, neem and karanj seed cakes vermin compost, etc. are manures. Oil-cake and compost normally consists of 3–6% of nitrogen, 2% phosphates and 1–1.5% potash. They are made easily available to plants. Bone meal, fish meal, biogas slurry, blood meal and press mud are the other forms of organic fertilizers.

 

(c) Biofertilizers

 

Inadequate supply, high costs and undesirable effects if used successively are the demerits of fertilizers or manures and hence the cultivator has to opt for some other type of fertilizer. Biofertilizers are the most suitable forms that can be tried. These consist of different types of micro organisms or lower organisms which fix the atmospheric nitrogen in soil and plant can use them for their day to day use. Thus they are symbiotic. Rhizobium, Azotobactor, Azosperillium, Bijericcia, Blue-green algae, Azolla, etc. are the examples of biofertilizers.

 

Pests and Pests Control

 

Pests are undesired plant or animal species that causes a great damage to the plants. There are different types of pests; they are microbes, insects, non insect pests and weeds.

 

Microbes

 

They include fungi, bacteria and viruses. Armillaria Root Rot (Oak Root Fungus) is a disease caused by fungi Armil-laria mellea (Marasmiaceae) and in this the infected plant become nonproductive and very frequently dies within two to four years. Plants develop weak, shorter shoots as they are infected by the pathogen. Dark, root-like structures (rhizomorphs), grow into the soil after symptoms develop on plants. The fungus is favoured by soil that is continually damp. Powdery mildew is another disease caused by fungus Uncinula necato on leaves, where chlorotic spots appear on the upper surface of leaf. On fruit the pathogen appears as white, powdery masses that may colonize the entire berry surface. Summer Bunch Rot is a disease in which masses of black, brown, or green spores develop on the surface of infected berries caused by a variety microbes like Aspergillus niger, Alternaria tennis, Botrytis cinerea, Cladosporium herbarum, Rhizopus arrhizus, Penicillium sp., and others.

 

Fomitopsis pinicola (Sw.) P. Karst. Belonging to family Fomitopsidaceae causes a diseases known as red-belted fungus. Several other fungi attacks the medicinal plants, like Pythium pinosurn causes pythium rhizome rot, Septoria digitalis causing leaf spot, little leaf disease by Phywphthora cinnamomi Rands (Pythiaceae), etc.

 

Crown gall disease caused by Agrobacterium tumefaciens (Rblzobiaceae). Galls may be produced on canes, trunks, roots, and cordons and may grow to several inches in diameter. Internally galls are soft and have the appearance of disorganized tissue. The pathogen can be transmitted by any agent that contacts the contaminated material. Galls commonly develop where plants have been injured during cultivation or pruning. Xylella fastidiosa is a bacterium causes Pierce’s Disease, in this leaves become slightly yellow or red along margins and eventually leaf margins dry or die.

 

Many viruses are also reported to cause necrosis of leaves, petioles and stems, they are tobacco mosaic virus, mosaic virus, cucumber mosaic virus, tobacco ring spot virus, yellow vein mosaic, etc.

 

Controlling techniques: Chemical fumigation of the soil, fungicide, bactericide, pruning, proper water and fertilizer management, good sanitation, heat treatment of planting stock, cut and remove the infected parts, geneti-cally manipulating the plants for producing plants to resist fungi and bacteria are practices that are used to prevent or minimize the effects produced by microbes.

 

Insects

 

Ants, they are of different varieties, Argentine ant: Linepi- thema humile, Gray ants: Formica aerata and Formica perpilosa, Pavement ant: Tetramorium caespitum., Southern fire ant: Solenopsis xyloni, Thief ant: Solenopsis molesta, they spoil the soil by making nest and they feed honey dew secreted in plants.

 

Branch and Twig Borer (Melalgus confertus) burrow into the canes through the base of the bud or into the crotch formed by the shoot and spur. Feeding is often deep enough to completely conceal the adult in the hole. When shoots reach a length of 10–12 inches, a strong wind can cause the infected parts to twist and break. The click beetle (Limo-nius canus) can feed on buds. Cutworms (Peridroma saucia) (Amathes c-nigrum) (Orthndes rufula) injures the buds and so the buds may not develop. Leafhoppers (Erythroneura elegantuhi) (Erythroneum variabilis) remove the contents of leaf cells, leaving behind empty cells that appear as pale yellow spots.

 

Oak twig pruners (Anelaphiis spp. Linsley) are known as shoot, twig and root insects that affects the above men-tioned parts.

 

Controlling techniques: Tilling the soil will also affects the nesting sites of ants and help to reduce their popula-tions, collection and destruction of eggs, larvae, pupae and adults of insects, trapping the insects, insecticides, creat-ing a situation to compete among males for mating with females, cutworms can be prevented by natural enemies like, predaceous or parasitic insects, mammals, parasitic nematodes, pathogens, birds, and reptiles,

 

Non insect pests

 

They are divided in to vertebrates and invertebrates. Ver-tebrates that disrupt the plants are monkeys, rats, birds, squirrels, etc. Non vertebrates are, Webspinning Spider Mites (Tetranychuspacificus) (Eotetranychus willamettei) (Tetrany-chus urticae) causes discoloration in leaves and yellow spots. Nematodes (Meloidogyne incognita) (Xiphinema americanutri) (Criconemella xenoplax) produces giant cell formation, dis-turbs the uptake of nutrients and water, and interferes with plant growth, crabs, snails are the other few invertebrates that causes trouble to the plant.

 

Controlling techniques: Construction of concrete ware houses, traps, biological methods, rodenticides, etc.

 

Weeds

 

Weeds reduce growth and yields of plants by competing for water, nutrients, and sunlight. Weed control enhances the establishment of new plants and improves the growth and yield of established plants. The skilled persons have many weed management tools available to achieve these objectives; however, the methods of using these tools vary from year to year and from place to place.

 

Soil characteristics are important to weed management. Soil texture and organic matter influence the weed species that are present, the number and timing of cultivations required, and the activity of herbicides. Annual species, such as puncturevine, crabgrass, horseweed, and Panicum spp., or perennials like johnsongrass, nutsedge, and bermudagrass are more prevalent on light-textured soil while perenni-als such as curly dock, field bindweed, and dallisgrass are more common on heavier-textured soils. Less preemergent herbicide is required for weed control on sandy, light soils, but residual control may be shorter than on clay or clay loam soils. Use low rates of herbicide on sandy soils or those low in organic matter. Clay soils are slower to dry for effective cultivation than sandy loam soils; thus, more frequent cultivation is practiced on lighter soils than heavy soils.

 

Few common weeds are, Bermudagrass, It is a vigorous spring- and summer-growing perennial. It grows from seed but its extensive system of rhizomes and stolons can also be spread during cultivation, Dallisgrass, It is a common perennial weed that can be highly competi-tive in newly planted plants; in established plants area it competes for soil moisture and nutrients. Dallisgrass seedlings germinate in spring and summer, and form new plants on short rhizomes that developed from the original root system. The other weeds are pigweeds Amaranthus spp. pineapple-weed Chamomilla suaveolens, nightshades Solanum spp., etc.

 

Apart from these, Parasitic and Epiphytic Plants like dodder (Cuscuta spp. L.), mistletoe (Phoradendron spp. Nutt.), American squawroot (Conopholis americana), etc., too affects the growth of plants,

 

Controlling techniques: Use of low rates of herbicides: Herbicides are traditionally discussed as two groups: those that are active against germinating weed seeds (preemergent herbicides) and those that are active on growing plants (postemergent herbicides). Some herbicides have both pre-and postemergent activity. Herbicides vary in their ability to control different weed species.

Preemergent herbicides are active in the soil against ger-minating weed seedlings. These herbicides are applied to bare soil and are leached into the soil with rain or irrigation where they affect germinating weed seeds. If herbicides remain on the soil surface without incorporation, some will degrade rapidly from sunlight. Weeds that emerge while the herbicide is on the surface, before it is activated by rain or irrigation, will not be controlled. Postemergent herbicides are applied to control weeds already growing in the vineyard. They can be combined with preemergent herbicides or applied as spot treatments during the growing season. In newly planted plants, selective postemergent herbicides are available for the control of most annual and perennial grasses, but not broadleaf weeds.

 

Frequent wetting of the soil promotes more rapid herbicide degradation in the soil. Herbicide degradation is generally faster in moist, warm soils than in dry, cold soils.

 

General Methods of Pest Controls

 


 

Other Factors that Affect the Cultivated Plants

 

Air Pollution

 

Chemical discharges into the atmosphere have increased dramatically during this century, but the total effect on plants is virtually unknown. It has been demonstrated that air pollutants can cause mortality and losses in growth of plants. Nearly all species of deciduous and coniferous trees are sensitive to some pollutants. There are many chemicals released into the atmosphere singly and as compounds. In addition, other compounds are synthesized in the atmosphere. Some chemicals can be identified through leaf tissue analysis and by analysing the air. Generally, pollution injury first appears as leaf injury. Spots between the veins, leaf margin discoloration, and tip burns are common. These symptoms can also be influenced by host sensitivity, which is effected by genetic characteristics and environmental factors.

 

Herbicide

 

Herbicides should be handled very carefully; misapplication of herbicides can often damage nontarget plants. The total extent of such damage remains unclear, but localized, severe damage occurs. Symptoms of herbicide injury are variable due to chemical mode of action, dosage, duration of expo-sure, plant species, and environmental conditions. Some herbicides cause growth abnormalities such as cupping or twisting of foliage while others cause foliage yellowing or browning, defoliation, or death.

 

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