Spirulina Commercial Cultivation: A Sustainable Superfood Solution

In recent years, there has been a growing interest in sustainable and nutritious food sources to meet the demands of an ever-expanding global population. One such superfood that has gained significant attention is spirulina. Spirulina, a blue-green algae, is not only packed with essential nutrients but also considered an environmentally friendly crop due to its efficient cultivation methods. In this article, we will delve deeper into the commercial cultivation of spirulina, including the intricacies of culture medium preparation, potential buyers, and its transformative impact on the food industry.

The Basics of Spirulina

Spirulina, scientifically known as Arthrospira platensis and Arthrospira maxima, is a microscopic, spiral-shaped, photosynthetic organism that thrives in warm, alkaline water bodies like lakes and ponds. Its rich nutrient profile includes high-quality protein, vitamins, minerals, antioxidants, and essential fatty acids.

Commercial Cultivation Process

Selection of Growth Environment:

Spirulina cultivation begins with the careful selection of a suitable growth environment. Commercial operations often utilize man-made open raceway ponds or closed-loop photobioreactors. These systems provide controlled conditions such as temperature, pH levels, and light exposure.

Culture Medium Preparation:

Preparing the culture medium is a critical step in spirulina cultivation. It typically consists of water, carbon dioxide, and nutrients. Nutrient sources include nitrate and phosphate salts, trace minerals, and in some cases, organic matter like urea. The composition and quality of the culture medium play a pivotal role in spirulina's growth and nutritional content.This newly formulated medium (RM6) contains  

Super phosphate (1.25 g l−1), 

Sodium nitrate (2.50 g l−1), 

Muriate of potash (0.98 g l−1), 

Sodium chloride (0.5 g l−1), 

Magnesium sulphate (0.15 g l−1), 

Calcium chloride (0.04 g l−1), 

and Sodium bicarbonate

 (commercial grade) 8 g l−1 for raising PH to 9.It also provides carbon source.

Inoculation:

Spirulina cultivation starts by introducing a starter culture into the prepared growth medium. This culture rapidly multiplies as it absorbs nutrients from the water, leading to a dense population of spirulina cells.

Nutrient Supply:

Spirulina requires a balanced supply of nutrients like nitrogen, phosphorus, potassium, and essential trace minerals. These are carefully monitored and adjusted to ensure optimal growth. Regular agitation of medium is required for uniform distribution of the nutrients, prevent clumping of cells.

Light Exposure:

Spirulina is photosynthetic, requiring adequate light for growth. Natural sunlight or controlled artificial light sources, like LED panels, are used to maintain optimal light exposure throughout the cultivation cycle.

Harvesting:

Spirulina is typically ready for harvest in 5-10 days, depending on environmental conditions and growth rates. Harvesting is often done through filtration or centrifugation, separating the spirulina biomass from the culture medium. Conventionally 500 nylon  mesh fabric  is used to harvest fresh Spirulina through filtration.

Potential Buyers and Market Trends

The spirulina market has seen substantial growth in recent years, driven by increased consumer awareness of its health benefits and sustainable production methods. Potential buyers and markets for spirulina include:

Nutritional Supplements Industry:

Spirulina is a popular ingredient in nutritional supplements, providing consumers with a convenient way to incorporate its nutrient-rich profile into their diets.

Food and Beverage Industry:

Spirulina is used in a variety of food products, including energy bars, smoothies, and pasta. Its natural blue-green color also finds application in natural food coloring.

Aquaculture:

Spirulina is utilized in aquaculture as a feed supplement, enhancing the nutritional content of fish, Pearl oysters and shrimp.

Health and Wellness Products:

Spirulina is a key component of health and wellness products, including detoxifying cleanses, energy boosters, and dietary powders.

Beauty products: Spirulina used in Face packs.

Challenges and Future Prospects

Despite its numerous advantages, commercial spirulina cultivation faces challenges such as contamination, temperature control, and scalability. Researchers are continuously working to optimize cultivation methods and address these issues.

In conclusion, spirulina's commercial cultivation offers a sustainable solution to the growing demand for nutrient-rich food sources. Its impressive nutrient profile, minimal environmental footprint, and adaptability make it a key player in the quest for a more sustainable and nourishing food future. With ongoing research and technological advancements, spirulina is poised to revolutionize the food industry and contribute to a healthier planet while meeting the demands of a discerning global market.

Micronutrients in plants

 Micronutrients, or trace elements, are required in relatively small amounts (equal to or less than 0.1 mg per gram of dry matter) by plants. Iron, manganese, copper, molybdenum, zinc, boron and chlorine have been established as micronutrients.

 Iron: Plants obtain iron in the form of ferric ions (Fe3+). It is required in larger amounts in comparison to other micronutrients. Functions: It is an important constituent of proteins like ferredoxin and cytochromes, involved in transfer of electrons. It is reversibly oxidised from Fe2+ to Fe3+ during electron transfer. It activates catalase. Though iron is not a constituent of chlorophyll, yet it is closely concerned with it and probably it plays a role as a catalyst. 

Symptoms of iron deficiency: Lack of mobility accounts for iron deficiency first developing in younger leaves. Chlorosis of the leaves is a typical symptom of iron deficiency. Initially, the intravenous regions of the leaves become chlorotic and on prolonged deficiency, veins also become chlorotic.

 Manganese: It is absorbed in the form of manganous cation (Mn2+). Functions: This element is an activator for a number of enzymes particularly involved in dehydration in the splitting of water to liberate oxygen during photosynthesis. It is also involved in nitrogen metabolism. 

Symptoms of manganese deficiency: Plants deficient in manganese show chlorosis and grey spots on leaves. 

Zinc: Plants obtain zinc as (Zn2+) ion. Functions: It activates various enzymes, especially carboxylases. It is required for the synthesis of auxin. 

Symptoms of zinc deficiency: The deficiency symptoms of zinc are malformed leaves, inter-veinal chlorosis in leaves, and stunted growth. The deficiency also results in a reduction in size of internodes and consequent rosette type of growth. 

Copper: It is absorbed as cupric ion (Cu2+). 

Functions: Copper is a component of several enzymes, such as polyphenol oxidase, ascorbic acid oxidase and, thus, plays a major role in plant metabolism. It is a component of plastocyanin, a compound involved in the electron transport in photosynthesis. 

Symptoms of copper deficiency: The young leaves exhibit necrosis at the tip, and then in the margins, resulting in the withered appearance. In fruit trees, it causes dieback of shoot, where leaves wither and fall and bark becomes rough and splits, exuding gummy substances. 

Boron: It is absorbed as BO3 3-, B4O7 2-. Functions: Boron is required for uptake and utilisation of Ca2+, membrane function, pollen germination, cell elongation, and cell differentiation. Boron is also involved in the translocation of carbohydrates. Symptoms of boron deficiency: The deficiency of boron results in death of root and shoot tips, loss of apical dominance, abscission of flowers, small size of fruits, absence of root nodules in leguminous plants, and stunted growth.

 Molybdenum: Plants obtain it in the form of molybdate ion (MoO4 2–). Functions: Molybdenum plays an important role in the nitrogen metabolism of plants, especially in the reduction of nitrate. It is a constituent of the enzyme nitrate reductase. 

Symptoms of molybdenum deficiency: Molybdenum deficiency may cause nitrogen deficiency, as it is a component of enzymes involved in nitrogen metabolism. Plants deficient in molybdenum show slight retardation of growth, inter-veinal chlorosis, etc. 

Chlorine: It is absorbed in the form of chloride anion (Cl–). Functions: With Na+ and K+, it helps in determining solute concentration and anion-cation balance in cells. Chlorine may be required for cell division in both leaves and roots. It is essential for water-splitting reaction in photosynthesis, which leads to oxygen evolution. Symptoms of chlorine deficiency: Chlorine deficiency in plants results in wilted leaves, stunted root growth, and reduced fruiting.

Macronutrients in plants

 Macronutrients Macronutrients are required in relatively large amounts by plants. These are carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur, potassium, calcium, magnesium and silicon. Carbon, Hydrogen and Oxygen: They are not minerals in origin, but are important structural constituents of protoplasm and other organic compounds. Of them, carbon is taken in as CO2 from air. Hydrogen is released from water during photosynthesis. Oxygen is generated within the plant during photosynthesis and is also absorbed in molecular form from air.

 Nitrogen: This is the mineral element required by plants in greatest amount. The chief source of nitrogen is the soil. It is absorbed as NO2 –, NO3 –, or NH4 + . This is required by all parts of a plant, NO2 –, NO3 – particularly the meristematic tissues. 

Functions: Nitrogen is an essential constituent of different proteins, nucleic acids, vitamins and hormones. Symptoms of nitrogen deficiency: The common symptom of nitrogen deficiency is chlorosis, which is yellowing of leaves. The symptom appears first in mature leaves and lastly in young leaves. Due to reduction in protein, plant growth remains stunted and lateral buds remain dormant. As a result cereals show wrinkling of grains. The nitrogen deficient plants develop purplish colouration due to the synthesis of pigment other than chlorophyll, like anthocyanin.

 Phosphorus: Plants absorb phosphorus from soil in the form of phosphate ions (either as H2PO4 – or HPO4 2–). 

Functions: Phosphorus is a constituent of plasma membrane, certain proteins, all nucleic acids and nucleotides, and is required for all phosphorylation reactions. It plays an important role in the energy transfer reactions. 

Symptoms of phosphorus deficiency: Deficiency of phosphorus causes delay in seed germination, stunted growth and results in the development of purple or red spots on leaves, premature fall of leaf and flower buds. 

Potassium: It differs from all other macronutrients in not being a constituent of any metabolically important compound. It is absorbed as potassium ion (K+). In plants, this is more abundant in meristematic tissues, buds, leaves and root tips. 

Functions: Potassium is involved in many of the physiological processes like respiration, photosynthesis, chlorophyll and protein synthesis and stomatal movement. Symptoms of potassium 

deficiency: The deficiency of potassium induces scorched leaf tips, shorter internodes, dieback, chlorosis in inter-veinal areas, loss of apical dominance, bushy habit, loss of cambial activity, plastid disintegration and increase in rate of respiration. Calcium: Plant absorbs calcium from the soil in the form of calcium ions (Ca2+). 

Functions: Calcium is required for the formation of calcium pectinate, which is the constituent of the middle lamellae in the cell walls. Meristematic and differentiating tissues require it. Calcium is also used in the mitotic spindle during cell division. It accumulates in older leaves. It is involved in the normal functioning of cell membranes. It activates certain enzymes and plays an important role in regulating metabolic activities. Symptoms of calcium deficiency: The deficiency of calcium results in stunted growth, necrosis of young meristematic regions, such as root tips or young leaves.

 Magnesium: It is absorbed by the plants in the form of divalent Mg2+. Functions: It activates enzymes in respiration and photosynthesis, and the synthesis of DNA and RNA. Magnesium is a constituent element of chlorophyll and maintains ribosome structure. 

Symptoms of magnesium deficiency: Magnesium is readily mobile and when its deficiency occurs, it is apparently transferred from older to younger leaves, where it can be reutilised in growth processes. As a result, deficiency symptoms develop first in older leaves. Deficiency of magnesium induces chlorosis between the leaf veins and necrotic or purple coloured spots on older leaves. Magnesium deficiency may cause premature leaf abscission. Sulphur: Plants obtain sulphur in the form of sulphate (SO4 2–). Sulphur is present in two amino acids, cysteine and methionine, and is the main constituent of several coenzymes, vitamins (thiamine; biotin; CoA) and ferredoxin.

 Functions: Sulphur increases the root development. It also increases the nodule formation in legumes. Symptoms of sulphur deficiency: The deficiency of sulphur causes chlorosis of younger leaves, stunted growth and anthocyanin accumulation. These symptoms are essentially similar to those of nitrogen deficiency because sulphur and nitrogen are constituents of proteins.

Fabaceae family

 Fabaceae This family was earlier known as Papilionoideae. The members of this family are commonly called legumes or pulses and the family contains some of our most valuable food crops. 

Vegetative Characters

 Habit: Plants are herbs, shrubs, trees or climbers. 

Root: Tap root system, much branched and with bacterial nodules.

 Stem: Erect or twin, branched and angular or cylindrical Leaves: Normally compound, usually trifoliate, modified partly or wholly into tendril with pulvinate leaf base.

 Floral Characters Inflorescence: Usually a raceme, rarely solitary axillary. 

Flowers: Pedicellate, zygomorphic, hermaphrodite and complete. 

Calyx: Sepals five, gamosepalous, imbricate aestivation. 

Corolla: Petals five, polypetalous, the posterior one large and outermost, the next two lateral ones (wings) and two anterior and innermost ones united (keel or carina), aestivation descending imbricate.

 Androecium: Stamens ten, diadelphous (9+1), introse, basifixed and dithecous. 

Gynoecium: Monocarpellary, ovary superior, placentation marginal with many ovules, style long slightly bent at the apex, flattened, stigma simple or capitate. Fruit: Legume, indehiscent; seed: exalbuminous with large embryo. 

Economic Importance The family provides various types of pulses, medicines, fibres, timbers, dyes and plants for gardens. 1. The fruits and seeds of gram (Cicer arietinum), pea (Pisum sativum), arhar (Cajanus cajan), sem (Dolichos lablab), moong (Phaseolus radiatus), soyabean (Glycine max) are rich in protein, and are used as vegetables and pulses. 2. The edible, oily seed of groundnut (Arachis hypogea) are used for food and as a source of oil. 3. The fresh juice of ratti (Abrus precatorius) leaves is said to be useful in leucoderma. Seeds of this plant have remarkably uniform weight. Seeds of Abrus precatorius were used by goldsmiths as standard weights for weighing gold and silver in previous time. 4. Muliathi (Glycyrrhiza glabra) is considered demulcent (soothing to irritated membranes), expectorant (loosening and helping to expel congestion in the upper respiratory tract), and stimulates mucous secretions of the trachea. 5. The juice of ‘agast’ (Sesbania grandiflora) flowers is believed to be beneficial in improving eyesight. 6. Sunn hemp (Crotalaria juncea) yields fibres, which are used for making twine and cord, mat, canvas, nets, sacks, etc. 7. Shisham (Dalbergia sissoo) and Indian rosewood (D. latifolia) yield a dye. 8. The plants of Lathyrus, Clitoria, Sesbania, and Erythrina (Indian coral tree) are grown for ornamental purposes. 

Liliaceae family

 This family is commonly known as the Lily family. It is a characteristic representative of monocotyledonous plants. It includes about 250 genera and 4000 species, distributed worldwide. About 200 species are available in India. 

Vegetative Characters Habit: Plants mostly herbs with perennating rhizome or bulb, a few climbers (Asparagus and Smilax), Yucca and Aloe are xerophytic. 

Root: Fibrous, tuberous in Asparagus. Stem: Solid or fistular, underground rhizome, bulb or corm, aerial-climbing or erect and may have phylloclades. Leaves: Radical or cauline, exstipulate, alternate, opposite or whorled, sessile or petiolate with sheathing base, venation parallel, reticulate in Smilax. In Asparagus, the leaves are reduced to minute scales (cladode). 

Allium cepa 

Floral Characters

 Inflorescence: It is variable, generally solitary axillary, panicled raceme or cymose umbel. Flower: Pedicellate, actinomorphic or zygomorphic, hermaphrodite or unisexual in Smilax and Ruscus, hypogynous, complete, rarely incomplete, trimerous rarely bi-or tetramerous; 

Perianth: Six in two whorls, scarious or membranous, polyphyllous or gamophyllous, petaloid or sepaloid, valvate aestivation. 

Androecium: Stamens six arranged in two whorls, polyandrous, may be epiphyllous and opposite to perianth lobes, filament long, anther dithecous, introrse or extrorse, versatile or basifixed.

 Gynoecium: Tricarpellary, syncarpous, ovary superior, trilocular, axile placentation, style simple, stigma trilobed.

 Fruit: Berry or capsule. Seed: Endospermic.

Economic Importance 1. Bulbs of onion (Allium cepa), garlic (A. sativum) are used as flavouring agents and food. Young shoots and tubers of Asparagus are used as food. 2. Roots of Smilax yield sarsaparilla, which is used as blood purifier. 3. Garlic (Allium sativum) has antiseptic and bactericidal characters. 4. Onion (Allium cepa) is useful in constipation and diarrhoea. 5. Aloin, a purgative is obtained from Aloe vera; rat poison from Urginea and Scilla. 6. The dried corms of Colchicum autumnale yield colchicine, which is used in cytology for doubling the number of chromosomes (polyploidy). 7. Asparagus, Dracaena, Aloe, Ruscus, Smilax, lilies and tulips are used as ornamentals. 8. Fibres are obtained from the leaves of Yucca gloriosa and Phormium tenax. 

Solanaceae family

 It is a large family, commonly called ‘potato family’ with 90 genera, and 2000 species including 60 from India. It is widely distributed in tropics, subtropics and even temperate zones. 

Vegetative Characters

 Habit: Plants are herbs or undershrubs and some of them are climbers.

 Root: Taproot, well developed, branched. Stem: Erect, branched, herbaceous or woody, solid, cylindrical, hairy or glabrous. 

Leaves: Cauline or ramal, simple, exstipulate, petiolate or sessile, arranged alternately, rarely opposite, pinnatisect in tomato, unicostate, reticulate venation. Floral Characters Inflorescence: Solitary, axillary, umbellate or helicoid cyme as in Solanum.

 Flower: Bracteate or ebracteate, pedicellate, complete, hermaphrodite, pentamerous, actinomorphic and hypogynous.

 Calyx: Sepals five, gamosepalous, tubular or campanulate, persistent, green or coloured, hairy. 

Corolla: Petals five, fused, tubular or infundibuliform, aestivation valvate or imbricate, coloured. 

Androecium: Stamens five, epipetalous, anther introrse, dithecous, basifixed or dorsifixed, filament deeply inserted in corolla tube. 

Gynoecium: Bicarpellary, syncarpous, ovary superior, obliquely placed, placentation axile, with many ovules in each locule, style simple, stigma bifid or capitate. Fruit: Capsule or berry with endospermic flat seeds.

Economic Importance 

1. The family includes many species cultivated for their edible fruits or tubers, such as the tomato, potato, eggplant and chilli pepper. 2. Deadly nightshade (Atropa belladonna) yield belladona for relieving pain externally, cough and excessive perspiration internally and atropine for dilating pupil. The root is the basis of the principal preparations of belladona. 3. Tobacco comes from the dried and cured leaves of Nicotiana tabacum. It is chewed, smoked or snuffed. Tobacco is intoxicant and stimulant but is habit forming and increases the incidence of heart trouble, lung cancer, and gum cancer, impotency in males and infant deformities in smoking mothers. Tobacco contains the alkaloid nicotine, a powerful neurotoxin that is particularly harmful to insects. 4. Henbane (Hyoscyamus niger) plant contains a relatively high concentration of alkaloids primarily atropine, hyoscyamine and scopolamine. It is used extensively as a sedative and pain killer and is specifically used for pain affecting the urinary tract, especially when due to kidney stones. 5. Roots of Ashwagandha (Withania somnifera) are used to cure rheumatism and general weakness. 6. Thornapple (Datura stramonium) gives an alkaloid called stramonium for relaxing bronchial muscles. 7. Some plants like night jasmine (Cestrum nocturnum), Poorman’s orchid (Schizanthus pinnatus), Petunia, are grown in garden for their beautiful flowers. 

Dispersal of Fruits and Seeds

 

The seeds or fruits where seeds are enclosed must be dispersed a certain distance from the “mother plant” so that they can produce effective seedlings. The reason for doing this is to avoid competing for the necessary resources such as water, nutrients or sunlight. 

Self dispersal mechanism (Autochory)

 Some fruits at maturity burst with a jerk and their fruit wall opens suddenly. Then the seeds are scattered here and there. This mechanism is also called explosive mechanism. In legumes, e.g. Abrus, pea (Pisum sativum), the fruit breaks into two valves, which twist spirally to throw the seeds. In Geranium, the ripe fruit breaks into five one seeded parts (cocci), each with one style. The styles bend upwardly and throw the seeds away. In case of balsam, when the fruit matures it bursts suddenly and the fruit wall splits into two valves, which roll up inwards, as a result the seeds are ejected with a great force and are dispersed to distant places. Dry and capsular fruits of Ruellia also burst suddenly, when they come in contact with water, i.e. after a shower of rain. The seeds are provided with jaculators or curved hooks, which are hygroscopic in nature. Getting water they straighten out suddenly and seeds come out in a jerk with a loud noise. 

Dispersal by Wind (Anemochory) Wind is one of the best carriers of seeds to distant places. Such seeds and fruits are having some morphological adaptations like wings, hairs, pappus etc., which are helping in dispersal mechanism. They are described as follows:

 (a) Light weight seeds: Very small, dry seeds of orchids and grains of grasses are easily carried by wind because they arc very light in weight. 

(b) Wings: The wing like membranous outgrowth from the pericarp of fruits and seeds help them to float in air and are carried to distant places, e.g. Acer, Dipterocarpus, Hopea, Shorea (fruits), Tecoma, Moringa (seeds). 

(c) Parachute mechanism: The fruits of family Asteraceae have persistent sepals modified into hairy structures called pappus. The fruit is known as cypsella. When the fruit matures, it opens in an umbrella like fashion and becomes very light due to pappus and float in air current easily. The hairy pappus is hygroscopic in nature. Whenever the fruits with pappus happen to pass through humid areas, they come down just like parachutist landing on the ground. Here, this mechanism is called parachute mechanism, found in sunflower (Helianthus), marigold (Tagets), etc. 

(d) Hairs: In Alstonia, madar (Calotropis) and cotton (Gossypium) a dense coating of hairs covers the testa of seeds. These hairy outgrowths help the seeds to float in air.

 (e) Censor mechanism: It is a common method of dispersal in the many seeded fruits like legumes, siliquas and capsules. After maturity when the fruits are violently shaken by strong wind, they burst and the seeds are thrown to a longer distance from the mother plant, this mechanism of dispersal is known as censor mechanism, e.g. prickly poppy (Argemone), thorn apple (Datura), mustard (Brassica), Aristolochia, etc.

 (f) Persistent styles: In Clematis, the fruit has persistent feathery style. It helps in dispersal by air. 

Dispersal by Water (Hydrochory) The fruits and seeds of aquatic plants or plants growing by waterside, need to be carried by water current to a long distance. In such plants the seeds and fruits develop floating devices in the form of spongy or fibrous coats, water-proof or buoyant nature of coats etc. In lotus (Nelumbium nucifera) the etaerio of achenes is embedded in spongy thalamus helps the fruits to float on water. Seeds of many aquatic plants like water lily (Nymphaea), Alisma, etc. are small and light and they can float on water due to the presence of aril, which contain air between the seed coat and embryo. The seed coat is impervious to water, hence protects the embryo inside. Then the latter germinates in favourable conditions at proper place. The fruit of coastal plants like coconut (Cocos nucifera), betel nut (Areca catechu), Devices for animal dispersa.

Dispersal by water etc. has a fibrous mesocarp that is a floating device. The hard endocarp protects the embryo from external injury; so the fibrous fruits are capable of floating long distances. The double coconut (Lodoicoa maldivica) is native to the Seychelles Islands, an island nation off the east coast of Africa in the Indian Ocean. Its fruits reach even to the coastal regions of India.

 Dispersal by Animals (Zoochory) The seeds and fruits, which are carried by the animals including human being, either develop certain structural peculiarities to attract the animals or carried by them unknowingly or they stick to the body of the animals automatically and are thus dispersed. 

(a) Forced zoochory: In this case, the fruit and seeds which are non-edible produce some special devices, which help them to stick to the clothes of men or the body of various animals

(i) Hooks and spines: The fruits and seeds fall on the ground are carried by birds and animals visiting these places. The presence of special devices like hooks, spines on the seed and fruit help them to cling to the fur of birds and animals and are carried to distant places. For instance, fruits of Xanthium and Urena bear curved hooks; Tribulus has sharp and rigid spines.

 (ii) Sticky glands of fruits and seeds: The sticky glands present on the surface of the fruits and seeds, help them to stick to the body of animals and are thus dispersed. Examples are Boerhaavia, Cleome, Datura, etc. 

(b) Compensated zoochory: The fruits have edible pulp. The seeds, if bigger, are thrown away, e.g. mango, apricot. If smaller, the seeds are eaten along with fruits, e.g. tomato (Lycopersicon esculentum), mulberry (Morus alba), guava (Psidium), fig, etc. The small seeds usually come out unharmed from the alimentary canals of animals. As the animals move from place to place, the seeds are also dispersed. It is the top method of dispersal as it is very sure and specific while other modes of dispersal are indiscriminate and less sure. 

(c) Dispersal by man: Man is the most important agent in the dispersal of seeds and his role can be seen in agriculture, horticulture and forestry. He is an agent of dispersal of new varieties of seeds into new areas, which are of economically

Type of inflorescences

 Inflorescence is the arrangement of flowers on the floral axis. The stalk bearing an inflorescence is called peduncle. It arises terminally or in axil and may have a number of flowers. Inflorescence has been classified into two types, viz. racemose and cymose. Besides, there is also a special type of inflorescence, which does not fit into these groups. 

A. Racemose Inflorescence In this type of inflorescence the main axis is unlimited in growth, branched or unbranched. It never terminates into a flower and bears flowers in acropetal succession. The main types are: 

1. Raceme: The main axis, which is elongated, bears stalked flowers, e.g. Brassica (mustard), Raphanus (radish), and dwarf gulmohar.

 2. Spike: This is like raceme but the flowers are sessile or unstalked, e.g. Adhatoda, Achyranthes (chaff-flower).

 3. Spikelet: Very small spike with one or few flowers called florets. Each spikelet has two sterile glumes and one fertile glume-bearing flower called lemma. One bracteole is present just opposite to lemma called palea. Each flower of the spikelet is enclosed by the lemma and palea. Flowers and glumes are arranged in two opposite rows on the spikelet, e.g. paddy (Oryza sativa), wheat (Triticum), and grasses. 

4. Catkin: This is like a spike but differs from latter in having a long and pendulous axis, usually bearing unisexual flowers, e.g. mulberry (Morus alba), Betula and oak.

 5. Spadix: This is a spike with fleshy axis enclosed by one or several large and brightly coloured bracts, called the spathes. Usually female flowers borne at the base and male flowers above, e.g. Musa paradisiaca (banana), Colocasia (aroids). 

6. Corymb: Here the axis is not elongated. It is short and bears stalked flowers in such a manner that they are placed almost at the same level, e.g. candytuft, Lantana. 

7. Umbel: This differs from corymb in having a very shortened and suppressed axis. Flowers have stalks of equal length and form a cluster. It is umbrella like in appearance, e.g. coriander, carrot. 

8. Head or Capitulum: The main axis is a flattened, more or less convex structure, the receptacle, on which the florets (small-flowers) . The whole inflorescence is surrounded by an involucre (a whorl of bracts) and bears only one or two types of flowers: inner disc florets and outer ray florets. The disc florets are usually bisex 

ual whereas the ray florets are unisexual (pistillate) or neuter, e.g. sunflower, zinnia, and marigold. 

Compound Racemose It is an indefinite or indeterminate inflorescence in which the peduncle is branched in a racemose fashion with each branch bearing flowers in acropetal or centripetal fashion.

 1. Panicle: Here the main axis (rachis) is branched. It is also called compound raceme e.g. gold mohur (Delonix), amaltas (Cassia fistula), neem (Azadirachta indica).

 2. Compound corymb: It is a modified corymb. The central axis or rachis is branched and the flowers are borne on these branches in corymb-like manner. It is also called corymb of corymbs, e.g. Pyrus, cauliflower, and candytuft. In cauliflower (Brassica oleracea var. botrytis), the flowers remain undeveloped.

 3. Compound umbel: It is modified umbel where inflorescence axis is branched. The branches arise from a single point in exactly umbel-like manner. These branches bear umbels, which are known as umbellules. A whorl of bracts, called involucre, is present at the base of the parent umbel. Similar whorls of bracts found at the bases of umbellules are called involucels. It is also called umbel of umbels. Compound umbel is characteristic of family umbelliferae, e.g. carrot (Daucus carota), fennel (Foeniculum vulgare, vern. saunf), coriander (Coriandrum sativum, vern. dhania). 

B. Cymose Inflorescence In this type the main axis is always limited in growth and terminates into a flower. They are usually stalked, and borne in a basipetal order. The main types are: 1. Uniparous or monochasial cyme: Here the main axis terminates into a flower and one lateral branch axis develops from its base, which also ends in a flower. There are two types of monochasial cyme: (a) Scorpioid type in which the lateral branches of the axis bearing a terminal flower alternate as in Ranunculus bulbosus, and (b) helicoid type in which each lateral branch bearing a terminal flower develops on the same side forming a helix as in Heliotropium. 

2. Biparous or dichasial cyme: Here two lateral branches develop, on either side of the terminal flower. The lateral branches may again branch similarly, e.g. jasmine (Jasminum), pink (Dianthus).

 3. Multiparous or polychasial cyme: Here more than two lateral branches arise from the base of the apical flower, e.g. madar (Calotropis). 

Special type of inflorescences

1. Hypanthodium: Here the main axis forms a cup-shaped receptacle with a small opening at the top. Flowers are enclosed within the cup in cymose groups. They are unisexual; male flowers are near the ostiole and fertile female flowers at the base of the cup, e.g. fig (Ficus), etc. 

 2. Cyathium: It is a compound inflorescence which looks like a flower. Here the cupshaped structure is formed by the involucre. The reduced flowers (without perianth) are placed on a receptacle. There is one central female flower represented by a single pistil. This is surrounded by a large number of male flowers each represented by a single stamen only. The stalked flowers are subtended by a bracteole. There are also nectar glands on the cup, e.g. Euphorbia. Fig. 5.28 Cyathium inflorescence 

3. Verticillaster: Here one inflorescence consisting of two clusters develops from each of the two opposite axils of the leaves. Each cluster is a dichasial cyme reduced to two scorpioids. Flowers are sessile and appear in a false whorl or vertically around the stem. It is characteristic of the family Labiatae as in sacred basil (Ocimum sanctum), Coleus. 

Leaf modifications

 Besides their usual function of photosynthesis leaves may be modified to perform other functions as well. Some of the important modifications of leaves are: 

1. Tendril: In some plants, the entire leaf or leaflet becomes tendrillar for the purpose of climbing, e.g. sweet and wild peas, and glory lily. 

2. Spines: In a number of plants, leaves become spiny and serve the purpose of defence, e.g. Opuntia, Argemone and Aloe.

 3. Hooks: In Bignonia unguis cati three terminal leaflets of compound leaf are modified into claw like hooks which help the plant in climbing. 

4. Scaly leaves: In onion leaves are in the form of fleshy scales. These are known as scalyleaves. 

5. Pitcher: In some insectivorous plants such as pitcher plant (Nepenthes), the lamina assumes the form of a pitcher with a lid to trap the insects. The inner walls of the pitchers possess a number of digestive glands that secrete a fluid.

 6. Phyllode: When the petiole becomes leaf-like, it is termed phyllodes, e.g. Australian Acacia. 

Stem modifications

 

Modifications are changes in form and function to suit varied needs like storage of food, reproductive growth and survival through unfavourable seasons, vegetative propagation, mechanical support, protection, photosynthesis, etc. Modifications occur in underground, subaerial and aerial stems. Underground Modifications The stems of some plants may remain underground permanently, generally in a dormant state, and produce aerial shoots annually under favourable conditions. They contain sufficient amount of reserve food materials and bear roots and buds. Such stems can be used as ‘seeds’ to produce new plant. 

Rhizome- It is thick, prostrate and branched stem growing horizontally beneath the soil surface. Nodes are marked as dry scars. They bear scale leaves, and branches with buds in their axils. The lower surface of the nodes gives out small slender adventitious roots, e.g. Zingiber officinale (ginger), Curcuma domestica (turmeric), some ferns and many aroids. 

Tuber-  It is the swollen tip of the underground branch. It stores large amount of reserve materials primarily starch, e.g. Solanum tuberosum (potato). The eyes of potato are nodes at each of which 1-3 buds are produced in the axils of small scale like leaves. Cutting of tubers propagates potatoes. Each piece of tuber should contain an eye or node for vegetative propagation. 

Bulb- It is highly reduced stem represented by a small disc like structure upon which numerous fleshy scaly leaves are borne (which store food material). The disc and leaves together are called bulb. On the upper side, disc bears terminal bud surrounded by number of leaves. The axillary buds are present between the axes of leaves. The adventitious roots are borne on the lower side of the disc. Bulbs are of two types: Tunicated. In tunicated bulb, the scaly leaves overlap one another to form concentric circles, e.g. Allium cepa (onion). Scaly or imbricate. The scaly bulb is one in which fleshy scale leaves may lie loose without forming concentric circles on the discoid stem, e.g. Allium sativum (garlic). 

Corm- This is a small underground stem, like the rhizome, but the main axis grows vertical by an apical bud. It bears scale leaves at the nodes in whose axils axillary buds are formed. They form daughter corms. Adventitious buds arise usually from the base of the corm. The corm is much contracted and is principally a storage organ and is much swollen due to the storage of food materials, e.g. Amorphophallus (zamikanda), Crocus sativus (saffron), and Colchicum autumnale. 

Subaerial Modifications In some species, the stem is partly aerial and partly underground. 

Runner- These are produced by creeping herbs. The runners are slender stems that run or creep, over the ground, often for considerable distances. At every node, it is rooted and bears leaves above ground. Axillary buds form new aerial shoots. Many grasses, Oxalis and mint propagate by runners. 

Stolon-  It is a slender lateral branch that arises from the base of the main axis. After growing aerially for sometime the branch arches downwards to touch the ground, where its terminal bud gives rise to a new shoot and roots, e.g. Jasminum (jasmine), Fragaria (wild strawberry). 

 Sucker- It is like a runner but originates from the basal and underground portion of the main stem. It is shorter and stouter than a runner. It grows horizontally for a distance partly below ground, striking roots at the nodes and then emerges obliquely bearing a leafy shoot, e.g. Chrysanthemum. 

Offset- It is stout and short runner like branch, which bends at the tip and gives rise to a rosette of leaves above and roots below, e.g. Pistia, Eichhornia (water hyacinth). 

Aerial Modifications Such modified stems perform unusual functions and are aerial in position. They greatly vary in form but can be distinguished easily by their position in the axil of a leaf or at the apex. 

Stem-tendril- It is a thin, soft, long, wiry, leafless and spirally coiled structure, mostly found in climbers and helps the plant in climbing. When the tendril comes in contact with a support it coils round that holding firmly, and climbs up easily, e.g. Vitis vinifera (grape) – terminal bud modified into tendril. In Passiflora (passion flower) axillary bud is modified into tendril.

 Thorn-  A thorn represents an axillary branch of limited growth. It is hard, often straight, pointed and may be branched. Thorns serve as defensive organs. Examples are seen in Citrus medica (lemon), Aegle marmelos (wood apple), Duranta and Bougainvillea. 

Phylloclade-  It is found in most of the xerophytic plants. In such plants, stem or its branches become modified into flat, fleshy and green leaf like structure with distinct nodes and internodes. The leaves are modified either into spines or scales to reduce transpiration. Phylloclades serve as photosynthetic and storage organs, e.g. Opuntia (prickly pear), Muehlenbeckia (cocoloba), Euphorbia, etc. 

Cladode- A cladode is a phylloclade with one or two internodes only. It resembles a leaf. A cladode arises in the axil of a much reduced scaly leaf, e.g. Asparagus, Ruscus aculeatus.

 Bulbil- It is a special type of multicellular structure, and functions as an organ of vegetative reproduction. It is modified from either a vegetative bud or flower bud. In Dioscorea (wild yam), the bulbil occurs as a single fleshy axillary bud but in case of Oxalis (Indian sorrel), a large number of small bulbils occur on the tip of the tuberous root. 

Root modifications

 

Modifications of Tap Root In many plants the tap root becomes swollen and assumes various forms. This happens due to the storage of food. The modifications may be of the following:

 Fusiform- The root is swollen in the middle and gradually tapers towards both sides, e.g. radish (Raphanus sativus). 

Napiform- The root is spherical, ball-shaped, and wider than high and tapers down, e.g. turnip (Brassica rapa). 

Conical-  The root is cone like, tapering smoothly from base to tip, e.g. carrot (Daucus carota)

 Tuberous- The roots are thick and fleshy, no definite shape, e.g. Mirabilis. 

Kinds of Adventitious Roots Adventitious root may be modified to carry on the storage of food, mechanical support and other vital functions. Some of the main types are: Storage of food

 Tuberous- These roots arise from nodes of stem and become tuberous and fleshy, e.g. sweet potato (Ipomoea batatus). 

Fasciculated- Several fleshy tuberous roots produced grow in clusters at the base of the stem, e.g. Asparagus and Dahlia. 

Annulated- When the root has a series of ring like swelling without any gap, just like larvae of butterfly, e.g. Ipecac. 

Moniliform or beaded-  Such type of root swells at different places forming a beaded structure, e.g. bitter gourd (Momordica charantia) and Vitis.

 Nodulose- The slender root swells suddenly at its tip for storage of food, e.g. mango-ginger (Curcuma amada). 

Mechanical support Prop roots-  There are large pillar like roots, which appear from large horizontal branches. These roots grow downwards, which may finally enter into soil, e.g. banyan (Ficus bengalensis). 

Stilt roots- There are cluster of roots that grow obliquely downwards from near the base of the stem, e.g. screw-pine (Pandanus) and maize (Zea mays). 

Climbing roots- These roots arise from the nodes and internodes of many climbers. They help the plants in fixing themselves to their support, e.g. betel vine (Piper betle), Pothos.

 Buttress roots-  Such roots arise from basal parts of main stem and spread in different directions in the soil. They are irregular, thick, and broad like planks of wood, e.g. Bombax. 

Floating roots-  In Jussiaea, an aquatic plant, tufts of spongy, soft and light roots arise from the nodes in addition to ordinary adventitious roots. These roots have innumerable air spaces and thus help in maintaining buoyancy and facilitate respiration. 

Epiphytic roots-  Such roots are found in epiphytes. These roots hang in the air. These roots have a spongy tissue called velamen. It helps in the absorption of moisture from air, e.g. Vanda (orchid). 

Vital functions Assimilatory or photosynthetic roots-  Roots of some plants develop chlorophyll and perform the function of photosynthesis, e.g. Trapa, Tinospora.

 Reproductive roots. Roots of same plants develop adventitious buds, which after separation from parent plant forms new plant, e.g. sweet potato (Ipomoea batatus). 

Sucking roots- In some parasite plant, adventitious roots arise from the plant and enter the host plant developing contact with xylem and phloem of host stem. Such roots are called haustoria, e.g. dodder (Cuscuta). 

DNA fingerprinting methodology.

DNA fingerprinting, also known as DNA profiling, is a revolutionary scientific technique that has transformed the fields of forensic science, paternity testing, and genetic research. This comprehensive guide will delve into each step of the DNA fingerprinting process, unraveling the science behind this powerful method of individual identification.

Step 1: Sample Collection

The first crucial step in DNA fingerprinting is sample collection. A variety of biological samples can be used, including blood, saliva, semen, hair, skin cells, and other tissues containing nucleated cells. The quality and quantity of the sample are essential for successful DNA analysis. Properly collected and preserved samples are vital to ensure that DNA is not degraded, providing accurate and reliable results.

Step 2: DNA Extraction

Once the sample is collected, the DNA must be extracted from it. DNA extraction involves breaking open the cells to release the genetic material contained within the nucleus. There are various methods for DNA extraction, such as the organic extraction method or using commercial DNA extraction kits. The choice of method depends on the nature of the sample and the quantity of DNA required for analysis.

Step 3: Polymerase Chain Reaction (PCR)

After DNA extraction, the amount of DNA obtained might be insufficient for analysis, especially when working with small or degraded samples. Polymerase Chain Reaction (PCR) is a critical technique used to amplify specific regions of DNA. It enables scientists to create millions of copies of the targeted DNA segments. The PCR process involves multiple cycles of denaturation, annealing, and extension, resulting in exponential DNA amplification.

Step 4: Selection of Genetic Markers

To distinguish individuals from one another, specific genetic markers with high variability within the human population are selected. These markers are regions of the DNA that contain Short Tandem Repeats (STRs), consisting of repeating sequences of nucleotides. The number of repeats in each STR varies among individuals, making them excellent genetic markers for identification.

Step 5: Gel Electrophoresis

With the DNA fragments amplified through PCR and the genetic markers selected, the next step is gel electrophoresis. This technique separates the amplified DNA fragments based on their size. A gel, typically made of agarose, is prepared, and the DNA samples, along with a DNA size marker, are loaded into wells at one end of the gel.

When an electric current is applied, the DNA fragments move through the gel at different rates based on their size. Smaller fragments move faster and travel further through the gel, while larger fragments move more slowly and remain closer to the wells. This separation creates distinct bands on the gel, representing the different lengths of DNA fragments containing the selected genetic markers.

Step 6: Visualization and Analysis

After gel electrophoresis, the DNA bands on the gel need to be visualized and analyzed. A DNA-specific stain, such as ethidium bromide, is used to make the DNA bands visible under ultraviolet light. The pattern of bands represents the unique DNA profile or fingerprint of the individual, akin to the ridges on a human fingerprint.

Step 7: Data Interpretation

The final step is data interpretation, where the DNA profile is compared with other profiles to establish relationships or identify individuals. The presence or absence of specific bands at particular positions on the gel determines the genetic markers of the individual. In forensic applications, the DNA profile from a crime scene can be compared to profiles from known suspects or a DNA database to identify potential matches.

Conclusion

DNA fingerprinting is a powerful and versatile technique with far-reaching applications. Each step of the process plays a critical role in obtaining accurate and reliable results. From sample collection to data interpretation, meticulous attention to detail is essential to ensure the successful application of DNA fingerprinting in forensic investigations, paternity testing, and various other fields of science and medicine. As technology continues to advance, DNA fingerprinting will remain at the forefront of identifying individuals and resolving complex genetic mysteries.