Application of fertilizers
Most of the soils usually contain sufficient amounts of essential mineral elements for the better crop production. Some of them are, however, deficient in certain elements. These elements are required to be supplemented externally by adding the appropriate fertilizers. Moreover, constant agricultural cultivation in the field may also cause depletion of certain elements which must be replenished in order to improve the fertility of soil. It is a common observation that at least three elements- Nitrogen, Phosphorus and Potassium (abbreviated as NPK) become deficient in the soil as a result of repeated cultivation. fertilizers
These elements must be replenished in the crop fields from time to time in the form of chemical fertilizers. The common fertilizers used in India as sources of these elements are – nitrate of soda, ammonium sulphate, ammonium nitrate, ammonium chloride, urea, calcium ammonium nitrate, superphosphate, bone meal, rock phosphate, calcium magnesium phosphate etc. The common fertilizers that supplements NPK is nitrophosphate with potash in varying proportions. fertilizers
The percentage of nitrogen, phosphorus and water-soluble potassium are labelled on the bags as 17-18- 9 or 15-15-15 and so on. The amount and type of fertilizers vary according to the soil condition, crop, season and other climatic conditions. fertilizers
HETEROTROPHIC NUTRITION IN PLANTS
Plants exhibiting heterotrophic nutrition are broadly categorized into three main groups, depending upon the source from which they get their nourishment-saprophytes, parasites and insectivorous (or carnivorous) plants –
1. Saprophytes:
Saprophytes are those plants which grow and live on dead decaying organic matter including animal and plant remains. The plants that grow as saprophytes utilize the organic matter present in the substratum. Most of these plants secrete some extra-cellular enzymes (viz. cellulases, amylases, chitinases, proteolases, etc.) which break down the complex organic compounds into simple forms. fertilizers
The simple forms are then absorbed by the plants. The saprophytes include a large number of fungi, bacteria, a few algae (e.g., Polytoma), mosses (e.g., Hyp- num, Splachnum, etc.), pteridophytes (e.g., a few species of Botrychium and Lycopodium) and some angiosperms. The well known examples of saprophytic angiosperms are – Neottia Monotropa Moneseis, Corallorhiza, Wullschleigelia aphylla etc. fertilizers
2. Parasites:
The parasitic plants grow and obtain their nutritional requirements from other living or- ganisms (hosts). There are two main categories of parasitic angiosperms – (i) Total or Holoparasites. The parasites which are non-green and obtain their total food (including organic nutrients, water and minerals) from the hosts are called holoparasites, e.g., Cuscuta, Cassytha, Orobanche, Balanophora, Rafflesia, Cistanche, etc. (ii) Partial or semi- parasites. They are green and can synthesize their own food but depend on host for water and mineral supply, e.g., Loranthus, Viscus, Arceutobium, Striga, Santalum, Thesium, etc. fertilizers
Description of some parasitic angiosperms are given below:
(a) Cuscuta
The genus Cuscuta belongs to family Convol- vulaceae. It is a total stem parasite of many an- giospermous plants (Zizyphus, Citrus, Duranta, Clover, etc.)ted Seeds of Cuscuta germinate in the soil. See- dlings are long, filamentous and without cotyledons. The young plants grow and perform circumutation or rotatory movement, with the result they twin around the stem and some times leaves of host plant. If the host is not available the young plants die. On establishing contact with the host the young see- dlings develop absorbing organs called haustoria. fertilizers
These are small modified adventitious roots which deeply penetrate into the body of host. The vascular tissue of parasite makes contact with that of the host through these haustoria. Recent studies have shown that penetration of haustoria is an enzymatic phenomenon and is not just mechanical. The haustoria are metabolically active organs which help in absorption of nutrients and provide the channel for their transportation. fertilizers
The mature plant then loses connection with the soil and becomes totally de- pendent on the host. The mature plant of Cuscuta is very long, filamentous, branched, non-chlorophylL, pale yellow in colour with small scale leaves. It produces bunches of whitish or yellowish bell shaped flowers (Fig.
(b) Viscum:
A few species of the genus Viscum (e.g., V. album, Mistletoe) are partial stem parasite and parasitize on a number of shrubs and fruit trees. The mature plant of Viscum is dichotomously branched with green leaves borne in pairs attached on each node of stem The shoot is attached to the host by means of haustoria. The primary haustorium reaches upto cortex of host. It sends secondary haustoria which make connections with the xylem of host and absorb water and minerals. fertilizers
(c) Orobanche (Broom rape):
Orobanche is a total root parasite that parasitizes on the roots of many angiospermous plants (such as Mustard, Tomato, Potato, Brinjal, etc.). Plants have no chlorophylls. The flowers are usually pinkish or bluish in colour. The tips of roots make haustorial contacts with the roots of hosts and absorb nourishment.
(d) Rafflesia:
The genus Rafflesia is a total root parasite. It has about 14 species commonly distributed in Indonesia and Burma. The vegetative parts of the parasite are highly reduced and represented by cellular filaments resembling fungal mycelium. These filaments are embedded in the soft tissue of host roots (such as Figs) while the flowers emerge out in the form of buds. The flowers of Rafflesia are the largest in the world. They are about 11 kg in weight and 1 m in diameter. fertilizers
e) Santalum album (Sandal wood tree):
It isan evergreen partial root parasite which grows at many places in South India. The young seedlings of S. album can grow independently upto a year but not beyond that. Within this period some of the roots develop haustoria which make contacts with the roots of nearby trees (Morinda, Dalbergia, Eucalyptus, etc.) They are normally green in colour but depend on host for water and mineral supply.
Should we be afraid of carnivorous plants?
No, you should not be afraid of lovely carnivorous (insectivorous) plants as long as your size is larger than small insects. They are completely harmless. They will do no harm to you even if you insert your finger inside the pitchers or fall on a bed of carnivorous plants. The reason is very simple. They catch small insects to get their partial nutrition. The digestive enzymes which they secrete are extremely weak and can digest only very small insects. So you should not worry
What is the biggest carnivorous plant?
The biggest and largest carnivorous plants are in the genus- Nepenthes. They are large climbers which reach upto several meters in height. The pitchers (traps) which these plants possess are also very large. These pitchers capture insects, flies or sometimes even small frogs. Rarely, these pitches capture some small birds or rodents.
Which is the most amazing carnivorous plant?
The most amazing carnivorous plant is probably Dionaea (The familiar Venus Flytrap). The trap of Dionaea consists of leaf lobes which quickly capture the prey dramatically.
3. Insectivorous (or Carnivorous) plants
Most green plants derive their nitrogen from the soil as solutes conducted through the root system. However, some of them obtain nitrogen from captured animal prey. Such plants which get their nitrogen from animals are called carnivorous or insectivorous plants. These plants usually grow in water logged and swampy soils deficient in nitrogenous compounds.
They have poorly developed roots and thus, they have to depend on captured insects for their nitrogen requirement. In fact, these plants do not live solely on the captured animals as they can manufacture their own organic food with the aid of chlorophyll present in their leaves and stems. These plants are, therefore, partly autotrophic and partly heterotrophic.
Some common insectivorous plants are briefly described below:
(a) Nepenthes (Pitcher plant).
The common Indian species is N. khasiana which grows in Assam. The plants are climbers or epiphytes. The leaves are usually large and modified into pitchers. The leaf base is large and flattened. The petiole is elongated and tendrillar whereas the proper leaf lamina is modified into a pitcher. The leaf apex is modified into a small lid which covers the opening of pitche . Depending on the species, pitchers may grow to about 1 foot (30 cm) in length, but more often they are about 5-7 inches long.The young pitcher of Nepenthes is closed by a small lid.
The contents of pitcher are sterile at this stage i.e., they are free from bacteria, etc. At maturity the mouth of pitcher opens due to outward bending of lid. The lid is immovable and protects the mouth from rain water. The mouth of pitcher is called rim which is ribbed and bears nectar secret- ing glands. These and other nectaries distributed on the surfaces of leaves and tendrils serve to attract the insect towards the pitchers. The insects, attracted towards the coloured lid and nectaries, stride along the rim of pitcher and usually result in downfall.
The upper half of pitcher is lined with slippery and waxy inner wall due to which the insects fall into the pitchers. A group of digestive and absorptive glands is situated below the waxy zone inside the upper half of the pitcher. The juices secreted by these glands aid the digestion of the drawned insects. The insect proteins are broken down to amino acids by the enzymes (viz., proteases) present in the digestive juices, which is then absorbed by the plant.
(b) Drosera (Sundew).
Plants usually occur in South Africa and Australia. They are mostly herbaceous and grow in water logged places. The mature plant bears about 6-12 leaves forming a rosette. Each mature leaf possesses large number of club shaped hairs called tentacles . Each tentacle is a stalked mucilage-secreting gland which is bright red in colour. The tip of gland secretes a sticky purple juice which shines like a dew drop in bright sunlight and hence the Drocera is commonly called sundew.
The small insects are attracted towards the shining leaf surfaces and come in contact with the tentacles. The tentacles are sensitive to touch and arch over the prey. The insect becomes incapacitated by the plant secretion. The leaf may also sometimes arch around the insects body. The secretion from glands appear to contain digestive enzymes which break down the insect’s organic compounds to a state in which it can easily be absorbed by the plant thus providing the nitrogenous source. The tentacles now again become straight to catch another insect.
(c) Utricularia (Bladder wort).
In India, it is commonly found in the Dal Lake of Kashmir. Most species are aquatic found free floating in water while some are terrestrial. The plant body is root- less, much branched slender stem which bears much dissected leaves. Some of the leaf lobes are modified into sensitive little sac like traps called bladders . Each bladder is stalked, pear shaped, hollow chamber and measures about 1-3 mm in diameter. It opens by a small opening which is guarded by a valve.
The valve opens inwardly. Outside of aperture it bears sensitive filiform hairs and glandular hairs (Fig. 2.18). The inner and outer surfaces of bladder bear a large number of glands.-MIDRIBThe bladder sucks small minute aquatic animals which enter into the sac through the opening. As soon as the insects enter into the bladder the valve closes and the animal gets entrapped. Within three days the animal dies and digested by the fluid. The digested products are soon assimilated.
(d) Pinguicula (butterwort).
In India it is mostly found in temperate parts of the Himalayas. The plants are herbs which bear a rosette of large fleshy and yellow leaves . Each leaf is trough shaped armed with glands scattred over its upper surface. The glands are of two types (i) The stalked glands (or mucilage glands) that secrete mucilage and (i) sessile glands (or digestive glands) which secrete digestive fluid.
If an insect happens to sit on the leaf it is trapped in the sticky fluid of mucilage glands. The edges of the leaf also curve over towards the trapped insect. The insects are then digested by the digestive juices 258which contain proteases. The digested food is y then absorbed by the leaf surface. The leaf y again unrolls to trap another animal.
(e) Dionaea (Venus’ Fly-trap).
It has a sole species-D. muscipula, distributed in damp, mossy spots in the South-Eastern states of the U.S.A. The plant is a herb which bears a ChowFosette of leaves. The leaves are large, consist nibrofa winged petiole and a terminal blade di lamina). The leaf lamina is modified into two Joothed jaws normally open at an angle of 40-50° forming the trap (Fig. 2.20). Each jaw bears about 12-20 teeth. The two sets of teeth interlock when closed to prevent the escape of larger prey.
The upper surface of each lobe (jaw) bears three triangularly arranged long irritable prongs called sensitive hairs or bristles and irregularly scattered many small digestive glands. If an insect (e.g., fly) sits on the trap, it touches the sensitive hairs which then become stimulated and cause closure of trap. The insect, enclosed within the trap, is then destroyed by juices secreted by the digestive glands. The broken-down products are absorbed by the leaf.
(f)Sarracenia (Pitcher plant).
The plant body is a small herb. Rosette of sessible pitchers emerge out from a short rhizome buried in the mud Each pitcher is formed from the whole leaf. It has an attractive Abrightly coloured and virtually immobile lid. The outer surface of pitcher bears a large num- ber of nector glands. The rain water flows into POT the pitchers which drowns the small living creaefures attracted towards ectaries and coloured lid.
(g) Aldrovanda (Water Flea-trap).
It is widely distributed, small, rootless, aquatic free-floating herb. The leaves are small and bilobed. Each lobe bears a large number of sensitive hairs and digestive glands on its upper surface to trap and digest the insects.
FAQ
1. Requirement of various inorganic and organic raw materials for building the structure and maintaining body functions of an organism is called nutrition.
2. Plants generally derive their inorganic nutrients from soil, water and atmosphere.
3. The absorption, distribution and metabolism of various mineral elements by plants is called mineral nutrition.
4. Basically, there are two modes of nutrition Autotrophic and Heterotrophic.
5 Autotrophic is a kind of nutrition in which the organisms manufacture their own organic food from simple inorganic raw materials.
6. Heterotrophic is a kind of nutrition in which the organisms fail to synthesize their own organic nutrients from inorganic substances. They are dependent on some other external sources for their organic nutrition.
7. Plants require inorganic nutrients for their growth, development, structure, physiology and reproduction.
8. Plants require 17 essential elements. They are C, H, O, N, P, K, S, Mg, Ca, Fe, B, Mn, Cu, Zn, Mo, Cl and Ni. All are mineral elements except C, O, H and N.
9. Inorganic nutrients are broadly categorized into two categories-Macronutrients and Micronutrients (or Traceelements) on the basis of the amount required by the plants.
10. Withholding of any one element may cause the deficiency symptoms in plants. These symptoms include reduction in growth, delaying of flowering, chlorosis, necrosis, anthocyanin pigmentation, promotion of leaf fall, wilting, etc.
11. Minerals are mainly absorbed by the roots which are in direct contact with the soil solution.
12. There are two modes of mineral absorption passive absorption and active absorption.
13. The driving force for passive absorption is physical (Le, non-metabolic) in origin. Energy-yielding metabolic processes are not involved in passive absorption.
14. The various modes of passive absorption are-Passive diffusion; Facilitated diffusion; Mass flow; Donnarequilibrium; and Ion exchange.
15. The driving force for active absorption is energy derived from metabolic processes. It is assumed that a carrier molecule is involved in solute transport across the membrane in active absorption.
16. The absorbed mineral elements are transported from roots to leaves through the xylem.
17. The atmospheric nitrogen (dinitrogen or Na N) is inert and cannot be used directly by plants.
18. The phenomenon of conversion of free nitrogen into nitrogenous salts to make it available for absorption by plants is called nitrogen fixation. It occurs by two methods-physical and biological
19. Physical nitrogen fixation occurs through natural physical processes such as lightning, electric discharge, thunderstorms, atmospheric pollution, etc.
20, Biological nitrogen fixation occurs through the agency of free-living (symbiotic) or symbiotic bacteria and cyanobacteria.Application of fertilizers
21. The most important symbiotic nitrogen-fixing bacteria is Rhizobium which is symbiotically associated with theroots of leguminous plants and forms root nodules.
22. The biological nitrogen formation occurs in presence of enzyme nitrogenase which is active in anaerobic conditions. The red pigment leghaemoglobin acts as oxygen scavenger in root nodules. Application of fertilizers
23. During biological nitrogen fixation, the dinitrogen is progressively reduced step by step to ammonia (NH) by the addition of pairs of hydrogen atoms. The process requires a hydrogen-donating system and ATP. Application of fertilizers
24. The product of nitrogen fixation is ammonia which is toxic to plants. Most of the ammonia produced by nitrogen fixers is either absorbed and assimilated by the higher plants or converted to nitrates by the process known as nitrification.Application of fertilizers
25. Ammonia is oxidised to nitrite and nitrate ions by a group of soil inhabiting nitrifying bacteria (Nitrosomonasand Nitrobacter).Application of fertilizers
26. Nitrate is reduced to ammonia with the help of enzymes-nitrate reductase and nitrite reductase. Application of fertilizers
27. The ammonium ions are safely assimilated by higher plants. They are subsequently incorporated into amino acids and other nitrogenous compounds in the plant.Application of fertilizers
28. Depleting mineral nutrients in the crop fields are replenished by addition of chemical fertilizers. The most common fertilizers are the NPK fertilizers.Application of fertilizers
29. Heterotrophic plants are broadly categorized into three main groups: Saprophytes, parasites and insectivorous (or carnivorus) plants.Application of fertilizers
30. Saprophytes are those plants which grow and live on dead decaying organic matter, eg. Neottia, Monotropa, Wullschleigcha aphylla, etc, Application of fertilizers
31. Parasites grow and obtain their nutritional requirements from other living organisms (hosts), eg, Cuscuta,Orobanche, Balanophora, etc. Application of fertilizers
32. Insectivorous plants are partly autotrophic and partly heterotrophic. They obtain their nitrogen requirement from captured animal prey.Application of fertilizers
33. Some common insectivorous plants are Nepenthes (Pitcher plant), Dronera (Sundew), Utricularia (Bladder wort Pingacida (Butter wort), Dionaea (Venus Fly-trap), Sarracenia (Sessile pitcher), Aldrovanda (Water Flea- trap).Application of fertilizers
Q What is mineral nutrition?
Ans. The absorption, distribution and metabolism of various mineral elements by plants is called mineral nutrition.
Q. Name the part of plant body which absorbs mineral nutrients.
Ans. Epiblema or Epidermis of young roots.
Q. . Name the insectivorous plant which produces sessile pitchers.
Ans. Sarracenia.
Q. Name an insectivorous plant which is in the list of endangered species.
Ans. nepenthese khasiana
Q. . Name the mineral element which is essential for photo oxidation of water in photosynthesis
Ans. manganese.
Q. Name the enzyme involved in biological nitrogen fixation. What are the two mineral elements needed for the activity of enzyme?
Ans. Nitrogenase, Iron and Molybdenum.
Q. What type of condition is created by leghaemo-globin in root nodules of a legume?
Ans. anerobic
