The relative nutrient status of a plant may be easily described using the following terms:Image result for soil
Deficiency range
Nutrient deficiencies occur in plants when an essential element is not taken up by the plant in sufficient amounts. As a result, yield will be limited by the element which is deficient. While slight to moderate deficiencies do not always result in visual deficiency symptoms, distinct visual symptoms appear in severe cases.
Critical range
Below the critical range of nutrients, an addition of the essential element will trigger an increase in yield. Above the critical range, the levels of essential nutrients are considered sufficient.
Sufficiency range
Within this range, additions of the essential nutrient will not result in any increase in yield. However, uptake of the nutrient may continue. Thus, the concentration of that essential nutrient in plant tissue will also increase. We refer to the uptake of an essential nutrient within the sufficiency range as luxury consumption.
Toxicity rangeToxicities occur when an essential (or nonessential) element is taken up in great enough quantities to actually reduce plant growth. As a result, toxicities can severely limit yield.

Nutrient Mobility

WITHIN PLANT

An important characteristic of some nutrients is the ability to move within the plant tissue. In general, when certain nutrients are deficient in the plant tissue, that nutrient is able translocate from older leaves to younger leaves where that nutrient is needed for growth. Nutrients with this ability are said to be mobile nutrients, and include nitrogen, phosphorus, potassiummagnesium, and molybdenum. In contrast, immobile nutrients do not have the ability to translocate from old to new growth. Immobile nutrients include calcium, sulfur, boron, copper, iron, manganese, and zinc.
Nutrient mobility, or immobility, provides us with special clues when diagnosing deficiency symptoms. If the deficiency symptom appears first in the old growth, we know that the deficient nutrient is mobile. On the other hand, if the symptom appears in new growth, the deficient nutrient is immobile.

WITHIN THE SOIL

Mobility of a nutrient within the soil is closely related to the chemical properties of the soil, such as CEC and AEC, as well as the soil conditions, such as moisture. When there is sufficient moisture in the soil for leaching to occur, the percolating water can carry dissolved nutrients which will be subsequently lost from the soil profile. The nutrients which are easily leached are usually those nutrients that are less strongly held by soil particles. For instance, in a soil with a high CEC and low AEC, nitrate (an anion) will leach much more readily than calcium (a cation). Additionally, in such a soil, potassium (a monovalent cation) will leach more readily than calcium (divalent cation) since calcium is more strongly held to the soil particles than potassium.
Silica from minerals also dissolves and leaches from the soil profile during the processes of weathering. It is this dissolution and leaching that transforms primary minerals to the more weathered, secondary minerals that make up the finely-textured soils of Maui.

Image result for soilThe quantity of aluminum and hydrogen in each of the 3 pools of acidity is not permanently fixed. Instead, the relative amounts of aluminum and hydrogen can change, as aluminum and hydrogen moves from pool to pool. Thus, the soil is said to have a buffering capacity. Buffering capacity is the ability of the soil to resist change. In the case of acidity, it is the ability of the soil to resist change in pH. Thus, aluminum and hydrogen of one pool will replenish the aluminum and hydrogen of another pool as these acid cations are removed.
For example, as aluminum and hydrogen are removed from soil solution, the acid cations of the CEC replenish the soil solution. Likewise, minerals containing aluminum and hydrogen dissolve and release these cations as they are removed from the exchangeable pool.

OUTLINE OF BUFFERING REACTIONS:

  • Exchangeable acidity will buffer changes in active acidity
  • Residual acidity will buffer changes in exchangeable and active acidity
Each soil has a unique buffering capacity. As a rule of thumb, finely-textured clay soils tend to have greater buffering capacities than coarse-textured soils.

Rule of Thumb

  • Finely-textured clay soils tend to have greater buffering capacities than coarse-textured soils
Recall that 90% of Hawaii’s soils fall into this category. As a result, most Hawaii soils largely buffer soil acidity. This has great implications onnutrient management since buffering capacity determines the amount of resources, such as lime, that must be added to correct soil acidity. Soils that have high buffering capacities require larger amounts of liming resources to raise the pH to a target value than soils with low buffering capacities.

:Environmental Factors Affecting the Productivity in Ecosystem

1. Solar radiation and temperature.
2. Moisture, i.e., leaf water potential, soil moisture, fluctuation of precipitation, and transpiration.
3. Mineral nutrition, i.e., uptake of minerals from the soil, rhizosphere effects, fire effects, salinity, heavy metals and nitrogen metabolism.
4. Biotic activities, i.e., grazing, above ground herbivores, below ground herbivores, predators and parasites and diseases of primary producers.
5. Impact of human populations, i.e., populations of different sorts, ionising radiations, such as atomic explosions, etc.
6. In aquatic systems, productivity is generally limited by light, which decreases with increasing water depth. In deep oceans nutrients often become limiting for productivity. Nitrogen is most important nutrient limiting productivity in marine ecosystems.
The largeness of primary productivity depends on the photosynthetic capacity of producers and the existing environmental conditions, such as solar radiation, temperature and soil moisture.
In tropical conditions, primary productivity may remain continuous throughout the year, provided adequate soil moisture remain available.
While in temperate regions, primary productivity is limited by cold climate and a short snow- free growing period during the year.
Primary productivity of the major ecosystems of the world is as follows:

The increasing abundance of greenhouse gases in the atmosphere has the following three main effects:
(i) CO2 fertilisation effect on plants
(ii) Global warming and
(iii) Depletion of ozone (O3) layer in the stratosphere.
Carbon dioxide (CO2) Fertilisation Effect on Plants:
The data produced in USA have shown that atmospheric carbon-dioxide concentration has been rapidly rising since 1959 as shown in the graph. If such rising trend continues, by the end of twenty first century the atmospheric concentration of CO2 shall increase to a level between 540 and 970 ppm.
Increase in CO2 concentration in atmosphere from1959 to 2001
When the CO2, concentration of the atmosphere is more or less doubled, the growth of many plants i.e., C3, plants in particular, under favourable conditions of water, nutrients, light and temperature, could increase by about thirty per cent on average, in the short term of few years or so.
The response of plants to elevated concentrations of CO2, is called carbon dioxide fertilisation effect.
Due to increased carbon-dioxide concentration, the rate of photosynthesis also increases, and the stomatal conductance decreases due to partial closure of stomata. Hence, the transpiration rate reduces, and water-use efficiency increases.
Such effect allows many species to grow successfully in regions of water scarcity.
Under higher atmospheric carbon dioxide concentrations, plants allocate, a greater proportion of photosynthate to roots. However, greater root production increases development of mycorrhiza and fixation of nitrogen in root nodules, thus, makes possible the plants to grow in soils which are poor in nutrition.
However, in natural conditions the beneficial effects of increased carbon dioxide may not be there because of negative effects of global warming.

The progress of human civilisation has, to a great extent, been moulded along the lines of development of the biological science. Man is a social creature. People live in towns and cities. This has created several health problems such as supply of pure water, disposal of sewage and prevention of contagious diseases, so that they may not break out in epidemic form. These problems are best solved by biology.
Bacterial enemies of man have been discovered, and remedies against their spread and destruction are now possible by vaccination and other measures. No longer do plagues bring terror to a district. Penicillin, streptomycin, terramycin, Chloromycetin, aureomycin, etc., are the magic bullets to shoot down the microbes, and all of them are the gifts of the biological science to mankind.
Life-histories of animal parasites invading man, and of animals which quickly transmit them to a town-dwelling community by acting as carriers have been worked out and effective measures for their control have been planned. Moreover, an expert biological knowledge is essential for selecting the right kind of raw materials for the manufacture of drugs, because most of them are either vegetable or animal products.
The few facts that are mentioned here serve to illustrate how biology may be applied to mitigate human sufferings and increase the life span of man. Modern man, unlike his primitive ancestors, does not depend upon fishing and hunting.
He cultivates plants and rears fishes as well as cattle to get his food and other necessities of life. This has resulted in the development of agriculture, fishery and animal husbandry which are applied aspects of the basic biological science. Better and productive varieties of crop plants such as rice, wheat, jute, sugar-cane, cotton and pulses Eire now bred experimentally and distributed throughout the country.
Disease-resistant grains are raised and seeds are vernalized by special treatments so as to yield the crop before the usual time of harvesting. Soil is saved from exhaustion by crop-rotation.
Image result for biology
Fishes are now reared in fisheries and the small fry distributed to fishermen with proper scientific instructions for growing them. Life-histories of the more important food-fishes are explored and suitable kinds are bred. Fishing industry has been improved by employment of adequate catching devices, such as traps and nets.
Trawlers are used for fishing in the open sea, so as to increase the number of catches, and fish-oils are manufactured as side products. We are really proud of the fact that during last few years spectacular advances have been made in agriculture in our country.
Employing scientific methods by way of selection of better seeds, adequate application of manures and improved irrigation facilities agricultural practices have been practically revolutionised. Similar improvements have also been made in fisheries, silk-producing insects and diaries.
Silk industry has been greatly improved by sericulture. In this, better kinds of silk moths are experimentally bred with a view to increasing the rigidity, fineness or other qualities of the silk produced by them. Biology, therefore, has contributed largely towards obtaining better varieties and larger yields of food and other human necessaries.
Forests and wild game-animals are national resources from which man derives useful materials such as timber, fur and even food. Climate and crop position of the country depend, to a certain extent, upon the biological communities residing in perfect harmony amongst the forests.
Proper and judicious conservation of the natural resources demands a fundamental knowledge of the principles of biology, so that they may be utilised at the right moment.
Successful plant breeding, animal husbandry and con­servation of forests are effective means for checking famine which is a scourge of the human society. Man has three powerful adversaries to fight with. These are famine, disease and death. Biology is an effective weapon against each of these three human terrors.

The following points highlight the top five cases on colour blindness in humans.
Case # 1. Of what type will be the children with reference to colour blindness, when a man is colour-blind and his wife is normal?
Solution:
The cause of the colour blindness is the presence of recessive (c) gene on the X chromosome.
Because man is colour-blind (Xc Y) and his wife is normal (XX), following will be the results while cross­ing:
Following will be the results after fertilization:
(i) XXC, i.e., normal but carrier daughter.
(ii) XY, i.e., normal son.
Results:
No child will be colour-blind.
Case # 2. When a haemophilic male is mated with a heterozygous haemopbilic female, what haemophilic proportion will be resulted in each sex?
Solution:
Haemophilia is a disease that causes delayed clotting of blood. It is due to a recessive gene ‘h’, located on X chromosome.
Haemophilic gene is represented by ‘h’
Haemophilic male = XhY
Heterozygous haemophilic female = XhX
Results:
One haemophilic daughter
One carrier daughter
One haemophilic son
One normal son.
Case # 3. When a haemophilic male is mated with a ho­mozygous non-haemophilic female-What will be the result?
Solution:
Haemophilic male = XhY
Homozygous non-haemophilic female = XX
Result:
A ratio of 2 (carrier daughter) and 2 (Normal son) will be produced.
Case # 4. Of what type will he the children with reference to colour blindness, when a woman is colour-blind and her husband is normal?
Solution:
Colour-blind woman = XCX
Normal man = XY
Result:
In such a case one normal and one colour-blind son, and one normal and one carrier daugh­ter would be resulted.
Case # 5. When both the parents are colour-blind, can they produce a normal daughter?
Solution:
Results:
The above results indicate that the colour-blind gene (c) is passed to both the X chromosomes of the daughter and so no normal daughter can be produced.

:

The important deficiency disorders include protein energy malnutrition (PEM) and disorders due to deficiencies of Vitamin A, iron and iodine. Defi­ciency of protein and energy or both, called PEM, has been identified as major health and nutritional problems in India.
Protein and energy intake are difficult to separate because diets adequate in energy are adequate in protein. Young children (0-6 years) require more protein for each kilogram of body weight than adults. So they are more prone to malnutrition. Malnutrition is not only an important cause of childhood mortality and morbidity, but it also leads to permanent impairment of physical and mental growth of those who survive.
(i) PEM:
It is an important nutritional problem among pre-school children. It leads to various degrees of growth retardation. This is due to lack of adequate quantity of protein or carbohydrate or both.
PEM is of 2 types: Kwashiorkor and Marasmus.
Kwashiorkor and Marasmus

Children Suffering from Kwashiorkor and Marasmus
The child suffering from PEM can recover if adequate quantities of protein and carbo­hydrate rich food are given.
(ii) Night blindness and Xerophthalmia:
These diseases are due to deficiency of vitamin A.
(iii) Anaemia:
This disease is caused by deficiency of iron.
(iv) Goitre:
Goitre is caused due to deficiency of iodine in food. In addition to above mentioned deficiency diseases, the following deficiency diseases may be mentioned. Name of deficient is written in the bracket. Rickets in children and osteomalacia in adult (vitamin D), muscular dystrophy (vitamin E), Beri beri (B1), Cheilosis (B2), Pellagra (vitamin B3), Megaloblastic anaemia (Folic acid), Pernicious anaemia (B12), Scurvy (vitamin C).


Jaundice is a yellowish colouration of the sclerae (whites of the eyes), skin and mucous membranes due to a build-up of a yellow compound called bilirubin. After bilirubin is formed from the breakdown of the heme pigment in aged red blood cells, it is transported to the liver, where it is processed and eventually excreted into bile.
The three main categories of jaundice are:
(1) Pre-hepatic jaundice, due to excess production of bilirubin;
(2) Hepatic jaundice, due to congenital liver disease — cirrhosis of the liver, or hepatitis; and
(3) Extra-hepatic jaundic due to blockage of bile drainage by gallstones or cancer of the bowel or the pancreas.
Because the liver of a newborn functions poorly for a week or so, many babies expe­rience a mild form of jaundice called neonatal jaundice that disappears as the liver matures. Usually, it is treated by exposing the infant to blue light which converts bilirubin into sub­stances the kidneys can excrete.

Epithelial cells of small intenstine showing absorption of nutrients
All these nutrients are absorbed via simple diffusion. Fatty acids and glycerol are insoluble in water, therefore, they cannot reach the blood stream directly. They are first incorporated into small, spherical, water soluble droplets called micelles with the help of the bile salts and phospholipids in the intestinal lumen.
A micelle is an aggregate of many molecules. From the micelles fatty acids, glycerides, sterols and fat soluble vitamins are absorbed into the intestinal cells by diffusion where they are resynthesized in the ER and are converted into very small fat molecules (droplets) called chylomicrons.


The latter are released from the intestinal cells into the lymph present in the lymphatic capillaries, the lacteals. Small quantities of short chain fatty acids are absorbed directly into the blood by diffu­sion rather than into the lymph. Fatty acids, glycerol and vitamins are absorbed in jejunum.

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