PLANTS AND ANIMALS OSMO-REGULATION

 

OSMO-REGULATION

Is the control of osmotic pressure within an organism. Blood and tissue fluid must be kept at a constant  osmotic pressure to avoid unnecessary movements of water in and out of cells by osmosis.

-Osmoregulation prevents the cells from bursting or shrinking.

Osmosis is the movement of a solvent from a dilute solution to a more concentrated solution through a membrane.

The water content and dissolved substances such as mineral salts in the cells must be controlled, ie. Control of osmotic concentration within an organism. If the osmotic pressure of blood and tissue fluid is too high, cells lose water by osmosis and the body becomes dehydrated.

The osmotic pressure of a solution depends upon its strength, ie, amount of dissolved substances it contains. Example osmotic pressure of a sugar solution increases with addition of sugar in it.

So osmoregulation is especially important in animal cells as they do not posses the strong cellulose cell walls found in plant cells.

Kidney: Are the organs associated with osmoregulation. They control the rate of osmosis between the blood plasma and the surrounding cells.

The body gain water by eating and drinking, and it loses water by urine, faeces (defacation), sweat and exhaled breath. This will produce corresponding changes in the blood concentration. The Hypothalamus in the brain will detect such changes and try to balance it. Failure in liver-insulin mechanism will also alter blood concentration.

If the blood is too concentrated, the hypothalamus will stimulate the pituitary gland to secrete into the blood the ADH (anti diuretic hormone) which causes the kidney tubules to absorb more water from glomerular filtrate back into the blood. Thus the urine is more concentrated, (Hypertonic Urine) and the further loss of water from the blood is reduced.

If the blood is too diluted, production fo ADH is suppressed and less water is absorbed from glomerular filtrate, thus urine is more diluted (Hypotonic Urine.) as means of eliminating excess water in the body.

Important roles of the kidney.

Without kidneys life is not possible. Single kidney can suffice the work. Kidney failure is caused by severe infection, low or high blood pressure.

Functions of the kidney

-Control the acid-alkali balance, (It maintain blood plasma at PH of 4)

-Maintain exact proportion of water in the blood.

-They expel salt above certain concentration, ie.  They regulate the osmotic pressure of the body fluids by regulating the concentration of salts in the blood.

-Regulate total volume of blood.

-expel (excrete) harmful waste matter from the body , ie. Urea.

-Help to conserve body’s  water supply so that more is available for perspiration (cooling by sweating), in hot weather. ie. Little but very concentrated urine.

-Over a ton of blood is filtered through kidneys in 24 hours.

Diagram of kidney tubule(nephrone).

Camels and scarcity of water.

Camels do not store any water in rumen. The fat hump is not so useful for it does not provide any water, because oxidation of fat leads to respiratory loss of moisture.

Camels are able to survive in the desert because:-

-They excrete small volume of urine which is more concentrated, (more hypertonic) than human urine. So high tolerance of water scarcity.

-They lose very little water in their sweat, (only when their body temperature rises more than 56 C.)

-Can survive even after losing ¹/₃ (one third) of their body weight due to loss of water. Man dies if he/she loses ¹/₅ of the body weight due to loss of water.

Blood sugar regulation in mammals.

Several mechanism involving nervous, hormonal and metabolic pathways are used to maintain a constant blood glucose level. The liver, together with a set of glands in the pancreas, control with great accuracy the amount of glucose sugar in the blood. The liver is unique in vertebrates and plays a key role in their metabolism.

Why maintain constant body’s sugar level.

-Sugar is the main source of energy in the body.

-Any slight changes in glucose concentration alter the blood’s osmotic pressure, and hence alter the rate at which water moves in and out of body cells by osmosis.

-When blood glucose is depleted faster than it can be replenished, it drops gradually resulting in Hypoglycaemia. This causes fatigue and affects the functioning of the brain, since the blood glucose is the only source of respiratory substrate in the brain.

Therefore, is important for the normal functioning of the body cells.

What increases blood sugar level.

Normal level of glucose in man’s arteries is 85 mg/100cm³. After a heavy meal of carbohydrates it may rise to 180mg/100cm³. Normally it does not fall below normal except during prolonged starvation.

How is blood sugar regulated.

When blood sugar level increases, the glands in the pancreas will produce Insulin, which stimulates the liver cells to extract more glucose from the blood. Liver converts glucose into glycogen to be stored in the liver. Liver can hold only 100g of glycogen. Any excess glucose in the blood is then converted into fats to be transferred to more permanent storage area, ie. Under the skin, and around various body organs.

When there is less glucose in the blood the pancreas slows down the production of insulin and produces glucagon which converts the stored glycogen into glucose which is then released into the blood. When all glycogen has been used up, then stored fat is converted into glucose. After prolonged starvation there will be no more fat in the body, here then protein is converted into glucose.

Therefore, in this way the liver keeps the body supplied with food for as long as possible when food is not available elsewhere.

The failure of the pancreas to produce sufficient insulin leads to Diabetes. The diabetic can not effectively regulate blood sugar level. It may rise to above 160 mg/100cm³ , leading to convulsion and coma. The diabetic condition can be corrected by regular injections of insulin.

Types of Diabetes.

1.    Diabetes Mellitus, When glucose is contained in the urine, ie. Blood sugar is high.

2.    Diabetes Insipidus, where person excretes large amount of urine and tends to drink enormous quantities of water to replace the loss in urine. Can be remedied by nasal  spraying with ADH (Anti diuretic hormone).

3.    Nephritis, When protein appears in the urine, ie. Protein filters through the glomeruli and appears in the urine.

OSMOREGULATION IN PLANTS.

Plants need less energy compared to animals because they do not move around, hence produces less heat and loose less water. The problem of plants is the absorption of heat from direct sunlight for photosynthesis. Leaves have a large surface area exposed to sun. Direct sunlight can cause temperature rising of leaves up to 50 degrees centigrade.

Terrestrial plants take up water mainly with their roots and leaves. Water is lost by transpiration through stomata pores, the lentils (in the bark) and cuticle of stems & leaves. Water loss is mainly regulated by the opening or closing of the stomata spores.

Factors affecting osmoregulation in plant are light, temperature and air humidity, wind, surface area.

Ways of controlling temperature in plants:

Air Stratification

Because hot air rises and cool air falls, the temperature in any given room will always tend to be warmer near the ceiling. This phenomenon is noticeable even in small rooms. However, in very large, open spaces such as a warehouse, the effect intensifies. It’s not uncommon for the floor-to-ceiling temperature differential in a room with a 40-foot ceiling to reach 30 degrees or more.
In winter, the problem is obvious: Heated air gets trapped where it is not needed, while building occupants shiver below. In summer, it might seem advantageous for the air near the floor to be cooler in such a space, but that’s not the case. In reality, the large stagnant mass of hot air overhead tends to cause the entire building to overheat. Occupants are left sweating, uncomfortable or in danger of heat exhaustion. If the air conditioning kicks into overdrive, workers must cope with air that’s too cold for comfort. Regardless of the season, the situation results in poor working conditions, lowered productivity and high utility bills.
Air flow is key to proper destratification. Large ceiling fans are particularly effective at mixing and circulating the air in a large space. Not only does the mix of air become more uniform, but the steady flow produces a gentle, evaporative cooling effect that can make the space feel up to 10 degrees cooler.

Stack Effect

Where the hot air near the top of a building has a means to escape, the same phenomenon of rising warmth gives rise to the stack effect. This refers to rising columns of air forming in a plant, similar to what happens in a chimney.
Stack effect creates negative pressure in the plant and can lead to a number of problems such as excessive energy loss, infiltration of unwanted substances like dust or cigarette smoke, dangerous backdrafting of combustion appliances, and reduced efficiency of air-handling equipment.
Helpful measures to combat stack effect include revolving doors, air sealing and strategic air flow control throughout the plant.

Condensation

Where temperature differentials exist, so does the possibility of condensation. Condensation happens when warm air hits a surface cool enough to reduce it to the dew point, allowing the water in the air to collect on the surface.
Condensation can cause many problems within a plant. Excessive moisture buildup leads to rust and corrosion, and facilitates the growth of mold and other harmful biological agents. When this occurs on a concrete floor, it is called sweating slab syndrome. This condition can be especially dangerous in a warehouse situation where the condensation results in slick floors. Handrails can also become slippery if condensation is allowed to persist.
Condensation issues can be resolved by correcting the air flow and/or dehumidifying the space. Commercial dehumidifiers can help reduce air moisture levels enough to prevent condensation in some cases. Fans are another good solution for many buildings, as they have both an evaporative and temperature-mitigating effect.

Air Flow Is Critical

Most temperature-control problems in large facilities are intimately connected with air flow. While it is tempting for workers to simply adjust the thermostat, this approach does not always result in the desired effect. In fact, it can create damaging or dangerous situations. If you are struggling with these or other unresolved temperature issues in your plant, consider having a heating, ventilation and air conditioning (HVAC) expert or building performance professional inspect your facility and recommend specific air-flow solutions for your site.

Pl  plants types (groups) as modified for water conservation

1. Storage Leaves:
Some plants of xerophytic habitats and members of the family Crassulaceae generally have highly thickened and succulent leaves with water storage tissue. These leaves have large parenchymatous cells with big central vacuole filled with hydrophilic colloid. This kind of adaptation helps plants to conserve very limited supply of water and resist desiccation (drying up).
2. Leaf Tendrils:
In weak- stemmed plants, leaf or a part of leaf gets modified into green thread­like structures called tendrils which help in climbing around the support.
The parts of leaf which get modified into tendrils are as follows:
(i) Entire Leaf is Modified into Tendril, e.g., Lathyrus aphaca (wild pea) (Fig. 4.19).
(ii) Upper Leaflets Modified into Tendrils, e.g, Pisum sativum (pea) (Fig. 4.20), Lathyrus odoratus (sweet pea).
(iii) Terminal leaflets Modified into Tendrils, e.g., Naravelia (Fig. 4.21).

(iv) Leaf Tip Modified into Tendril, e.g., Gloriosa (Glory lily) (Fig. 4.22).
(v) Petiole Modified into Tendril, e.g., Clematis (Fig. 4.23).
(vi) Stipule Modified into Tendril, e.g., Smilax (Fig. 4.24).

3. Leaf-spines:

Leaves of certain plants become wholly or partially modified for defensive purpose into sharp, pointed structures known as spines. Thus, in prickly pear (Opuntia; fig. 4.25) the minute leaves of the axillary bud are modified into spines. The leaf-apex in date-palm, dagger plant (Yucca) etc., is so modified, while in plants like prickly or Mexican poppy (Argemone), Amercian aloe (Agave), Indian aloe (Aloe), etc., spines develop on the margin as well as at the apex. In barberry the leaf itself becomes modified into a spine; while the leaves of the axillary bud are normal.

4. Scale-leaves:
Typically these are thin, dry, stalkless, membranous structures, usually brownish in colour or sometimes colourless. Their function is to protect the axillary bud that they bear in their axil. Sometimes scale-leaves are thick and fleshy, as in/onion; then their function is to store up water and food. Scale-leaves are common in parasites, saprophytes, underground stems, etc. They are also found in Casuarina, Asparagus etc.

5. Leaflet Hooks:
In Bignonia unguiscati the three terminal leaflets of leaf get modified into claw like hooks which help in climbing (Fig. 4.29).
6. Leaf Roots:
In case of Salvinia three leaves are present at one node. Out of these two leaves are normal and third gets modified into adventitious roots which help in floating over the surface of water (Fig. 4.30).

7. Phyllode:
In Australian Acacia (Fig. 4.31) the petiole or any part of the rachis becomes flattened or winged taking the shape of the leaf and turning green in colour. This flattened or winged petiole or rachis is known as the phyllode. The normal leaf which is pinnately compound in nature develops in the seedling stage, but it soon falls off. The phyllode then performs the functions of the leaf. In some species, however, young or even adult plants are seen to bear the normal compound leaves together with the phyllodes.
There are about 300 species of Australian Acacia (Acacia moniliformis), all showing the phyllodes. In lerusalem thorn (Parkinsonia; fig. 4.32), a small prickly tree, the primary rachis of the bipinnate leaf ends in a sharp spine, while each secondary rachis is a phyllode being green and flattened. The leaflets are small and fall off soon. The phyllode then performs the functions of the leaflets.

8. Insect Catching Leaves:

In insectivorous plants, the leaves are especially adapted to catch and digest insects to fulfil their nitrogen requirement. Some of the adaptations are given below.

(i) Leaf-Pitcher:
This is a device to catch insects for fulfilling the deficiency of nitrogen in the medium where plant is growing. In case of Nepenthes, Dischidia and Sarracenia leaf-lamina is modi­fied into pitcher-like structure called leaf-pitcher.
Nepenthes (Fig. 4.33), also called pitcher-plant bears special type of leaves. Leaf-base is winged, petiole is tendrillar and lamina is modified into pitcher-like structure having a coloured lid which attracts the insects and keeps the pitchei closed during immaturity. The rim of the pitcher is internally lined by backwardly directed hair and a large number of minute scales due to which the insect slips and is captured.
The inner walls of the pitcher have glands which secrete a digestive fluid into the cavity of the pitcher. The insect is digested here and waste material settles down at the bottom. Sarracenia has pitchers in the from of rosetts. The pitchers are similar to those of Nepenthes but are sessile.
Pitchers are also found in Dischidia, an epiphytic climber. Rain water and debris accumulate inside the pitchers. The roots from the nodes of the stem grow into the cavity of the pitcher and absorb water.
(ii) Leaf Bladder:
Utricularia (Fig. 4.34) is another insectivorous plant which grows in water. It bears highly dissected submerged leaves. Some of the segments of the leaf are modified into bladders or utricles.
The inner wall of the bladder is lined by digestive glands. The opening of the bladder is provided with a valve which opens inwards. On the valve and rim of the opening are present long and branched bristles. Minute water animals get entangled in the bristles, valve opens inwards and animals go in and valve gets closed. These are digested inside the vessel.

-  Pla