11th Class

R.Q. is the ratio of the volume of \[C{{O}_{2}}\]released to the volume of oxygen taken in respiration and is written as \[R.Q.=\frac{Volume\,of\,C{{O}_{2}}\,evolved}{Volume\,of\,{{O}_{2}}\,absorbed}=\frac{C{{O}_{2}}}{{{O}_{2}}}\] R.Q. is usually measured by Ganong's respirometer. (1) When carbohydrates are the respiratory substrate (=germinating wheat, oat, barley, paddy grains or green leaves kept in dark or tubers, rhizomes, etc.) \[\underset{\text{Glucose}}{\mathop{{{C}_{6}}{{H}_{12}}{{O}_{6}}}}\,+6{{O}_{2}}\to 6C{{O}_{2}}+6{{H}_{2}}O;\,\,\frac{C{{O}_{2}}}{{{O}_{2}}}=\frac{6}{6}=1\]  (Unity) (2) When fats are the respiratory substrate (=germinating castor, mustard, linseed, til seeds) for fatty substances R.Q. is generally less than one . (i) \[\underset{\text{Stearic}\,\text{acid}}{\mathop{{{C}_{18}}{{H}_{36}}{{O}_{2}}}}\,+26{{O}_{2}}\to 18C{{O}_{2}}+18{{H}_{2}}O;\frac{C{{O}_{2}}}{{{O}_{2}}}=\frac{18}{26}=0.7\](Less than unity) (ii) \[\underset{\text{Tripalmitin}}{\mathop{2{{C}_{51}}{{H}_{98}}{{O}_{6}}}}\,+145{{O}_{2}}\to 102C{{O}_{2}}+98{{H}_{2}}O;\frac{C{{O}_{2}}}{{{O}_{2}}}=\frac{102}{145}=0.7\] (Less than unity) (3) When protein are the respiratory substrate (=germinating gram, pea, bean, mung seeds) value of R.Q. is less than unity (0.5-0.9). (4) When organic acids are the respiratory substrate (i)\[\underset{\text{Malic}\,\text{acid}}{\mathop{{{C}_{4}}{{H}_{6}}{{O}_{5}}}}\,+3{{O}_{2}}\to 4C{{O}_{2}}+3{{H}_{2}}O;\frac{C{{O}_{2}}}{{{O}_{2}}}=\frac{4}{3}=1.33\] (More than unity) (ii) \[\underset{\text{Oxalic}\,\text{acid}}{\mathop{2{{(COOH)}_{2}}}}\,+{{O}_{2}}\to 4C{{O}_{2}}+2{{H}_{2}}O;\frac{C{{O}_{2}}}{{{O}_{2}}}=\frac{4}{1}=4\] (More than unity) Some other organic acids and their R.Q. are – Succinic acid (1.14), Taurtric acid (1.6) and Acetic acid (1). (5) When more...

There are three phases of respiration : (1) External respiration : It is the exchange of respiratory gases (\[{{O}_{2}}\]and\[C{{O}_{2}}\]) between an organism and its environment. (2) Internal or Tissue respiration : Exchange of respiratory gases between tissue and extra cellular environment . Both the exchange of gases occur on the principle of diffusion. (3) Cellular respiration : It is an enzymatically-controlled stepped chemical process in which glucose is  oxidised inside the mitochondria to produce energy-rich ATP  molecules with high-energy bonds. So, respiration is a biochemical process.

 (1) Entner-Doudoroff pathway Discovery : Entner-Doudoroff path discovered by Entner & Doudoroff. This pathway is also called glycolysis of bacteria. Certain bacteria such as Pseudomonas sacchorophila, P. fluorescens, P. lindeneri and P. averoginosa lack phosphofructokinase enzyme. They can not degrade glucose by glycolytic process.     (2) Pentose phosphate pathway (i) Discovery : It is also called as Hexose monophosphate (HMP) shunt or Warburg Dickens pathway or direct oxidation pathway. It provides as alternative pathway for breakdown of glucose which is independent of EMP pathway (glycolysis) and Krebs cycle. Its existence was suggested for the first time by Warburg et al. (1935) and Dickens (1938). Most of the reaction of this cycle were described by Horecker et al. (1951) and  Racker (1954). (ii) Occurrence : Pentose phosphate  pathway that exists in many organisms. This pathway takes more...

Many external and internal factors affecting the rate of respiration are as follows : (1) External factors (i) Temperature : With every \[10{}^\circ C\] rise of temperature from \[0{}^\circ C\] to \[30{}^\circ C\]the rate of respiration increases 2 to 2.5 times (i.e., temperature coefficient \[({{Q}_{10}}{}^\circ )\] is = 2 to 2.5), following Vant Hoff’s Law. Maximum rate of respiration takes place at \[{{30}^{o}}C,\]there is an initial rise, soon followed by a decline. Higher the temperature above this limit, more is the initial rise but more is the decline and earlier is the decline in the rate of respiration. Probably this is due to denaturation of enzymes at high temperature. Below \[0{}^\circ C\]the rate of respiration is greatly reduced although in some plants respiration takes place even at \[-20{}^\circ C.\] Dormant seeds kept at \[{{50}^{o}}C\]survive. (ii) Supply of oxidisable food : Increase in soluble food content readily available for utilization as more...

(1) Iron Source : It is present in the form of oxides in the soil. It is absorbed by the plants in ferric as well as ferrous state but metabolically it is active in ferrous state. Its requirement is intermediate between macro and micro-nutrients. Functions (i) Iron is a structural component of ferredoxin, flavoproteins, iron prophyrin proteins (Cytochromes, peroxidases, catalases, etc.) (ii) It plays important roles in energy conversion reactions of photosynthesis (phosphorylation) and respiration. (iii) It acts as activator of nitrate reductase and aconitase. (iv) It is essential for the synthesis of chlorophyll. Deficiency symptoms (i) Chlorosis particularly in younger leaves, the mature leaves remain unaffected. (ii) It inhibits chloroplast formation due to inhibition of protein synthesis. (iii) Stalks remain short and slender. (iv) Extensive interveinal white chlorosis in leaves. (v) It may develop necrosis aerobic respiration severely affected. (vi) In extreme deficiency scorching of leaf margins and tips more...

The role of different elements is described below : (1) Carbon, hydrogen and oxygen : These three elements, though can not be categorised as mineral elements, are indispensible for plant growth. Carbon, hydrogen and oxygen together constitute about 94% of the total dry weight of the plant. Carbon is obtained from the carbon dioxide present in the atmosphere. It is essential for carbohydrate and fat synthesis. Hydrogen and oxygen would be obtained from water which is absorbed by the plants from the soil. Some amount of oxygen is also absorbed from the atmosphere. (2) Nitrogen Source : The chief source of nitrogen for green plants is the soil. It is absorbed mainly in the form of nitrate ions The major sources of nitrate for the plants are sodium nitrate, potassium nitrate, ammonium nitrate and calcium nitrate. Functions : Nitrogen is an essential constituent of proteins, nucleic acids, vitamins and many more...

The method of taking in and synthesis of various types of foods by different plants and animals is called nutrition. Generally plants are autotrophic in their mode of nutrition, but there are some examples which are heterotrophic in their mode of nutrition. These plants are unable to manufacture their own food due to lack of chlorophyll or some other reasons. (1) Parasites : These plants obtain either their organic food prepared by other organisms or depend upon other plants only for water and minerals with the help of which they can synthesize their own food. The living organism from which the parasite obtains its organic food or water and minerals is called host. Any part of the body of parasite is modified into a special organ called haustorium which enters into the cells of host and absorbs food or water and minerals from the host. Parasites can be classified into more...

Ash analysis : The plant tissue is subjected to a very high temperature (550-600°C) in an electric muffle furnace and is reduced to ash. The plant ash left behind forms a very small proportion of plants dry weight ranging from 2 to 10% only. Analysis of plant ash shows that about 92 mineral elements are present in different plants. Out of these, 30 elements are present in each and every plants and rest are in one or other plants. Out of these 30 elements, 16 elements are necessary for plants and are called essential elements. Solution culture (Hydroponics) : In this method plants are grown in nutrient solutions containing only desired elements. To determine the essentiality of an element for a particular plant, it is grown in a nutrient medium that lacks or is deficient in this element. The growing of plants with their roots in dilute solutions of mineral more...

Higher plants generally utilize the oxidized forms such as nitrate \[(NO_{3}^{-})\] and nitrite \[(NO_{2}^{-})\] or the reduced form \[(NH_{4}^{+})\] of nitrogen which is made available by a variety of nitrogen fixers. Nitrogen can be fixed by three methods : Process of Nitrogen fixation On the basis of agency through which the nitrogen is fixed the process is divided into two types abiological and biological. (1) Abiological : They are two types : (i) Natural or Atmospheric nitrogen fixation : By photochemical and electrochemical reactions, oxygen combines with nitrogen to form oxides of nitrogen. Now they get dissolved in water and combine with other salts to produce nitrates. Physical nitrogen fixation out of total nitrogen fixed by natural agencies approximately 10% of this occurs due to physical processes such as lightening (i.e., electric discharge), thunder storms and atmospheric pollution. Due to lightening and thundering of clouds, \[{{N}_{2}}\] and \[{{O}_{2}}\] of the more...

P.R. Stout and D.R. Hoagland (1939) proved that mineral salts are translocated through xylem. After absorption of minerals by root, ions are able to reach xylem by two pathways. (1) Apoplast pathway : In this pathway inflow of water takes place from the cell to cell through spaces between cell wall polysaccharides. Ions thus are able to move from cell wall of epidermis to cell walls of various cells in cortex, cytoplasm of endodermis, cell wall of pericycle and finally into xylem. (2) Symplast pathway : In this pathway ions move through cytoplasm of epidermis and finally move through cytoplasm of cortex, endodermis, pericycle through plasmodesmata and finally into xylem. Minerals in xylem are carried along with water to other parts of the plant along transpiration stream. Minerals reaching leaves take part in assimilation of organic compounds and then transported to other parts of the plant through phloem.