Current Affairs 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 there is incomplete oxidation of carbohydrates (In the respiration of succulents i.e., Bryophyllum, Opuntia). \[2{{C}_{6}}{{H}_{12}}{{O}_{6}}+3{{O}_{2}}\to 3{{C}_{4}}{{H}_{6}}{{O}_{5}}+3{{H}_{2}}O;\frac{C{{O}_{2}}}{{{O}_{2}}}=\frac{0}{3}=0\] (Zero) (6) Respiration in the absence of O2 (in anaerobic respiration) \[{{C}_{6}}{{H}_{12}}{{O}_{6}}\xrightarrow{\text{Zymase}}2{{C}_{2}}{{H}_{5}}OH+2C{{O}_{2}}\]; \[\frac{C{{O}_{2}}}{{{O}_{2}}}=\frac{2}{0}=\infty \](Infinite)

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 place in the cytoplasm and requires oxygen for its entire operation. (iii) Description : There are two types of evidences is support of the existence of such an alternative pathway-works on the inhibiting action of malonic acid on the Krebs cycle and studies with the radioactive \[({{C}^{14}}).\] Twelve molecules of \[NAD{{H}_{2}}\] formed in the reaction can be oxidised back to 12 NADP with the help of the cytochrome system and oxygen of the air. \[12\text{ NADP}{{\text{H}}_{\text{2}}}+6{{O}_{2}}\underset{\text{System}}{\mathop{\xrightarrow{\text{Cytochrome}}}}\,\text{12}{{\text{H}}_{\text{2}}}\text{O}+\text{12NADP}\] In this electron transfer process, 36 molecules of ATP are synthesized.   (iv) Significance of PPP (a) It is the only pathway of carbohydrate oxidation that gives \[NADP{{H}_{2}},\]Which is needed for synthetic action like synthesis of fatty acid (in adipose tissues) and amino acids (in liver). (b) It synthesizes 3C-glyceraldehyde-3-P, 3C-dihydroxy acetone phosphate, 4C-erythrose-4-P, 5C-ribulose phosphate, 5C-xylulose phosphate, 5C-ribose phosphate, 6 C-Fructose 6-phosphate, 7C-sedoheptulose-7-phosphate. (c) It is the major pathway by which necessary ribose and deoxyribose are supplied in the biosynthesis of nucleotides and nucleic acid. (d) Erythrose 4 phosphate for the synthesis of lignin, oxine, anthocyanine and aromatic amino acid (phenylalanine, tyrosine, and tryptophan). (e) Young growing tissues appears to use to the Krebs cycle as the predominant pathway for glucose oxidation, while aerial parts of the plants and other tissues seem to utilise the PPP as well as the Krebs cycle. (f) It gives \[6C{{O}_{2}},\]required for photosynthesis. (g) Ribulose five phosphate is used in photosynthesis to produce RuBP which act as primary \[C{{O}_{2}}\]acceptor in \[{{C}_{3}}\]cycle. (3) Cyanide resistant pathway : Cyanide-resistant respiration seems to be widespread in higher plant tissues. Cyanide prevents flow of electron from Cyt \[{{a}_{3}}\] to oxygen, so called ETC inhibitor. In these plant tissues resistance is due to, a branch point in the ETS preceeding the highly cyanide-sensitive cytochromes. The tissues lacking this branch point, or alternate pathway and blockage of cytochromes by cyanide, inhibits the electron flow. Significance (i) The role of alternative pathway is that it may provide a means for the continued oxidation of NADH and operation of the tricarboxylic acid 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 respiratory substrate, generally leads to an increase in the rate of respiration upto a certain point when some other factor becomes limiting.  (iii) Oxygen concentration of the atmosphere : The amount of oxygen in the environment of plants is increased or reduced upto quite low values the rate of respiration is not effected. On decreasing the amount of oxygen to 1.9% in the environment aerobic respiration become negligible (extinction point of aerobic respiration) but anaerobic respiration takes place. (iv) Oxygen poisoning : The significant fall in respiration rate was observed in many tissues in pure \[{{O}_{2}},\]even at N.T.P. This inhibiting effect was also observed in green peas when they are exposed to pure oxygen exerting a pressure of 5 atm- the respiration rate fall rapidly. The oxygen poisoning effect was reversible, if the exposure to high oxygen pressure was not too prolonged. (v) Water : With increase in the amount of water the rate of respiration increases. In dry seeds, which have \[8-12%\] of water the rate of respiration is very low but as the seeds imbibe water the respiration increases. As water is necessary for activity of enzymes. (vi) Light : Respiration takes place in night also which shows that light is not essential for respiration. But light effects the rate of respiration indirectly by increasing the rate of photosynthesis due to which concentration of respiratory substrates is increased. More the respiratory substrate more is the rate of respiration. (vii) Carbon dioxide\[(C{{O}_{2}})\]:  If the amount of CO2 in the air is more than the usual rate of respiration is decreased. Germination of seeds is reduced and rate of growth falls down. Heath, (1950) has shown that the stomata are closed at higher cone. of \[C{{O}_{2}},\] due to which oxygen does not penetrate the leaf and rate of respiration is lowered. (viii) Inorganic salts : The chlorides of alkali cations of Na  and K, as also the divalent cations of Li, and Ca and Mg, generally increase the rate of respiration as measured by the amount of \[C{{O}_{2}}\]evolved. Monovalent chlorides of K and Na increases the rate of respiration, while 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 may occur. (2) Manganese Source : Like iron, the oxide forms of manganese are common in soil. However, manganese dioxide (highly oxidised form) is not easily available to plants. It is absorbed from the soil in bivalent form \[(M{{n}^{++}}).\] Increased acidity leads to increase in solubility of manganese. In strong acidic soils, manganese may be present in toxic concentrations. Oxidising bacteria in soils render manganese unavailable to plants at pH ranging from 6.5 to 7.8. Functions (i) It acts as activator of enzymes of respiration (malic dehydrogenase and oxalosuccinic decarboxylase) and nitrogen metabolism (nitrite reductase). (ii) It is essential for the synthesis of chlorophyll. (iii) It is required in photosynthesis during photolysis of water. (iv) It decreases the solubility of iron by oxidation. Hence, abundance of manganese can lead to iron deficiency in plants. Deficiency symptoms (i) Chlorosis (interveinal) and necrosis of leaves. (ii) Chloroplasts lose chlorophyll, turn yellow green, vacuolated and finally perish. (iii) 'Grey spot disease' in oat appears due to the deficiency of manganese, which leads to total failure of crop. (iv) 'Marsh spot's in seeds of pea. (v) Deficiency symptoms develop in older leaves. (3) Copper Source : Copper occurs in almost every type of soil in the form of complex organic compounds. A very small amount of copper is found dissolved in the soil solution. It is found in natural deposits of chalcopyrite (CuFeS2). Functions   (i) It activates many enzymes and is a component of phenolases, ascorbic acid oxidase, tyrosinase, cytochrome oxidase. (ii) Copper is a constituent of plastocyanin, hence plays a role in photophosphorylation. (iii) It also maintains carbohydrate nitrogen balance. Deficiency symptoms (i) Both vegetative and reproductive growth are reduced. (ii) The most common symptoms of copper deficiency include a disease of fruit trees called 'exanthema' in which trees start yielding gums on bark and 'reclamation of crop plants', found in cereals and legumes. (iii) It also causes necrosis of the tip of the young leaves (e.g., Citrus). The disease is called 'die back'. (iv) Carbon dioxide absorption is decreased in copper deficient trees. (v) Wilting of entire plant occurs under acute 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 other organic molecules as chlorophyll. Nitrogen is also present in various hormones, coenzymes and ATP etc. It plays an important role in protein synthesis, respiration, growth and in almost all metabolic reactions. Deficiency symptoms (i) Impaired growth (ii) Yellowing of leaves due to loss of chlorophyll, i.e., chlorosis. (iii) Development of anthocyanins pigmentation in veins, sometimes in petioles and stems. (iv) Delayed or complete suppression of flowering and fruiting. Excessive supply of nitrogen produces following symptoms : (i) Increased formation of dark green leaves. (ii) Poor development of root system. (iii) Delayed flowering and seed formation. (3) Phosphorus Source : Phosphorus is present in the soil in two general forms, organic and inorganic. Plants do not absorb organic phosphorus, either from the solid or solution phase of soil. However, organic compounds are decomposed and phosphorus is made available to plants in inorganic form. Soil solution contains phosphorus in inorganic forms as the phosphate ions obtained as  and When pH is low phosphate ions are present in the form of  When pH is high, phosphate ions are represented in Functions (i) Phosphorous is present abundantly in the growing and storage organs such as fruits and seeds. It promotes healthy root growth and fruit ripening by helping translocation of carbohydrates. (ii) It is present in plasma membrane, nucleic acid, nucleotides, many coenzymes and organic molecules as ATP. (iii) Phosphorus plays an indispensable role in energy metabolism i.e., hydrolysis of pyrophosphate. Thus it is required for all phosphorylation reactions. Deficiency symptoms (i) Leaves become dark green or purplish. (ii) Sometimes development of anthocyanin pigmentation occurs in veins which may become necrotic (Necrosis is defined as localised death of cells). (iii) Premature fall of leaves. (iv) Decreased cambial activity resulting in poor development of vascular bundles. (v) Sickle-leaf disease. (4) Sulphur Source : Sulphur is present as sulphate  in mineral fraction of soil. In industrialized areas, atmospheric sulphur dioxide  and sulphur trioxide ; in low concentration) may be important sources of sulphur nutrition. Functions (i) Sulphur is a constituent of amino-acids like cystine, cysteine and methionine; vitamins like biotin and thiamine, and coenzyme A. 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 two categories : (i) Total parasites. (ii) Semiparasites or partial parasites. (i) Total parasites : These plants never possess chlorophyll, hence they always obtain their food from the host. They may be attached to branches, stem (stem parasites) or roots (root parasites) of the host plants. Total stem parasite : Cuscuta is a rootless, yellow coloured, slender stem with small scale leaves, which twines around the host. The parasite develops haustoria (Small adventitious sucking roots) which enter the host plant forming contact with xylem and phloem of the host. It absorbs prepared food, water and minerals from the host plant. Total root parasite : Total root parasites are common in the families like Orobanchaceae, Rafflesiaceae, Balanophoraceae, etc. Orobanche, Rafflesia and Balanophora are some of the common root parasites. Orobanche is commonly known as broom rape. It has scale leaves and pinkish or bluish flowers. The tip of the root of parasite makes haustorial contact with the root of host and absorbs food from the host. Orobanche is usually parasitic upon brinjal, tobacco. In Rafflesia (stinking corpse lily) another root parasite, vegetative parts of the plant are highly reduced and represented by cellular filaments resembling fungal mycelium. These filaments get embedded in the soft tissue of the host while the flowers emerge out in the forms of buds. Balanophora occurs as a total stem parasite in the roots of forest trees. (ii) Semiparasite or partial parasite : Such parasitic plants have chlorophyll and, therefore, synthesize their organic food themselves. But they fulfill their mineral and water requirements from their host plants. These are two types : Partial stem parasites : The well known example of partial stem parasite is Viscum album (mistletoe) which parasitizes a number of shrubs and trees. The mature plant of Viscum is dichotomously branched with green leaves born in pairs attached on each node of stem. The shoots are attached to the host by means of haustoria. The primary haustoria reaches upto cortex of the host which runs logitudinally. It sends secondary haustoria which make connection with the xylem of the host and absorb water and minerals 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 salts instead of soil led to increased understanding of plant nutrition. This cultivation of plants by placing the roots in nutrient solution is called hydroponics. Probably the first recorded use of soilless culture was by Woodward in 1699. By 1860, the culture solution technique was modernized by Sachs and he showed the essentiality of nitrogen for plant growth. Another significant worker for studying the essentiality of elements was Knop (1865). The method of growing plants in aqueous nutrient solutions as employed by Sachs and Knop is used experimentally and commercially today and known as hydroponic culture. Now a days a chelating agent Na2-EDTA (Disodium salt of ethylene diamine tetra acetic acid. EDTA (Ethylene diamine tetra-acetic acid) is a buffer which is used in tissue cultures) is added. Hydroponics or soilless culture helps in knowing (1) The essentiality of mineral element. (2) The deficiency symptoms developed due to non-availability of particular nutrient. (3) Toxicity to plant when element is present in excess. (4) Possible interaction among different elements present in plant. (5) The role of essential element in the metabolism of plant. Solid medium culture : In this method either sand or crushed quartz is used as a rooting medium and nutrient solution is added to it. The nutrient medium is provided by one of the following methods : Drip culture : It is done by dripping over the surface. Slop culture : It is done by having the medium over the surface. Sub-irrigation : Here the solution is forced up from the bottom of the container.

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 air react to form nitric oxide (NO). The nitric oxide is further oxidised with the help of \[{{O}_{2}}\] to form nitrogen dioxide \[(N{{O}_{2}}).\] \[{{N}_{2}}+{{O}_{2}}\xrightarrow{\text{Lightening}}2NO\] \[2NO+{{O}_{2}}\xrightarrow{\text{Oxidation}}2N{{O}_{2}}\] \[N{{O}_{2}}\]combines with \[{{H}_{2}}O\] to form nitrous acid \[(HN{{O}_{2}})\] and nitric acid \[(HN{{O}_{3}}).\] The acid falls along with rain water. Now it acts with alkaline radicals to form water soluble \[NO_{3}^{-}\] (nitrates) and \[NO_{2}^{-}\](nitrites). \[2N{{O}_{2}}+{{H}_{2}}O\xrightarrow{{}}HN{{O}_{2}}+HN{{O}_{3}}\] \[HN{{O}_{3}}+Ca\,\,\,or\,\,K\,\,salts\xrightarrow{{}}Ca\,\,or\,\,K\,\,Nitrates\] The nitrates are soluble in water and are directly absorbed by the plants. (ii) Industrial nitrogen fixation : Nitrogen and hydrogen combines to form ammonia industrially, under pressure and temperature. (2) Biological nitrogen fixation : The conversion of atmospheric nitrogen into inorganic or organic usable forms through the agency of living organisms is called biological nitrogen fixation. The process is carried by two main types of microorganisms, those which are "free living" or asymbiotic and those which live in close symbiotic association of with other plants. (i) Asymbiotic biological nitrogen fixation : This is done by many aerobic and anaerobic bacteria, cyanobacteria (blue green algae) and some fungi e.g. : Free living bacteria : Free living N2 fixing bacteria add 10–25 kg of nitrogen /ha/annum. Aerobic                        –             Azotobacter Anerobic                      ­–             Clostridium Photosynthetic         –             Chlorobium Chemosynthetic       –             Thiobacillis Cyanobacteria (blue-green algae) e.g., Anabaena, Nostoc, Tolypothrix cylindrospermum, Calotherix and Aulosira etc. They add \[2030kg\] of \[{{N}_{2}}\]per hactare of soil and water bodies. Free living fungi e.g., Yeast cells and Pullularia. (ii) Symbiotic biological nitrogen fixation : Symbiotic bacteria are found in the root nodules of the members of family Leguminosae. The best known nitrogen fixing symbiotic bacterium is Rhizobium leguminosarum (Bacillus radicicola). Rhizobium penetrates to the cortex of root through infection thread. Simultaneously cortical cells or root are stimulated to divide more vigorously to form nodules on the root. Neither bacterium nor plant alone can fix nitrogen in such cases. Nitrogen fixation is actually the outcome of symbiotic relationship between the two. When a section of root nodules is observed the presence of a pigment, leghaemoglobin is seen to impart pinkish colour to it. This pigment is closely related to haemoglobin and helpful in creating optimal condition for 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.