Osmotic Adjustment

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Osmotic Adjustment in plants

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OSMOTIC ADJUSTMENT:

OSMOTIC ADJUSTMENT Geetika, 2012A41D

Slide2:

1 Osmosis  is the spontaneous net movement of solvent molecules through a partially permeable membrane into a region of higher solute concentration, in the direction that tends to equalize the solute concentrations on the two sides. It may also be used to describe a physical process in which any solvent moves, without input of energy, across a semi-permeable membrane (permeable to the but not the solute) separating two solutions of different concentrations.  Although osmosis does not require input of energy, it does use  kinetic energy   and can be made to do work. Osmosis Geetika, 2012A41D

Osmotic pressure:

Osmotic pressure Osmotic pressure  is the pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane.   It is also defined as the minimum pressure needed to nullify osmosis. The phenomenon of osmotic pressure arises from the tendency of a pure solvent to move through a semi-permeable membrane and into a solution containing a solute to which the membrane is impermeable. This process is of vital importance in biology as the cell's membrane is selective toward many of the solutes found in living organisms. 2 Geetika, 2012A41D

Osmotic Adjustment:

Osmotic Adjustment 3 Osmotic adjustment in higher plants refers to the maintenance of turgor by lowering of osmotic potential arising from the net accumulation of solutes in response to water deficits.  Source of animation : http://www.authorstream.com Geetika, 2012A41D

Osmotic Adjustment:

Osmotic Adjustment Turgor pressure on plant cells In biology, turgor pressure or turgidity is the pressure of the cell contents against the cell wall, in plant cells, determined by the water content of the vacuole, resulting from osmotic pressure. 4 Geetika, 2012A41D

The mechanism of osmotic adjustment:

The mechanism of osmotic adjustment Organic solutes Many plants are in response to environmental stresses of salinity and drought by accumulating organic solutes, which are known as compatible solutes and reported to be nontoxic even in relatively high concentrations (Zhang et al. 2002 a). Compatible solutes are low molecular weight and highly soluble compounds. Generally, they protect plants from stress through different courses, including contribution to cellular osmotic adjustment, detoxification of reactive oxygen species, protection of membrane integrity, and stabilization of enzymes or proteins ( Ashraf and Foolad 2007). Compatible solutes are usually referred to as important osmolytes in osmotic adjustment (Table 1). 5 Geetika, 2012A41D

Slide7:

Main organic osmolytes in osmotic adjustment on different plants and algae Species Stress Organic osmolytes Beta vulgaris L. (Sugar beet) Drought Glycinebetaine Distichlis spicata L. (Halophytic grass) Salt Proline Medicago truncatula and Phaseolus vulgaris (Legumes) Salt Trehalose Nicotiana tabacum L. (Tobacco) Drought Proline Oryza sativa L. (Rice) Salt Total soluble sugar(Glucose Fructose and Sucrose) , Triticum aestivum L. (Durum wheat) Drought Proline Triticum aestivum L. (Spring wheat) Salt Glycine betaine Bangiopsis subsimplex (Stylonematophyceae) Salt Sorbitol Dixoniella grisea (Rhodellophyceae) Salt Mannitol Dunaliella salina (Chlorophyta) Salt Glycerol Dunaliella tertiolecta (Chlorophyta) Salt Glycerol 6 Geetika, 2012A41D

The mechanisms of osmotic adjustments resist drought and salinity stresses in plants.:

The mechanisms of osmotic adjustments resist drought and salinity stresses in plants. 7 Geetika, 2012A41D

Role of enzymes in osmotic adjustments :

Role of enzymes in osmotic adjustments In osmotic adjustment, some enzymes play main roles in the synthesis of osmolytes to alleviate or eliminate saline and drought environmental stresses. 8 Geetika, 2012A41D

Role of enzymes in osmotic adjustments :

Role of enzymes in osmotic adjustments Researchers have found that betaine aldehyde dehydrogenase (BADH), pyrroline-5- carboxylate reductase (P5CR), and ornithine-d- aminotransferase (OAT) were enhanced in two varieties of reed (DR and HSR) (Zhu et al. 2003), whereas proline oxidase (PO) activities were inhibited , which suggested that changes in the activities of enzymes is involved in osmotic adjustment and might play important roles in the adaptation of reed plants to more extreme arid and saline habitats. Reed plants 9 Geetika, 2012A41D

Glycine betaine:

Glycine betaine Glycine betaine is an important osmolyte in some plants. Glycine betaine is synthesized by several plant families in response to saline or drought stress ( Munns 2002; Ashraf and Harris 2004; Su et al. 2006) Its primary effect on plant cells is to balance the osmotic potential of intracellular and extracellular ions to keep water and reduce salinity toxicity. It also functions as a compatible solute to stabilize the structure of proteins to protect the major enzymes, protect membrane structures, protect photosynthetic apparatus, and protect cytoplasm and chloroplasts from adverse effects of Na+ ( Raza et al. 2007). 10 Geetika, 2012A41D

Slide12:

In plants, glycine betaine is synthesized in chloroplasts. Several enzymes play important catalytic roles in the pathway of glycine betaine synthesis. These are choline monooxygenase (CMO) from beet ( Beta vulgaris L.), betaine aldehyde dehydrogenase (BADH) from spinach ( Spinacia oleracea L.), which have been introduced into different plants and enhanced salt and drought stress tolerances (Yang et al. 2008; Zhang et al. 2008). ...........Glycine betaine 11 Geetika, 2012A41D

Slide13:

In sugar beet ( Beta vulgaris L.), for example, glycine betaine is accumulated to a high level and plays the main role in osmotic adjustment under osmotic stress ( Chołuj et al. 2008). In two spring wheat ( Triticum aestivum L.) cultivars, the important determinants of salt tolerance are aintenance and acquisition of both K+ and Ca2+ according to Ashraf and Harris (2004), who postulated that K+/Na+ and Ca2+/Na+ ratios might be valid selection criteria for assessing salinity tolerance of different crop species. In both cultivars, application of glycine betaine resulted in an increased K+/Na+ and Ca2+/Na+ ratios under saline conditions, therefore it was concluded that glycine betaine played an important role in resistance to osmotic stress ( Raza et al. 2007). ...........Glycine betaine 12 Geetika, 2012A41D

Proline:

Proline Proline is an important amino acid for plant resistance to osmotic stress, and the accumulation of proline in plants was usually related to increased contents of L-glutamic acid, which is one of the possible precursors for proline biosynthesis (Ashraf and Foolad 2007; Kishor et al. 2005). Pyrroline-5-carboxylate synthetase (P5CS) and pyrroline-5-carboxylate reductase (P5CR) are key enzymes in proline biosynthetic pathway (Ashraf and Foolad 2007). 13 Geetika, 2012A41D

..............Proline:

P5CS is a rate-limiting enzyme in this pathway. For example, over-expressing P5CS in transgenic tobacco ( Nicotiana tabacum L.) plants have shown increased concentration of proline and resistance to drought stress (Gubisˇet al. 2007). In some plants under drought stress, the accumulation of proline was also related to the increased contents of other precursors for proline biosynthesis, including ornithine and arginine, and ornithine D-aminotransferase (OAT) is the key enzyme responsible for the ornithine pathway (Zhu et al. 2003; Ashraf and Foolad 2007). ..............Proline 14 Geetika, 2012A41D

..............Proline:

In durum wheat , for example, a positive correlation was observed between proline level and osmotic potential, and it was concluded that proline is an important osmolyte in osmotic adjustment under salinity stress ( Poustini et al. 2007). In plants, the accumulation of proline normally occurs in the cytosol, and it contributes substantially to the cytoplasmic osmotic adjustment in response to drought or salinity stress ( Ashraf and Foolad 2007). ..............Proline 15 Geetika, 2012A41D

..............Proline:

For example, when cells of the halophytic grass Dis - tichlis spicata L. treated with higher salinity, there have been considerable accumulation of proline concentrations in the cytosol (Ketchum et al. 1991). ..............Proline Dis- tichlis spicata L 16 Geetika, 2012A41D

Glycerol :

Glycerol In some plants, glycerol is the main osmolyte, which is synthesized from glucose. Glycerol-3-phosphate dehydrogenase (G3PDH) plays a major role in glycerol biosynthesis. Glycerol is also often a major osmolyte in some algae subjected to salinity stress. For example, D. Salina accumulates glycerol to counterbalance the osmotic pressure due to the high salinity of the surrounding medium ( Hadi et al. 2008; Mishra et al. 2008). 17 Geetika, 2012A41D

Biosynthetic pathway of glycerol:

Biosynthetic pathway of glycerol 18 Geetika, 2012A41D

.................Glycerol :

The extracellular osmotic pressure is combated in Dunaliella by changing the intracellular glycerol content. The glycerol is synthesized rapidly when salinity increases, and glycerol transforms to starch when salinity drops (Chen and Jiang 2009). For example, the cells of another green alga Unaliella tertiolecta ( Chlorophyta ) could adapt to the different concentration of saline by synthesizing or eliminating the intracellular glycerol to balance the osmotic potential of intracellular and extracellular ( Goyal 2007 a, 2007b). .................Glycerol 19 Geetika, 2012A41D

.................Glycerol :

Glycerol may be an effective osmotic element at high salinities. First, the high solubility of glycerol cannot be matched by most other compatible solutes. Second, glycerol is chemically inert and therefore non-toxic. Third, glycerol is an end-product metabolite, and therefore its accumulation is unlikely to offset major metabolic pathways. Fourth, the energetic cost of glycerol synthesis from glucose is relatively low and it does not depend on the availability of nitrogen (Chen and Jiang 2009) .................Glycerol 20 Geetika, 2012A41D

Sugars:

Sugars In several plants, sugars are main osmolytes for osmotic adjustment, including sucrose, trehalose, glucose and fructose, etc. The sugar content was a very sensitive factor for salt tolerance improvement and the increase in total sugar content in plant cells was observed with NaCl treatment (Liu and van Staden 2001). 21 Geetika, 2012A41D

Sugars:

Sugars Sugars diversion plays a key role in the adaptive processes linked with NaCl-tolerance, such as NaCl and Cl– translocation and (or) compartmentation, solute synthesis for interdependent mechanisms of growth and osmotic adjustment, and protein turn-over (Liu and van Staden 2001). 22 Geetika, 2012A41D

Slide24:

The accumulation of sugars appears to be common in some plants when they grow under osmotic stress. For example, Cha-um et al. (2009) found the total soluble sugar level in a salt-tolerant rice variety was higher than in the salt-sensitive variety, and that sugars enhance resistance to salt-induced osmotic stress in rice plants. Sugars 23 Geetika, 2012A41D

Sugars:

It was also found that, in root nodules of legumes ( Medicago truncatula and Phaseolus vulgaris ), the synthesis and accumulation of trehalose was enhanced as a compatible solute which was resistant to salt stress ( Lo´pez et al. 2008). In the red alga Bangiopsis subsimplex ( Stylonematophyceae ), sorbitol was the main low molecular weight carbohydrate and its level increased linearly with increasing salinities, indicating its important function as an osmolyte and compatible solute under high salt conditions ( Eggert et al. 2007 a). Sugars Red alga Bangiopsis subsimplex 24 Geetika, 2012A41D

Sugars:

In another red alga Dixoniella grisea hodellophyceae), the main low molecular weight carbohydrate is mannitol, which increased with increasing salinities, indicating its role as an osmolyte for the first time in a unicellular red alga (Eggert et al. 2007 b). Sugars Dixoniella grisea hodellophyceae 25 Geetika, 2012A41D

The effect of inorganic ions in osmotic adjustment:

The effect of inorganic ions in osmotic adjustment To maintain an osmotic gradient for the uptake of water, many halophytic plants accumulate inorganic ions to a concentration equal to or greater than that of the surrounding solution (Merchant and Adams 2005). 26 Halophytic plants Geetika, 2012A41D

.............Inorganic ions:

.............Inorganic ions In some plants, inorganic ions play more important roles in osmotic adjustment than that of compatible solutes For example, in contrast to organic solutes, inorganic ions formed the largest component contributing to osmotic adjustment in grapevines ( Vitis vinifera L., cv. Savatiano ), which seem to save energy and enable grapevines to grow in less favorable conditions ( Patakas et al. 2002). 27 Vitis vinifera L., cv. Savatiano Geetika, 2012A41D

.............inorganic ions :

.............inorganic ions Sodium ion, K+, and Ca2+ are the main inorganic ions in some halophytic plants under osmotic stress, and these ions prevent plants from harm caused by drought and salinity stresses by absorbing water into cells. In Cynara cardunculus , a robust thistle widespread in arid and semi-arid regions where high salinity is frequently present, osmotic adjustment was mainly due to inorganic ions and not to other organic solutes. Sodium ion is usually less toxic than K+ at high concentrations in C. cardunculus thriving in salty environments . 28 Cynara cardunculus Geetika, 2012A41D

.............inorganic ions :

The induction of a specific water stress stimulated Na+ but not K+ uptake and translocation to the shoot, indicating, once again, that C. cardunculus plants were well adapted to the presence of moderately high Na+ concentrations, and that this plant used Na+ to counteract the low water potential in the environment (Benlloch-Gonza´lez et al. 2005). 29 .............inorganic ions Cynara cardunculus Geetika, 2012A41D

.............inorganic ions :

According to Duan et al. (2007), tolerance to salinity stress in Suaeda salsa was linked through the mechanism of Na+ uptake, which is used for osmotic adjustment. The presence of salt decreases the water potential, so plants have problems with absorption of water. Vacuolar compartmentation of ions serves a function to maintain the appropriate water potential by enhancing the absorption of water. 30 .............inorganic ions Suaeda salsa Geetika, 2012A41D

.............inorganic ions :

Quintero et al. (2000) have shown that the mechanism of confinement of toxic Na+ in the vacuole contributed to the maintenance of sublethal ion levels in the cytosol for osmotic adjustment. 31 .............inorganic ions Geetika, 2012A41D

.............inorganic ions :

In a study by Moghaieb et al. (2004), additional Na+ in Salicornia europaea and Suaeda maritima grown at higher salt concentration accumulated in the vacuole and provided an osmotic driving force for the uptake of water in highly saline environments, which is consistent with the salt-accumulating character of the halophyte Sesuvium 32 .............inorganic ions Salicornia europaea Suaeda maritima halophyte Sesuvium Geetika, 2012A41D

.............inorganic ions :

Quintero et al. (2000) have also shown that uptake of ions for osmotic adjustment must reach the leaves at a rate that did not exceed the capacity of leaf cells to accumulate them in the vacuole. Thus, salt exclusion in the root and salt sequestration in the cell vacuoles have been presumed to be critical co-ordinated determinants for salt tolerance. In addition, some studies indicate that in several plants K+ or Ca2+ are regarded as the most important cationic osmolytes and accumulated to an osmotically significant degree in cells (Laurie et al. 2002; Reddy and Reddy 2004). 33 .............inorganic ions Geetika, 2012A41D

.............inorganic ions :

For example , three species of cassava were grown in greenhouse conditions and subjected to water deficit treatments, and it was found that the concentration of K+ increased in response to water stress, which was positively correlated with the extent of osmotic adjustment (Alves and Setter 2004). Ma et al. (2009) have shown that Ca2+ participates in many physiological and biochemical reactions in plants as a common second messenger through coupling both cellular and intercellular signal transduction networks, and the change of Ca2+ concentration and distribution in plant cells may be considered as the plant’s responses and adaptations to the outside environment. 34 .............inorganic ions Cassava Geetika, 2012A41D

.............inorganic ions :

In the presence of Ca2+, for example, wheat ( Triticum aestivum) showed significantly more accumulation of osmolytes in response to water stress by osmotic adjustment ( Nayyar 2003). Besides cations introduced above, Cl – is also an important inorganic ion and might also play key roles in osmotic adjustment. For example, Shabala et al. (2000) suggested a role of the hyperosmolarity induced influx of K+ and Cl – in plant (e.g., bean) cells that could be sufficient for osmotic adjustment without additional accumulation of organic solutes. 35 .............inorganic ions Triticum aestivum Geetika, 2012A41D

Slide37:

Main inorganic ions in osmotic adjustment on different plants. Species Stress Inorganic ions Arabidopsis thaliana Salt Na+ Cynara cardunculus (Cardoon) Salt Na+ Manihot esculenta (Cassava) Drought K+ Oryza sativa L. (Rice) Salt Cl – Salicornia europaea and Suaeda maritime (Halophytic plant) Salt Na+ Sesuvium portulacastrum (Sea purslane ) Salt Na+ Suaeda salsa ( Chenopodiaceae ) Salt Na+ Triticum aestivum L. (Wheat) Drought Ca2+ Vicia faba L. (Bean) Salt, Drought K+,Cl – 36 Geetika, 2012A41D

Slide38:

OTHER MECHANISMS INVOLVED IN DROUGHT RESISTANCE ALONGWITH OSMOTIC ADJUSTMENT 37 Geetika, 2012A41D

Osmotic Adjustment in Sorghum Mechanisms of Diurnal Osmotic Potential Changes:

Osmotic Adjustment in Sorghum Mechanisms of Diurnal Osmotic Potential Changes The objective of this experiment was to determine the relative contribution of passive versus active mechanisms involved in diurnal changes in sorghum ( Sorghum bicolor L. Moench) leaf tissue in response to water stress. A single sorghum hybrid (cv ATx623 x RTx430) was grown in the field under variable water supplies. and relative water content were measured diumally on expanding and the uppermost fully expanded leaves before flowering and on fully expanded leaves during the grain-filling period . Sorghum 38 Sorghum bicolor L. Moench Geetika, 2012A41D

Slide40:

Diurnal changes in total osmotic potential in response to water stress was 1.1 megapascals before flowering and 1.4 megapascals during grain filling in comparison with 0.53 megapascal under well-watered conditions. 39 .................Sorghum Geetika, 2012A41D

Slide41:

Under water-stressed conditions, passive concentration of solutes associated with dehydration accounted for 50% (0.55 megapascal ) of the diumal AI,, before flowering and 47% (0.66 megapascal ) of the change during grain filling. Net solute accumulation accounted for 42% (0.46 megapascal ) of the diumal A*I' before flowering and 45% (0.63 megapascal ) of the change during grain filling in water-stressed leaves. The relative contribution of changes in nonosmotic volume (decreased turgid weight/dry weight) to diumal A*I' was less than 8% at either growth stages. Water stress did not affect leaf tissue elasticity or partitioning of water between the symplasm and apoplasm . .................Sorghum 40 Geetika, 2012A41D

Influence of Osmotic Adjustment on Leaf Rolling and Tissue Death in Rice (Oryza sativa L.):

Influence of Osmotic Adjustment on Leaf Rolling and Tissue Death in Rice ( Oryza sativa L.) Osmotic adjustment aids in the drought resistance of rice by delaying leaf rolling and by delaying leaf death 41 Geetika, 2012A41D

Genetic Manipulations of Osmotic Adjustment:

Genetic Manipulations of Osmotic Adjustment Geetika, 2012A41D 42

Requirements for genetic manipulations and improvement:

Requirements for genetic manipulations and improvement GENETIC VARIABILITY : Required high HERITABILITY: Required High GENETIC GAIN: Required High GENETIC CONTROL: Monogenic/ oligogenic /polygenic Geetika, 2012A41D 43

Genetics of osmotic adjustment in breeding maize for drought tolerance:

Genetics of osmotic adjustment in breeding maize for drought tolerance Robert G  Guei  and C E  Wassom (1993) Genetic variation for osmotic adjustment has been reported in several crops. Little is known about its inheritance and potential use as selection criteria in tropical maize ( Zea mays  L.). Two tropical lowland maize populations were used in this study to quantify the magnitude of genetic variability in osmotic adjustment; to estimate components of its genetic variance and heritability; and to determine the importance of this trait in breeding tropical maize for improved drought tolerance. Geetika, 2012A41D 44

Genetics of osmotic adjustment in breeding maize for drought tolerance:

Genetics of osmotic adjustment in breeding maize for drought tolerance Robert G  Guei  and C E  Wassom (1993) Full-sibs within half-sib groups were developed using the Design I mating scheme and evaluated at two locations in Mexico for two seasons using water stress and non-stress environments. Results showed that in both populations, dominance genetic effects were more important than additive effects in controlling the expression of the trait. However, very little genetic variability was present in either population for the trait, although more genetic variation was detected with data collected at flowering stage, when water stress was more severe than at the vegetative stage. Non-significant phenotypic and genotypic correlations were found between osmotic adjustment and yield. Not much genetic gain could be expected from selection for osmotic adjustment in these populations. Geetika, 2012A41D 45

POSSIBILITIES OF BREEDING WHEAT COMBINING HIGH OSMOTIC ADJUSTMENT CAPACITY AND SUITABLE BREADMAKING QUALITY :

POSSIBILITIES OF BREEDING WHEAT COMBINING HIGH OSMOTIC ADJUSTMENT CAPACITY AND SUITABLE BREADMAKING QUALITY Amalia Neacşu , Gabriela Şerban , Constantina Bănică , Nicolae N. Săulescu (2009) High osmotic adjustment (OA) is a desirable trait for improving wheat performance under drought. Previous reports showed that the gene that controls osmotic adjustment has a negative effect on dough strength , because of a difference in peroxidase activity, due to linkage between the endosperm peroxidase, Per-A4, locus, and the osmoregulation locus. Geetika, 2012A41D 46

Genetic variation for osmotic adjustment in crop plants:

Genetic variation for osmotic adjustment in crop plants Geetika, 2012A41D 47

POSSIBILITIES OF BREEDING WHEAT COMBINING HIGH OSMOTIC ADJUSTMENT CAPACITY AND SUITABLE BREADMAKING QUALITY :

POSSIBILITIES OF BREEDING WHEAT COMBINING HIGH OSMOTIC ADJUSTMENT CAPACITY AND SUITABLE BREADMAKING QUALITY Amalia Neacşu , Gabriela Şerban , Constantina Bănică , Nicolae N. Săulescu (2009) Quality parameters of doubled haploid lines were analysed, DH lines were derived from a cross between A large variation, only slightly associated with the capacity for osmotic adjustment was found among lines in all quality parameters, including dough strength. Distribution of high OA and low OA lines overlapped and, although best values for all parameters were found in low OA lines, the difference between the parameters of the best low OA and the best high OA lines was relatively small. These results suggest that breeding high OA cultivars with improved quality is feasible. a high OA, lower quality cultivar (Izvor) a low OA cultivar with higher quality (Jiana). x DH Geetika, 2012A41D 48

QTL Mapping for Osmotic Adjustment in Rice:

QTL Mapping for Osmotic Adjustment in Rice Research was conducted to identify and map quantitative trait loci (QTL) associated with dehydration tolerance and osmotic adjustment of rice. Osmotic adjustment capacity and lethal osmotic potential were determined for 52 recombinant inbred lines grown in a controlled environment under conditions of a slowly developed stress. The lines were from a cross between an Indica cultivar, Co39, of lowland adaptation and a Japonica cultivar, Moroberekan , a traditional upland cultivar. The QTL analysis was conducted using single marker analysis (ANOVA) and interval analysis (Mapmaker/QTL). Geetika, 2012A41D 49

QTL Mapping for Osmotic Adjustment in Rice:

QTL Mapping for Osmotic Adjustment in Rice The measurements obtained and the QTL identified were compared to root traits and leaf rolling scores measured on the same lines. One major locus was associated with osmotic adjustment. The putative locus for osmotic adjustment may be homoeologous with a single recessive gene previously identified for the same trait in wheat. The putative osmotic adjustment locus and two of the five QTL associated with dehydration tolerance were close to chromosomal regions associated with root morphology. Geetika, 2012A41D 50

QTL Mapping for Osmotic Adjustment in Rice:

QTL Mapping for Osmotic Adjustment in Rice In this population, osmotic adjustment and dehydration tolerance were negatively associated with root morphological characters associated with drought avoidance. High osmotic adjustment and dehydration tolerance were associated with Co39 alleles and extensive root systems were associated with Moroberekan alleles. To combine high osmotic adjustment with extensive root systems, the linkage between these traits will need to be broken. Alternatively, if the target environment is a lowland environment with only brief water deficit periods, selection for drought tolerance characteristics without consideration of the root system may be most appropriate. Geetika, 2012A41D 51

Inheritance of osmotic adjustment:

Inheritance of osmotic adjustment Geetika, 2012A41D 52

Inheritance of osmotic adjustment:

Inheritance of osmotic adjustment Geetika, 2012A41D 53

Inheritance of osmotic adjustment:

Inheritance of osmotic adjustment Geetika, 2012A41D 54

Inheritance of osmotic adjustment:

Inheritance of osmotic adjustment Geetika, 2012A41D 55

QTL Mapping for Osmotic Adjustment in Rice:

QTL Mapping for Osmotic Adjustment in Rice Geetika, 2012A41D 56

Comparison of conserved region of qtls in rice and wheat-for osmotic adjustment:

Comparison of conserved region of qtls in rice and wheat-for osmotic adjustment Geetika, 2012A41D 57

Breeding scheme to develop lines with high osmotic adjustment:

Breeding scheme to develop lines with high osmotic adjustment Geetika, 2012A41D 58

CONCLUSIONS :

CONCLUSIONS Osmotic adjustment (OA) is receiving increasing recognition as a major mechanism for drought resistance. Osmotic adjustment occurs in saline and dehydrating soils. Osmotic adjustment results from solute accumulating aster than it is used . Growth is inhibited first, decreasing solute use, but remaining growth is more rapid than in absence of osmotic adjustment. Solute may be obtained from inorganic salts in soil and from products of photosynthesis . Solute accumulates in vacuole and cytosol . Osmotic adjustment maintains ability to absorb water from environment thus maintaining water volume and Turgor. 59 Geetika, 2012A41D

CONCLUSIONS:

CONCLUSIONS Lots of genetic variability exists for OA in plants Heritability values of low to high have been reported in different breeding material and crops QTL mapping has been done for OA and it has been improved using genetic engineering techniques. Screening of more genetic material is required. Geetika, 2012A41D 60

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