Increasing Polyethylene Glycol Concentration Research Articles

Impact of Fire Recurrence and Water Stress on the Root Nucleolar Activity of Maritime Pine (Pinus pinaster Ait.) Individuals Whose Seeds Were Harvested in Post-Fire Naturally Regenerated Stands

The main role of the nucleolus is ribosomal biogenesis, but it also responds to stress with changes in number, area, and/or morphology. Nucleoli with transcriptionally active ribosomal RNA genes are selectively stained by silver nitrate. Hypothesising that fire recurrence and/or polyethylene glycol (PEG)-induced water stress would cause nucleolar changes in Pinus pinaster roots, nucleolar parameters were analysed upon the germination of seeds harvested in post-fire naturally regenerated stands with different fire regimes. An unburned stand was used as a control. The nucleoli number varied from 1 to 15 among stands and PEG treatments, but a mode of five or six nucleoli was found. The number of nucleoli per interphase (N) increased (p < 0.001) with fire recurrence (stand effect). Increasing PEG concentration (treatment effect) decreased the nucleoli number, notably in the stand with the highest fire recurrence. The nucleolar area decreased (p < 0.001) with increased nucleoli number, fire recurrence, and/or PEG concentration. Fire recurrence and water scarcity are forecasted for future climate scenarios. As demonstrated earlier, these factors could influence protein synthesis or the cell cycle’s regularity, which are crucial processes for root growth and pine seedling establishment. Furthermore, this work revealed that nucleolar parameters could be suitable biomarkers for pine stress studies.

Synthesis and Characterisation of Cellulose Acetate/Polyethylene Glycol Membrane from Pineapple Hump by Phase Inversion Method

Cellulose is a natural polymer contained in growing fibres, such as pineapple fibres. Cellulose can be modified into cellulose acetate, a modified polymer that can be used in the synthesis of a cellulose acetate/polyethylene glycol (CA/PEG) membrane. The phase inversion method was used in this study to produce CA/PEG membranes. Variations in polyethylene glycol (PEG) concentration with a ratio of 1:1 to cellulose acetate, where variations in PEG concentrations used are 2%, 5% and 8%. Acetone and dimethylformamide are used as organic solvents. Membrane morphological analysis using scanning electron microscopy (SEM) and functional group analysis using a Fourier transform infrared (FTIR) spectrometer were performed for membrane characterisation. The result of the synthesis of the CA/PEG membrane is in the form of a thin white layer. The characterisation results of the FTIR spectrometer showed the vibration of the carbonyl bond at wavenumber 1729 cm−1 and the vibration of the hydroxyl bond torque at the wave number 648 cm−1, where the vibration intensity decreased with each addition to the concentration. The results of SEM characterisation show that the increase in PEG concentration increases the percentage porosity of the membrane. The membranes with 2%, 5% and 8% PEG have porosity percentages of 51.54%, 68.70% and 73.50%, respectively. As the membrane with 2% PEG has the lowest percent porosity, it has more potential in removing or filtering solutes from a fluid.

Elucidating Drought Tolerance Potential of Maize (Zea mays L.) Inbred Lines through Polyethylene Glycol Induced Drought Stress

Drought is one of the most distressing environmental stresses restraining the crop production . Drought undermines the plant growth from seedling to maturity and the studies have unveiled that the harmful impact of drought results in crops due to the damages perceived during crucial stages of development namely, germination, seedling development and flowering stages. Biometric elements and indices at an early growth stage could be employed in designing the selection criteria to figure out the drought tolerant genotypes. Breeding for drought-prone environments is constrained by lack of suitable selection indices of drought stress resistance. The present study was conducted to determine the reliability of in-vitro screening method for initiating drought breeding programme. Poly ethylene glycol (PEG) has been used often as abiotic stress inducer in many studies to screen drought tolerant germplasm. The present investigation was carried out to reveal the drought tolerance potential of 103 maize inbred lines by in-vitro screening under three levels of PEG levels viz., 0% as control, 10% and 20% and evaluating their effect on the root parameters like primary root length, number of seminals roots , number of lateral roots and root biomass. The seedlings exhibited a significant variation for all the traits analyzed. All the root parameters had highest value under control and had significant decline with increasing PEG concentrations (0% < 10% < 20%). The inbreds showing the best level of drought tolerance at all levels of PEG induced stress can be used as a source of drought tolerance for the improvement of drought tolerant hybrids . The variation among maize inbreds for these traits was found to be an ideal indicator to screen the drought tolerant genotypes at early growth stages.

Impact of water stress on morpho-physiological and biochemical traits in rice genotypes

Laboratory and field screening were performed in nine rice genotypes i.e., TM 12061, TM 12077, TM 12012, TM 14035, TM 16017, Senthuram, Vandhana, TKM 12 and Anna (R) 4 to assess their drought tolerant potential. For laboratory screening, the effect of different levels of Poly Ethylene Glycol (PEG) concentration viz., -0.2, -0.4, -0.6 and -1.0 MPa on germination, shoot length and root length were studied. There was a considerable decrease in the germination potential among all the genotypes with increase in PEG concentration. The TM 12077 showed higher level of tolerance to PEG induced drought stress showing 30.8 % germination with 3.2 cm and 8.85 cm shoot and root length, respectively at higher level of concentration (1.0 MPa). In the field screening under managed stress condition, TM 12077 and TM 12012 showed higher accumulation of proline (4.15 mg/g). Chlorophyll stability index was more than 80 % in the genotypes TM 12012, TM 12077 and TM 12061. The genotype TM 14035, the varieties Anna (R) 4 and Vandhana matured early in 115 days. Number of tillers per plant, number of panicles/sqm and yield/hectare were maximum in TM 12077. While considering both laboratory and field screening, the genotypes TM 12077, TM 12012 and TM 12061 were found promising for water stress environment and can be utilized as donors in the drought tolerance breeding programs. High heritability coupled with moderate to high GA as per cent of mean recorded for plant height, tillers per plant, chlorophyll stability Index and total chlorophyll content indicates the presence of additive gene effects and their improvement through direct selection. Bangladesh J. Bot. 52(4): 1041-1046, 2023 (December)

Effect of Polyethylene Glycol (PEG) on Germination and Seedling Parameters of Maize Varieties

In an experimental framework employing a Factorial Randomized Complete Block Design (FRBCD), a study was conducted in July 2022 at the Crop Science Institute, NARC, Islamabad. The objective was to assess the impact of different Polyethylene Glycol (PEG) concentrations on two maize cultivars Sargodha 202 and OPV-3 under drought stress conditions. With triplicate replications, each experimental unit consisted of a pot filled with 4.5 kg of dry sand, where 10 seeds were planted. The 45-day study incorporated four treatment groups: T0 (Control), T1 (10% PEG), T2 (20% PEG), and T3 (30% PEG).
 Data analysis revealed that increasing PEG concentrations led to a decline in key parameters such as germination rate, root elongation, and shoot development, while concurrently escalating seedling mortality in both cultivars. Statistical evaluations, carried out through the Least Significant Difference (LSD) method at a 5% significance level, highlighted notable differences between the treatment outcomes. Sargodha 202 exhibited superior performance relative to OPV-3, recording a germination rate of 91.66% as opposed to OPV-3's 83.33%. Furthermore, Sargodha 202 demonstrated enhanced root (13.08 cm) and shoot (50.08 cm) lengths in comparison to OPV-3, which showed 10.58 cm for root and 45.83 cm for shoot length. Sargodha 202 also displayed elevated levels of both root and shoot moisture content and a higher crop growth rate compared to OPV-3. Collectively, these results underscore the greater resilience and adaptability of Sargodha 202 under PEG-induced drought conditions.

IMPACT OF POLYETHYLENE GLYCOL-INDUCED OSMOTIC STRESS ON MAIZE GERMINATION, GROWTH, AND PHYSIOLOGICAL RESPONSE

Drought stress is a significant environmental concern affecting crop growth, development, and yield. A laboratory experiment was conducted to examine the germination characteristics of four maize genotypes under varying levels of osmotic stress (0%, 2.5%, 5%, 7.5%, 10%) using polyethylene glycol (PEG) 6000 as an osmoticum. The experiment followed a factorial design within a Completely Randomized Design (CRD) framework with three replications. Varying concentrations of PEG influenced the germination and early growth of plants. An interesting finding was that as the concentration of PEG increased, there was a noticeable decrease in plant growth, indicating a negative correlation between the two. The findings indicated that subjecting maize plants to water stress treatments significantly affected various growth parameters (with a statistical significance level of P<0.05). Furthermore, with the increase in PEG concentration, there was a gradual decline in both respiration and transpiration rates, resulting in a decrease in protein concentration. There is a significant decrease in relative water content (RWC) in both shoot and root by 28.65% and 11.13%, respectively, compared with the control. When maize seedlings were subjected to water deficit by treating them with 2.5 to 10% PEG, there was a significant decrease (by 60.05%) in the level of chlorophyll 'b' while the decrease (by 33.25%) in chlorophyll 'a' content was comparatively less pronounced.

Drought stress induced by polyethylene glycol (PEG) in local maize at the early seedling stage

Drought stress adversely impacts growth, crop production, reproductive organ development, and yield characteristics in maize. As a drought-sensitive crop, maize (Zea mays L.) shows considerable varietal differences. A study was conducted at the Tissue Culture Laboratory, Department of Biology, Faculty of Mathematics and Natural Sciences, University of North Sumatra, Medan, Indonesia in order to identify drought-tolerant maize varieties. During germination and early seedling growth, 16 local accessions were evaluated for drought tolerance. Based on local climate and soil conditions, these specific accessions were chosen. The varieties were tested against five levels of drought stress imposed by Polyethylene glycol 6000 (PEG-6000) at 10, 20, 30, 40, and 50%. An experiment with three replications was conducted using a completely randomized design. In the study, local maize accessions (BI3, SB5, DS2, and MN3) and the hybrid variety (H) showed the capability of tolerating drought stress. Generally, germination time, germination percent and vigor index, root and shoot length, shoot ratio, and fresh and dry weight were decreased by increasing PEG concentrations (up to 50%). According to ANOVA results, shoot water content was not significantly affected by the PEG, nor was the interaction between the PEG and the accessions. The root water content, however, was significantly affected by PEG, and the interaction between PEG and accessions. Although interactions between accessions with low PEG concentrations improved germination characteristics, the root histology of the accessions varied. According to drought tolerance indexes, five maize accessions are drought-tolerant, including H (0.683), SB5 (0.617), DS2 (0.565), MN3 (0.512), and BI3 (0.504). The drought-tolerant varieties are recommended in regions with low rainfall or low water sources since they are less water-intensive and produce higher yields.

In-vitro selection of drought tolerant doubled haploid rice lines using polyethylene glycol (PEG)

The present study was conducted to determine the response of 55 double haploid (DH) rice lines developed for drought tolerance from the cross Swarna × IR159B in polyethylene glycol (PEG) induced drought stress under in-vitro conditions (DH lines named as double haploid rice lines-DRL). Drought stress was created using PEG-6000 at different level of external water potential. Analyzed seedling traits of DRLs showed significant differences in response to different PEG concentrations. A decrement in plant growth at seedling stage with the increase in PEG concentration was observed as expected. Among 55DRLs, 14 DRLs were found to be drought tolerant sustaining the stress level till -7.5 bar as of the tolerant checks. Further, Drought linked SSRs were also evaluated in developed rice lines. Out of 8 SSRs, RM55 (R2 value- 13.5%) and RM259 (R2 value- 13.9%) found to be exhibiting significant association with the shoot/root ratio at - 7.5 bar stress level. Out of 14 DRLs, 9 DRLs were found to be showing drought tolerant in phenotypic and genotypic screening. Hence, PEG induced stress screening method used in this study will serve as the baseline for screening of rice lines for drought tolerance at very early stage without exploitation of much resource.

Effects of Drought Stress Induced by Hypertonic Polyethylene Glycol (PEG-6000) on Passiflora edulis Sims Physiological Properties.

Passion fruit is known to be sensitive to drought, and in order to study the physiological and biochemical changes that occur in passion fruit seedlings under drought stress, a hypertonic polyethylene glycol (PEG) solution (5%, 10%, 15%, and 20%) was used to simulate drought stress in passion fruit seedlings. We explored the physiological changes in passion fruit seedlings under drought stress induced by PEG to elucidate their response to drought stress and provide a theoretical basis for drought-resistant cultivation of passion fruit seedlings. The results show that drought stress induced by PEG had a significant effect on the growth and physiological indices of passion fruit. Drought stress significantly decreased fresh weight, chlorophyll content, and root vitality. Conversely, the contents of soluble protein (SP), proline (Pro), and malondialdehyde (MDA) increased gradually with the increasing PEG concentration and prolonged stress duration. After nine days, the SP, Pro and MDA contents were higher in passion fruit leaves and roots under 20% PEG treatments compared with the control. Additionally, with the increase in drought time, the activities of antioxidant enzymes such as peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) showed an increasing trend and then a decreasing trend, and they reached the highest value at the sixth day of drought stress. After rehydration, SP, Pro and MDA contents in the leaves and roots of passion fruit seedlings was reduced. Among all the stress treatments, 20% PEG had the most significant effect on passion fruit seedlings. Therefore, our study demonstrated sensitive concentrations of PEG to simulate drought stress on passion fruit and revealed the physiological adaptability of passion fruit to drought stress.

In Vitro Selection of Mungbean Genotypes for Drought Tolerance by Polyethylene Glycol Induced Water Defi cit

Drought stress is a major constraint affecting growth and yield of several economic crops including mungbean [Vigna radiata (L.) Wilczek]. In vitro selection for drought tolerance is an alternative method for early determination of drought tolerant plants. The objective of this study was to perform in vitro selection of mungbean genotypes under water stress induced by polyethylene glycol (PEG) 6000. Seeds of 18 genotypes were germinated in Murashige and Skoog (MS) liquid medium supplemented with different concentrations of PEG 6000 (0, 8, 12 and 16%). Germination percentage, promptness index, root length tolerance index, seed vigor index, seedling length tolerance index, seedling fresh weight tolerance index and seedling dry weight tolerance index were measured. The results showed reduced germination and growth in all genotypes with increasing PEG concentrations. Various genotypes responded differentially at 16% PEG. Interestingly, K-851, EG-MG-13, VI000411 A-G, and CES 44 showed a higher germination percentage, root length, seedling length and seed fresh weight than other genotypes, demonstrating their drought tolerance potential. However, their water stress responses need to be confi rmed under greenhouse and/or fi eld conditions before they can be used as parents in breeding programs to improve drought tolerance.

Evaluation of nano-silicon efficiency on compatible solutes and nutrient status of Damask rose affected by in vitro simulated drought stress

BackgroundDrought stress is a critical environmental factor that disturbs plant performance. However, some non-essential elements such as silicon can improve water deficit tolerance by modulating photosynthesis assimilates and compatible solutes production. Therefore, the present work was conducted to modulate polyethylene glycol (PEG)-induced water deficiency under in vitro culture in Damask rose genotypes (Maragheh and Kashan) by nano-silicon (SiO2-NPs) treatment. A completely randomized factorial experiment was used as three concentrations of SiO2-NPs (0, 50, and 100 mg L−1) and five concentrations of PEG (0, 25, 50, 75, and 100 g L−1). Then, the comparative effects of water deficiency on vegetative traits, metabolites, and nutrients were studied.ResultsThe drought promoted a significant decrease in chlorophyll, fresh/dry weight, biomass, and an increase in electrolyte leakage. The amount of micro- and macronutrients were affected by drought stress and decreased in both genotypes. In contrast, the activity of polyphenol oxidase (PPO) and total phenolic compounds (TPC) along with biochemical traits was increased. Treatment with SiO2-NPs improved the leaf area index (LAI), chlorophyll, and biomass under severe water deficiency. The concentration of compatible solutes such as carbohydrates, total flavonoid content (TFC), TPC, anthocyanin, and antioxidative capacity enhanced by the application of SiO2-NPs by about twofolded. As well as an increase in PEG concentration, the absorption of nutritional elements such as P, K, Mn, Fe, Zn, and Cu was decreased. However, SiO2-NPs application especially at 100 mg L−1 increased the amount of nutrient absorption.ConclusionsIn general, the drought tolerance in Damask rose was associated mainly with its suitable manipulation of antioxidant production and orderly enhancement of nutrient adsorption, so that the effect of SiO2-NPs in improving the qualitative and quantitative characteristics of ʻKashanʼ was more than that of ʻMaraghehʼ. These results briefly highlight that the SiO2-NPs may provide greater tolerance to drought stress in Damask rose.Graphical

Rheology of nano ZnO - Hydroxypropyl Methylcellulose (HPMC) based suspensions and structural properties of resulting films

Effect of polyethylene glycol (PEG) and ZnO nanoparticles concentration on rheological properties of the hydroxypropyl methylcellulose (HPMC) based film forming suspensions (FFS) and, on the structural properties of the resulting films were characterized. Rheological properties of FFS were not significantly affected by PEG concentration and ZnO NPs incorporation. Intrinsic viscosity [η] of aqueous HPMC solution obtained from extrapolation of Huggins and Kraemer plot was 0.115–0.118 (L/g). Coating thickness calculated as a function of coating solution viscosity, concentration and draining time for strawberry coating was 1.26–1.49 μm. Tensile strength (TS) of HPMC film decreased while water vapour permeability (WVP) increased with increasing PEG concentration. Elongation at break (%E) increased up to 25% PEG concentration and decreased afterward. Incorporation of ZnO NPs improved the tensile strength and barrier properties of HPMC film. Relaxation percentage and stress decay rate increased with increasing plasticizer concentration while decreased with incorporation of ZnO NPs. • Rheological behaviour of aqueous HPMC solution (4% w/v) was Newtonian. • Calculated Intrinsic viscosity [η] of aqueous HPMC solution was 0.115–0.118 (L/g). • Relaxation % and stress decay rate showed positive correlation with PEG concentration. • Added ZnO nanoparticles improves the HPMC film properties.

Thermodynamic complexation mechanism of zinc ion with 8-hydroxyquinoline-5-sulfonic acid in molecular crowding environment

A crowded molecular environment, which is universally observed in biological cells, changes the thermodynamics and kinetics of biochemical reactions compared to bulk solution. Although molecular crowding has received significant attention, a fundamental explanation of the molecular crowding effect based on thermodynamic parameters, including enthalpy (ΔH) and entropy changes (ΔS), is insufficient. Herein, the complexation mechanism of zinc ions with quinolinol derivative in a molecular crowding environment was investigated using polyethylene glycol (PEG) based on the changes in ΔH and ΔS. For 1:1 complexation, which is only promoted by the osmotic pressure effect, ΔH and ΔS decreased with increasing PEG concentration (CPEG) because the number of dehydration molecules decreased. In the 1:2 complexation system, which is affected by the osmotic pressure and volume exclusion effects, no obvious dependences of ΔH and ΔS on CPEG were observed. This is because the osmotic pressure and volume exclusion effects contributed oppositely to ΔH and ΔS. The results presented herein provide fundamental knowledge for protein-metal interactions, and it is expected that these data will attract the attention of many physical chemists and biochemists.

IDENTIFICATION OF DROUGHT-TOLERANT KABULI CHICKPEA (CICER ARIETINUM L.) GENOTYPES AT THE EARLY SEEDLING STAGE

Chickpea (Cicer arietinum L.) is negatively affected by drought stress at all the growth stages, including germination and seedling emergence. The recent study aimed to investigate the drought-tolerant Kabuli chickpea genotypes at the seedling stage under osmotic stress conditions. An in vitro screening technique evaluated the 120 different genotypes of Kabuli chickpea for drought tolerance by using different concentrations of polyethylene glycol (8000) solution, viz., T0: Control, T1: -0.19 MPa, and T2: -0.47 MPa, arranged in a completely randomized design. Data were recorded on germination percentage, root length, shoot length, seedling length, root/shoot ratio, dry matter, seedling vigor index, and proline content. The results of a pooled analysis of variance revealed significant variability among genotypes, different polyethylene glycol treatments, as well as, between genotypes and treatments. The increase of polyethylene glycol levels negatively affected most of the parameters under study, except for proline content, which increased with an increase in polyethylene glycol concentration. The study results indicated that the advanced lines, 15KCC-106, 13KCC-114, 6KCC-103, GP-37, FS-10, and 12KCC-106, performed better under different osmotic stress conditions and gained selection as drought-tolerant advanced lines at early seedling stage. These advanced lines suitably combine with their desirable traits to cope with the drought condition and can serve as a baseline for the improvement of Kabuli chickpea breeding material for drought tolerance.

Effect of PEG-simulated Drought Stress on Seed Germination of Three Medicinal Liquorice (Glycyrrhiza) Species

Background: Glycyrrhiza is an important medicinal plant that has been in shortage in recent years because of high demand and exhaustive harvesting. Investigating the drought tolerance of liquorice species can inform the artificial cultivation of liquorice under different water conditions and help address the shortage. Methods: Seeds of G. uralensis, G. glabra and G. inflata were treated with different concentrations of polyethylene glycol (PEG)-6000 solutions to simulate different levels of drought stress. The germination process germination rate, germination index, vigour index, stress tolerance index and recovery germination percentage of seeds were measured. Drought tolerance was evaluated using the membership function. Result: Low concentrations of PEG promoted the seed germination of G. glabra and G. inflata, whereas high concentrations inhibited the seed germination of all three plants. The degree of inhibition increased with increasing PEG concentration. Under mild PEG stress, the drought tolerance of G. uralensis was highest and that of G. glabra was the lowest. However, under severe PEG stress, the drought tolerance of G. glabra was the highest and that of G. uralensis was the lowest. Therefore, seeds of G. uralensis should be sown in relatively moist soil and those of G. glabra in relatively arid soil.

Polyethylene glycol mediated drought stress impacts on germination, growth and accumulation of proline in rice (Oryza sativa L.)

Drought is one of the major stress factors affecting the growth and development of plants, and is responsible for considerable crop yield losses worldwide. An experiment was conducted to compare three rice (Oryza sativa L.) varieties (BRRI dhan49, BRRI dhan71 and BRRI dhan75) for drought tolerance based on some growth parameters and physiological status in germination stage. Drought stress was imposed by five levels of polyethylene glycol (PEG) (0%, 10%, 15%, 20% and 25%). Rice varieties showed good germination with PEG concentration up to 15%. At 20% PEG concentration, a sharp reduction in germination percentage was observed and the highest germination percentage (55.53%) was found in the variety BRRI dhan71. Seeds of all the varieties treated with 25% PEG did not germinate. Seedling growth in terms of plumule and radicle length, fresh weight and dry weight decreased with increasing drought stress in all the varieties. Among the varieties, BRRI dhan71 was found to be the best at 20% PEG for seedling growth. Drought stress treatments decreased seedling length and weight vigor index in rice, whereas the highest seedling length and weight vigor index were obtained from BRRI dhan71. Accumulation of proline increased along with the increase of PEG concentration. The highest proline accumulation (3.08 mmol g-1 leaf) was obtained from the BRRI dhan71 at the higher treatment (20% PEG). This result suggests that BRRI dhan71 showed best performance under drought stress because of its own nature of tolerance. SAARC J. Agric., 20(1): 107-119 (2022)

Fabrication and Performance of Shape-Stable Phase Change Composites Supported by Environment-Friendly and Economical Loofah Sponge Fibers for Thermal Energy Storage

Exploration of low-cost, short-process, environment-friendly, and well-behaved phase change composites is of great significance. The renewable biomass loofah sponge (LS) fibers exhibit superior characteristics such as unique microtubules, substantial micrometer-scale channels, and exceptionally high porosities and have great potential of being utilized to exploit high-performance phase change composites. Herein, we proposed a facile strategy for fabricating a novel shape-stable phase change composite (PCLS) supported by LS fiber microtubules incorporating polyethylene glycol (PEG). The LS fibers with a porous tubular structure provided superior encapsulation and mechanical support for PEG. Encapsulation capacity of LS fibers for PEG was not affected by the duration of vacuum impregnation but increased with the increase in PEG concentration (lower than 0.24 g/mL) and then tended to the maximum of ∼56.5%. Differential scanning calorimetry results showed that the resultant PCLS had a melting/crystallization temperature of 41.7/32.3 °C and a heat enthalpy of 98.9/86.1 J/g, which contributed to great thermal energy storage/retrieval capability. The fabricated PCLS also featured excellent thermal cycling reliability for long-term use. Thermogravimetric analysis results suggested that there were two steps of degradation process for the resultant PCLS and corresponded to the decomposition of PEG and LS fibers, respectively. Infrared thermal images demonstrated that the resultant PCLS showed good infrared stealth ability and could effectively reduce infrared heat radiation. Self-assembly temperature control performance measurement indicated that the fabricated PCLS displayed superior temperature regulation ability. Such innovative PCLS holds great promise for widespread applications in solar thermal-energy storage, thermal regulation, thermal insulation, and thermal camouflage and stealth.

In vitro response of vanilla (Vanilla planifolia Jacks. ex Andrews) to PEG-induced osmotic stress

Drought-induced water stress affects the productivity of the Vanilla planifolia Jacks. ex Andrews crop. In vitro culture technique is an effective tool for the study of water stress tolerance mechanisms. This study aimed to evaluate the morphological, physiological and biochemical response of V. planifolia under in vitro water stress conditions induced with polyethylene glycol (PEG). In vitro regenerated shoots of 2 cm in length were subjected to different concentrations of PEG 6000 (0, 1, 2 and 3% w/v) using Murashige and Skoog semi-solid culture medium. At 60 days of culture, different growth variables, dry matter (DM) content, chlorophyll (Chl), soluble proteins (SP), proline (Pro), glycine betaine (GB), stomatal index (SI) and open stomata (%) were evaluated. Results showed a reduction in growth, Chl content, SP, SI and open stomata (%) with increasing PEG concentration, whereas DM, Pro and GB contents rose with increasing PEG concentration. In conclusion, PEG-induced osmotic stress allowed describing physiological and biochemical mechanisms of response to water stress. Furthermore, the determination of compatible Pro and GB osmolytes can be used as biochemical markers in future breeding programs for the early selection of water stress tolerant genotypes.

Growth response of diploid and tetraploid taro (Colocasia esculenta (L.) Schott) shoot culture to drought stress using polyethylene glycol

Taro genetic improvement through polyploidy induction is expected to be tolerant to abiotic stress. Several studies have shown that polyploidy plants have a higher adaptability to dry environments. In vitro selection technique for evaluation of plant tolerance to drought stress can be done by applying polyethylene glycol (PEG) as a selection agent. The aim of the research was to investigate the growth response of diploid and tetraploid taro shoot culture to drought stress using PEG. The experiment was conducted using a completely randomized design with two factors. The first factor was the concentration of PEG at 0, 5, 10, 15 and 20%. The second factor was Bentul taro clones which were 1 diploid clone and 2 tetraploid clones (clones 4.6.3 and 5.4.4). PEG was added to liquid MS medium containing 2 mg/l BAP. Observations of growth variables were carried out every week until the six weeks of culture. Fresh and dry weights, mortality percentage and proline content were determined at six weeks of culture. The results showed that the addition of PEG in liquid medium significantly affected the number of leaves, petiole length, number of roots, fresh and dry weights, as well as shoot mortality percentage. Differences in clones significantly affected the number of leaves, fresh and dry weights. The two factors tested (PEG and clones), gave an interaction on the number of leaves, fresh and dry weights. The proline content in all diploid and tetraploid clones showed an increase with increasing PEG concentration. The LC50 value in diploid clones was 9.82%, in tetraploid clones 4.6.3 and 5.4.4 were 14.14 and 15.45%, respectively. The results showed that PEG at 10% and 15% could be used for in vitro selection to drought stress both for diploid and tetraploid taro.

Effect of PEG Induced Drought Stress on Seed Germination and Seedling Growth of Greengram Genotypes

Greengram (Vigna radiata L. Wilczek) is the third most important pulse crop and drought is the most severe constraint to greengram growth and productivity. The present study was conducted to identify the drought tolerant greengram genotypes. Four greengram varieties used for standarization of drought stress using Polyethyleneglycol (PEG) 6000. The effect of water stress caused by different concentration of PEG 6000 are control (0 MPa), -0.4MPa, -0.5 MPa, -0.6MPa and -0.7 MPa. Increasing PEG concentration decrease the germination percentage, root length, shoot length, fresh weigh and dry weight of seedlings. At -0.5 MPa shows 50% seedling mortality , So control and -0.5 MPa level of drought stress was used for screening the greengram genotypes. Under PEG induced drought situations, parameters such as germination percentage, growth indices and proline content were recorded in all greengram genotypes. Compared to control, PEG induced drought stress (-0.5MPa) decrease all these parameters studied, where as drought has increased the proline content in all greengram genotypes screened. Among the greengram genotypes VGG17019 and VGG17004 posses higher germination percentage, GSI and proline content indicates high level of tolerance to drought stress.