Pulsed magnetic field improves seed quality of aged green pea seeds by homeostasis of free radical content.

To elucidate the mechanism responsible for magnetic field induced seed invigoration in aged seeds an experiment was conducted on six year old garden pea seeds stored under controlled (20 °C and 40% RH) condition. Aged seeds were magnetoprimed by exposing to pulsed magnetic field (PMF) of 100 mT for 1 h in three pulsed modes. The 6 min on and off PMF showed significant improvement in germination (7.6%) and vigor (84.8%) over aged seeds. Superoxide and hydrogen peroxide production increased in germinating primed seeds by 27 and 52%, respectively, over aged seeds. Nicotinamide adenine dinucleotide (reduced) (NADH) peroxidase and superoxide dismutase involved in generation of hydrogen peroxide showed increased activity in PMF primed seeds. Increase in catalase, ascorbate peroxidase and glutathione reductase activity after 36 h of imbibition in primed seeds demonstrated its involvement in seed recovery during magnetopriming. An increase in total antioxidants also helped in maintaining the level of free radicals for promoting germination of magnetoprimed seeds. A 44% increase in level of protein carbonyls after 36 h indicated involvement of protein oxidation for counteracting and/or utilizing the production of ROS and faster mobilization of reserve proteins. Higher production of free radicals in primed seeds did not cause lipid peroxidation as malondialdehyde content was low. Lipoxygenase was involved in the germination associated events as the magnitude of activity was higher in primed aged seeds compared to aged seeds. Our study elucidated that PMF mediated improvement in seed quality of aged pea seeds was facilitated by fine tuning of free radicals by the antioxidant defense system and protein oxidation.

Pre-sowing static magnetic field treatment for improving water and radiation use efficiency in chickpea (Cicer arietinum L.) under soil moisture stress.

Soil moisture stress during pod filling is a major constraint in production of chickpea (Cicer arietinum L.), a fundamentally dry land crop. We investigated effect of pre-sowing seed priming with static magnetic field (SMF) on alleviation of stress through improvement in radiation and water use efficiencies. Experiments were conducted under greenhouse and open field conditions with desi and kabuli genotypes. Seeds exposed to SMF (strength: 100 mT, exposure: 1 h) led to increase in root volume and surface area by 70% and 65%, respectively. This enabled the crop to utilize 60% higher moisture during the active growth period (78-118 days after sowing), when soil moisture became limiting. Both genotypes from treated seeds had better water utilization, biomass, and radiation use efficiencies (17%, 40%, and 26% over control). Seed pre-treatment with SMF could, therefore, be a viable option for chickpea to alleviate soil moisture stress in arid and semi-arid regions, helping in augmenting its production. It could be a viable option to improve growth and yield of chickpea under deficit soil moisture condition, as the selection and breeding program takes a decade before a tolerant variety is released. Bioelectromagnetics. 37:400-408, 2016. © 2016 Wiley Periodicals, Inc.

Biochemical and biophysical changes associated with magnetopriming in germinating cucumber seeds.

Seeds of cucumber were exposed to static magnetic field strength from 100 to 250 mT for 1, 2 or 3 h. Germination-percentage, rate of germination, length of seedling and dry weight increased by 18.5, 49, 34 and 33% respectively in magnetoprimed seeds compared to unexposed seeds. Among different magnetic field doses, 200 mT for 1 h showed significant effect on germination parameters and hence selected for studying changes in water uptake, (1)H transverse relaxation time (T(2)), hydrolytic enzymes, reactive oxygen species and antioxidant enzyme system in germinating seeds. Water uptake and T(2) values were significantly higher in treated seeds during imbibition. The activities of hydrolytic enzymes, amylase and protease were greater than the untreated controls by 51% and 13% respectively. Superoxide radicals also enhanced by 40% and hydrogen peroxide by 8% in magnetically exposed seeds. In magetoprimed seeds, increased activities of antioxidant enzymes, superoxide dismutase (8%), catalase (83%) and glutathione reductase (77%) over control was recorded. We report that magnetopriming of dry seeds can be effectively used as a pre-sowing treatment for seed invigoration in cucumber. Unlike other priming treatments seed is not required to be dehydrated after priming, allowing easy storage.

Pre-treatment of seeds with static magnetic field ameliorates soil water stress in seedlings of maize (Zea mays L.).

The effect of magnetic field (MF) treatments of maize (Zea mays L.) var. Ganga Safed 2 seeds on the growth, leaf water status, photosynthesis and antioxidant enzyme system under soil water stress was investigated under greenhouse conditions. The seeds were exposed to static MFs of 100 and 200 mT for 2 and 1 h, respectively. The treated seeds were sown in sand beds for seven days and transplanted in pots that were maintained at -0.03, -0.2 and -0.4 MPa soil water potentials under greenhouse conditions. MF exposure of seeds significantly enhanced all growth parameters, compared to the control seedlings. The significant increase in root parameters in seedlings from magnetically-exposed seeds resulted in maintenance of better leaf water status in terms of increase in leaf water potential, turgor potential and relative water content. Photosynthesis, stomatal conductance and chlorophyll content increased in plants from treated seeds, compared to control under irrigated and mild stress condition. Leaves from plants of magnetically-treated seeds showed decreased levels of hydrogen peroxide and antioxidant defense system enzymes (peroxidases, catalase and superoxide dismutase) under moisture stress conditions, when compared with untreated controls. Mild stress of -0.2 MPa induced a stimulating effect on functional root parameters, especially in 200 mT treated seedlings which can be exploited profitably for rain fed conditions. Our results suggested that MF treatment (100 mT for 2 h and 200 for 1 h) of maize seeds enhanced the seedling growth, leaf water status, photosynthesis rate and lowered the antioxidant defense system of seedlings under soil water stress. Thus, pre sowing static magnetic field treatment of seeds can be effectively used for improving growth under water stress.

Characterization of water distribution and activities of enzymes during germination in magnetically-exposed maize (Zea mays L) seeds.

Magnetic seed treatment is one of the physical pre-sowing seed treatments to enhance the performance of crop plants. In our earlier experiment, we found significant increase in germination and vigour characteristics of maize (Zea mays L.) seeds subjected to magnetic fields. Among various combinations of magnetic field (MF) strength and duration, best results were obtained with MF of 100 mT for 2 h and 200 mT for 1 h exposure. The quicker germination in magnetically-exposed seeds might be due to greater activities of germination related enzymes, early hydration of membranes as well as greater molecular mobility of bulk and hydration water fractions. Thus, in the present study, changes in water uptake during imbibition and its distribution and activities of germinating enzymes during germination were investigated in maize seeds exposed to static magnetic fields of 100 and 200 mT for 2 and 1 h respectively by nuclear magnetic resonance (NMR) spectroscopy. The magnetically-exposed seed showed higher water uptake in phase II and III than unexposed seed. The longitudinal relaxation time T1 of seed water showed significantly higher values and hence greater molecular mobility of cellular water in magnetically-exposed seeds as compared to unexposed. Component analysis of T2 relaxation times revealed the early appearance of hydration water with least mobility and higher values of relaxation times of cytoplasmic bulk water and hydration water in magnetically-exposed over unexposed seeds. Activities of alpha-amylase, dehydorgenase and protease during germination were higher in magnetically-exposed seeds as compared to unexposed. The quicker germination in magnetically-exposed seeds might be due to greater activities of germination related enzymes, early hydration of membranes as well as greater molecular mobility of bulk and hydration water fractions.

Effect on germination and early growth characteristics in sunflower (Helianthus annuus) seeds exposed to static magnetic field.

Seeds of sunflower (Helianthus annuus) were exposed in batches to static magnetic fields of strength from 0 to 250mT in steps of 50mT for 1-4h in steps of 1h. Treatment of sunflower seeds in these magnetic fields increased the speed of germination, seedling length and seedling dry weight under laboratory germination tests. Of the various treatments, 50 and 200mT for 2h yielded the peak performance. Exposure of seeds to magnetic fields improved seed coat membrane integrity and reduced the cellular leakage and electrical conductivity. Treated seeds planted in soil resulted in statistically higher seedling dry weight, root length, root surface area and root volume in 1-month-old seedlings. In germinating seeds, enzyme activities of alpha-amylase, dehydrogenase and protease were significantly higher in treated seeds in contrast to controls. The higher enzyme activity in magnetic-field-treated sunflower seeds could be triggering the fast germination and early vigor of seedlings.

Characterization of water binding and germination traits of magnetically exposed maize (Zea mays L.) seeds equilibrated at different relative humidities at two temperatures.

A study was undertaken to characterize the water sorption properties and enhancement in germination and seedling vigour of maize (Zea mays L.) seeds exposed to static magnetic fields of 100 mT and 200 mT for 2 and 1 h, respectively. Water sorption isotherms were constructed for magnetically- exposed and unexposed seeds by equilibrating over different saturated salt solutions at 25 and 35 degrees C. The germination and vigour parameters were evaluated for magnetically-exposed and unexposed seeds, equilibrated over the wide range of relative humidities (RHs) at 25 and 35 degrees C. Moisture content increased with increase in RH and decreased with increase in equilibrium temperature. The germination and vigour reduced at high and very low humidities. Magnetically-exposed seeds maintained higher germination and vigour at both temperatures and all RHs, indicating the better quality of magnetically-exposed seeds. The leachate conductivity of magnetically-exposed seeds was lower than unexposed seeds at all RHs, suggesting better membrane integrity in magnetically-exposed seeds. Analysis of the isotherms using D'Arcy-Watt equation revealed that irrespective of the temperature, in magnetically-treated seeds weak binding sites were more and strong and multi-molecular binding sites were less compared to the unexposed seeds. Total binding sites were more in unexposed control seeds. The modification of binding properties of seed water and increased seed membrane integrity in magnetically-exposed seeds might have enhanced the germination traits and early seedling growth of maize.

Exposure of seeds to static magnetic field enhances germination and early growth characteristics in chickpea (Cicer arietinum L.).

Seeds of chickpea (Cicer arietinum L.) were exposed in batches to static magnetic fields of strength from 0 to 250 mT in steps of 50 mT for 1-4 h in steps of 1 h for all fields. Results showed that magnetic field application enhanced seed performance in terms of laboratory germination, speed of germination, seedling length and seedling dry weight significantly compared to unexposed control. However, the response varied with field strength and duration of exposure without any particular trend. Among the various combinations of field strength and duration, 50 mT for 2 h, 100 mT for 1 h and 150 mT for 2 h exposures gave best results. Exposure of seeds to these three magnetic fields improved seed coat membrane integrity as it reduced the electrical conductivity of seed leachate. In soil, seeds exposed to these three treatments produced significantly increased seedling dry weights of 1-month-old plants. The root characteristics of the plants showed dramatic increase in root length, root surface area and root volume. The improved functional root parameters suggest that magnetically treated chickpea seeds may perform better under rainfed (un-irrigated) conditions where there is a restrictive soil moisture regime.

Evaluation of water binding, seed coat permeability and germination characteristics of wheat seeds equilibrated at different relative humidities.

The relative binding of seed water and seed coat membrane stability were measured in two contrasting wheat (Triticum aestivum L) varieties, HDR 77 (drought-tolerant) and HD 2009 (susceptible) using seed water sorption isotherms, electrical conductivity (EC) of leachates and desorption-absorption isotherms. Analysis of sorption isotherm at 25 degrees C showed that the seeds of HDR 77 had significantly higher number of strong binding sites, with correspondingly greater amount of seed water as strongly bound water, as compared to HD 2009. Total number of binding sites was also higher in HDR 77 than HD 2009, which explained the better desiccation tolerance and higher capacity to bind water in seeds of HDR 77. EC of seed leachate in both varieties did not change with respect to change in equilibrium relative humidity (RII), indicating the general seed coat membrane stability of wheat seeds. However, absolute conductivity values were higher for HD 2009. showing its relatively porous seed coat membrane. Significantly lower area enclosed by the desorption-absorption isotherm loop in HDR 77, as compared to HD 2009 also indicated the greater membrane integrity of HDR 77. Germination and seedling vigour of HD 2009 were reduced when equilibrated over very low and very high RH. In contrast, germination and vigour in HDR 77 were maintained high, except at very high RH, indicating again its desiccation tolerance. Thus, the study demonstrated the relative drought tolerance of HDR 77, on the basis of seed water-binding characteristics and seed membrane stability. Seed membrane stability as measured by seed leachate conductivity or as area under dehydration-rehydration loop may be used as a preliminary screening test for drought tolerance in wheat.

Proton NMR transverse relaxation time and membrane stability in wheat leaves exposed to high temperature shock.

Electrolyte leakage from leaves and NMR transverse relaxation time (T2) of leaf water were used to differentiate between heat-tolerant (NIAW 845) and susceptible (HD 2428) wheat (Triticum aestivum L.) cultivars. The leaves were exposed to high temperature shock in the range 30 to 55 degrees C and the damage caused, when evaluated by the two approaches was in close agreement. The critical temperature of injury leading to loss of membrane integrity was lower (39.1 degrees C) for susceptible cultivar, compared to tolerant cultivar (44.2 degrees C). Component analyses of NMR data revealed the existence of two fractions of cellular water in leaf tissues, namely, bound and free bulk water with distinct relaxation times. A dramatic reduction in the proportion of free water and a corresponding increase in bound water was observed in response to increase in temperature. This change in proportion occurred around 38 degrees C and 43 degrees C in HD 2428 and NIAW 845 respectively. The high temperature induced irreversible damage to cellular membrane integrity led to loss of compartmentation of cellular water fractions. The tolerant cultivar maintained its membrane integrity and cell water compartmentation until a temperature of 43 degrees C and susceptible could maintain it only until 38 degrees C.

Characterisation of germinating and non-germinating wheat seeds by nuclear magnetic resonance (NMR) spectroscopy.

Experiments were conducted to characterise the changes, especially of water status in germinating and non-germinating wheat seeds by nuclear magnetic resonance (NMR) spectroscopy. NMR relaxation time ( T(2)) measurements showed tri-phasic or bi-phasic characteristics during different stages of hydration, depending on the seed's ability to germinate. Component analysis of T(2) data revealed the existence of only two components, bound and bulk water, in dry seeds. In contrast, both the germinating and non-germinating wheat seeds had a three-component water proton system (bound, bulk and free water) in phase I of hydration. During the lag phase (phase II) of hydration, bulk water component of non-germinating seeds disappeared completely, resulting in a two component water proton system. Nevertheless, the three component water proton system was observed in the germinating seeds in phase II. Following phase II, rapid hydration (phase III) was observed in germinating seeds only. Water protons were re-organised and there were increases in bulk and free water but decreases in bound water concomitantly. Comparison of the physical state of water in these seeds by NMR spectroscopy with that of tissue leachate conductivity measurement suggests that the seed membrane system was affected more evidently in non-germinating seeds, leading to the disorganised cell structure. The present study provides evidence that the reorganisation of physical state of water in germinating wheat seeds during hydration is essential for its subsequent event of germination.