Days Of Submergence Research Articles

The Effect of Aminocyclopropane Carboxylic Acid (ACC) and Silver Nitrate (AGNO3) on Green Super Rice Seedlings for Submergence Tolerance

This internship reported titled as “The effect of Aminocyclopropane Carboxylic acid (ACC) and Silver Nitrate (AGNO3) on green super rice seedlings for submergence tolerance” aimed to identify submergence tolerant rice genotypes and the role of two chemicals i.e. Aminocyclopropane Carboxylic acid (ACC) and Silver Nitrate (AGNO3) in enhancing submergence tolerance of rice. The trial comprised a pot experiment that was conducted at the experimental field of National Agriculture Research Council (NARC) to evaluate the effect on various newly developed lines of green super rice for submergence tolerance. The experiment was designed in randomized complete block within three replications. The treatments consisted of eleven rice genotypes and two chemicals. Five plants of each genotype were transplanted in to pots which were then treated with ACC, AGNO3 or control (without any chemical). Both these chemicals were applied after one week of transplantation. The data were collected before submergence, after seven days of submergence and after fourteen days of submergence on various agronomic parameters including plant height, leaf length and number of leaves. The results indicated that plant height of genotype NRPC-7 resulted in the tallest plants among all the tested genotypes. Greater leaf length was observed in NRPC-9 in control treatments while maximum number of leaves under the treatment of ACC was observed in genotype NRPC-8. It was concluded that the above-mentioned genotypes were highly tolerated to submergence and can be used in breeding program for submergence tolerant variety development

Genetic analysis and screening of Indian landraces of rice for submergence tolerance in target production environment (TPE)

Complete submergence is one of the most important abiotic stress constraining rice production in India. From the past few decades effect of this stress has intensified and is anticipated to increase in coming years as a result of global climate change. Rice has developed many adaptive mechanisms to grow well in flood ecosystems however, too much water for long time at any stage of plant growth can lead to serious injuries like decaying of plant parts, lodging and reperfusion causing total crop loss. Because of these conditions, farmers usually rely on traditional landraces that can survive through this stress, despite the fact that these tends to be very low yielding. In the present study, 660 rice landraces along with checks were subjected to screening for submergence tolerance at vegetative stage in target production environment. Identification of tolerant genotypes was based on the survival percentage of plants and recovery by which they grown new tillers and leaves. Principle component analysis revealed three principle components accounted for 99.9 per cent of total variation. Regeneration percentage of tillers found to be the most discriminating character and possess additive gene action. Confirmation through cluster analysis grouped the tolerant and susceptible genotypes in the respective clusters. Results of screening showed that, out of 660 accessions, three accessions viz., IC388692, IC377169 and IC205953 have highest tolerance to 14 days of submergence and the survival ability was similar to the tolerant checks FR13A and CO 43-Sub1. Apart from the above three accessions, eight accessions viz., IC216378, IC126210, IC114413, IC386238, IC133584, IC114971, RL-1312 and RL-3055 scored 1 for faster regeneration of tillers denoting the ability to have good tolerance for submergence stress.

Pyramiding Submergence Tolerance and Three Bacterial Blight Resistance Genes in Popular Rice Variety Hasanta through Marker-Assisted Backcross Breeding

Flash flooding (FF) along with bacterial blight (BB) outbreak are very destructive for rice production in the rainfed shallow-lowland (RSL) ecosystem. The presence of dynamic Xoo races with varying levels of genetic diversity and virulence renders their management extremely challenging under RSL. In this context, the marker-assisted improvement of plant resistance/tolerance has been proven as one of the most promising strategies towards the development of sustainable cultivars. The present study demonstrates the marker-assisted introgression of the submergence tolerant (Sub1) and three bacterial blight resistant genes (Xa21 + xa13 + xa5) into the genetic background of Hasanta, a long duration popular rice variety in the eastern coastal region of India. The rice genotypes, Swarna Sub1 (carrying Sub1) and IRBB66 (carrying Xa21 + xa13 + Xa7 + xa5 + Xa4) had maximum genetic similarity (0.84 and 0.73, respectively) with Hasanta; recurrent parent (RP) was used as donor. The forward analysis of target genes in F1s, IC1F1s and backcross (BC) generations was performed by linked/genic markers (Sub1bc2; pTA248, xa13prom and RM122), whereas background recovery of RP in each BC and segregating generations was performed utilizing 108 hypervariable SSR markers. Intervened speed breeding (SB) strategy and intensive phenotyping could lead the development of near isogenic lines (NILs) as to the RP in all basic traits. The performance of the near isogenic lines (NILs, BC2F3 and BC2F4), HS 232-411-391-756-37, HS 232-411-391-809-8, HS 232-411-391-756-18, HS 110-224-197-10-36, HS 232-411-391-809-81, HS 110-224-197-10-41 and HS 232-411-391-809-63 establishes the utility of marker-assisted backcross-breeding (MAB) and SB in accelerated trait introgression. The introgressed lines carrying Sub1 + Xa21 + xa13 + xa5 showed 76% to 91% survival under 14 days of submergence and durable BB resistance (percent disease index-PDI of 2.68 ± 0.26 to 6.22 ± 1.08 and lesion length, LL of 1.29 ± 0.12 to 4.2 ± 0.64 cm). Physiological analysis revealed that improved NILs, carrying Sub1 gene conquered adaptive physiological modulations, had reduced the consumption of soluble sugar and the degradation of total chlorophyll contents (TCC), and an enhanced level of Alcohol Dehydrogenase activity (ADH) and proline accumulation in all submergence regimes. The pyramided lines attained complete product profile of RP, that will contribute to sustainable rice production under RSL, particularly in the coastal region that has substantial acreage under the variety Hasanta.

Eco-Physiological Traits Related to Recovery from Complete Submergence in the Model Legume Lotus japonicus.

Submergence is a severe form of stress for most plants. Lotus japonicus is a model legume with potential use in assisting breeding programs of closely related forage Lotus species. Twelve L. japonicus genotypes (10 recombinant inbred lines (RILs) and 2 parental accessions) with different constitutive shoot to root dry mass ratios (S:R) were subjected to 7 days of submergence in clear water and allowed to recover for two weeks post-submergence; a set of non-submerged plants served as controls. Relative growth rate (RGR) was used to indicate the recovery ability of the plants. Leaf relative water content (RWC), stomatal conductance (gs), greenness of basal and apical leaves, and chlorophyll fluorescence (Fv/Fm, as a measure of photoinhibition) were monitored during recovery, and relationships among these variables and RGR were explored across genotypes. The main results showed (i) variation in recovery ability (RGR) from short-term complete submergence among genotypes, (ii) a trade-off between growth during vs. after the stress indicated by a negative correlation between RGR during submergence and RGR post-submergence, (iii) an inverse relationship between RGR during recovery and S:R upon de-submergence, (iv) positive relationships between RGR at early recovery and RWC and gs, which were negatively related to S:R, suggesting this parameter as a good estimator of plant water balance post-submergence, (v) chlorophyll retention allowed fast recovery as revealed by the positive relationship between greenness of basal and apical leaves and RGR during the first recovery week, and (vi) full repair of the submergence-damaged photosynthetic apparatus occurred more slowly (second recovery week) than full recovery of plant water relations. The inclusion of these traits contributing to submergence recovery in L. japonicus should be considered to speed up the breeding process of the closely related forage Lotus spp. used in current agriculture.

Quantifying and mapping inundation regimes within a large river‐floodplain ecosystem for ecological and management applications

AbstractSpatial information on the distribution of ecosystem patterns and processes can be a critical component of designing and implementing effective management programs in river‐floodplain ecosystems. For example, translating how flood pulses detected within a stream gauge record are spatially manifested across a river‐valley bottom can be used to evaluate whether the current distribution of physical conditions has the potential to support priority habitats or if intervention is needed to meet desired goals. The size and complexity of large river‐floodplain systems can make mapping inundation dynamics a challenging task. We used a geospatial model to simulate 40 years (1972–2011) of daily surface‐water inundation depths for 11,331 km2 of the Upper Mississippi River System floodplain. We identified discrete inundation events at each 4‐m × 4‐m pixel in the model as sequential days of submergence. We then quantified and mapped four aspects of inundation regime – event frequency, duration, magnitude, and timing – for each pixel. The spatial distribution of inundation regime attributes varied within and among multiple levels of river organization, including navigation pools and geomorphic reaches, but only event timing exhibited a strong down‐river trend. Non‐linear relations among inundation attributes and their geospatial distributions likely reflect complex interactions among topographic, hydrologic, and anthropogenic constraints on flooding dynamics. Together, our results reveal spatial gradients in inundation dynamics not captured by hydrologic data alone. Characterizing such diversity in inundation dynamics is important for testing hypotheses about ecological processes, developing models of ecosystem functions, and informing management actions.

Alteration in plant spacing improves submergence tolerance in Sub1 and non-Sub1 rice (cv. IR64) by better light interception and effective carbohydrate utilisation under stress.

Besides genetic improvement for developing stress-tolerant cultivars, agronomic management may also add considerable tolerance against different abiotic stresses in crop plants. In the present study, we evaluated the effect of six different spacing treatments (S1: 10 × 10 cm; S2: 15 × 10 cm; S3:15 × 15 cm; S4:20 × 10 cm; S5: 20 × 15 cm; S6: 20 × 20 cm (row-row × plant-plant)) for improving submergence tolerance in rice. A high yielding submergence intolerant rice cultivar IR64 was tested against its SUB1 QTL introgressed counterpart (IR64-Sub1) for 12 days of complete submergence for different spacing treatments in field tanks. Relatively wider spaced plants showed higher individual plant biomass and early seedling vigour, which was particularly helpful for IR64 in increasing plant survival (by 150% in S6 over S1) under 12 days of submergence, whereas the improvement was less in IR64-Sub1 (13%). Underwater radiation inside the plant canopy, particularly beyond 40 cm water depth, was significantly greater in wider spacing treatments. Leaf senescence pattern captured by SPAD chlorophyll meter reading and chlorophyll fluorescence imaging data (Fm, Fv/Fm) taken at different time intervals after stress imposition suggested that there was lesser light penetration inside the canopy of closer spaced plants, and that it might hasten leaf senescence and damage to the photosynthetic system. The initial content of total non-structural carbohydrate (NSC) was higher in wider spaced plants of IR64, and also the rate of depletion of NSC was lesser compared with closer spaced plants. In contrast, there was not much difference in NSC depletion rate under different spacing in IR64-Sub1. Further, higher antioxidant enzyme activities in wider spaced plants (both IR64 and IR64-Sub1) after de-submergence indicated better stress recovery and improved tolerance. Taken together we found that wider spacing (row-row: 20 cm and plant-plant: 15 cm and more) can significantly improve submergence tolerance ability in rice, particularly in submergence intolerant non-Sub1 cultivar like IR64, perhaps due to better underwater light penetration, delayed leaf senescence and slower depletion of NSC reserve.

Survival and root structure changes of rice seedlings in different cultivars under submergence condition

Abstract. Rachmawati D, Maryani MM, Kusumadewi S, Rahayu F. 2019. Survival and root structure changes of rice seedlings in different cultivars under submergence condition. Biodiversitas 20: 3011-3017. Submergence affects plant growth and fitness in natural and agricultural ecosystem. Plant survival to submergence is strongly influenced by the water level and duration of submergence. The objective of this study was to determine the survivalysiological and root anatomical changes of two rice cultivars seedlings to submergence The experiment used completely randomized design with three factors, cultivar (IR-64’ and ‘Inpara 5’), depth and duration of submergence. Depth of submergence consisted of 3 levels: without, partial and complete submergence. Fourteen days old seedlings were treated for 5, 10 and 15 days of submergence. The observed parameters were seedling survival, chlorophyll content, soluble sugar and starch content, plant biomass, and root anatomical structure. The results showed that seedlings survival of ‘IR-64’ and ‘Inpara 5’ decreased by increasing depth and duration of submergence. Increasing depth of submergence decreased chlorophyll content, soluble sugar content and plant biomass. Anatomically, depth and duration of submergence showed a greater increased in root cortex thickness, aerenchyma tissue diameter and the percentage of cortex to be aerenchyma of rice ‘IR-64’ and ‘Inpara 5’. Fifteen days of complete submergence significantly decreased seedlings survival and increased the diameter of aerenchyma in both ‘IR-64’ and ‘Inpara 5’.

The Influence of Dormancy Break Requirements on Germination and Viability Responses to Winter Submergence in Acorns of Three Bottomland Red Oak (Sect. Lobatae) Species

Abstract The objective of this study was to examine the relation of dormancy break requirements to winter submergence effects on germination and viability in cherrybark, willow, and Nuttall oak acorns. Acorns were submerged in a greentree reservoir and received 0, 21, 42, 63, or 84 days of winter submergence, followed by 8 weeks of incubation in four temperature regimes (15/6°, 20/10°, 25/15°, and 30/20° C). Winter submergence substituted for cold stratification requirements of cherrybark oak acorns, and dormancy break was achieved with 63 days of submergence. Although winter submergence exerted a positive effect on germination in Nuttall and willow oak acorns, dormancy break was not achieved in acorns of either species. Germination percentages were highest in the 30/20° C incubation temperature—cherrybark oak acorns (75–83 percent), followed by Nuttall oak (33–55 percent) and willow oak (14–52 percent). Among treatment combinations, all willow oak nongerminants were viable. Viability loss in cherrybark and Nuttall oak acorns was greatest in the 63- and 84-day treatments. The dynamics of acorn germination in response to winter hydrologic regime is influenced by submergence duration that may, or may not, satisfy dormancy break requirements in acorns of these red oak species.

Physiology, gene expression, and metabolome of two wheat cultivars with contrasting submergence tolerance.

Responses of wheat (Triticum aestivum) to complete submergence are not well understood as research has focused on waterlogging (soil flooding). The aim of this study was to characterize the responses of 2 wheat cultivars differing vastly in submergence tolerance to test if submergence tolerance was linked to shoot carbohydrate consumption as seen in rice. Eighteen-day-old wheat cultivars Frument (intolerant) and Jackson (tolerant) grown in soil were completely submerged for up to 19days while assessing responses in physiology, gene expression, and shoot metabolome. Results revealed 50% mortality after 9.3 and 15.9days of submergence in intolerant Frument and tolerant Jackson, respectively, and significantly higher growth in Jackson during recovery. Frument displayed faster leaf degradation as evident from leaf tissue porosity, chlorophylla , and metabolomic fingerprinting. Surprisingly, shoot soluble carbohydrates, starch, and individual sugars declined to similarly low levels in both cultivars by day 5, showing that cultivar Jackson tolerated longer periods of low shoot carbohydrate levels than Frument. Moreover, intolerant Frument showed higher levels of phytol and the lipid peroxidation marker malondialdehyde relative to tolerant Jackson. Consequently, we propose to further investigate the role of ethylene sensitivity and deprivation of reactive O2 species in submerged wheat.

Hydrostatic and blast initiated implosion of environmentally degraded Carbon-Epoxy composite cylinders

The underwater collapse mechanics of environmentally degraded filament-wound Carbon-Epoxy composite tubes were investigated in this study. The composite tubes were submerged in an elevated temperature saline water solution for 35 and 70 days. The temperature of the saline bath was held at 65 °C, in which case the 35 and 70 days duration simulates 3.8 and 7.6 years of service life in accordance with Arrhenius’ equation and a reference temperature of 17 °C. Experiments were performed underwater in a pressure vessel designed to simulate a free-field environment by maintaining constant hydrostatic pressure throughout the collapse event. Two cases of implosion were studied: implosion initiated by increasing the hydrostatic pressure in the vessel until the critical collapse pressure was reached; and by detonating an explosive charge while the composite structure was subjected to 80% of its critical collapse pressure. Three-Dimensional Digital Image Correlation was coupled with high-speed photography to obtain the full-field displacements and velocities of the composite tubes during collapse. Moreover, the pressure fields created during the structural collapse were recorded with tourmaline pressure transducers and coupled with the full-field deformations to analyze the collapse mechanics. Mass saturation was reached during the first 35 days of submergence in the saline water bath. For the implosion initiated by hydrostatic pressure, the composite tubes submerged in the saline water bath displayed different behavior in comparison to the tubes with no exposure. The critical collapse pressure decreased by 20% after 35 days of exposure to the elevated temperature water bath when compared to the non-weathered tubes, and 24% after 70 days of exposure to the elevated temperature water bath when compared to the non-weathered tubes. The full-field data showed that the weathered structures collapsed with higher center-point velocities, which arise from substantial cracking and damage accumulation during the collapse event, as well as lower structural stiffness. The aged composite tubes had a lower overpressure pulse due to an increase in damage. For the blast initiated implosions, the reduced structural stiffness resulted in a quicker instability event. Lastly, further weathering after saturation led to a decrease in structural strength and performance.

Effects of Exogenous Application of Protocatechuic Acid and Vanillic Acid to Chlorophylls, Phenolics and Antioxidant Enzymes of Rice (Oryza sativa L.) in Submergence.

In this study, effects from application of protocatechuic acid (PA) and vanillic acid (VA) and their mixture on the submergence tolerance of rice were examined. The treatment of 0.01 mM PA and VA did not show significant increase of rice growth as compared to the controls. However, at higher concentrations (0.1–1.0 mM), rice shoot was elevated in submergence by 20.8–22.4%. The survival percentage of rice seedlings at any dose of PA, VA and their mixture was significantly higher than the controls. In general, the mixture of PA and VA was more active to promote shoot elongation and survival in submergence than sole treatment of either PA or VA. The amount of chlorophyll b by PA was significantly increased, while no change in chlorophyll a content was observed. VA remarkably reduced malondialdehyde quantity at three days of submergence, while no significant difference among treatment was observed in PA, the mixture, and respective controls. The two phenolic acids promoted contents of phenolics and flavonoids in rice leaves and roots, however the quantities of endogenous PA and VA in rice were not markedly differed after PA and VA treated on roots of rice seedlings. The ascorbate peroxidase and superoxide dismutase activities were enhanced, while the expression of genes encoding antioxidant enzymes was favored. VA increased the expression level of ascorbate peroxidase genes in higher levels than PA and their mixture, while no significant difference was observed in the other genes including superoxide dismutase, catalase, glutathione reductase, and peroxidase. Findings of this study showed that PA and VA increased the submergence tolerance of rice by promoting the photosynthetic and anti-oxidative processes in rice seedlings. The treatment of PA and VA mixture on seedling roots was potent to promote the submergence tolerance in rice.

Physiological characterization of SUB1 trait in rice under subsequent submergence and re-aeration with interaction of chemical elicitors

In the present study, the sensitivity of two chemical elicitors: polyamine (PA) and salicylic (SA) acid were exercised for submergence sensitivity in Swarna Sub1A rice variety. Under 5 days of submergence, the antioxidation responses were more distinguished in plants against control. Along with the anti-oxidation modules, significant changes in biomolecule loss were registered through lipid and protein oxidation by 1.91 and 1.46 -fold respectively. PA and SA treated plants were the reliever to recover the membrane potential. Total carbohydrate and reducing sugars were varied under submergence by down regulation of 36.66 and 44.44% as compared to control. This was also supported by regulation of ?-amylase activity under submergence that also recovered significantly with PA and SA treatments against submergence. In association with carbohydrate metabolism, Under submergence Swarna Sub1A recorded to be prone with oxidative stress through O2.- (1.55 fold) and peroxide (1.70-fold) over-accumulation but recovered as PA and SA applied. In both cases, sustenance of non-enzymatic anti-oxidant like total carotenoid and lycopene content were also contributory through down-regulation. The enzymatic anti-oxidation paths like SOD, GPX, CAT and GR were regulated by 11.11, 19.54, 13.65, 10.03% declined respectively and thoroughly discussed with reference to PA and SA interactions.

Experimental and computational investigation of the blast response of Carbon-Epoxy weathered composite materials

Abstract An experimental study with corresponding numerical simulations was conducted to investigate the blast response of weathered Carbon-Epoxy composite plates. The dynamic behavior of the composite plates with and without prior exposure to an aggressive marine environment was explored using a shock tube apparatus coupled with a high speed photography system. In order to simulate prolonged exposure in an aggressive marine environment, specimens were submerged in an elevated temperature, 3.5% salt solution for 0, 30 and 60 days. The saline solution temperature was maintained at 65 °C to accelerate the aging process. Finite Element Modeling (FEM) for the blast loading experiments was performed using the Ls-Dyna code. Models have been developed for both the simply supported and fixed boundary condition cases. Tensile and four point bend tests were performed to characterize the quasi-static mechanical behavior of the composite material before and after prolonged exposure to aggressive marine environments. After 30 and 60 days of submergence, the tensile modulus decreased by 11% and 13%, the ultimate tensile strength decreased by 12% and 13%, and the ultimate flexural strength decreased by 22% and 22%, respectively. Dynamic blast loading experiments were performed on simply supported and fully clamped specimens, to determine the effects of the boundary conditions on the Carbon-Epoxy specimen response. The Weathered (30 and 60 days) and Non-Weathered (0 day) specimens displayed dramatically different behavior after being subjected to a blast load. For the simply supported case, Non-Weathered specimens displayed an average maximum out of plane displacement of 20 mm and recovered elastically. Weathered specimens, both 30 and 60 days exhibited similar initial transient behavior but failed catastrophically due to through thickness cracking at the point of maximum deflection. For the fixed boundary condition, the Non-Weathered specimens displayed an average maximum out of plane displacement of 5.57 mm, whereas the 30 day and 60 day weathered specimens displayed a maximum out of plane displacement of 6.89 mm and 6.96 mm, respectively. The corresponding numerical simulations matched well with the experimental data. However, for the fixed boundary case, the beam vibration of the simulation was off phase with the experimental results due to imperfect boundary conditions in the experiments.

Association of Candidate Genes With Submergence Response in Perennial Ryegrass.

Perennial ryegrass is a popular cool-season grass species due to its high quality for forage and turf. The objective of this study was to identify associations of candidate genes with growth and physiological traits to submergence stress and recovery after de-submergence in a global collection of 94 perennial ryegrass accessions. Accessions varied largely in leaf color, plant height (HT), leaf fresh weight (LFW), leaf dry weight (LDW), and chlorophyll fluorescence (Fv/Fm) at 7 days of submergence and in HT, LFW and LDW at 7 days of recovery in two experiments. Among 26 candidate genes tested by various models, single nucleotide polymorphisms (SNPs) in 10 genes showed significant associations with traits including 16 associations for control, 10 for submergence, and 8 for recovery. Under submergence, Lp1-SST encoding sucrose:sucrose 1-fructosyltransferase and LpGA20ox encoding gibberellin 20-oxidase were associated with LFW and LDW, and LpACO1 encoding 1-aminocyclopropane-1-carboxylic acid oxidase was associated with LFW. Associations between Lp1-SST and HT, Lp6G-FFT encoding fructan:fructan 6G-fructosyltransferase and Fv/Fm, LpCAT encoding catalase and HT were also detected under submergence stress. Upon de-submergence, Lp1-SST, Lp6G-FFT, and LpPIP1 encoding plasma membrane intrinsic protein type 1 were associated with LFW or LDW, while LpCBF1b encoding C-repeat binding factor were associated with HT. Nine significant SNPs in Lp1-SST, Lp6G-FFT, LpCAT, and LpACO1 resulted in amino acid changes with five substitutions found in Lp1-SST under submergence or recovery. The results indicated that allelic diversity in genes involved in carbohydrate and antioxidant metabolism, ethylene and gibberellin biosynthesis, and transcript factor could contribute to growth variations in perennial ryegrass under submergence stress and recovery after de-submergence.

Exogenous Application of Nitrogen and Cytokinin on Growth, Carbohydrate, and Antioxidant Metabolism of Creeping Bentgrass after De-submergence

Recovery from submergence stress is vital for plant regrowth. The objective of this study was to characterize plant growth, carbohydrate, and antioxidant metabolism of creeping bentgrass (Agrostis stolonifera) to foliar application of nitrogen and cytokinin (CK) after de-submergence. Creeping bentgrass (cv. Penncross and 007) were submerged under the water for 14 days and then foliar-sprayed at 1, 2, 3, 7, and 14 days after de-submergence with six types of chemical treatments, respectively: 1) water (W); 2) 10 mm urea (N10); 3) 20 mm urea (N20); 4) 10 µm CK; 5) N10 with CK (N10CK); and 6) N20 with CK (N20CK). Leaves were harvested at 20 days after chemical applications for various measurements. Compared with the nonstressed plants, plant height (HT), chlorophyll index (Chl), leaf dry weight (DW), water-soluble carbohydrate content (WSC), activities of superoxide dismutase (SOD), and ascorbate peroxidase (APX) decreased, but catalase (CAT) and peroxidase (POD) activities, malondialdehyde (MDA), and total soluble protein (TSP) content increased in both cultivars exposed to 14 days of submergence. After de-submergence, plants treated with N alone (N10, N20) or combined with CK (N10CK, N20CK) generally had higher HT, DW, Chl, TSP, and a lower amount of MDA, compared with treatments of W or CK alone, whereas treatment using CK resulted in higher WSC for both cultivars. Foliar applications of N and CK had some effect on SOD, CAT, POD, and APX activities after de-submergence, but the effects were not consistent across chemicals and cultivars. The results indicated that foliar application of N or combined with CK promoted plant growth and reduced lipid peroxidation after de-submergence. The results also suggested a more positive role of foliar N application in comparison with a complex regulation of CK on creeping bentgrass regrowth after de-submergence.

Submergence induced changes of molecular species in membrane lipids in Arabidopsis thaliana

The composition of membrane lipids is sensitive to environmental stresses. Submergence is a type of stress often encountered by plants. However, how the molecular species of membrane lipids respond to submergence has not yet been characterised. In this study, we used a lipidomic approach to profile the molecular species of membrane lipids in whole plants of Arabidopsis thaliana that were completely submerged for three days. The plants survived one day of submergence, after which, we found that the total membrane lipids were only subtly decreased, showing significant decreases of monogalactosyldiacylglycerol (MGDG) and phosphatidylcholine (PC) and an increase of phosphatidic acid (PA); however, the basic lipid composition was retained. In contrast, three days of submergence caused plants to die, and the membranes deteriorated via the rapid loss of 96% of lipid content together with a 229% increase in PA. The turnover of molecular species from PG and MGDG to PA indicated that submergence-induced lipid changes occurred through PA-mediated degradation. In addition, molecular species of extraplastidic PG degraded sooner than plastidic ones, lyso-phospholipids exhibited various patterns of change, and the double-bond index (DBI) remained unchanged until membrane deterioration. Our results revealed the unique changes of membrane lipids upon submergence and suggested that the major cause of the massive lipid degradation could be anoxia.

Physiological basis of submergence tolerance in rice genotypes with reference to carbohydrate metabolism

Rice genotypes viz., Swarna Sub1A, FR13A and Swarna were evaluated for their carbohydrate profiles on seven days of submergence. Swarna Sub1A showed minimum increase in proline content than FR13A and Swarna. The depletion of total carbohydrate in roots was recorded having maximum and minimum depletion in Swarna and FR13A respectively. In shoots the depletion was maximum in Swarna Sub1A and minimum in Swarna. Depletion of starch under submergence was maximum in Swarna Sub1A and minimum in Swarna. Sucrose was maximally consumed in Swarna Sub1A and minimally in Swarna in shoots. Invertase activity was increased in roots in Swarna and FR13A but it declined in Swarna Sub1A. In shoots, the activity got declined in Swarna and FR13A and increased in Swarna Sub1A. SPS activity in shoots was down regulated under submergence with maximum and minimum values in FR13A and Swarna respectively. Amylase activity was significantly upregulated in other two varieties but got declined in Swarna Sub1A. Cellulose in root and shoot was accumulated maximally and minimally in Swarna and FR13A respectively. Hemicellulose was accumulated with maximum and minimum values in Swarna Sub1A and in FR13A respectively in roots whereas it was maximum in Swarna Sub1A and minimum in Swarna in shoots. Abbreviations FW, Fresh weight; DW, Dry weight; DNSA, 3,5 Dinitrosalicylic acid; DTT, Dithiothreitol; MOPS, 3-(N-morpholino) propanesulfonic acid; ATP, Adenosine triphosphate; GA, Gibberellic acid; ABA, Abscissic acid; ROS, Reactive Oxygen Species; SPS, Sucrose Phosphate Synthase.

Changes in proline accumulation, amino acid, sugar and chlorophyll content in leaf and culm of Phourel-amubi, a rice cultivar of Manipur in response to flash flood

Rice (Oryza sativa L.) growth is generally hindered by prolonged exposure to excess of water during its vegetative or reproductive stage. To determine the effect of flood on the plant and to understand the tolerance mechanism of the rice cultivar, variations in the plant height, dry matter, and contents of chlorophyll, total soluble sugar, free amino acid and proline were determined in leaves and culm of Phourel-amubi, a rice cultivar of Manipur under 5, 10 and 15 days of submergence and non-submerged (control) condition. Plant height, dry matter and proline accumulation increased with the increase in days of submergence (highest with 15 days submergence). Total chlorophyll, both chlorophyll a and chlorophyll b content were found to decrease with period of submergence. Likewise concentration of soluble sugar in leaves decreased with submergence but in the case of culm, the sugar concentration gradually increased from control to 15 days submergence. Total free amino acid concentration also decreased with submergence. However, proline accumulation both in leaves and culm gradually increased with submergence, and highest content were observed under 15 days submergence.

Effects of submergence in water on seed germination and vigor of the Copaifera lucens (Fabaceae) seedlings

We analyzed the tolerance of Copaifera lucens seeds to submersion in water to assess the use of this species for direct seeding in riparian forest restoration programs. Seeds were submerged in water for 2, 4, 8, 16 and 32 days or not submerged (control = 0 days of submergence). For the control and at the end of each period of submersion, germination and seedling vigor tests were carried out. For germination tests, seeds were sown in plastic pots containing sand and kept in laboratory conditions. The percentage of seed germination, the germination rate and the average germination time were analyzed. For seedlings, total biomass, leaf area, leaf mass per area and leaf area ratio were analyzed. Submersion time drastically affected the dissolved oxygen content and seed germination. Between 4 and 8 days of submersion there was a decrease from 83.8% to 15.6% in the germination percentage. No seed germination occurred after 16 days of submersion. Although there was a significant decrease in the percentage of seed germination between 4 and 8 days of submersion, seedling vigor was not affected. Seeds of this species were partially tolerant to submersion in water, suggesting that C. lucens is a promising species for direct seeding in riparian forest restoration projects.

Histologic Changes in Traumatized Skeletal Muscle Exposed to Seawater

Wounds were created by incision in skeletal muscle of 2 mixed-breed canine cadavers at multiple time points from 0.5 to 74.5 hours postmortem and were exposed to artificial seawater (35 parts per thousand), 0.9% saline (8 parts per thousand), or freshwater for 24 hours before fixation for histology. Discoid and segmental disintegration of myofibers deep to the severed edges was observed in injuries inflicted within 6.5 hours of death and exposed to 0.9% saline and seawater and was not observed in injuries made at later time points or in other treatments. Exposure to artificial seawater had pronounced effects on histomorphology that markedly diminished with increasing postmortem wounding interval. In a third cadaver, these changes were shown to be detectable with confidence following up to 10 days of submergence in seawater at 22.2°C despite decomposition. These findings are important for evaluation of skeletal muscle injuries that are exposed to seawater, such as those occurring in marine animals, and may assist in recognizing wounds inflicted either antemortem or within the supravital period.