Early Stages Of Imbibition Research Articles

CONCEPT OF SEED DETERIORATION: REASON, FACTORS, CHANGES DURING DETERIORATION AND PREVENTIVE MEASURES TO OVERCOME SEED DEGRADATION

Seed deterioration is when a seed loses its vigor and eventually loses viability. Seed viability is an important trait that directly influences seedling emergence and crop yield. The rate of seed deterioration varies on several factors. Our main aims were to express the methods for testing seed deterioration, factors influencing seed aging, stages of seed deterioration, changes associated with seed deterioration, Practical approaches to overcome seed deterioration, and the role of reactive oxygen species during seed aging. From this investigation, it can be concluded that high temperatures and high relative humidity can hasten the degradation of seeds. An increase in the loss of seed leachate, a drop in respiration rates and ATP production, a loss of enzyme activity, and organelle structural breakdown are often seen as changes as seeds age. Various factors can cause seed aging, but the main cause is probably oxidative damage brought on by free radicals and reactive oxygen species (ROS). Protein oxidation, lipid peroxidation, chromosomal abnormalities, and DNA damage can all be induced by ROS, which can have critical interactions with any macromolecule of biological significance. In the early stages of imbibition, some repairs may occur, and seeds will lose their viability within a short period. Seed deterioration can be retrieved through different priming and exogenous application of plant growth regulators.

Wettability alternation and interface tension modification for enhanced oil recovery in oil-wet carbonates: A comparative study of different surfactants

With the ever-growing demand for oil and gas today, and the increasing difficulty of recovering hydrocarbons from carbonate reservoirs, it is vital to apply enhanced oil recovery (EOR) techniques. Carbonate reservoirs typically have natural fractures and are found to have oil-wet matrixes natively, making EOR in these reservoirs more challenging. Wettability alteration is a viable mechanism in this scenario. However, there is an ambiguity about which chemical solutions perform better in carbonate reservoirs. This study assessed the capabilities of various surfactants and their ability to alter wettability and interfacial tension under surface and reservoir conditions. Fifty-six surfactants from four different chemical groups (cationic, anionic, zwitterionic/amphoteric, and nonionic) were screened for their stability and emulsification. Then, spontaneous imbibition experiments were performed on an Indiana limestone outcrop to assess the impact of wettability and interfacial tension on oil recovery for both aged and non-aged cores. Results show that six out of the eleven successful surfactants were nonionic. Furthermore, we found that, for oil-wet rocks, wettability alteration increases production in the early stages of imbibition, while the reduction in interfacial tension increases the recovery in the later stages by unlocking trapped oil in the pore matrix. Exploratory data analysis showed that IFT is the most correlated parameter with the recovery from the aged cores, while contact angle was highly correlated with both aged and non-aged cores. Finally, a generalized automated spontaneous imbibition model was derived based on the dimensionless exponential and hyperbolic functions. The fitting results show that both the exponential and hyperbolic models complied with the trend of spontaneous imbibition. However, the exponential model better matches the surfactant imbibition data. The results from this work help unlock the potential of carbonate reservoirs and maximize the oil recovery to solve the current global energy challenge.

Imbibition Characteristic of Fractured Tight Sandstone Reservoir

“Fracture network stimulation + imbibition replacement” is a new attempt to effectively develop tight sandstone reservoirs, and the fractures provide conditions for fluid imbibition replacement. On the basis of nuclear magnetic resonance and pseudo-color processing technology, combined with the imbibition experiments, this paper studies the imbibition process of fractured tight sandstone reservoirs, clarifies the effect of each level of pore-throat on imbibition, and realizes the visualization of the imbibition process. The results show that, in fractured tight sandstone reservoirs, the fluid displacement occurs in fractures first, followed by pore-throat. Most of the imbibition recovery is contributed by the macropore, the contribution of the mesopore to imbibition recovery is very weak, and the contributions of the micropore and the pinhole are even less. In the process of imbibition, capillary force and gravitational force are key parameters controlling fluid flow in pores and fractures. The replacement of fluid normally takes place in the early stage of imbibition, especially on the first day of imbibition, then the imbibition rate gradually decreases and finally tends to be stable.

A KARRIKIN INSENSITIVE2 paralog in lettuce mediates highly sensitive germination responses to karrikinolide.

Karrikins (KARs) are chemicals in smoke that can enhance germination of many plants. Lettuce (Lactuca sativa) cv. Grand Rapids germinates in response to nanomolar karrikinolide (KAR1). Lettuce is much less responsive to KAR2 or a mixture of synthetic strigolactone analogs, rac-GR24. We investigated the molecular basis of selective and sensitive KAR1 perception in lettuce. The lettuce genome contains two copies of KARRIKIN INSENSITIVE2 (KAI2), which in Arabidopsis (Arabidopsis thaliana) encodes a receptor that is required for KAR responses. LsKAI2b is more highly expressed than LsKAI2a in dry achenes and during early stages of imbibition. Through cross-species complementation assays in Arabidopsis, we found that an LsKAI2b transgene confers robust responses to KAR1, but LsKAI2a does not. Therefore, LsKAI2b likely mediates KAR1 responses in lettuce. We compared homology models of KAI2 proteins from lettuce and a fire-follower, whispering bells (Emmenanthe penduliflora). This identified pocket residues 96, 124, 139, and 161 as candidates that influence the ligand specificity of KAI2. Further support for the importance of these residues was found through a broader comparison of pocket residues among 281 KAI2 proteins from 184 asterid species. Almost all KAI2 proteins had either Tyr or Phe identity at position 124. Genes encoding Y124-type KAI2 are more broadly distributed in asterids than in F124-type KAI2. Substitutions at residues 96, 124, 139, and 161 in Arabidopsis KAI2 produced a broad array of responses to KAR1, KAR2, and rac-GR24. This suggests that the diverse ligand preferences observed among KAI2 proteins in plants could have evolved through relatively few mutations.

Modeling the spontaneous imbibition of non-Newtonian fluids into the fractal porous media of tight reservoirs

This study proposes a new fractal model to describe the spontaneous-imbibition process of non-Newtonian fluids in tight reservoirs. In the new fractal model, the imbibed mass can be mainly expressed as a function of pore-geometry parameters, the rheological properties of non-Newtonian fluid, and contact angle. We validated the new model against experiments, which were conducted on three core samples collected from a tight reservoir in the Ordos Basin. Comparative analysis shows a relatively good match in imbibition profiles obtained by modeling and experiments at the early stage of imbibition. Unlike the Newtonian fluids, the modeling results suggest a non-linear relationship between imbibition distance and the square root of time when the tortuosity and non-Newtonian fluids are considered. This study may thus provide new insights into modeling the fracturing-fluid flow in tight reservoirs.

Simulation of imbibition in porous media with a tree-shaped fracture following the level-set method

Imbibition is an important mechanism for enhancing oil recovery in low-permeability reservoirs, such as shale and tight sandstone, and a tree-shaped network has been successfully used to characterize fracturing fracture. Therefore, understanding the imbibition mechanism in porous media with a tree-shaped fracture (TFPM) is important for developing low-permeability reservoirs. In this study, a simulation model for imbibition in TFPM was established based on the level-set method, and the model was verified by comparing it with an analytical solution. The influences of the fracture width, bifurcation angle, tortuosity, and water flow rate on imbibition in TFPM were then discussed. Based on the results, the following points have been established: (1) During the early stage, the imbibition in TFPM included countercurrent and a combined imbibition, and only countercurrent imbibition occurred during the later stage. (2) At a constant fracture width ratio, increasing the primary fracture width could reduce the residual oil in the TFPM, thereby improving the oil recovery factor. (3) At a fracture bifurcation angle ranging from 0° to 45°, the oil recovery factor increased as the bifurcation angle increased. (4) At a fracture tortuosity of 1.0 to 1.24, changes in tortuosity had little effect on the oil recovery factor during the early stage of imbibition, while it significantly affected the distribution of the residual oil. (5) At a water flow rate of 5 mm/s, the simulated oil recovery factor in the TFPM was highest. This investigation can provide a reference for the development of low-permeability reservoirs.

Single count of radicle emergence, DNA replication during seed germination and vigour in alfalfa seed lots

Previous work on alfalfa seeds has illustrated the close association between the rate of germination and vigour. This study examined single early counts of radicle emergence (RE) as an indirect method to measure the rate of germination in alfalfa, and investigated cell cycle activities in the early stages of imbibition. The 6-hour interval counts of just germination (JG) and germination percentages (G) of 14 seed lots at 20, 17, 15 and 13°C were compared with final emergence and mean emergence time. Single counts of JG and G were strongly correlated with mean just germination time (MJGT), mean germination time (MGT) (P < 0.01) and field performance. The results indicate that single counts of RE after 24 hours at 20°C could be used to predic the vigour of alfalfa seeds. The embryo root tip cells of six seed lots with low, medium and high vigour were used for analysis of DNA replication by flow cytometry 3, 6, 12, 18 and 24 hours after imbibition. The 4C/2C ratio 18 hours after imbibition and the increase in 4C/2C ratio between 6 and 12 hours after imbibition was associated with the vigour of the seed lot and has the potential to predict seed vigour.

Imbibition into Capillaries with Irregular Cross Sections: A Modified Imbibition Equation for Both Liquid–Gas and Liquid–Liquid Systems

Due to discrepancies observed between many experimental results and predictions from the Bell–Cameron–Lucas–Washburn (BCLW) imbibition equation, the BCLW equation was often modified by considering the effects of pore/throat characteristics. As previous works mainly focused on liquid–gas systems, the effects of the viscosity ratios are neglected. In this study, the nonwetting-/wetting-phase-viscosity ratio ( $$ \Psi $$ ) is varied by four orders of magnitude (0.018 to 8), which covers the common fluid viscosity in waterflooded tight reservoirs. Capillaries with irregular cross sections (namely, complex capillaries), which are recognized to more representative for porous media, are used to theoretically study imbibition kinetics in both the liquid–gas and liquid–liquid system. To considering the effects of viscosity ratio, we propose a modified imbibition equation based on the Poiseuille law and a piecewise method to calculate the equivalent radius for complex capillaries. The predictivity of the new imbibition equation is mathematically validated in varying viscosity ratios and geometries characteristics (such as the radius levels and the numbers/length ratios of radius levels). The study proves that an equivalent straight capillary can globally predict imbibition behaviors in complex capillaries. Except for a few scenarios, the equivalent radius of the straight capillary is affected by capillary geometries and viscosity ratios. Only in the early stage of imbibition ( $$ l_{x} /l \le 0.12\Psi /\left( {\Psi - 1} \right) $$ ), the modified imbibition equation can be expressed as a power-law relation (i.e., $$ l_{x} /l \propto \frac{1}{\Psi }t^{\alpha } $$ ) as $$ {\Psi } $$ is higher than 1. In general, it is more suitable to express the imbibition equations in a quadratic form, especially for liquid–liquid imbibition systems.

Effect of Nitric Oxide on Seed Germination and Dormancy in Empress Trees

Freshly harvested empress tree (Paulownia elongata) seeds have physiologic dormancy. The aim of this study was to investigate the effects of exogenous and endogenous nitric oxide (NO) on the dormancy and germination of empress tree seeds. After treatment with different concentrations of sodium nitroprusside (an NO-releasing compound) solution, the germination percentage of seeds under 12 h of continuous light was significantly greater. Seed germination percentage was promoted significantly by 10–4 M sodium nitroprusside plus cold stratification compared with seeds treated with cold stratification only. At different hours during imbibition, empress tree seeds treated with 2-(4-carboxyphenyl)-4, 4, 5, 5- tetramethylimidazoline -1-oxyl-3-oxide potassium salt (c-PTIO), NG-nitro-L-arginine methyl ester (L-NAME), and sodium tungstate showed reduced seed germination percentages. During the early hours of imbibition, c-PTIO or sodium tungstate treatment inhibited seed germination significantly. The results showed that both exogenous and endogenous NO can release empress tree seed dormancy. Endogenous NO oxide was involved in dormancy release and germination of seeds during the early stages of imbibition. Wider application of NO may be used for breaking seed dormancy in other species.

Investigation on the Application of NMR to Spontaneous Imbibition Recovery of Tight Sandstones: An Experimental Study

In this paper, the nuclear magnetic resonance (NMR) technique is applied to exploring the spontaneous imbibition mechanism in tight sandstones under all face open (AFO) boundary conditions, which will benefit a better understanding of spontaneous imbibition during the development of oil & gas in tight formations. The advantages of nuclear magnetic resonance imaging (NMRI) and NMR T2 are used to define the distribution of remaining oil, evaluate the effect of micro structures on imbibition and predict imbibition recovery. NMR T2 results show that pore size distributions around two peaks are not only the main oil distributions under saturated condition but also fall within the main imbibition distributions range. Spontaneous imbibition mainly occurs in the first 6 h and then slows down and even ceases. The oil signals in tiny pores stabilize during the early stage of imbibition while the oil signal in large pores keeps fluctuating during the late stage of imbibition. NMRI results demonstrate that spontaneous imbibition is a replacement process starting slowly from the boundaries to the center under AFO and ending with oil-water mixing. Furthermore, the wetting phase can invade the whole core in the first 6 h, which is identical with the main period of imbibition occurring according to NMR T2 results. Factors influencing the history of oil distribution and saturation differ at different periods, while it is dominated by capillary imbibition at the early stage and allocated by diffusion at later time. Two imbibition recovery curves calculated by NMRI and NMR T2 are basically consistent, while there still exists some deviations between them as a result of the resolutions of NMRI and NMR T2. In addition, the heterogeneity of pore size distributions in the two samples aggravates this discrepancy. The work in this paper should prove of great help to better understand the process of the spontaneous imbibition, not only at the macroscopic level but also at the microscopic level, which is significant for oil/gas recovery in tight formations.

Relationships between ultrastructure of embryo cells and biochemical variations during ageing of oat (Avena sativa L.) seeds with different moisture content

This experiment was designed to determine the relationship between the ultrastructure of the embryo cells and the changes in antioxidant enzymatic activities and lipid peroxidation in oat (Avena sativa L.) seeds with different moisture contents (4, 10 and 16 %) that were aged for 0, 8, 16, 24, 32 and 40 days in 45 °C. The results showed that the declining in the germination percentage and integrity of cell ultrastructure in oat aged seeds were presented during the aged process, and these changes would be enhanced by the higher moisture content. There were consequent changes for biochemical reactions and lipid peroxidation exhibited. For oat seeds with 4 and 10 % moisture content, SOD and CAT were much more sensitive than APX at the early stages of imbibition after mild ageing, the activities of SOD, CAT, APX and MDHAR at 4 h of imbibition decreased significantly (P < 0.05) after being aged from 32 to 40 days. On the contrary, MDA and H2O2 contents both did not increase further. Upon imbibition the activities of DHAR and GR increased after mild ageing, declined after further ageing and maintained a stable level after ageing from 24 to 40 days at those moisture levels. Both activities were higher after ageing at 4 % moisture content than at 10 %. The decline in integrity of ultrastructural cells was related with accumulation of H2O2 during seed ageing, and favoured by the decrease of SOD, CAT, APX and MDHAR activities after imbibition. The activities of antioxidant enzymes and contents of MDA and H2O2 in oat seeds with 16 % moisture content all gradually decreased after ageing from 8 to 40 days, also the ultrastructure of embryo cells was severely damaged. Its ultrastructure was destroyed much more quickly in the seeds with higher moisture content. The level of moisture content could accelerate the seed deterioration, and mitochondrial damages were probably the main reason for oat seed ageing. However, the activities of antioxidant enzymes were the key factor to repair the damage from lipid peroxidation and to maintain the integrity of cell ultrastructure for oat aged seeds during imbibition.

Capillary pressure and relative permeability estimated from a single spontaneous imbibition test

Under certain boundary conditions during spontaneous brine imbibition into oil-saturated porous rocks, it is possible for co- and counter-current flow to occur simultaneously. These circumstances are formalized into a special Two-Ends-Open (TEO) boundary condition; one end face of the core is exposed to brine and the other end face is exposed to oil. The behavior of imbibition with the new boundary condition (termed TEO-free spontaneous imbibition) is analyzed using a simple piston-like displacement model. The model allows interpretation of properly conducted experiments and the determination of the pressure, referred to as the capillary back pressure, which resists oil production at the water-wetted face where limited spontaneous countercurrent imbibition occurs. The opposite end face (in contact with oil) has zero capillary back pressure and oil is produced from this end as well, but co-currently. In experiments, oil production was monitored at each core end face to quantify oil production by counter-current imbibition from the face contacted by brine versus co-current imbibition from the face in contact with oil. In the experiments, oil production by counter-current flow only occurred in the very early stage of imbibition. This was because the counter-current imbibition contribution to oil production was curtailed by the action of the capillary back pressure. The influence of the capillary back pressure on the imbibition mechanism for variations in rock permeability and core length was investigated. For 9 tests in all, an average of 96% of total recovery was produced co-currently. The simple theory was used to analyze the co-current-only stage of imbibition. The theory gave an estimate of the relative permeability to brine behind the front and also of the effective capillary pressure generated at the imbibition front. In some experiments, the pressure in the core was monitored in addition to production and this enabled the absolute permeability and the capillary back pressure at the open face to be calculated directly.

Arabidopsis nudix hydrolase 7 plays a role in seed germination

Arabidopsis nudix hydrolase 7 (Atnudt7) mutants exhibit reduced seed germination phenotype following after-ripening. The role of AtNUDT7 in seeds and during early stages of imbibition was examined. Seeds of Atnudt7-1 and Col-0 following 3 days of imbibition were used to profile changes in NADH- and ADP-ribose pyrophosphohydrolase enzyme activities, expression of nudix family genes closely related to AtNudt7, and AtNUDT7 protein levels. Changes in pyridine nucleotides, phytohormones, reactive oxygen species and poly(ADP-ribose) levels in after-ripened seeds and 1 day after imbibition were also analyzed. Changes in AtNUDT7 gene expression, protein levels and enzyme activities in WT seeds and during early stages of imbibition were correlated. Atnudt7-1 seeds lacked NADH pyrophosphohydrolase activity that led to very high catabolic redox charge. Abscisic acid (ABA) levels were higher in Atnudt7-1 mutant while salicylic acid, gibberellic acid, and reactive oxygen species (ROS) levels were higher in WT seeds. In Atnudt7-1, there was excess ROS accumulation 1 day after imbibition. PAR levels were significantly higher in Atnudt7-1 mutant when compared to WT during imbibition. Based on these observations, we conclude NADH pyrophosphohydrolase activity conferred by AtNUDT7 is important for NAD:NADH homeostasis in seeds. Perturbations to this key redox couple alter ABA and ROS levels in the seeds that in turn lowers germination.

Using RNA-Seq to profile soybean seed development from fertilization to maturity.

To understand gene expression networks leading to functional properties and compositional traits of the soybean seed, we have undertaken a detailed examination of soybean seed development from a few days post-fertilization to the mature seed using Illumina high-throughput transcriptome sequencing (RNA-Seq). RNA was sequenced from seven different stages of seed development, yielding between 12 million and 78 million sequenced transcripts. These have been aligned to the 79,000 gene models predicted from the soybean genome recently sequenced by the Department of Energy Joint Genome Institute. Over one hundred gene models were identified with high expression exclusively in young seed stages, starting at just four days after fertilization. These were annotated as being related to many basic components and processes such as histones and proline-rich proteins. Genes encoding storage proteins such as glycinin and beta-conglycinin had their highest expression levels at the stages of largest fresh weight, confirming previous knowledge that these storage products are being rapidly accumulated before the seed begins the desiccation process. Other gene models showed high expression in the dry, mature seeds, perhaps indicating the preparation of pathways needed later, in the early stages of imbibition. Many highly-expressed gene models at the dry seed stage are, as expected, annotated as hydrophilic proteins associated with low water conditions, such as late embryogenesis abundant (LEA) proteins and dehydrins, which help preserve the cellular structures and nutrients within the seed during desiccation. More significantly, the power of RNA-Seq to detect genes expressed at low levels revealed hundreds of transcription factors with notable expression in at least one stage of seed development. Results from a second biological replicate demonstrate high reproducibility of these data revealing a comprehensive view of the transciptome of seed development in the cultivar Williams, the reference cultivar for the first soybean genome sequence.

Flux of transcript patterns during soybean seed development

BackgroundTo understand gene expression networks leading to functional properties of the soybean seed, we have undertaken a detailed examination of soybean seed development during the stages of major accumulation of oils, proteins, and starches, as well as the desiccating and mature stages, using microarrays consisting of up to 27,000 soybean cDNAs. A subset of these genes on a highly-repetitive 70-mer oligonucleotide microarray was also used to support the results.ResultsIt was discovered that genes related to cell growth and maintenance processes, as well as energy processes like photosynthesis, decreased in expression levels as the cotyledons approached the mature, dry stage. Genes involved with some storage proteins had their highest expression levels at the stage of highest fresh weight. However, genes encoding many transcription factors and DNA binding proteins showed higher expression levels in the desiccating and dry seeds than in most of the green stages.ConclusionsData on 27,000 cDNAs have been obtained over five stages of soybean development, including the stages of major accumulation of agronomically-important products, using two different types of microarrays. Of particular interest are the genes found to peak in expression at the desiccating and dry seed stages, such as those annotated as transcription factors, which may indicate the preparation of pathways that will be needed later in the early stages of imbibition and germination.

Genes involved in ethylene and gibberellins metabolism are required for endosperm-limited germination of Sisymbrium officinale L. seeds

The rupture of the seed coat and that of the endosperm were found to be two sequential events in the germination of Sisymbrium officinale L. seeds, and radicle protrusion did not occur exactly in the micropylar area but in the neighboring zone. The germination patterns were similar both in the presence of gibberellins (GA(4+7)) and in presence of ethrel. The analysis of genes involved in GAs synthesis and breakdown demonstrated that (1) SoGA2ox6 expression peaked just prior to radicle protrusion (20-22 h), while SoGA3ox2 and SoGA20ox2 expression was high at early imbibition (6 h) diminishing sharply thereafter; (2) the accumulation of SoGA20ox2 transcript was strongly inhibited by paclobutrazol (PB) as well as by inhibitors of ET synthesis and signaling (IESS) early after imbibition (6 h), while SoGA3ox2 and SoGA2ox6 expression was slowly depressed as germination progressed; (3) ethrel and GA(4+7) positively or negatively affected expression of SoGA3ox2, SoGA20ox2, and SoGA2ox6, depending on the germination period studied. Regarding genes involved in ET synthesis, our results showed that SoACS7 was expressed, just prior to radicle emergence while SoACO2 expression slowly increased as germination progressed. Both genes were strongly inhibited by PB but were almost unaffected by externally added ethrel or GA(4+7). These results suggest that GAs are more important than ET during the early stages of imbibition, while ET is more important at the late phases of germination of S. officinale L. seeds.

Water movement into dormant and non-dormant wheat (Triticum aestivum L.) grains

The movement of water into harvest-ripe grains of dormant and non-dormant genotypes of wheat (Triticum aestivum L.) was investigated using Magnetic Resonance Micro-Imaging (MRMI). Images of virtual sections, both longitudinal and transverse, throughout the grain were collected at intervals after the start of imbibition and used to reconstruct a picture of water location within the different grain tissues and changes over time. The observations were supplemented by the weighing measurements of water content and imbibition of grains in water containing I2/KI which stains starch and lipid, thereby acting as a marker for water. In closely related genotypes, with either a dormant or a non-dormant phenotype, neither the rate of increase in water content nor the pattern of water distribution within the grain was significantly different until 18 h, when germination became apparent in the non-dormant genotype. Water entered the embryo and scutellum during the very early stages of imbibition through the micropyle and by 2 h water was clearly evident in the micropyle channel. After 12 h of imbibition, embryo structures such as the coleoptile and radicle were clearly distinguished. Although water accumulated between the inner (seed coat) and outer (pericarp) layers of the coat surrounding the grain, there was no evidence for movement of water directly across the coat and into the underlying starchy endosperm.

Genomic organization and expression profile of a gene encoding makorin RING zinc finger protein in germinating pea (Pisum sativum L.var.Alaska) seeds

The makorin RING finger protein gene (MKRN) family encodes proteins with a characteristic array of zinc-finger motifs. In the present study, we characterized the structure and expression of MKRN gene from pea (Pisum sativum L.Var.Alaska). Pea MKRN cDNA encoded a putative protein, makorin, with four C3H zinc-finger-motifs, one Cys-His putative zinc-finger motif, and one RING zinc-finger motif. The presence of this distinct motif organization clearly established this gene in pea as a true MKRN ortholog. We also isolated RNA from embryonic axes of seeds at various stages of imbibition and germination, including dry seeds, and studied the temporal expression profile of MKRN by RT-PCR. This analysis revealed that MKRN transcripts were present at very low levels, even in dry seeds. The expression of MKRN increased slowly in imbibition period, leveled off in the germination period, and declined in the seedling growth stage. Our reference genes, cytoskeletal actin (ACT) and tubulin (TUB1), were expressed from the early stages of imbibition and steadily increased during germination and plateaued 16–35 h after germination. Similar to MKRN transcripts, TUB1 and ACT transcripts were also detected in dry embryo cDNA. After 62 h of germination, a tissue-dependent expression pattern of MKRN was observed highest in root, moderate in stem, and lowest in plumule. The presence of MKRN transcripts in dry seed and the very early induction of MKRN in germination suggest a developmental role for makorin in pea.

Differences in transcription products and in translation and enzymatic activities during the early stages of imbibition of Phacelia tanacetifolia seeds with germination inhibited by light

Differences in transcription products and in translation and enzymatic activities during the early stages of imbibition of Phacelia tanacetifolia seeds with germination inhibited by light

Differences in transcription products and in translation and enzymatic activities during the early stages of imbibition of Phacelia tanacetifolia seeds with germination inhibited by light

To elucidate the inhibitory effect of light on the germination of the negatively photo‐blastic seeds of Phacelia tanacetifolia Benth. (cv. Bleu Clair). we have compared the changes that occur during the first 24 h of imbibition in the dark and in the light. Here, we give data on transcription products, translation activity, activities of some enzymes involved in the metabolic reactivation of seeds (glucose‐6‐phosphate dehydrogenase, pyruvate kinase, glucokinase and malate dehydrogenase), and the capability to absorb L‐[U‐14C]‐leucine. During the first stages of imbibition, the changes in the protein pattern and in the mRNA populations that occurred were not related to the light/dark regimes. Differences due to the light treatment did not appear until after 24 h. when new microsomal proteins appeared in the dark and some mRNA populations encoding low molecular mass polypeptides were increased in the light. The translation activity, measured as L‐[U‐14C]‐leucine incorporated into proteins and as the ratio polysomes/monosomes, increased with time in both darkness and light, but to a much higher extent in the dark. The activities of the four enzymes tested were higher in the light than in the dark before 16 h, then decreased in the light and increased sharply in the dark. Together with the behaviour of the increase in the ratio polysomes/monosomes in the dark, this suggests an increased rate of protein degradation in the dark during the period 0–16 h. The absorption of L‐[U‐14C]‐leucine was severely inhibited by light during the whole period studied, as expected since light inhibits the reactivation of the transport mechanisms at the plasma membrane. In seeds imbibed in the dark and then transferred to light, the inhibition by light of absorption and of incorporation into proteins of L‐[U‐14C]‐leucine, as well as the inhibition of the increase in the ratio poly‐somes/monosornes, was effective before the 22nd h; after which time the control exerted by light disappeared.