Unaged Seeds Research Articles

Calidad y vigor en semilla de cebada <i>cv</i>. Brennus

Barley in Mexico is an important crop for the brewing industry and animal feed. The physical and physiological quality and vigor of a batch of seed cv. Brennus was evaluated. The seed was divided by size (small and large) with a 2.5 mm sieve and subjected to different conditioning (aging and non-aging). The study variables were seed purity (SP), thousand seed weight (P1000S), volumetric weight (PV), moisture content (H), germination percentage, emergence speed, plumule length, dry matter in the plumule and seedling vigor index. The analysis of variance was performed under a completely randomized experimental design with factorial arrangement and four replications. Means were compared using Tukey's test (P < 0.05). The lot presented 98% SP, 1.8% inert material and 0.2% other seeds, P1000S was 42 g, PV 68 kg hL-1 and H was 7%. There were statistical differences (P < 0.05) between seed size, seed conditioning and interaction of both factors for most variables. Small and large unaged seeds showed similarity in germination, emergence speed, plumule length and seedling vigor index. The aging treatment had a negative effect on these variables regardless of size; however, the most extensive damage was seen on the large seeds. The seed lot has poor physical and physiological quality and vigor.

Physical and physiological quality of oat (Avena sativa L. cv. Turquesa) seeds

bjective: The objective of this study was to determine the physical and physiological quality of a batch of oat (Avena sativa L. cv. Turquesa) seeds. Design/Methodology/Approach: The following physical quality variables were evaluated: seed purity, weight of a thousand seeds, volumetric weight, and moisture content. Physiological quality was evaluated through a germination and emergence speed test, which also was used to measure seed vigor. A completely randomized experimental design, with factorial arrangement, and four repetitions was used. The factors analyzed were seed size (small and large) and aging (with and without aging). Results: The following results were recorded: 99.52% seed purity; 34.31 g weight of a thousand seeds; 54.80 kg hl-1 volumetric weight; and 6.50% moisture content. Regarding treatment germination, no significant differences were found between the seed size and the size × aging interaction (P = 0.422). The aging treatment reduced germination from 96.50% (unaged seeds) to 89.25% (aged seeds). The emergence speed did not show significant differences regarding seed size (P = 0.066) and size × aging interaction (P = 0.868). The aging treatment had a negative impact on the emergence rate. The aged seeds emerged at a 15.55 plants d-1 speed, while unaged seeds reached a 17.88 plants d-1 speed. Study Limitations/Implications: This study only evaluated one batch of oat seeds. Findings/Conclusions: The seeds have an adequate physical and physiological quality to establish oat crops. In addition, the seed batch was highly vigorous, because it maintained >80% germination rate after the aging treatment.

Comparative assessment of onion seed longevity under ambient storage and artificial ageing conditions

A study was carried out to assess the storage potential of onion genotypes under natural as well as accelerated ageing conditions. Freshly harveted seeds of thirty onion genotypes were subjected to nine months of natural ageing as well as accelerated ageing for 3 and 6 days (42oC and 75% RH). Significant effects of seed ageing on germination percent, seed vigour index, mean germination time and germination index were recorded. Germination percent ranged from 56.0- 96.0 percent in unaged seeds, which declined to 31.0-82.0 and 18.0-83.0 percent respectively after natural (9 months) and accelerated ageing treatments (6 days). In the current study, the seed germination and vigour indices decreased significantly, whereas the mean germination time increased for all the genotypes under both ageing treatments. Further, cluster analysis was utilized to categorize the onion genotypes into good or poorer storers. A significant and positive correlation was found among both natural as well as artificial ageing treatments. The study facilitated the categorization of onion genotypes into distinct storage groups by evaluating their performance under both natural as well as accelerated ageing.

Small auxin-up RNA gene OsSAUR33 promotes seed aging tolerance in rice

Seed aging tolerance during storage is a generally important trait for crop production. Yet the role of small auxin-up RNA genes in conferring seed aging tolerance is largely unknown in rice. In this study, one small auxin-up RNA gene, OsSAUR33, was identified as being involved in the regulation of seed aging tolerance in rice. The expression of OsSAUR33 was significantly induced in aged seeds compared with unaged seeds during the seed germination phase. Accordingly, imposed disruption of OsSAUR33 significantly reduced seed vigor vis-à-vis the wild type (WT) in response to natural storage or artificial aging treatments. The rice OsSAUR33 gene promotes the vigor of aged seeds by enhancing their reactive oxygen species (ROS) level during seed germination. A significantly delayed accumulation of ROS was observed in the aged seeds of Ossaur33 mutants in comparison with WT during seed germination. Hydrogen peroxide (H2O2) treatments promoted the vigor of aged seeds in various rice varieties. Altogether, our results provide timely theoretical and technical insights for the trait improvement of seed aging tolerance in rice crops.

Karrikinolide stimulated seed germination of artificially aged marrow, cabbage and pepper seeds through repair of cell structure and enzyme activity

• Priming with karrikinolide (KAR 1 ) enhanced seed germination in aged marrow, cabbage and pepper seeds. • Repair mechanism of seed aging by the treatments operated through repairing cell structure reducing solute leakage lower electrical conductivity and less K leakage in treated seeds. • Treatments with smoke extract affected ROS enzyme activity i.e. catalase, ascorbate peroxidase and superoxide dismutase activity of aged seeds. • Smoke extract treatments can be an efficient tool for enhancing seedling quality in marrow, cabbage and pepper seeds. The aging process induces the deterioration of seed vigor and viability. Priming methods have been shown to regenerate and rejuvenate aged crop seeds. Several studies have established that plant-derived smoke from burning plant material enhances germination and post-germination. Karrikinolide (KAR 1 ), which has been identified as a molecule derived from smoke, can improve the germination of seeds of a range of plant species. However, the effect of KAR 1 on aged seeds is not well known. Therefore, this study was carried out to determine the impact of KAR 1 and hydropriming on germination and repair mechanism in unaged and artificially aged pepper, marrow, and cabbage seeds. Aged seeds were artificially produced at 40 ± 1 °C and 100% relative humidity for 48 h in cabbage and 72 h in marrow and pepper. KAR 1 (10 −7 M) was applied by dipping seeds in solution at a weight ratio of 1:5 seed: solution for 16 h at 20 °C. Hydropriming was applied under the same conditions using distilled water. Following the treatments, germination, seedling emergence, electrical conductivity, potassium leaching, and enzyme analysis were determined. Results showed that KAR 1- treated seeds had the lowest electrical conductivity and potassium leakage in unaged and artificially aged seeds in all three species. The influence of KAR 1 was more prominent on catalase activity in both artificially aged and unaged seeds. Additionally, KAR 1 treatment improved germination and fresh and dry weights of seedlings in all three species. The results of the present study show that the application of KAR 1 can help improve the performance of marrow, cabbage and pepper seeds in artificially aged (low-quality) seed germination.

Influence of Different Priming Materials on Germination and Alpha-Amylase Enzyme of Hybrids Sorghum (Sorghum bicolor L. Moench. x Sorghum sudanense Staph.) Seeds

Germination is considered a critical step in the development cycle of the plant. But no information is available regarding seed priming with Putrescine, Jasmonic acid, Kinetin, Potassium Nitrate (KNO3), Salicylic acid at a time in the aged and non-aged seeds of sorghum cultivars. However, to know the effect of seed priming with the aforesaid chemicals in the aged and non-aged seeds of sorghum cultivars on the germination rate, germination vigour and alpha-amylase activity, research was conducted under laboratory condition, at Field Crops Central Research Institute, Ankara, Turkey. Aged and unaged seeds of Sugar Grazer II and Digestivo hybrid silage sorghum cultivars were used as the seed material of the experiment. Putrescine, Jasmonic acid, Kinetin, KNO3 and Salicylic acid were used as priming chemicals. The results revealed that aged and un-aged seeds of the cultivars showed different responses to similar chemical and KNO3 application to un-aged seeds had a positive effect on germination rate and alpha-amylase, Whereas Jasmonic acid and Putrescine applications had a positive effect on the aged seeds. Priming with putrescine, KNO3 and jasmonic acid showed the best results in the experiment.

Evaluating the effect of aging process on the physicochemical characteristics of rice seeds by low field nuclear magnetic resonance and its imaging technique

In-depth investigation of the storability of rice seeds directly relies on the accuracy of the artificial accelerated aging method. In this study, Shennong 265 rice seed samples that underwent a 28 d artificial accelerated aging cycle were monitored by low field nuclear magnetic resonance (LF-NMR) and its imaging technique, the transverse relaxation times and proton density-weighted images of which were acquired at 0, 7, 14, 21 and 28 d during the aging process. Subsequently, the acquired information processed by NMR inversion and corresponding image processing software was combined with results from the standard germination test to describe the physicochemical characteristics of the rice seeds during the aging process. Results suggest that the rate of the T2 decay curve and the T2 relaxation time of the unaged rice seeds are higher than those of the aged rice seeds, and both values increase in positive correlation with the artificial aging duration. In addition, the contents of bound water, free water and total water of the aged seeds are all higher than those of the unaged seeds, although with prolonged aging, the contents of bound water and total water of the rice seeds fluctuates, whilst the content of free water consistently increases. Proton density images of the rice seed samples at different times of the aging process indicate that water distribution inside the seeds is inhomogeneous. Lastly, as aging duration increases, both the germination rate and germination potential of the seeds decrease. This study has determined the physiological and biochemical changes that the seeds undergo during aging, and revealed the relationship between these changes and the viability and vigor of the seeds, thereby providing references for studies on the internal mechanisms of seed deterioration.

ZmDREB2A regulates ZmGH3.2 and ZmRAFS, shifting metabolism towards seed aging tolerance over seedling growth.

Seed aging tolerance and rapid seedling growth are important agronomic traits for crop production; however, how these traits are controlled at the molecular level remains largely unknown. The unaged seeds of two independent maize DEHYDRATION-RESPONSIVE ELEMENT-BINDING2A mutant (zmdreb2a) lines, with decreased expression of GRETCHEN HAGEN3.2 (ZmGH3.2, encoding indole-3-acetic acid [IAA] deactivating enzyme), and increased IAA in their embryo, produced longer seedling shoots and roots, than the null segregant (NS) controls. However, the zmdreb2a seeds, with decreased expression of RAFFINOSE SYNTHASE (ZmRAFS) and less raffinose in their embryo, exhibit decreased seed aging tolerance, than the NS controls. Overexpression of ZmDREB2A in maize protoplasts increased the expression of ZmGH3.2, ZmRAFS genes and that of a Rennila LUCIFERASE reporter (Rluc) gene, which was controlled by either the ZmGH3.2- or ZmRAFS-promoter. Electrophoretic mobility shift assays and chromatin immunoprecipitation assay quantitative polymerase chain reaction showed that ZmDREB2A directly binds to the DRE motif of the promoters of both ZmGH3.2 and ZmRAFS. Exogenous supplementation of IAA to the unaged, germinating NS seeds increased subsequent seedling growth making them similar to the zmdreb2a seedlings from unaged seeds. These findings provide evidence that ZmDREB2A regulates the longevity of maize seed by stimulating the production of raffinose while simultaneously acting to limit auxin-mediated cell expansion.

Artificial seed aging reveals the invisible fraction: Implications for evolution experiments using the resurrection approach

Non-random mortality is a key driver of evolution, but mortality that occurs early in life leaves adult traits of individuals that died unknown. This can lead to the invisible fraction problem, which causes difficulty in measuring selection and evolution in natural and experimental populations. Furthermore, seeds or other propagules that are stored intentionally or that persist in dormant states in nature can experience storage conditions that alter adult traits. Invisible fraction and storage condition effects can cause bias in evolutionary studies such as those using the resurrection approach of comparing ancestors and descendants in common environments. To investigate invisible fraction and storage condition effects, we subjected seeds of Brassica rapa Fast Plants to artificial aging under hot, humid conditions. We grew plants from artificially aged seeds alongside unaged control seeds for two generations and measured morphological and phenological traits on adult plants. We found that the plants from artificially aged seeds flowered later than those from unaged seeds in both the first and second generation, indicating storage condition and invisible fraction biases. However, the difference in flowering time was smaller in the second generation, indicating that the refresher generation decreased the storage condition effect. We also found that seeds that survived artificial aging were smaller than seeds that did not survive, indicating a potential physical basis for non-random mortality in storage. These results suggest that invisible fraction and storage condition effects can bias the results of resurrection experiments, and that the proper storage of seeds for use in resurrection experiments, as well as a refresher generation, are critical for valid results. The results also demonstrate that artificial aging can be used as a tool for studying mortality of propagules in nature, such as in soil seed banks, thus providing insight into evolutionary processes that would otherwise remain obscure.

Mass-based germination dynamics of Rudbeckia mollis (Asteraceae) seeds following thermal and ageing stress

AbstractSeed mass is an important plant functional trait linked to germination. For instance, higher-mass seeds often display greater germination compared to lower-mass seeds when exposed to non-stressful conditions. Yet, knowledge pertaining to germination dynamics for different mass-based seed fractions following exposure to abiotic stress is lacking. Here, we assess the germination response of relatively fresh, mass-separated Rudbeckia mollis (Asteraceae) seeds to various simulated seasonal temperatures, supra-optimal temperatures and increasing ageing stress duration. Air density separation yielded three mass-based classes, called light (393 ± 35 μg), intermediate (423 ± 29 μg) and heavy (474 ± 38 μg). Water uptake kinetics indicated that imbibition (0–6 h) and germination lag (6–24 h) were independent of seed mass. Similarly, germination and viability loss of fresh seeds following exposure to seasonal and supra-optimal constant temperatures were independent of mass. However, seed mass influenced germination following increasing ageing stress, with light seeds germinating to a significantly greater extent than intermediate or heavy seeds. For example, final germination per cent in light-class seeds was about 1.7 times greater than intermediate or heavy seeds after 20 d of saturated salt accelerated ageing (SSAA). Seeds stored for 1 year in the laboratory displayed mass-dependent germination patterns similar to seeds following SSAA. Mass-independent germination responses may be a strategy to maintain an annual life history in otherwise difficult environments when R. mollis seeds are relatively fresh. However, differences in germination response between aged and unaged seeds suggest that mass-dependent viability loss may occur in R. mollis.

Prediction of viability of leek (Allium porrum) seeds by a new test

The objective of this research was to determine the suitability of boiling water test in the prediction of seed viability in leek seed and to compare this test with standard germination and vigour test. Basic principle of boiling water test is the evaluation of radicle protrusion from the seeds immersed to boiling water for certain time. The viability of aged and unaged leek seeds in boiling water test was correlated with standard germination and vigour test. In this research. the mean germination of unaged leek seeds varied from 29,639% to 70,18% depending on the cultivars. While the range of boiling water test in unaged leek seeds was between 35.57% to 51,06%, the range for emergence was between 27,63% to 72,05%. The viability of aged and unaged leek seeds in boiling water test was correlated with standard germination test. According to the results of this research, it might be assessed that boiling water test is a rapid and simple method to measure seed viability by evaluating radicle protrusion of leek seeds in boiling water. In conclusion. boiling water test as a new viability test for leek seed could be used as a rapid method for determining the viability in leek seeds.

Reactive oxygen species release, vitamin E, fatty acid and phytosterol contents of artificially aged radish (Raphanus sativus L.) seeds during germination

Seeds of Raphanus sativus L. subjected to accelerated ageing were investigated for reactive oxygen species (ROS) release and for content of vitamin E (tocopherol, TOC, and tocotrienol, TOC-3), fatty acids and phytosterols in seed coats, cotyledons and embryonic axes during germination. In unaged seeds, ROS release occurred mainly in seed coats of non-imbibed seeds and in seedlings (48 h of imbibition). TOC and TOC-3 were mainly represented by the γ-isoform, abundant in embryonic axes. Fatty acids were mainly found in cotyledons. In seed coat and embryonic axis, phytosterols consisted mainly of sitosterols. The effects of ageing were mainly visible in embryonic axes at 48 h of imbibition. Deterioration was associated with a decrease in fresh weight increase percentage, germination percentage, α-TOC and total fatty acid content. An increase in ROS release from seed coats and in γ-TOC, δ-TOC, γ-TOC-3 content in embryonic axis was also observed. The use of γ-TOC and total fatty acids in embryonic axis as parameters of seed quality evaluation during storage was suggested.

Substrates of the Arabidopsis thaliana Protein Isoaspartyl Methyltransferase 1 Identified Using Phage Display and Biopanning

The role of protein isoaspartyl methyltransferase (PIMT) in repairing a wide assortment of damaged proteins in a host of organisms has been inferred from the affinity of the enzyme for isoaspartyl residues in a plethora of amino acid contexts. The identification of PIMT target proteins in plant seeds, where the enzyme is highly active and proteome long-lived, has been hindered by large amounts of isoaspartate-containing storage proteins. Mature seed phage display libraries circumvented this problem. Inclusion of the PIMT co-substrate, S-adenosylmethionine (AdoMet), during panning permitted PIMT to retain aged phage in greater numbers than controls lacking co-substrate or when PIMT protein binding was poisoned with S-adenosyl homocysteine. After four rounds, phage titer plateaued in AdoMet-containing pans, whereas titer declined in both controls. This strategy identified 17 in-frame PIMT target proteins, including a cupin-family protein similar to those identified previously using on-blot methylation. All recovered phage had at least one susceptible Asp or Asn residue. Five targets were recovered independently. Two in-frame targets were produced in Escherichia coli as recombinant proteins and shown by on-blot methylation to acquire isoAsp, becoming a PIMT target. Both gained isoAsp rapidly in solution upon thermal insult. Mutant analysis of plants deficient in any of three in-frame PIMT targets resulted in demonstrable phenotypes. An over-representation of clones encoding proteins involved in protein production suggests that the translational apparatus comprises a subgroup for which PIMT-mediated repair is vital for orthodox seed longevity. Impaired PIMT activity would hinder protein function in these targets, possibly resulting in poor seed performance.

Causes of differences in seed quality among cowpea (<i>Vigna unguiculata</i> (L.) Walp) cultivars

Three cowpea cultivars differing in seed coat colour, IT83S-818 (white, black-eye), TVX 2724-01F (brown) and IT82D-32 (dark brown), were aged using the controlled deterioration method (20% seed moisture content and incubated at 40 oC) for 0, 1, 2 and 4 days. Time to 50 per cent germination (t50) and final germination percentage were determined to assess the vigour differences that exist among these cultivars. In unaged seeds, the white cultivar germinated quicker than the pigmented cultivars as a result of the characteristically higher rate of water uptake, which enhanced rapid hydration of the embryonic cells for quicker germination. When ageing progressed, however, the white cultivar germinated more slowly with a lower final germination percentage since the embryonic cells possibly became weaker and leaky leading to reduced vigour and eventually, loss of germinability. In contrast, the pigmented cultivars germinated more slowly before seeds were aged due to their slower rates of water uptake; germination became quicker as ageing progressed due to increasing softening of the seed coats. Thus, the pigmented cultivars showed decreases in the time to 50 per cent germination during ageing. They, however, retained high germination percentages throughout the ageing period, which is an indication of high vigour. These three cultivars, together with two other unpigmented cultivars, IT81D-1137 (white) and TVX 3236 (cream and brown) were subsequently examined for the incidence of disease pathogens. It was observed that the unpigmented cultivars had higher levels of the importasnt seed pathogens such as Fusarium species and Aspergillus flavus which cause reduction in germination. These seeds also showed susceptibility to mechanical damage caused by hand-beating of dry pods in sacs. These differences in behaviour between the two groups of cowpea cultivars, pigmented and unpigmented, were attributed to differences in tannin and lignin contents in their seed coats.

Effects of ageing on peroxidase activity and localization in radish (Raphanus sativus L.) seeds.

Peroxidase activity was assayed in crude extracts of integument, cotyledons and embryo axis of radish seeds, deteriorated under accelerated ageing conditions. Over five days of ageing, in which germination decreased from 100 to 52%, the enzyme activity in integument was higher than that in other seed parts, increasing in the first days of ageing and then decreasing sharply in extremely aged seeds. Polyacrylamide gel electrophoresis analysis showed four peroxidase isoenzymes with MM of 98, 52.5, 32.8 and 29.5 kDa in the embryo axis of unaged seeds, and only the 32.8 and 29.5 kDa MM isoforms in the integument and cotyledons. In these parts of the seed, only the 29.5 kDa MM isoenzyme increased in activity in early days of ageing and decreased there-after. In the embryo axis, the 29.5 kDa MM isoenzyme activity increased slowly in the first day of ageing, while the 98 and 52.5 kDa MM isoenzyme activities disappeared. A cytochemical localization of peroxidase activity in the various tissues showed that main differences between unaged and extremely aged seeds occurred in the embryo axis.

Seed vigour-related DNA marker in rice shows homology with acetyl CoA carboxylase gene

Germination potential, i.e. vigour manifested at sensu stricto germination, was studied in 22 rice varieties to distinguish between the genetic control for low vigour (lv) at fresh harvest and lv after ageing of seeds. For identifying seed vigour-associated DNA marker(s), correlative studies between (1) physiological parameters viz. germination of (a) unaged seeds under optimum and cold stressed condition, (b) aged seeds under optimal condition and (2) growth-associated biochemical parameters viz. alcohol dehydrogenase (ADH) and esterase (EST) activity during early germination of fresh seeds and antioxidant potential in dry embryos of fresh and aged (1 year) seeds were undertaken. ADH and EST activity as well as antioxidant potential showed positive correlation with speed of embryo emergence and early seedling growth of seeds. The reduction of antioxidant potential in aged seeds also appeared proportional to germination performance. Random amplified polymorphic DNA analysis between the varieties was correlated with the above-mentioned vigour parameters, using multiple regression analysis. This led to the identification of four bands associated with the vigour trait at 99% significance level; of these, the ~ 900-bp DNA fragment (named as HVAC 19), through basic local alignment search tool nucleotides analysis, revealed a sequence homology with acetyl CoA carboxylase (ACCase) gene of wheat at 94% similarity level.

Effect of Accelerated Ageing on Germination and Vigor in Lentil (Lens culinaris Medikus) Seed

ABSTRACT Seed lots of three lentil (Lens culinaris) cultivars (ILL 5883, ILL 7012 and Precoz), with similar production and storage history were aged for 1, 2 or 3 days at 40 ± 0.5°C and 100% relative humidity (RH). The effects of ageing were evaluated via standard germination tests, speed of germination, seedling dry weight, and vigor index. Of the three cultivars, ILL 5883 and Precoz retained their viability better than ILL 7012 after 1 day of ageing. ILL 5883 appeared to be the most tolerant of ageing conditions and its performance was consistently superior to that of the other two cultivars. The three-day ageing treatment severely damaged all seeds and led to a significant reduction in germination percentage in both ILL 7012 (1%) and Precoz (5%). Ageing for three days also significantly reduced vigor in ILL 7012: Values for indices of both speed of germination and vigor were 0.6 and 11.25 as opposed to 12.5 and 1439.61 in unaged seeds, respectively. In general, an increase in the duration of accelerate...

The interaction between salinity stress and seed vigour during germination of soyabean seeds

Seeds of six soyabean (Glycine max (L.) Merr.) cultivars were germinated between paper towels moistened with a range of solutions of both NaCI (32.2 to 421.1 mmolal NaCI) and polyethylene glycol (PEG, 5-30% w/v). The solutions of NaCI and PEG used had the same water potentials within the range -0.23 to -1.9 MPa. After 8d the ungerminated seeds were transferred to towels moistened with deionised water for 7d. Cultivars differed in their response to salinity and failure of seeds to recover from high salinity when transferred to deionised water, revealed the toxicity of NaCl. In contrast, the increase in germination during the recovery period after exposure to PEG suggested that PEG was not toxic. At the same external water potential, the lower mean germination time (MGT) and higher final germination in NaCl than in PEG could be explained by the more rapid imbibition in NaCl solutions and achievement of a moisture content that allowed germination. The influence of seed vigour on the response of soyabean to stress was examined using seeds having high percentage germination but a range of seed vigour, produced by rapid ageing at 15% moisture content (MC) and 45°C for up to 9h. The germination of aged seeds having reduced vigour fell with increased salinity (330, 421 mmolal NaCI) but there was no significant interaction between salinity and seed ageing. Transfer of unaged and aged seeds to 0 MPa after exposure to NaCI resulted in a greater increase in the germination of unaged seeds. The negative correlation of seed leachate conductivity and MGT with the increase percentage germination after transfer to 0 MPa suggested that seed vigour influences the ability of seeds to recover from saline conditions.

The effect of controlled hydration treatment on germination and seedling emergence of unaged and aged pepper seeds during development

Pepper (Capsicum annuum L.) seeds were harvested 50, 60, 70, and 80 days after anthesis (daa) and 50, 55, 60, 65, 70, 75, and 80 daa in 2000 and 2001, respectively. After drying, a proportion of each sample was aged at 20% moisture content, 45 °C for 24 h. Both unaged (UA) and aged (A) seeds were hydrated in aerated water at 25 °C for 48 h (controlled hydration, CH). Seed quality was then assessed by counting germination after 3 days, normal germination percentage after 14 days, seedling emergence, and fresh and dry weight. Maximum seed quality of unaged seeds occurred 70 daa in 2000, and between 65 and 75 daa in 2001. CH treatment improved seed quality in both unaged (UA) and aged (A) seed lots. The maximum benefit was observed in seed lots harvested 60 and 70 daa in 2000, and 65, 70, and 75 daa in 2001. There was less improvement in the less mature (50-55 daa) and overmatured (80 daa) seed samples. It was concluded that CH treatment could be used to improve seed quality in seed lots harvested in once-over mechanical practices that contain immature and overmature seed proportions together.

Ageing‐induced changes in glutathione system of sunflower seeds

The glutathione system is thought to be involved in defence mechanisms present in plant tissues. The efficacy of this system was evaluated in large seeds of sunflower (Helianthus annuus L. cv. Peredovik) in response to accelerated ageing (43°C/75% relative humidity from 1 to 11 days). Differences between the embryo axis and cotyledons in relation to the glutathione system were also investigated. Additionally, lipid peroxidation was determined by measuring the malondialdehyde (MDA) content. All assays were performed using dry seeds and seeds subsequently hydrated by imbibition in distilled water for 12 h at 25°C. Accelerated ageing caused a marked decrease in seed viability, accompanied by an increase in mean germination time. There were no changes in total glutathione in dry seeds. However, the distribution in its reduced (GSH) and oxidized (GSSG) forms revealed that ageing produced a slow conversion from GSH to GSSG. As the ageing period increased, this effect was accompanied by a decrease in glutathione reductase (GR, EC 1.6.4.2) activity. The results also indicated that the GSH system exerts a different response in the embryo axis as compared with the cotyledon: (1) the GSH levels decreased less in the cotyledons than in axes of aged seeds, and (2) the GSSG level in cotyledons was independent of ageing, while its amount increased in aged embryo axes. These different responses, in conjunction with the lower MDA levels in large as compared with small seeds, indicate a possible protective role of the reserve lipids. The efficacy of the GSH system in aged seeds was associated with seed viability, as revealed by multiple regression analysis. Upon imbibition, aged seeds were able to restore their GSH levels, reaching values approximating those of unaged seeds.