Water uptake and splitting of wild oat caryopsis

Imbibition and germination experiments were conducted on the caryopses of wild oats (Avena fatua L.). The embryo envelopes, pericarp and aleurone layer, which completely cover the embryo-endosperm, do not form barriers against water uptake. The initial uptake of water is passive and the water moves across the pericarp with ease as it contains cracks; it is, however, transported across the aleurone layer through its cell walls into the endosperm and embryo of the caryopsis. The starchy endosperm enlarges due to water uptake causing the pericarp to rupture, thus exposing the aleuronelayer-covered seed. The aleurone layer is structurally heterogenous consistings of radially compressed irregular cells and cuboidal or radiallys tretched cells; the latter contains thicker walls. The former type is present along the abaxial side of the embryo and in the crease on the adaxial side of the caryopsis; the latter type covers the endosperm. The physical distention of the endosperm due to water uptake causes the rupture of the pericarp and the aleurone layer, and facilitates the emergence of the radicle and coleorhiza of the embryo during caryopsis germination.     

Architectural and biochemical changes in embryonic tissues of maize under cadmium toxicity

Heavy metals greatly alter plant morphology and architecture, however detailed mechanisms of such changes are not fully explored. Two experiments were conducted to investigate the influence of cadmium (CdCl₂·2.5H₂O) on some germination, morphological, biochemical and histological characteristics of developing embryonic tissue of maize. In the first experiment, maize seeds were germinated in increasing levels of CdCl₂ (200–2000 μm ) in sand and measurements were taken of changes in germination and seedling development attributes. Based on these parameters, 1000 μM CdCl₂ was chosen for detailed biochemical and histological measurements. In the second experiment, seeds were germinated in Petri dishes and supplied with 0 (control) or 1000 μM CdCl₂ (Cd‐treated). Radicle, plumule, coleoptile and coleorhiza were measured for biochemical and histological changes. The highest amount of Cd was in the coleorhiza and radicle. Free proline, soluble sugars, anthocyanin, soluble phenolics, ascorbic acid, H₂O₂ and MDA were significantly higher in coleorhizae, followed by the coleoptile, radicle and plumule. Although the radicle and coleorhiza were relatively poor targets of Cd than the other tissues, Cd stress reduced cortical cell size and vascular tissues, and deformed xylem and phloem parenchyma in all plant parts. In conclusion, the main reason for reduced germination was the influence of Cd on architecture of the coleorhiza and coleoptile, which was the result of oxidative stress and other physiological changes taking place in these tissues.     

The Morphology of Germination in Setaria lutescens (Gramineae): The Effects of Covering Structures and Chemical Inhibitors on Dormant and Non-dormant Florets

The sequence of organ emergence in embryos of the yellow foxtailgrass (Setaria lutescens) is similar to that reported for othergrasses: coleorhiza, radicle, coleoptile and first leaf. Thecoleorhiza emerges by forcing open a hinged flap on the lemma.Coleorhiza trichomes form soon after emergence. The radicleprotrudes through the abaxial surface of the coleorhiza. Thecoleoptile elongates in a downward direction initially as itpasses between the lemma and palea, but immediately turns upward.The first leaf emerges by protruding through a slit-like creaseon the adaxial surface of the coleoptile. Embryos excised fromdormant florets are shown to germinate as well as those fromnon-dormant florets. Experiments are described which show theinhibitory effects of the embryo covering structures; the lemma,palea and caryopsis coat. Other experiments are discussed concerningthe effects on germination of the inhibitors abscisic acid andcycloheximide. An intermediate concentration of cycloheximide(10^–4 M) does not decrease germination percentage, butrather inhibits radicle growth but no coleoptile elongation.The significance of these observations is discussed.     

燕麦属颖果微形态特征及其分类学意义

为探讨燕麦属颖果微形态特征的分类学意义,采用体视显微镜和扫描电子显微镜观察燕麦属27种颖果的微形态特征,结合分子系统发育证据分析其分类学意义。燕麦属颖果有纺锤形、倒披针形、椭圆形3种形状,条纹、棱纹、网纹3种纹饰。燕麦属颖果形状、纹饰和花柱基宿存模式具有有限的属下分类学意义,颖果大小和表面大毛密度具有种间鉴定价值,而颖果腹面形态、压扁方式、胚比不具有种间鉴定价值。大穗燕麦(Avena macrostachya Balansa ex Coss.Durieu)颖果纺锤形,条纹纹饰,隶属于燕麦属颖果微形态特征的变异范围。大粒裸燕麦(A.nuda L.)与普通栽培燕麦(A.sativa L.)颖果大小、形状及纹饰特征的差异支持将大粒裸燕麦作为独立种处理。燕麦属颖果大小、表面大毛密度、胚比变异幅度大,推测与分布区广幅的气候变异相适应,凹腹面颖果体积相对缩减,有利于颖果快速发育、成熟,推测与燕麦属植物在温带、寒带分布区适生期较短相适应。     

Morphology of the perennial ryegrass (Lolium perenne; Poaceae) coleorhiza and emerging radicle with continuous or discontinuous hydration

This study was conducted using scanning electron microscopy to characterize morphological changes in the maturing perennial ryegrass (Lolium perenne L.) coleorhiza and emerging radicle during continuous hydration or hydration interrupted by dehydration. With continuous hydration, coleorhizae emerged and cell expansion led to a progressive increase in tissue size. Coleorhiza cells developed extensions like epidermal root hairs. Although coleorhiza cells appeared undamaged by radicle emergence, they began deteriorating when the radicle had reached a length of approximately 2 mm. In response to dehydration, coleorhiza cells shrank but did not rupture. If dehydration was initiated during an early stage of coleorhiza development, greater tissue shrinkage occurred at -150 MPa than at -4 MPa; otherwise, coleorhizae showed no differential response due to dehydration water potential. Upon rehydration, coleorhizae dehydrated at -4 MPa regained cell turgor within 24 hr, while coleorhizae dehydrated at -150 MPa did not. Loss of the coleorhiza (due to desiccation) did not preclude radicle emergence, which occurred upon rehydration. Radicles up to 2 mm in length were more tolerant of dehydration than were coleorhizae. These results suggest that the coleorhiza may be an expendable tissue during germination, as its likely protective and absorptive roles are lost following a single harsh dehydration event.     

Distribution of Cadmium,Lead, Nickel,and Strontium in Imbibing Maize Caryopses

Seed germination is tolerant to heavy metals apparently because the seed coat is impermeable to metal ions. However, it is not clear whether the seed coat is a universal barrier for all metals. In addition, depending on their physical and chemical properties, a distribution of various metals may differ within an imbibing caryopsis, and therefore they produce dissimilar effects on seed germination. The toxic effects of Cd(NO₃)₂, Pb(NO₃)₂, Ni(NO₃)₂, and Sr(NO₃)₂ were estimated from the germination rates of maize (Zea mays L.) caryopses following two-day incubation with these salts. The distribution of heavy metals and Sr was studied by histochemical methods based on the formation of colored complexes with dithizone (Cd and Pb), dimethylglyoxyme (Ni), and sodium rhodizonate (Sr). Although the metals under study did not affect maize radicle protrusion, they inhibited seed germination in the following order: Cd > Ni ≈ Pb > Sr. Cd and Pb accumulated mainly in the seed coat cells, but Sr and Ni in the embryo cells and in the cells of endosperm (Sr) and scutellum (Ni). Although Cd was found only in the seed coat, it was the strongest inhibitor of seed germination. Apparently, due to high toxicity, Cd exerted its inhibitory effect at the concentrations too low for histochemical assay. In spite of easy translocation across the seed coat of imbibing caryopses, Sr did not considerably inhibit radicle protrusion and seed germination, apparently because of its low toxicity and predominant localization in the apoplast of embryo and endosperm cells.__________Translated from Fiziologiya Rastenii, Vol. 52, No. 4, 2005, pp. 635–640.Original Russian Text Copyright © 2005 by Seregin, Kozhevnikova.     

Cell wall peroxidase activity,hydrogen peroxide level and NaCl-inhibited root growth of rice seedlings

The changes in cell-wall peroxidase (POD) activity and H₂O₂ level in roots of NaCl-stressed rice seedlings and their correlation with root growth were investigated. Increasing concentrations of NaCl from 50 to 150 mM progressively reduced root growth and increased ionically bound cell-wall POD activity. NaCl had no effect on covalently bound cell-wall POD activities. The reduction of root growth by NaCl is closely correlated with the increase in H₂O₂ level. Exogenous H₂O₂ was found to inhibit root growth of rice seedlings. Since ammonium and proline accumulation are associated with root growth inhibition caused by NaCl, we determined the effects of NH₄Cl or proline on root growth, cell-wall POD activity and H₂O₂level in roots. External application of NH₄Cl or proline markedly inhibited root growth, increased cell-wall POD activity and increased H₂O₂ level in roots of rice seedlings in the absence of NaCl. An increase in cell-wall POD activity and H₂O₂ level preceded inhibition of root growth caused by NaCl, NH₄Cl or proline. NaCl or proline treatment also increased NADH-POD and diamine oxidase (DAO) activities in roots of rice seedlings, suggesting that NADH-POD and DAO contribute to the H₂O₂ generation in the cell wall of NaCl- or proline-treated roots. NH₄Cl treatment increased NADH-POD activity but had no effect on DAO activity, suggesting that NADH-POD but not DAO is responsible for H₂O₂ generation in cell wall of NH₄Cl-treated roots.     

Reactive oxygen species,ABA and nitric oxide interactions on the germination of warm-season C<Subscript>4</Subscript>-grasses

Hydrogen peroxide (H₂O₂) as a source of reactive oxygen species (ROS) significantly stimulated germination of switchgrass (Panicum virgatum L.) seeds with an optimal concentration of 20 mM at both 25 and 35°C. For non-dormant switchgrass seeds exhibiting different levels of germination, treatment with H₂O₂ resulted in rapid germination (<3 days) of all germinable seeds as compared to seeds placed on water. Exposure to 20 mM H₂O₂ elicited simultaneous growth of the root and shoot system, resulting in more uniform seedling development. Seeds of big bluestem (Andropogon gerardii Vitman) and indiangrass [Sorghastrum nutans (L.) Nash] also responded positively to H₂O₂ treatment, indicating the universality of the effect of H₂O₂ on seed germination in warm-season prairie grasses. For switchgrass seeds, abscisic acid (ABA) and the NADPH-oxidase inhibitor, diphenyleneiodonium (DPI) at 20 μM retarded germination (radicle emergence), stunted root growth and partially inhibited NADPH-oxidase activity in seeds. H₂O₂ reversed the inhibitory effects of DPI and ABA on germination and coleoptile elongation, but did not overcome DPI inhibition of root elongation. Treatment with H₂O₂ appeared to enhance endogenous production of nitric oxide, and a scavenger of nitric oxide abolished the peroxide-responsive stimulation of switchgrass seed germination. The activities and levels of several proteins changed earlier in seeds imbibed on H₂O₂ as compared to seeds maintained on water or on ABA. These data demonstrate that seed germination of warm-season grasses is significantly responsive to oxidative conditions and highlights the complex interplay between seed redox status, ABA, ROS and NO in this system.     

Transport of assimilates in the developing caryopsis of rice (Oryza sativa L.)

The movement of water in the dorsal region of the developing rice caryopsis was studied using solutions of the heavy metals lanthanum and uranium. In the electron microscope electron-opaque deposits were confined to the cell walls of the pigment strand indicating that this is the main route for the water which enters and leaves the caryopsis during grain filling. The pathway of assimilates into the developing caryopsis was examined using isolated caryopses which had taken up solutions of fluorescent dyes and also by autoradiography of caryopses which had transported ¹⁴C-labelled assimilates in vivo. The results show that assimilates unloaded from the phloem move through the pigment strand and circumferentially via cells of the nucellus before entering the endosperm. A scheme is presented for the interrelations of water and assimilate transport during grain filling     

Peroxidase mediated hydrogen peroxide production in barley roots grown under stress conditions

All applied metals (Co, Al, Cu, Cd) and NaCl inhibited barley root growth. No root growth inhibition was caused by drought exposure, in contrast to cold treatment. 0.01 mM H₂O₂ stimulated root growth and GA application did not affect root growth at all. Other activators and inhibitors of H₂O₂ production (SHAM, DTT, 10 mM H₂O₂, 2,4-D) inhibited root growth. Loss of cell viability was most significant after Al treatment, followed by Cd and Cu, but no cell death was induced by Co. Drought led to slight increase in Evans blue uptake, whereas neither NaCl nor cold influenced this parameter. DTT treatment caused slight increase in Evans blue uptake and significant increases were detected after 2,4-D and 10 mM H₂O₂ treatment, but were not induced by others stressors. Metal exposure increased guaiacol-POD activity, which was correlated with oxidation of NADH and production of H₂O₂. Exposure to drought caused a minor change in NADH oxidation, but neither H₂O₂ production nor guaiacol-POD activity was increased. Cold and NaCl application decreased all monitored activities. Increase in NADH oxidation and guaiacol-POD activity was caused by 10 mM H₂O₂ and 0.01 mM 2,4-D treatment, which also caused enhancement of H₂O₂ production. Slight inhibition of all activities was caused by 0.01 mM H₂O₂, GA, DTT; more pronounced inhibition was detected after SHAM treatment. The role of H₂O₂ production mediated by POD activity in relation to root growth and cell viability under exposure to some abiotic stress factors is discussed.     

Weedy adaptation in Setaria spp. IV. Changes in the germinative capacity of S. faberii (poaceae) embryos with development from anthesis to after abscission

Studies were conducted evaluating germinability states in giant foxtail (Setaria faberii) embryos, as well as surrounding tissues (hull, caryopsis), with germination assays. Further, seed age, fascicle arrangement, flowering patterns, and elongation in the inflorescence were evaluated. Both qualitatitive and quantitative morphological observations of the hull and the caryopsis were revealed by precisely determined fertilized spikelet age from anthesis until after seed abscission. Red coloration of the placental pad at ≈ 11 d after anthesis is probably a morphological indicator of physiological maturity. Germinability of giant foxtail embryos changed with development. Four qualitatively different types of embryo germination were observed during development of the seed: early disorganized callus growth at the basal, coleorhizal end of the embryo; germination of immature embryos with shortened and thickened axes; germination of the scutellum; and germination and growth of the coleoptile and coleorhiza in embryos aged 7 d after anthesis and older. Axis-specific embryo germinability was also observed. Inhibition of the embryo could be localized to the coleoptile, the coleorhiza, or both. These studies provide evidence for a complex model of germinability regulation based on the independent, asynchronous actions of the embryo, caryopsis, and hull compartments, as well as on their dependent, synchronous action. These studies provide evidence for a dynamic, developmental model of giant foxtail germinability regulation resulting in phenotypes with a wide range of germinability shed from an individual panicle. These diverse germinability phenotypes are found at all stages of development, but particularly when the seed is shed and the soil seed bank is replenished.     

Seed dormancy in Avena fatua: Interacting effects of nitrate, water and seed coat injury

In experiments conducted under controlled conditions. KNO₃ (50 or 100 m M ) promoted germination of a dormant strain (AN 474) of Avena fatua when either one or two holes were pierced in the lower (adaxial) surface of the caryopsis in contact with the nitrate solution. Germination was increased by increasing either the KNO₃ concentration or the number of holes in the seed coat. The germination response induced by the application of water to a hole pierced in the upper surface of the caryopsis was. increased by pre-treatment of the intact caryopsis with KNO₃. Treatment with either 50 or 100 m M KNO₃ caused a transient reduction in embryo water content of intact cary-opses, but increased the nitrate and amino- N content of pierced caryopses prior to germination. Supplying a 100 m M solution of KNO₃ to pierced caryopses reduced the total water potential and osmotic potential of the embryo, and increased its pressure potential by the same amount as an equimolar solution of KC1; however, while both treatments promoted germination, the KNO₃ induced more rapid germination than the KCI. Both treatments also increased the K⁺ content of the embryo, the KNO₃ again having the greater effect. These results are consistent with the hypothesis, based on our previous investigations, that KNO₃ promotes germination of dormant caryopses by accumulating in the embryo where it acts osmotically to increase water uptake. It is also postulated, that, in contrast to KCI, KNG₃ may combine an osmotic effect on water uptake with a nutritional effect on protein synthesis.     

Dormancy Implications of Phosphorus Levels in Developing Caryopses of Wild Oats (Avena fatua L.)

The element phosphorus made up 0.5% of the dry weight of dehulled Avena fatua caryopses 7 days after anthesis (DAA), half of it inorganic (P_i). Caryopses detached and pierced 7 DAA germinated in vitro with a rapid drop in P_i levels. By 15–20 DAA caryopsis dry weight had increased three- to fourfold, but phosphorus made up less than 0.04% of the dry weight of this enlarged caryopsis. Caryopses at this stage germinated readily without piercing if incubated in vitro. A further decrease in P_i accompanied by a marked increase in phytate phosphorus began about 15 DAA and continued during later seed maturation. By 20 DAA, when embryos were relatively mature and endosperm cell division had ceased, a decrease in caryopsis water content (as a percentage of dry weight) began, and seed dormancy became apparent. As starch and phytate reserves accumulated, P_i and water levels of the caryopsis diminished. Higher levels of endogenous P_i coincided with the anabolic events of initial seed formation and, to a lesser extent, with anabolic events of seed germination. Decreasing P_i levels coincided with accumulation of nutrient reserves, lowering of water content, and the initiation of dormancy. The data suggest that (1) enzymes associated with the formation and development of the embryo may be activated by the high P_i levels present during initial seed differentiation; (2) embryo quiescence and dormancy are facilitated by the drop of P_i levels which accompanies the accumulation of starch and phytate reserves; and (3) the increase in P_i which accompanies seed afterripening aids in the termination of dormancy and the resumption of germination. Received August 15, 1996; accepted December 2, 1996     

Abiotic stress�Cinduced inhibition of root growth and ascorbic acid oxidase activity in barley root tip is associated with enhanced generation of hydrogen peroxide

Using short-term treatments, the aim of this study was to analyze the role of hydrogen peroxide in the regulation of AAO activity during Cd, Cu or IAA treatments in barley root tips. For analysis individual barley root segments were obtained by the gradual cutting of each root from the tip to the base 1, 2, 3 or 6 h after short-term treatments. Already a short 30 min exposure of barley roots to Cd induced significant root growth inhibition in a Cd concentration dependent manner, which was accompanied by a marked reduction of AAO activity. At Cu concentration which had no effect on the root growth a significant increase in AAO activity was observed. This increased AAO activity was detected only in ionically-bound CW fraction. In contrast, Cu at higher concentration and IAA inhibited both ionically-bound CW AAO isozymes. Prompt inhibition of AAO activity immediately after short-term treatment was observed only in the case of H₂O₂ treatment suggesting that H₂O₂ may act as an inhibitor of AAO. This was further supported by the observation that all Cd-, Cu- or IAA-induced root growth and AAO activity inhibition in barley roots was connected with an elevated production of H₂O₂.     

Effect of hydrogen peroxide on seedling growth and antioxidants in two wheat cultivars

This study aimed to investigate seed germination, seedling growth, and antioxidative responses in two wheat cultivars, Ningchun and Xihan, exposed to different H₂O₂ concentrations. Ningchun exhibited higher germination rate but lower root and shoot growth than Xihan when exposed to H₂O₂ treatment. Assays using fluorescent dye H₂DCFDA and propidium iodide showed a significantly enhanced H₂O₂ content and a cell elongation inhibition in H₂O₂-treated roots. The malondialdehyde content was elevated with increasing exogenous H₂O₂ concentration. Moreover, treatments of seedlings with H₂O₂ scavenger, catalase (CAT), and antioxidant, butylated hydroxytoluene, partly abolished H₂O₂-induced negative effect on root growth. In both untreated and H₂O₂-treated leaves, SOD activity in Ningchun was higher than that in Xihan, but POD and APX activities in Ningchun were lower than those in Xihan, leading to elevated H₂O₂ level in Ningchun leaves but decreased H₂O₂ content in Xihan ones under H₂O₂ treatment.     

Systematic significance of mature embryo of bamboos

The mature embryo of seven species belonging to five genera of Indian bamboos is described. In all these the basic pattern of embryo organisation is same: the scutellar and coleoptilar bundles are not separated by an internode, the epiblast is absent, the lower portion of the scutellum and the coleorhiza are separated by a cleft and the margins of embryonic leaves overlap. The features unique to fleshy fruited bamboos are: presence of a massive scutellum, the juxtaposition of plumule and radicle and the occurrence of a bud in the axil of the coleoptile. The fleshy fruit bearing bamboos should be classified into one group, the tribeMelocanneae. Evidence is provided to recognise additional groups in the subfamilyBambusoideae.     

Salinity induced the changes of root growth and antioxidative responses in two wheat cultivars

This study aimed to investigate the inhibitory mechanism of root growth and to compare antioxidative responses in two wheat cultivars, drought-tolerant Ningchun and drought-sensitive Xihan, exposed to different NaCl concentrations. Ningchun exhibited lower germination rate, seedling growth, and lipid peroxidation than Xihan when exposed to salinity. The loss of cell viability was correlated with the inhibition of root growth induced by NaCl stress. Moreover, treatments with H₂O₂ scavenger dimethylthiourea and catalase (CAT) partly blocked salinity-induced negative effects on root growth and cell viability. Besides, the enhancement of superoxide radical and H₂O₂ levels, and the stimulation of CAT and diamine oxidase (DAO) as well as the inhibition of glutathione reductase (GR) were observed in two wheat roots treated with salinity. However, hydroxyl radical content increased only in Xihan roots under NaCl treatment, and the changes of soluble peroxidase (POD), ascorbate peroxidase (APX), superoxide dismutase (SOD), and cell-wall-bound POD activities were different in drought-tolerant Ningchun and drought-sensitive Xihan exposed to different NaCl concentrations. In conclusion, salinity might induce the loss of cell viability via a pathway associated with extracellular H₂O₂ generation, which was the primary reason leading to the inhibition of root growth in two wheat cultivars. Here, it was also suggested that increased H₂O₂ accumulation in the roots of drought-tolerant Ningchun might be due to decreased POD and GR activities as well as enhanced cell-wall-bound POD and DAO ones, while the inhibition of APX and GR as well as the stimulation of SOD and DAO was responsible for the elevation of H₂O₂ level in drought-sensitive Xihan roots.     

Localization of wheat-germ agglutinin in developing wheat embryos and those cultured in abscisic acid

The time course of appearance of wheat-germ agglutinin (WGA) in the various embryonic tissues during embryogenesis in Triticum aestivum L. was studied by sensitive immunofluorescence and peroxidase-antiperoxidase detection systems. The radicle, root cap and coleorhiza first accumulated WGA in early Stage II (8-10 d post-anthesis) prior to the main period of embryo growth, while WGA was found in the epiblast and coleoptile in early and late State III, respectively. Stage III is characterized by maximum embryo growth, followed by desiccation which occurs in Stage IV. When Stage-II embryos were precociously germinated in the absence of abscisic acid (ABA) no WGA was detected in the coleoptile and epiblast of the young seedlings. In the presence of ABA, Stage-II embryos did not germinate but WGA precociously accumulated in the coleoptile and epiblast. The levels and distribution of WGA in the resulting embryo resembled those in a fully mature, dry embryo (Stage V). Barley possesses a seed lectin similar to WGA, but it is never detected in coleoptiles. Some but not all of the barley cultivars tested were found to accumulate lectin in this organ of mature embryos when treated with ABA. Thus, ABA appears to be involved in the highly regulated temporal and spatial expression of WGA during embryogenesis in cereals.Abbreviations ABA abscisic acid - DIC differential interference contrast - PAP peroxidase-antiperoxidase - WGA wheat-germ agglutinin     

Water-soluble phenolic compounds in the coat control germination and peroxidase reactivation in <Emphasis Type="Italic">Triticum aestivum</Emphasis> seeds

In this work, we investigated the inhibitory effects of water-soluble phenolic compounds (WSPCs) in the coat of after-ripening wheat (Triticum aestivum L.) seeds on the processes of germination and peroxidase reactivation. Wheat bran has a WSPC content of 862.5 μg gallic acid equivalent g⁻¹ dry weight. When seeds were incubated in the water extract of bran, germination, peroxidase reactivation, and coleoptile and radicle growth were suppressed in a WSPC concentration-dependent manner. The inhibitory effects were significantly ameliorated by removing WSPCs from bran extract by treating with 1% insoluble polyvinylpolypyrrolidone. Pretreatment of seeds with 0.1% H₂O₂ reduced the WSPC content in the coat, which was confirmed using Fourier transform infrared microspectroscopy. With H₂O₂ pretreatment, seed germination, peroxidase reactivation, and post-germination seedling growth were significantly stimulated. Application of the known phenolics caffeic acid, feruic acid, or vanillin to the germination medium blocked seed germination and suppressed peroxidase reactivation. The results described here indicate that WSPCs act as endogenous inhibitors in the coat to control germination of Triticum aestivum seeds, and that inhibition of germination is at least partially caused by suppressing peroxidase reactivation.