Effect of Light and Ethylene upon Cytokinin Levels in Seed of Spergula arvensis

The breaking of dormaney in Spergula orvensis L. seed by lightand ethylene is accompanied by severalfold increases in thelevels of endogenous cytokinins prior to germination, the largestrise being observed in the cytokinin-ribotide fraction. Pretreatmentof seed with cytokinins does not, however, substitute for thelight or ethylene requirements.     

蔷薇种子的休眠及解除方法

分析了蔷薇(Rosa L.)种子休眠原因、解除休眠方法以及环境条件对休眠与萌发的影响.蔷薇种子休眠的主要原因有瘦果果皮和种皮的限制作用,胚生理休眠以及果肉、瘦果果皮、种皮和胚中的抑制物质.解除休眠的方法包括去除瘦果果皮限制、解除胚的生理休眠、去除抑制物质等.种子发育过程中及成熟后,环境因子,如温度、水分和光照,对种子休眠和萌发有影响.此外,微生物、果实采集时间也对种子休眠及萌发有较大影响.蔷薇种子的休眠机制复杂,且种间差异很大.     

The Possible Role of Low Temperature in Breaking the Dormancy of Seeds of Fraxinus excelsior L.

It has been shown that the growth-inhibiting substances presentin the embryo and endosperm of F. excelsior are not removedduring pretreatment or during the actual germination process.On the other hand, evidence is presented that the inhibitormay be physiologically effective in preventing germination.A biological assay technique using embryos of the same speciesfrom which the growth substances were extracted was used todemonstrate the production of a germination and growth-promotingsubstance during the process of low temperature after-ripeningand its apparent counteraction of the effect of the endogenousinhibitor.     

曼陀罗种子休眠机理与破眠方法研究

通过对曼陀罗种子生活力测定、发芽试验、吸水率测定及种子萌发抑制物研究,揭示曼陀罗种子休眠机理,并利用物理、化学法处理曼陀罗种子,以探寻打破曼陀罗种子休眠的最佳方法.结果表明:(1)新采收的曼陀罗种子为综合休眠,休眠原因包括:种皮障碍、缺少萌发所需激素以及种皮和种仁中存在萌发抑制物,其中种皮障碍是限制种子萌发的首要因素.(2)室温存储6个月可解除曼陀罗种子种仁的休眠,但种皮障碍始终是其种子萌发的限制因素.(3)机械摩擦、浓H2SO4处理和NaOH处理均可打破除曼陀罗种皮的休眠障碍,促进种子萌发,其中用10% NaOH处理90 min为破除曼陀罗种皮休眠障碍的最佳方法,且发芽率比对照提高了83%.     

Light-Sensitivity of Hazel Seeds with Respect to the Breaking of Dormancy

Light breaks the dormancy of hazel (Corylus avellana L.) seedswhen the testa is removed. Light, acting via phytochrome, alsopromotes the germination of hazel seeds when the embryonic axisis surgically uncovered. In such seeds with the axis uncoveredremoval of the testa is antagonistic to the light promotionof germination. (Received January 17, 1982; Accepted April 25, 1983)     

Implication of Ethylene in the Release of Secondary Dormancy in Amaranthus caudatus L. Seeds by Gibberellins or Cytokinin

Ethephon (Eth), gibberellin A₃, A_{4 + 7} (GA₃, GA_{4 + 7}), and 6-benzyladenine (BA) removed secondary dormancy of Amaranthus caudatus seeds. The GAs and BA potentiated the effect of ethephon or 1-aminocyclopropane-1-carboxylic acid (ACC), an ethylene biosynthesis precursor, in terms of the rate or final percent of germination. Aminoethoxyvinylglycine (AVG), an ACC synthase activity inhibitor, was observed to simultaneously inhibit the release from dormancy effected by GA₃ or BA as well as the ethylene production stimulated by these regulators. Breaking of secondary dormancy by GA₃, GA_{4 + 7} or BA was prevented by 2,5-norbornadiene (NBD), an inhibitor of ethylene binding. Ethylene completely or markedly reversed the inhibitory effect of NBD. We thus conclude that the removal of secondary dormancy in Amaranthus caudatus seeds by gibberellin or benzyladenine involves ethylene biosynthesis and action.     

A Population Study of Spergula arvensis: II. Genetics and Breeding Behaviour

Genetical work has shown that one locus and two alleles areinvolved in the inheritance of a seedcoat character of Spergulaarvensis and that the hetero-zygous plants are intermediatebetween the two types of homozygous plants. It is thus possibleto translate directly the observed geographical distributionof plant frequencies into distribution of gene frequencies.The inheritance of a hairiness character is less straightforward,but in this case also there is a close relation between phenotypefrequency distribution and gene frequency distribution. Using the fact that plants heterozygous for the seedcoat characterare easily recognizable, it is possible to make an estimateof the amount of outbreeding in nature. The values obtainedrange from o to 3 per cent.     

Dormancy in Seeds of Charlock (Sinapis arvensis L.): Early Effects of Gibberellic Acid on the Synthesis of Amino Acids and Proteins

Charlock (Sinapis arvensis L.) seeds were imbibed with 10 mm GA(3) for 24 hours at 0 C. After equilibration at 25 C, a 5-fold increase in radioactivity in the amino acids labeled from 2-(14)C-acetate was observed within 2 hours. The total amount of amino acids was reduced to half, and the specific radioactivity increased approximately 10-fold, indicating a diversion of metabolites for amino acid and protein synthesis in GA(3)-treated seeds. The rate of incorporation of l-(14) C-leucine into protein was doubled. Autoradiographs showed that enhancement of protein synthesis was localized in the shoot and root meristems, the developing vascular tissues, and in the endosperm cells inside the testa.     

Effect of Ethylene on the Qualitative and Quantitative Composition of the Phenol Content of Carrot Roots

Carrot (Daucus carota L.) roots stored at 3 ± 1°C in an atmosphere containing 100 μ1/I of ethylene had their total phenol content increased markedly as compared to control samples kept in air. The increase was two-fold: i. higher level of pre-existing phenols, particularly isochlorogenic acid, ii. de novo synthesis of (at least) four compounds, two of which were identified as 3-methyl-6-methoxy-8-hydroxy-3,4-dihydroisocoumarin, and 5-hydroxy-7-methoxy-2-methylchromone, which are not normally present in carrot tissues.     

A Population Study of Spergula arvensis: I. Two Clines and their Significance

Two seed-coat forms (the presence or absence of papillae) andtwo hairiness forms (medium or densely hairy) of Spergula arvensisare differently distributed through the British Isles, theirrelative frequencies being correlated with latitude and altitude.The proportions of the non-papillate and densely hairy formsincrease with increasing distance from Kent to the north-north-westand also with increasing altitude. A possible explanation is that the diverse forms indicate selectivedifferences. Experiments have been carried out to test thishypothesis and the evidence supports it. The non-papillate formproduces a lower proportion of fertile capsules than the papillateform when grown at a high temperature and low humidity. Alsothe non-papillate seeds germinate more readily than the papillateseeds at low temperatures, whereas at higher temperatures thereverse is true. It is suggested that hybrid vigour, fluctuating selection intensities,and migration may all play a part in maintaining the observeddistribution of the various forms.     

榛树种子的休眠和萌发

鉴定榛子各部分浸提液的结果显示 ,果皮、种皮及胚都存在导致休眠的抑制物质 ;榛树果实有一定的吸水性 ,据此推测种子休眠可能不是因果皮的不透水性造成 ;0 .5、2、5mg·L-16 BA可以解除种子休眠 ,促进萌发。     

钙处理对桃冷藏期间呼吸速率和乙烯释放以及与褐变相关酶活性的影响

桃冷藏期间3?Cl2处理的效果最好,呼吸速率、乙烯释放量、过氧化物酶(POD)和多酚氧化酶(PPO)活性均显著下降(P≤0.05).     

The Effect of Ethylene and Temperature on ATP Accumulation from Various Substrates in Peanut (Arachis hypogaea L. ) Seeds

Peanut (Arachis hypogaea L. ) seed powder accumulated ATP fromAMP and phosphoenolpyruvate (PEP) at a rate of approx. 100 pmolmin^–1mg^– powder at 35° C. When peanut seed powderwas incubated with various substrates, which may result in PEPor AMP (ADP) synthesis, then ATP accumulated. The best substratecombinations examined so far were AMP + succinate, NADH₂, andAMP + malate + NAD, with activities of 33, 12 and 12 pmol min^–mg^–1powder,respectively; AMP + malate showed very low activity. Some combinationsexhibited linear activities with time, while others had an exponential-typeprofile. The temperature dependence of the ATP accumulationdemonstrated by the Ahrrenius plot had a double phase with atransition point at 25° C. The Ea values between 15°C and 25° C were 25 000–50 000 cal/mol, while above25° C the Ea values fluctuated between 6000 and 8000 cal/mol(depending on the substrate). The AMP + PEP combination exhibiteda single-phase profile between 15° C and 40° C, withan Ea value of 22 000 cal/mol. In the presence of some substrates,ethephon (ethylene) had a stimulatory effect and caused an increasein the Ea values at the high temperature phase. A comparisonof seed powder from dormant seeds with that from non-dormantseeds revealed that some substrate combinations accumulate ATPfaster in non-dormant seeds and others do so in dormant seeds. Key words: Arachis hypogaea, ATP, Ethylene, Dormancy, Peanut, Seed     

The Activity of Principal Antioxidant Enzymes and the Content of Metabolites in Dormancy Breaking and Germination of Davidia involucrate Seeds

The principal antioxidant enzymes and metabolites were reported to play a very important role in eliminating reactive oxygen species and maintaining vigour in dormancy breaking and germination of Davidia involucrate seeds. However, the researches on the change laws of content and activity are seldom. In present study, we chose Davidia involucrate seeds which collected from the Mabian Nature Reserve as experimental materials, and then investigated the activity of principal antioxidant enzymes and the content of metabolites in dormancy breaking and germination of the seeds. The results showed that the activity of peroxidase (POD), catalase (CAT), superoxide dismutase (SOD) and glutathione reductase (GR) exhibited an increasing trend but the activity of total antioxidant capacity (T AOC) decreased greatly in early stage of stratification. Comparing with the decrease of protein (Pr), the content of ascorbic acid (Vc) and free amino acid (FAA) significantly increased. In middle stage of stratification, the activity of SOD and T AOC increased firstly and then decreased at last. The activity of POD always maintained a higher level although the activity of CAT and GR decreased greatly. In terminal stage of stratification, the activities of POD, GR, T AOC and the content of FAA and Vc exhibited an increasing trend, while the activity of CAT and SOD maintained a low level. In germination stage, the activity of all antioxidant enzymes and the content of Vc and FAA were increased obviously (P < 005), but the content of the protein was decreased. These results suggested that Davidia involucrata seeds may have a good ability to efficiently remove the effects on cell structure caused by reactive oxygen species (ROS) by keeping the interaction of antioxidant enzymes and metabolites successively during the period of dormancy breaking and germination. This adjustment helps to ensure the germination of seeds by acceleration the post ripening in morphological and physiological of progresses.     

Phytochrome Transformation and Action in Seeds of Rumex crispus L. during Secondary Dormancy

Promotion of germination by red light fails after prolonged dark imbibition of Rumex crispus L. seeds, indicative of a secondary dormancy. The degree and rate of inception of the dormancy increases with increasing temperature. Following establishment of the dormancy, germination response to red light can be restored by either prolonged cold treatment or brief high temperature shifts. Loss of phytochrome was not a factor in the initial establishment of the dormancy. When the seeds are in secondary dormancy, the chromophore of phytochrome can be transformed to the far red-absorbing form, but the far red-absorbing form cannot induce germination. The responses to changes in temperature suggested dependence of germination on order disorder transitions in components of the seeds.     

Ethylene Inhibition of Phytochrome-Induced Germination in Potentilla norvegica L. Seeds

Germination of Potentilla norvegica L. (rough cinquefoil) seeds stimulated by fluorescent irradiations of nearly 24 hours was inhibited by ethylene at <1 microliter per liter. Sensitivity to ethylene inhibition was highest during and immediately after the irradiation. By delaying ethylene treatment until about a day after the light potentiation, seeds escaped the inhibition. Ethylene inhibition may be readily reversed upon release of the gas and reirradiation of the seeds. Imbibition of seeds at 10 or 15°C, or at high temperatures of 35 and 40°C, partially prevented subsequent inhibition by ethylene. Alternating temperatures during germination nearly overcame the inhibition from 1 microliter per liter ethylene, but not higher doses. With brief red-irradiation and alternating temperatures, 0.1 microliter per liter ethylene promoted germination about 2-fold. These data suggest that ethylene may loosely associate on a site required for phytochrome action. The effect of temperature that opposed the inhibition may be to deny the association of ethylene with the site. Loose association is supported by the reversal of inhibition by gas release and increased temperature during germination. A blocking effect was shown by the failure of phytochrome to act when ethylene was present.     

Breaking of Dormancy in Xanthium Seeds by Kinetin Mediated by Light and DNA-dependent RNA Synthesis

Kinetin was able to break the dormancy of the “upper seed” (in bur) of Xanthium by antagonizing the endogenous inhibitor present in the embryo. Other growth substances like indoleacetic acid, gibberellic acid and cycocel were without effect. Breaking of dormancy by kinetin was dependent on reversible phytochrome system and DNA-dependent RNA synthesis. Protein synthesis is possibly not involved in the act of dormancy breaking. Endogenous inhibitor possibly participates in the mechanism of repression of genie site(s). It is suggested that an interplay of endogenous inhibitors, kinins and other factors (light, temperature, etc.) regulate dormancy, germination and differentiation by repression and derepression of DNA sites.     

Studies on the Dormancy of Calluna vulgaris (L.) Hull, During Winter: Classification of Dormancy

Experiments are described in which plants of Calluna vulgariswere transferred from a high altitudinal blanket bog to controlledenvironment rooms under a range of conditions, to determinethe type of dormancy mechanism which occurs in this speciesduring the winter months. It was found that in autumn, Callunaexhibits semi-dormancy, bud break not occurring under shortphotoperiods. From December onwards, bud break will occur under short photoperiodsif warm temperatures are applied; at this time the plants arein a state of post-dormancy. Calluna lacks a period of truedormancy since it can always be forced to resume growth by longphotoperiods. Although in autumn, plants will not break dormancy under shortdays, after experiencing the natural outdoor conditions of winter,they will break dormancy equally readily under long and shortdays when brought into warm controlled environment rooms inthe spring. Calluna vulgaris (L.) Hull., heather, dormancy, pre-dormancy, post-dormancy, semi-dormancy