Representing Cumulative Germination. 1. A Critical Analysis of Single-value Germination Indices

Several single-value germination indices, including Kotowski'scoefficient of velocity, Maguire's speed of germination, Czabator'sgermination value, Diavanshir and Pourbiek's germination value,Timson's cumulative germination, Lehle and Putnam's Richardsfunction index, Smith and Millett's sprouting index, and Tuckerand Wright's regression index, were evaluated to test theirability to distinguish superior from inferior germination. Allexcept Timson's cumulative germination method were essentiallyno better for ranking germination responses than data on totalgermination; Kotowski's coefficient of velocity, Smith and Millet'ssprouting index, and Lehle and Putnam's Richards function indexwere markedly inferior. Because of the ambiguity inherent inany index that combines, into a single value, data about theonset, rate and extent of germination, none of the indices couldbe recommended as a way of summarizing germination. Cumulative germination, single-value germination indices, germination index, germination     

Photocontrol of the Germination of Onoclea Spores: IV. Metabolic Changes during Germination

The changes in levels of metabolites during photoinduced germination of Onoclea sensibilis L. spores are described. Proteins and lipids, which constitute 25 and 20%, respectively, of the unimbibed spores on a dry weight basis, are hydrolyzed at the time of differentiation and elongation of the germling cells and may be utilized for these processes. Sucrose degradation, starch synthesis, and active respiration occur during dark imbibition, but these processes are accelerated by red or far red irradiation. Endogenous sucrose is the probable source of the carbon skeleton for starch synthesis.     

Biochemical Studies of Bacterial Sporulation and Germination XXI. Temperature-Sensitive Mutants for Initiation of Germination

Mutants of Bacillus megaterium have been isolated that are temperature-sensitive for the initiation of germination.     

Germination of Tagetes minuta L. I. Temperature Effects

Initial studies have indicated that Tagetes minuta achenes haveboth a temperature and a light requirement for germination.Temperatures tested were 10, 20, 25, 30 and 35 °C. Germinationwas optimal at 25 °C under white light conditions. Underthese conditions 100 per cent of achenes germinated within 7days of imbibition. There was no germination at 10 or 35 °Ceither in the light or in the dark. Achenes imbibed and incubatedat 35 °C for 4 days showed no visible signs of germinationbut on transfer to 25 °C, 100 per cent of these achenesgerminated within 24 h. Furthermore, achenes given this hightemperature (35 °C) treatment could be dried at 25 °C,re-imbibed at 25 °C and again 100 per cent of achenes germinatedwithin 24 h of re-imbibition. This rapid germination responsefollowing removal from the high temperature regime could alsobe induced by transfer to temperatures of 20 °C or 20 °C(16 h) alternating with 10 °C (8 h). Tagetes minuta L., weed seeds, germination, temperature, light     

短梗南蛇藤种子的萌发特性

本文观察了短梗南蛇藤种子的形态和萌发过程,研究了温度、层积方法和时间、假种皮浆液、光照等对短梗南蛇藤种子萌发的影响。结果表明,短梗南蛇藤种子对温度较敏感,较适合萌发的温度为15～20℃。低温层积和变温层积均能显著提高种子发芽率、发芽势和发芽指数,层积20d效果最好。假种皮浆液联合层积处理对种子萌发有显著促进作用,其中联合低温层积20d或联合变温层积10d效果最好。光照在一定程度上抑制种子萌发。     

Phytochrome and Seed Germination. III. Action of Prolonged Far Red Irradiation on the Germination of Tomato and Cucumber Seeds

Prolonged irradiation with continuous or intermittent far red prevents the germination of tomato and cucumber seeds. The inhibitory efficiency of intermittent far red decreases with the lengthening of the interval between successive irradiations, and with the increase of temperature. If each far red irradiation is followed by red, germination is restored. Intermittent far red is less inhibitory than intermittent red-far red when red is given immediately before each far red. This effect is more evident when the interval between successive irradiation becomes longer.     

Biochemical Studies of Bacterial Sporulation and Germination XVII. Sulfhydryl and Disulfide Levels in Dormancy and Germination

A fourfold increase in sulfhydryl content upon germination of Bacillus megaterium spores was observed by the standard fluorescein mercuric acetate assay as reported by others. However, assay of ruptured dormant spores or the use of N-ethylmaleimide and a denaturing agent on intact spores showed a constant sulfhydryl level in dormancy and in germination. The apparent increase in sulfhydryl groups observed on germination was shown to be due to inaccessibility of most sulfhydryl groups in the dormant spore to sulfhydryl reagents. The disulfide content of dormant spores showed no change on germination, nor was any evidence found for production of low-molecular-weight sulfhydryl or disulfide compounds during germination.     

Germination of Tagetes minuta L. II. Role of gibberellins

The effect of the application of gibberellins to Tagetes minuta L. achenes (seeds) was determined at both 25°C, the optimal germination temperature, and 35°C, at which temperature the achenes are thermoinhibited. Both GA₃ and GA₄₊₇ accelerated germination at 25°C. Seed germination at 25°C was inhibited by paclobutrazol, but on subsequent application of GA₄₊₇ rapid germination was induced. Following application of GA₃ or GA₄₊₇ to thermoinhibited seeds, a significantly higher final germination percentage was observed than in the distilled water control. However, endogenous gibberellin levels in germinating and thermoinhibited seeds did not differ significantly.     

Germination inhibitors

The Botanical Review - The presence of germination-inhibiting substances in plants seems to be a wide-spread phenomenon. They occur in all parts of plants —in fruit pulp, fruit coats,...     

Water Relations of Beetroot Seed Germination: I. Microbial Factors, with Special Reference to Laboratory Germination

Laboratory test results obtained with two seed lots of the cultivarDetroit Globe have shown: (1) 8 ml of water in a 9-cm diameterpetri-dish are excessive for good germination of 25 two-seededclusters, either natural or ‘rubbed’, which germinatewell in 3 ml of water. (2) Some of this depression in germinationis due to a ‘direct’ effect of the excessive water-supply.(3) But the benefit from either surface sterilization or theuse of aureomycin, a bacteriostatic antibiotic, indicates thatsome of the depression of germination in the presence of excesswater is the result of bacterial colonization of the seed clusters.The excess water effect can also be mitigated by preliminary‘rubbing’ of the seed clusters, presumably by removalof some of the bacterial inoculum, provided that the rubbingprocess itself does not injure the seeds. (4) There is goodevidence that the bacteria depress the germination of the seedsby competing with them for oxygen. (5) The effect of the bacterialpopulation on germination in excess water can be aggravatedby preliminary washing of the seed clusters. This is probablydue to a delicate equilibrium between the bacteria and at leastpart of the fungal population of the seeds which when retainedmay produce an antibacterial substance; but the water-solublephenolic acids contained in the seed clusters may also be involved:at high concentrations these inhibit germination, but they mayalso depress bacterial activity, even at lower than germination-inhibitingconcentrations. (6) Fungicides aggravate the depression of germinationon over-wet paper in the laboratory, but are of value in thefield. (7) There is evidence that different limiting factorsmay operate on different seed lots and care must be taken notto generalize from results obtained from a limited number ofseed samples.     

Delayed Germination in Reed Canary-Grass Phalaris arundinacea L.

Dormancy in reed canary-grass can be overcome by removing thepalea from the caryopsis, by scarifying the seed, or by prickingthe palea with a pin. The dormancy appears to be due to a water-solubleinhibitor which is present either in the caryopsis or the embryo. There is apparently an interaction between the inhibitor andoxygen, as the effect of the inhibitor passes off quickly underconditions of good aeration. It is possible that free oxygenmay be required to act as hydrogen acceptor in an aerobic dehydrasesystem. Inhibitory effect of the aqueous extract is only shownin the light; when caryopses are germinated in aqueous extractof caryopses in darkness no inhibition of germination is found.The inhibitor has no effect on the germination of lettuce seed. These feature are discussed in relation to other work on seeddormancy and the means of improving germination in the field.     

Phytochrome and Seed Germination: VI. Phytochrome and Temperature Interaction in the Control of Cucumber Seed Germination

Phytochrome control of cucumber seed germination is temperature-dependent. A prolonged exposure to radiation from broad spectrum far red sources (Pfr/P = 0.05 to 0.07) prevents germination at temperatures below 20 C. Above 20 C there is no inhibition and it appears as if there is an escape from phytochrome control. However, radiation from a monochromatic, narrow band 730 nanometer source (Pfr/P < 0.02) inhibits germination at temperatures above 20 C. This result supports the idea that, even at high temperatures, Pfr is responsible for the activation of germination. After 4 days of exposure to far red, a short red irradiation is quite effective in promoting germination if temperatures during the dark incubation periods are maintained below 20 C; red becomes effective at temperatures above 20 C. Promotion of germination will take place at a temperature of 25 C or higher without red irradiation. Again, we have an apparent escape from phytochrome control at high temperatures. However, if higher temperatures are used for only short periods, 2 to 6 hours, in combination with short red irradiation, one can demonstrate that activation of germination at high temperatures is still dependent on phytochrome. Phytochrome is probably destroyed during prolonged exposure to far red. Thus, the subsequent short red irradiation establishes levels of Pfr which may not be sufficient to promote germination at low temperatures but are probably adequate at high temperatures.     

Reserve Mobilization During Germination of Tagetes minuta L.

Levels of albumins, globulins and starch were measured in dryTagetes minuta L. achenes (seeds) germinating at 25 °C andin those thermo-inhibited at 35 °C. In addition, the compositionof amino acids, fatty acids and free sugars was determined. In germinating seeds, albumins increased, while globulins decreased.At 35 °C, only a delayed decrease in globulins occurred.However, in both, the amino acids serine and glutamate increased.Lipid composition remained constant except for a slight declinein linoleic acid in the germinating seeds. At 25 °C, starchlevels increased with time while at 35 °C, there was onlya transient increase. Sucrose was the major free sugar foundin the seeds at all times, but its levels declined in the germinatingseeds. This was accompanied by an increase in the proportionsof glucose and fructose. No such changes in sugar compositionwere observed in the thermo-inhibited seeds. Tagetes minuta L., seed germination, reserve mobilization, thermo-inhibition     

Germination and peptidoglycan solubilization in Bacillus megaterium spores.

During initiation of Bacillus megaterium QM B1551 spore germination, trichloroacetic acid-soluble, nondialyzable peptidoglycan fragments with an average molecular weight of 20,000 were excreted. This solubilization of peptidoglycan was measured in vitro as the amount of trichloroacetic acid-soluble hexosamine released from a suspension of broken spores. HgC12, a potent inhibitor of initiation, had no effect on the in vitro solubilization of peptidoglycan. In vivo, HgC12 had no effect on peptidoglycan release from spores that had lost heat resistance, but HgC12 did block complete absorbance loss. These results suggest that mercury inhibits some reactions that normally occur before loss in heat resistance but not the subsequent peptidoglycan release, and mercury inhibits other reactions involved with complete absorbance loss.     

Seed Germination in Buchnera hispida Buch.--Ham. ex D. Don

The effects of host-produced germination stimulant, light and2-chloroethylphosphonic acid (CEPA) on the germination of seedsof Buchnera hispida collected from Sorghum farms in Bornu Provinceof the North Eastern State of Nigeria were investigated. Lightinduced the germination of about 30 per cent of the seeds inthe absence of host-produced germination stimulant. There waslittle or no germination in the dark. Neither water pretreatmentnor the host stimulant was required for germination. GenerallyCEPA had little or no effect on germination. Light-stimulatedgermination required an induction period of 6 to 8 days in light.This induction period could be shortened if seeds were incubatedin water for a period in the dark prior to transfer to light.The results of our experiments indicate that an endogenous germinationmetabolite is synthesized and accumulated in light. Also thereis evidence to suggest that some steps leading to its formationcan be accomplished in the dark.     

Phytochrome and Seed Germination. IV. Action of Light Sources With Different Spectral Energy Distribution on the Germination of Tomato Seeds

Germination of tomato seeds exposed to a single, saturating irradiation from light sources of different spectral energy distribution seems to be dependent upon the photostationary P_FR/P_R ratio established by the irradiation. Germination of tomato seeds exposed to prolonged irradiations from the same light sources does not seem to be controlled solely by the P_FR/P_R ratio induced and maintained by the irradiation.