Chalazal germination inTrichodesma amplexicaule Roth.

Seed germination studies onTrichodesma amplexicaule were carried out. Seeds show abnormal behaviour of germination which is termed "Chalazal germination". This abnormal behaviour of germination is due to the presence of an obturator at the micropylar end. Seeds showed maximum (60 per cent) germination with 110 min concentrated H₂SO₄ treatment.     

Adaptive diversification of germination strategies.

Evolution of the germination rate (the proportion of newly produced and dormant seeds that germinates every year) of annual plants is investigated, when the environment is temporally stochastic and spatially heterogeneous. The environment consists of two habitats with synchronous stochastic variation in the annual yield and permanent difference in constant seed survival rates. Density dependence operates within the habitats, which are connected via restricted seed dispersal. We find that instead of a single common evolutionarily stable strategy the coexistence of several germination strategies is possible and that in an initially monomorphic population evolutionary branching may occur. During evolutionary branching the population undergoes disruptive selection and splits into two branches of different lineages that converge to the evolutionarily stable coalition of different germination strategies. It is shown that spatial heterogeneity and restricted dispersal are essential for evolutionary branching. Disruptive selection on the germination rate presents yet another possibility for parapatric speciation.     

Studies on germination of chrysanthemum pollen I. Effect of sugars on germination

1. 1. The percentage of chrysanthemum pollen stained with Nitroblue tetrazolium ranged from 60 to 90 %, indicating the presenceof active succinate dehydrogenase in the pollen.
2. 2. Exogenousapplication of oligosaccharides such as sucrose,lactose andraffinose at concentration of 20 to 35 % favoredgerminationof chrysanthemum pollen. However, the germinationrate was notelevated higher than 10 % in most of the chrysanthemumcultivars.
3. 3. Sugar content of chrysanthemum pollen was less than 10%of the fresh weight. The sugar was composed of glucose, fructoseand sucrose, the amount of sucrose being about four times asmuch as that of glucose or fructose.
4. 4. The ß-fructofuranosidaseactivity of chrysanthemumpollen was very high. These and relevantresults suggest thatthe poor germination of chrysanthemum pollenis due neitherto abortion nor to the deficiency of specialsugars in the pollen.

(Received November 14, 1967; )     

Phytochrome and seed germination. V. Changes of phytochrome content during the germination of cucumber seeds

Cucumber seeds are light-sensitive, dark-germinating seeds. Inhibition of germination can be induced by prolonged exposure to continuous or intermittent FR. The dark germination process and the response to FR are phytochrome controlled. Phytochrome can be detected in these seeds by differential spectrophotometry in vivo. Spectrophotometrically measurable phytochrome increases during dark germination. The rate of increase is temperature dependent. Light treatments which are inhibitory for germination result in phytochrome contents lower than those of the seeds germinating in darkness. Treatments which restore germination also restore phytochrome formation.     

Glucose-triggered germination of Bacillus megaterium spores.

Triggering of germination in Bacillus megaterium QM B1551 spores with D-glucose was studied. First, the interaction of glucose with spores for less than 1 min resulted in triggering almost 90% of the spores after the glucose was removed by dilution. Therefore only a brief time is needed for glucose to trigger germination, and then the continuous presence of glucose is not necessary. Detectable uptake of glucose began 2 to 3 min after absorbance loss started, and a non-metabolizable glucose analog, methyl-alpha-D-glucopyranoside, triggered germination in the absence of detectable uptake. Several inhibitors that reduced or eliminated glucose uptake did not block triggering of germination. Therefore, glucose uptake may be a relatively late event and not a prerequisite for triggering of germination.     

Quercus suber L. Somatic embryo germination and plant conversion: Pretreatments and germination conditions

Summary Osmoticum (high sucrose concentration) and chilling (4°C) treatments were assayed in order to promote germination (radicle elongation) and plant conversion of Quercus suber somatic embryos. Those treatments were applied before embryos were set to germinate on Murashige and Skoog (MS) liquid medium. Chilling for 2 mo. improved germination rate (best results close to 100%). On the other hand, that treatment increased plant conversion, especially when high sucrose concentration was used. The best results were obtained with 150 g l⁻¹ sucrose (75% of cultured embryos converted to plants). Incubation conditions during germination were also studied. Although there were no significant differences on final results, warmer temperatures and darkness increased germination rate. The influence of the different treatments on shoot morphology was also studied. The highest percentages of shoots with normal leaves obtained were close to 25%.     

Polyamine biosynthesis during germination of yeast ascospores.

The role of the diamine putrescine during germination and outgrowth of ascospores of Saccharomyces cerevisiae was examined. Ornithine decarboxylase activity increased and declined rapidly during germination and outgrowth; peak activity was attained after the cells had proceeded through the G1 interval of the cell cycle, whereas minimal activity was present at the completion of the first cell division. alpha-Methylornithine inhibited both ornithine decarboxylase activity and the in vivo accumulation of putrescine. In the presence of alpha-methylornithireak dormancy and proceed through one cell division. Subsequent cellular growth, however, was retarded but not completely inhibited. The supplementation of Methylglyoxal bis(guanylhydrazone) to sporulation medium greatly inhibited this sexual process. These data suggest that the synthesis of putrescine is not required for the breaking of spore dormancy, but that polyamine biosynthesis may be essential for meiosis and sporulation.     

镉对水稻种子萌发的影响

以不同类型的319个水稻品种为研究对象,研究了10 mg·L^-1 Cd²⁺处理对水稻种子萌发的影响.结果表明:Cd²⁺对种子发芽率影响较小,对根系生长的影响显著,且大于对芽生长的影响;不同类型水稻种子萌发对Cd的响应差异较大,敏感顺序为粳稻>籼稻>杂交稻;两系不育系根系长度和根系数量受Cd的抑制程度显著高于三系.应用快速聚类方法,可以将参试品种划分为耐受型、中间型和敏感型3种不同的敏感类型.     

Properties of Bacillus megaterium temperature-sensitive germination mutants.

Bacillus megaterium mutants JV-9 and JV-10 are temperature sensitive for initiation of spore germination. At 46 C, they did not lose heat resistance, dipicolinic acid, or absorbance, indicating that the temperature-sensitive blocks are very early in the sequence of initiation reactions. Strain JV-9 was temperature sensitive for initiation by glucose alone, and strain JV-10 was temperature sensitive for initiation by glucose, L-leucine, L-proline, KBr, or calcium dipicolinate. The kinetics of initiation were followed after two kinds of temperature change (shift-up and shift-down) experiments. Mutant spores incubated for different times at 46 C and then shifted down to 30 C showed no significant differences in the rates of absorbance decrease, i.e., no stimulation or inhibition. Conversely, when mutant spores were incubated for different times at 30 C, a fraction of the population initiated germination, and after shift-up to 46 C an additional fraction continued initiation while a third fraction stopped. This latter fraction did initiate germination when the temperature was lowered to 30 C. The kinetics of initiation after shift-up and shift-down in temperature suggest that the early events in initiation reagents, whereas the other four initiated sensitivity for all of the above initiation reagents, whereas the other four initiated very poorly. It was suggested that the lesion in strain JV-10 may result in the formation of one temperature-sensitive protein. Revertants of strain JV-9 could not be isolated.     

Temperature-pH effect upon germination of bacterial spores.

Using several kinds of criteria for the germination of bacterial spores, germination-pH curves were drawn for Bacillus subtilis spores observed at different temperatures. The experiments revealed that optimum pH for spore germination was markedly changed by changing the incubation temperature; the optimum pH for germination was 7.4 at 37 degrees C and 5.4 at 10 degrees C. A possible mechanism involved in this phenomenon is discussed.