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.     

温度和盐分胁迫对新疆鼠尾草种子萌发的影响

利用控制实验研究了温度和盐分胁迫对新疆鼠尾草种子萌发的影响.结果显示:新疆鼠尾草种子萌发的最适温度为25℃.盐胁迫对新疆鼠尾草种子的萌发均有明显的抑制作用,随着盐浓度的增加,萌发率和萌发速率下降.在适宜萌发温度下,新疆鼠尾草耐盐极限值0.2 mmol/L.     

The Deleterious Effect of Water and Low Temperature on Germination of Pea Seed

Some pea seeds were killed or damaged by soaking in water, andthe damage was aggravated by low temperatures. Low-vigour seedlots were more sensitive to injury than high-vigour lots. Reducedwater uptake in osmotic solutions resulted in less damage andmost injury occurred during the initial phase of imbibition. More electrolytes exuded from dead and low-vigour seeds thanfrom high-vigour seeds and increased exudation at low temperaturewas associated with a higher incidence of dead seeds. Death is thought to be caused by a sudden inrush of water whichdisrupts the sub-cellular organization and membranes of a proportionof seeds predisposed to injury.     

Phytochrome and Seed Germination. I. Temperature Dependence and Relative P(FR) Levels in the Germination of Dark-germinating Tomato Seeds

Germination of the dark-germinating seeds of 3 varieties of tomato is controlled by the phytochrome system. Germination is inhibited by far red radiation and repromoted by red applied after far red. At low temperatures, 17 to 20°, a single, low energy far red irradiation is sufficient to inhibit germination in all 3 varieties. At higher temperatures far red is less effective in the inhibition of the germination of the tomato seeds. The phytochrome fraction present as P_FR in the dark-germinating seeds of the Ace variety is about 40% of the total phytochrome present.     

Effect of Water Stress, Seed Coat Restraint, and Abscisic Acid upon Different Germination Capabilities of Two Tomato Lines at Low Temperature

Two tomato (Lycopersicon esculentum Mill.) lines with greatly different capabilities to germinate at 10°C were compared with respect to sensitivity to experimental treatments which affect the water status of the embryo. Germination rates and final percentages could be drastically changed (at 25°C) by (a) removing the mechanical constraint from the radicle tip, (b) imposing water stress by an osmoticum, (c) stress hardening of the seeds through osmotic pretreatment, and (d) inhibiting embryo expansion by abscisic acid (ABA). All treatments showed a similar difference in germination vigor between the two lines indicating that cold sensitivity is in fact a matter of water relations rather than of phase transitions in membrane lipids. Inhibition of germination by ABA was completely abolished by removing the mechanical constraint from the radicle tip. Osmotic stress of −3 bar which quantitatively replaced this constraint in inhibiting germination also restored the sensitivity to ABA. It is concluded that all these treatments act on the balance between the hydraulic extension force of the embryo radicle and the opposing force of the seed layers covering the radicle tip. The difference in cold sensitivity between the two seed lines resides either in the osmotic potential or the pressure potential of the germinating embryo.     

温度和水分及盐分胁迫对银沙槐种子萌发的影响

利用控制实验研究了温度、湿度、干旱和盐分胁迫等生态因子对银沙槐种子萌发的影响,以探索银沙槐种子对各种生态因子的适应性。结果显示:(1)银沙槐种子在20℃、25℃恒温和15℃/25℃、20℃/30℃、10℃/20℃变温环境中的发芽率较高且无显著差异,其在20℃恒温、15℃/25℃、20℃/30℃变温条件下的发芽指数较高,但差异不显著。(2)土壤含水量在1%～5%之间,各水分处理间种子发芽率差异显著(P<0.05),而在5%～25%间种子发芽率变化不显著。(3)盐胁迫和水分胁迫对银沙槐种子的萌发均有明显的抑制作用,可显著降低种子萌发率(P<0.05);种子发芽指数和活力指数均随渗透势和NaCl浓度增大而显著减小(P<0.05);恢复萌发率随渗透势和NaCl浓度的增加而显著增加(P<0.05)。研究发现,银沙槐种子萌发最适温度为20℃恒温和15℃/25℃变温,最适土壤含水量为10%～25%;种子萌发对盐分和干旱胁迫表现出不同程度的耐受性,萌发过程中主导抑制因素为渗透胁迫,离子毒害作用甚微;银沙槐种子休眠机制和萌发特征表现出它对生境的良好适应性。     

γ-氨基丁酸浸种对番茄种子及幼苗耐盐性调节的生理机制

以番茄‘金棚一号’为材料,研究了外源γ-氨基丁酸(GABA)浸种处理对NaCl胁迫下种子萌发及幼苗生长和生理代谢的影响。结果显示:(1)NaCl胁迫显著抑制了番茄种子的萌发和胚根生长,同时导致番茄幼苗体内活性氧(O2.-、H2O2)大量积累,膜脂过氧化程度加重,幼苗叶片光合系统Ⅱ活性显著降低,幼苗的生长受到严重抑制。(2)外源GABA浸种能够显著提高盐胁迫下番茄种子的萌发和胚根的生长,并以10.00mmol.L-1 GABA浸种处理效果最好。(3)外源GABA浸种处理显著提高了NaCl胁迫下番茄幼苗根系和叶片抗氧化酶(SOD、POD和CAT)活性,降低了活性氧(O2.-、H2O2)的产生和膜脂过氧化程度,通过维持较高的光合系统Ⅱ活性,促进了幼苗的生长及生物量积累,但GABA的缓解效应存在较大的浓度差异,其中以10.00mmol.L-1 GABA处理效果较好。研究表明,10.00mmol.L-1 GABA浸种处理能够通过促进番茄种子萌发和幼苗生长来缓解盐胁迫的伤害。     

Low Pressure and Ethylene in Lettuce Seed Germination

The extent and manner of ethylene involvement in germination of lettuce (Lactuca Sativa L. cv. Mesa 659) seed at a moderate temperature (20°C) were investigated. Inhibition of germination at low pressure of 150 mmHg in an oxygen flow-through system was alleviated to a marked extent by ethylene. Carbon dioxide was ineffective by itself but caused further alleviation of inhibition in presence of ethylene and oxygen. Other seed treatments which partially alleviated the inhibition caused by low pressure included soaking in 10μM of fusicoccin and a prior treatment with acetone. Of the two ethylene adsorbents used, Purafil was more effective in inhibiting germination in a closed container. Although the ethylene biosynthesis inhibitor, 8-hydroxyquinoline (1.0 mM). showed no effect on ethylene production, it markedly inhibited germination and the effect was partially reversed by ethylene and GA₃. An ethoxy analog of rhizobitoxine, on the other hand, had little or no effect on germination but strongly inhibited the ethylene production. Although no causal relation of ethylene to germination was established, the evidence presented here implicates ethylene, together with other gases, in the regulation of germination.     

不同温度条件下水稻种子活力QTL的定位分析

为了揭示基因型与环境温度之间的互作对种子活力的影响,利用1个粳籼交来源的重组自交系群体,采用纸卷法在15、20和25℃条件下进行发芽试验,考察了发芽率、芽长、根长及干重等4个种子活力相关性状。结合一张含有198个DNA标记的连锁图谱,用作图软件QTL Mapper1.0定位与种子活力相关的QTL。共检测到34个主效应QTL。这些QTL中的绝大多数(82％)成簇分布于第3、5和8号染色体的5个不同染色体区段上,分别被命名为QTL qSV-3-1、qSV-3-2、qSV-5、qSV-8-1和qSV-8-2。其中,QTL qSV-3-1、qSV-3-2和qSV-8-1对种子活力的效应大小和方向在3个温度条件下均较一致;而QTL qSV-5和qSV-8-2主要在20和25℃条件下起作用,在15℃低温条件下作用甚微或不起作用。表明种子活力QTL具有显著的基因型与环境温度之间的互作,而且这种互作具有明显的QTL特异性。芽长是唯一同时受5个与种子活力高度相关的染色体区段共同影响的指标,因此,相对而言,作为水稻种子活力的测定指标,芽长是最具有代表性的。     

Mechanical Resistance of the Seed Coat and Endosperm during Germination of Capsicum annuum at Low Temperature

Decoated pepper (Capsicum annuum L. cv Early Calwonder) seeds germinated earlier at 25°C, but not at 15°C, compared to coated seeds. The seed coat did not appear to impose a mechanical restriction on pepper seed germination. Scarification of the endosperm material directly in front of the radicle reduced the time to germination at both 15°C and 25°C.

The amount of mechanical resistance imposed by the endosperm on radicle emergence before germination was measured using the Instron Universal Testing Machine. Endosperm strength decreased as imbibition time increased. The puncture force decreased faster when seeds were imbibed at 25°C than at 15°C. The reduction in puncture force corresponded with the ability of pepper seeds to germinate. Most radicle emergence occurred at 15°C and 25°C after the puncture force was reduced to between 0.3 and 0.4 newtons.

Application of gibberellic acid₄₊₇ (100 microliters per liter) resulted in earlier germination at 15°C and 25°C and decreased endosperm strength sooner than in untreated seeds. Similarly, high O₂ concentrations had similar effects on germination earliness and endosperm strength decline as did gibberellic acid₄₊₇, but only at 25°C. At 15°C, high O₂ concentrations slowed germination and endosperm strength decline.

     

臭椿种子萌发最适条件研究

采用不同浓度赤霉素(GA3)处理臭椿种子,在不同温度及不同光照条件下,研究了GA3、温度及光照对臭椿种子萌发的影响。结果表明,40 mg.L-1的GA3质量浓度、30℃温度以及自然光暗交替处理为臭椿种子萌发的最适条件,臭椿属于喜高温型种子。     

Transcriptome Sequencing and Analysis of Chilling Tolerance Mutant Tomato under Low Temperature

Russian Journal of Plant Physiology - Τhe tomato plant (Lycopersicon esculentum Mill.) is particularly vulnerable to chilling injury. Hence research on screening out the cold-resistance gene...     

Examination of the Possibility of the Involvement of the Alternative Respiration in Seed Germination

The possibility that the alternative respiration (AR) is involvedin seed germination was followed during and after imbibitionby noting the changes in the sensitivity to the respiratoryinhibitors, KCN and salicylhydroxamic acid (SHAM). This wascarried out by measuring oxygen uptake of mitochondrial preparationsfrom storage cotyledons and of the whole axis in a selectionof legumes (Vigna mungo, V. radiata, V. angularis, V. sinensisPhaseolus vulgaris, Pisum sativum and Dolichos lablab). Theextent of participation of AR in the respiration of cotyledonarymitochondria was variable according to species and time afterimbibition, and varied even within the same genus ( Vigna).In some species, AR was not observed. As to the axis, SHAM treatmentby itself had little effect on the rate of respiration, but,when applied with KCN, reduced oxygen uptake to an extent greaterthan KCN treatment alone. It was suggested that AR was not necessarilyimportant for seed germination. Key words: Alternative respiration, mitochondria, seed germination     

Vigna Radiata Seed Germination under Salinity

Salinity reduced mung bean (Vigna radiata Wilczek) radicle and root elongation, delayed and inhibited hypocotyl elongation and mobilization of reserves from the cotyledons to the embryo axis. Fresh and dry masses and water content of the embryo axes were reduced. Under salinity, a net leakage of K to the media increased with time and increasing NaCl concentrations. Sugars present in the cotyledons of seeds were of primary importance for growth of the embryo axis upto 18 h after sowing whereas breakdown of starch by amylase contributed later, the contribution being delayed and reduced with increasing NaCl concentration. Even when amylase activity in the cotyledons was progressively reduced with increasing NaCl concentration, the increasing contents of soluble sugars in the cotyledons indicated that sugars were not limiting for mung bean seedling growth under salinity.     

Tomato Seed Germination. Osmotic Pretreatment and Far Red Inhibition

At 25 °C germination of tomato (Lycopersicon lycopersicum)seeds is inhibited by continuous and intermittent far red illumination.It is also inhibited by a single 30 min far red irradiationgiven 8 h from the start of imbibition. The incubation of seedsin a mannitol solution inhibitory for germination has no effecton the final germination percentage after seeds are subsequentlytransferred to water. A 30 min far red irradiation at the timeof transfer results in partial inhibition of germination. Thisinhibition can be released by the continuation of osmotic incubationfor several days before the transfer to water. At the end ofa 7 d dark period of osmotic incubation, inhibition of subsequentgermination in water can be realized only by continuous farred illumination. Seeds osmotically pretreated for 7 d and afterwardsdried-back show a mean time to 50% germination significantlylower than that of untreated seeds. Moreover, besides singleand intermittent, even continuous far red light has no inhibitoryeffect on the germination of these seeds. It is concluded that,in addition to the already known germination advantages, osmoticpresowing treatment also induces the ability of seeds to germinateunder unfavourable light conditi.     

The Genetic Control of Time to Germination in Tomato

The time to germination of seeds derived from crosses betweenLycopersicon pimpinellifolium and five varieties of L. esculentumwas analysed in the F₁ and F₂2 generations and in seeds derivedfrom inter-crossing the F₁ hybrids. Inheritance of time to germinationwas largely additive and closely related to seed size. Therewere marked maternal and paternal effects particularly whereL. pimpinellifolium was involved. Variation in time to germinationcould easily be modified by selection but probably at the expenseof seed size and embryo size at emergence. Seed characteristicsare a compromise between the contending advantages of size atemergence, rapidity of germination, and the number of seedsproduced.