濒危植物西康玉兰种子休眠、萌发及贮藏特性

研究了西康玉兰(Magnolia wilsonii)种胚的形态大小,温度、层积、硝酸钾、浸种处理和GA_3对种子休眠及萌发的影响.通过将种子脱水至不同含水量和在两种温度(4℃和一20℃)下贮藏100 d后测其生活力,分析各处理对西康玉兰种子活力的影响.结果表明:西康玉兰种子胚尚未分化完全,需经过低温层积完成生理后熟;低温层积和GA3可打破种子休眠.种子最适萌发温度为25/20℃.由此推测,西康玉兰种子具有形态生理休眠特性.西康玉兰种子当含水量降至5.39%,存活率为53.50%.不同含水量的种子贮藏在-20℃条件下,100 d后种子全部死亡;但在4℃下含水量为10.31%的种子存活力高达76%.因此,西康玉兰种子极可能属于中间性种子,其适宜贮藏环境为4℃下的干藏或湿藏.     

外源激素在西洋参种胚后熟中的作用研究

西洋参(Panax Quinquefolium L.)种胚需经形态后熟和生理后熟后才能萌发.经过激素(GA100ppm+KT50ppm+BA20ppm)处理的西洋参种子,在后熟过程中鲜重增加,β—淀粉酶活性增强,过氧化物酶活性保持较高水平.在生理后熟期,可溶性蛋白量逐渐增多.激素处理加速了胚体内物质的分解和合成,促使胚迅速发育和分化,缩短了种胚完成形态和生理后熟的时间,使种子提早一年萌发.     

不同发育时期水曲柳种子的形态生理变化及其层积处理后的萌发效应

探讨不同发育时期水曲柳种子的外部形态和生理变化及其层积处理后的萌发效应结果表明：水曲柳开花120d后为成熟脱水阶段,开花110d后种子的胚长和胚乳干重趋于稳定,花后110～120d期间种子胚干重趋于稳定;花后70～100d采集的种子不耐层积,层积处理后逐渐死亡,花后110d采集的种子经层积处理后可以萌发;110d后采集的水曲柳种子经暖温（20℃）16周＋低温（5℃）12周的层积处理后,其休眠破除的效果较好,适当延长暖温层积时间有利于提高种子萌发率。     

濒危植物巴东木莲种子休眠与萌发特性的研究

巴东木莲(Manglietia patungensis)为我国特有种, 属国家重点保护植物。为找出其生殖环节中的致危因素, 作者对巴东木莲种子休眠与后熟过程中的形态和萌发特性进行了研究。结果表明, 巴东木莲种胚发育不完全可能是种子休眠的主要原因, 在其后熟过程中胚不断分化、发育成熟; 种皮具有较好的透性, 与休眠的关系不大; 种子不同部位均存在萌发抑制物, 胚乳中高含量的萌发抑制物是影响胚萌发的重要因素。内源激素ABA和IAA在巴东木莲种子休眠与萌发过程中起着重要作用, ABA是引起休眠的关键因素, IAA有助于种子的萌发, IAA/ABA相对含量的变化对种子的休眠和萌发产生重要影响。巴东木莲种子的休眠是由种子本身的形态和生理特点引起的综合休眠, 在4℃低温保湿条件下才能完成其形态和生理后熟过程, 而自然条件下, 巴东木莲种子成熟时正值秋季少雨, 很容易失水而不能完成其后熟过程而失去生活力, 这可能是导致该物种自然更新困难的重要原因。     

南川升麻种子休眠与萌发的研究

南川升麻（ＣｉｍｉｃｉｆｕｇａｎａｎｃｈｕａｎｅｎｓｉｓＨｓｉａｏ）的种子自然脱落时尚处于球形胚发育阶段,需要长时间的越冬过程才能完成胚的后熟。室内采用低温湿润或不同浓度的ＧＡ３处理,可以不同程度地加快其胚的后熟过程。休眠种子用０．１ｇ／ＬＧＡ３处理１周后,在低温（１～５℃）湿润条件下存放约９０ｄ,萌发率可达到７０％以上。     

野生鸭儿芹种子休眠特性及破除方法

鸭儿芹种子具有休眠特性,且休眠期长,不经任何处理的种子很难萌发,影响其人工种植。研究了鸭儿芹种子的休眠特性和解除休眠的最佳方法,为我国人工种植野生鸭儿芹提供理论依据。结果表明:TTC法对种子活力的测定表明有活力的种子为(55.33±3.71)%;切破种皮种子与完整种子吸水率在前12 h相差较大,但最终吸水率相差不大,分别达到(70.00±1)%和(68.32±0.32)%,表明种皮并不阻碍种子吸水;种子中存在内源抑制物,其粗提液在较低浓度下即可抑制芹菜种子的萌发;鸭儿芹种子成熟时胚未分化完全,胚率为(28.65±2.488)%,经过低温处理后完成后熟,胚率达到(65.93±3.86)%,萌发率达到100%,因此鸭儿芹种子具有形态生理休眠特性。清水浸种和低温冷藏共同处理可有效解除其休眠,浸种和低温冷藏具有交互效应,浸种36 h、5℃冷藏30d即可解除其休眠,萌发率达到100%,发芽势达到(91.11±0.91)%。已破除休眠的种子适宜其萌发的温度范围扩大(15.0—27.5℃),而且在土壤中也可较好地萌发,萌发率达到(96.67±3.33)%,发芽势达到(71.11±1.93)%。     

山茱萸种子的休眠原因与萌发条件

山茱萸种子的萌发受到种皮抑制物、胚生理后熟程度以及当年低温的阻抑。种子秋播后需经3个月高温(15～22℃)、2个月低温(5～16℃)的湿沙层积,才能完成生理后熟,于次年春天萌发。并研究了种子层积过程中氧的作用、种皮的单宁和ABA含量、胚乳转化、G6PDH(6—磷酸葡萄糖脱氢酶)和 6PGDH(6—磷酸葡萄糖酸脱氢酶)与萌发的关系。     

大百合种子休眠特性及休眠破除

对哀牢山自然保护区大百合种子休眠原因、休眠破除方法进行了研究,为大百合的种子繁殖提供理论与技术依据.结果表明:大百合种子休眠的主要原因是胚发育不全,种子休眠类型为复杂的形态生理休眠.温度是影响胚生长和分化的主要因素,经高温到低温的变温[25℃/15℃(60 d)→15℃/5℃(60 d)→4℃(50 d)]层积处理,种子可完成后熟而萌发,所需时间约170 d,比自然条件下层积所需时间缩短了11～12个月.     

五种野生栒子种子的休眠与快速萌发

经浓硫酸处理解除种壳机械束缚力,和250ppmGA浸种及2～4℃冷湿处理打破种子生理休眠后的5种野生枸子,其有胚的种子均100％发芽,萌发整齐、迅速,3～7d内即完成;包括种子预处理时间在内,不超过4个月就可获得幼苗。解除休眠的种子,其萌发温度范围很宽,在3～25℃内均可萌发。     

药用植物种子生物学特性的多样性(摘要)

本文对药用植物种子形态结构多样性、休眠习性的多样性、萌发习性的多样性进行了研究。1　药用植物种子形态和结构的多样性(1 )种子外部形态的多样性 ;(2 )种子内部结构的多样性 :①种皮结构的多样性 ;②胚的结构多样性 ;③胚乳的多样性。2　药用植物种子休眠习性的多样性(1 )种皮休眠 ;(2 )胚休眠 :①胚未完全分化引起的休眠 ;②生理休眠。3　药用植物种子萌发习性的多样性(1 )低温型种子 ,萌发最适温度 1 5℃左右。(2 )中温型种子 ,萌发最适温度 2 0～ 2 5℃。(3 )高温型种子 ,萌发最适温度 3 0℃。(4)变温型种子 ,萌发要求有昼夜一定变化…     

THE EFFECT OF THE INTERACTION OF TEMPERATURE WITH AFTER-RIPENING REQUIREMENT AND COMPENSATING TEMPERATURE ON GERMINATION OF SEED OF FIVE SPECIES OF ROSA

Seeds of 5 rose species, Rosa multiflora Thunb. ‘Cathayensis,’ R. × reversa Waldst. & Kit., R. setigera Michx. ‘Beltsville,’ R. setigera Michx. ‘Serena,’ and R. wichuraiana Crepin, varied in after-ripening requirement from 30 days at 4.4 C for R. multiflora to 90 days for R. setigera ‘Serena.’ The compensating temperature varied from near 12.8 C for R. × reversa to a value near 29.4 C for R. setigera ‘Beltsville.’ In this report compensating temperature is used to describe that temperature at which mature, moist seed does not germinate, after-ripening does not take place, and dormancy does not change. Seed germination was reduced by interruption of the after-ripening period with intervals at temperatures above the compensating temperature. The interruptions were more effective in reducing germination when more frequent and when the temperature during the interval was higher. Species differed in their sensitivity to high-temperature reduction of germination. Those having the longest after-ripening requirement were most sensitive. Germination of seeds which had the minimum after-ripening treatment was repressed more by high temperature than germination of those seeds which had an excess of after-ripening. The decrease in germination resulted from imposition of a secondary dormancy of the embryo, and probably also from reversal of the after-ripening effect upon the primary dormancy imposed by the seed coat.     

Possible involvement of volatile compounds in the after-ripening of cocklebur seeds

The mechanism of emergence from primary dormancy, the process of after-ripening, in cocklebur (Xanthium pennsylvanicum) seeds was examined in relation to the involvement of volatile compounds and to the relative humidity (RH) in which the seeds were stored. The after-ripening of these seeds proceeds only at water contents between 7 and 14% which are conditioned under RHs of 33% to 53% and are identified with water-binding region II. After-ripening of cocklebur seeds occurred even in water-binding region I. imposed by 12% RH. when exposed to HCN gas during the storage period. Exposure of dormant seeds to acetaldehyde (ethanal) retarded after-ripening. even in water-binding region II. thus decreasing germinability. This decrease of germinability by ethanal was found also in the after-ripened seeds, suggesting that ethanal accelerates seed deterioration rather than retarding the after-ripening. The contents of ethanal. ethanal and HCN were high only in the dormant seeds held at 12% RH. Regardless of RH. a possible conversion of ethanal to ethanol. perhaps via alcohol dehydrogenase. was far larger in dormant than in non-dormant seeds. In contrast, the reverse conversion of ethanol to ethanal was more profound in non-dormant seeds. Pre-exposure of both types of seeds to HCN reduced the contents of both ethanal and ethanol at 12% RH. The contents of various adenylales including ATP in seed tissues were higher in dormant seeds stored at 12% RH than in non-dormant seeds after-ripened at 44% RH. It is suggested that emergence of cocklebur seeds from primary dormancy by HCN treatment at 12% RH may result from the reduction in the contents of ethanal via an unknown mechanism incurring the consumption of ATP. This implies involvement of volatile compound metabolism at the water-binding region II in the after-ripening process of cocklebur seeds.     

PHOTOCONTROL OF DEVELOPMENT OF EXCISED ERAGROSTIS EMBRYOS

• 1 Both the germination of intact seeds and the development of excised embryos depend on their after-ripening. Shortly after the harvest, the intact seeds of Eragrostis ferruginea are in dormancy and germinate neither in the light nor in the dark. The ability of seeds to germinate under both conditions, however, gradually increases with the progress of after-ripening. The development of excised embryos, on the other hand, is readily induced in the light and dark even shortly after the harvest. As the after-ripening proceeds, however, the ability of excised embryos to develop gradually decreases and is finally lost 18 months after the harvest. The after-ripened embryos whose ability to develop is completely reduced become light sensitive again when they are supplied with the yeast extract of a low concentration, and develop readily even in darkness at a high concentration of the extract.
• 2 The photorequirement for development of excised embryos is scarcely affected by oxygen concentrations, and the embryo growth can take place equally in both light and darkness in the atmosphere containing 100 to 10 percent of air, while it can not be induced in pure nitrogen.
• 3 The promotion of embryo development by light is observed at the time when the ability of embryos to develop declines. The effectiveness of the irradiation is very similar to that in intact seed germination.

     

Variation in the loss of seed dormancy during after-ripening of wild and cultivated rice species

BACKGROUND AND AIMS: The aim of this paper was to verify the variation in the loss of seed dormancy during after-ripening and the interspecific and interpopulation variability in the degree of dormancy of seven wild and two cultivated rice species comprising 21 populations and two cultivars. METHODS: Four wild rice species from South America, Oryza glumaepatula, O. latifolia, O. grandiglumis and O. alta, and two O. sativa cultivars were tested in one experiment. In a second experiment, five wild species, O. punctata, O. eichingeri, O.rufipogon, O. latifolia and O. glumaepatula, and one cultivated species (O. glaberrima) were evaluated. Initial germination tests were performed soon after the seeds were harvested and subsequently at 2-month intervals, for a total of six storage periods in the first experiment and three in the second. All tests were conducted in the dark at a temperature of 27 degrees C. KEY RESULTS: Different patterns of after-ripening among populations within and between species were observed. CONCLUSIONS: The cultivated species (O. sativa and O. glaberrima) and, amongst the wild species, the tetraploids O. latifolia, O. grandiglumis and the diploids O. eichingeri and O. punctata, had weak dormancy, losing it completely 2 months after harvest, while O. rufipogon and O. glumaepatula exhibited pronounced dormancy. The latter showed different patterns of after-ripening between populations indigenous to the Amazon region and those originating in the Paraguay River system. Seeds of Solimoes (Amazon) and Japura origin showed weak dormancy whereas those of Paraguay origin showed deep dormancy. Ecological differences among natural habitats may be involved in such differentiation.     

PHYSIOLOGY OF LIGHT-REQUIRING GERMINATION IN ERAGROSTIS SEEDS

The photorequirement for the germination of Eragrostis seedsdecreases with the progress of their after-ripening, and thegermination occurs whether in continuous light or in darknessat the final stage of after-ripening. The dehydration of seedsor the puncturing of seed coats also results in a decrease ofphotorequirement for germination. The rate of water absorptionof seeds increases with the germination capacity under continuousdark condition. However, there is no correlation between therespiration rate and the germination capacity; respiration isstimulated in the punctured seeds, but not in the after-ripenedseeds. The after-ripened or punctured seeds which no longer have aphotorequirement become light-sensitive again, when they areallowed to germinate in the air of low oxygen concentrations.The assumption is presented that the permeability to oxygenof the seed coat may be a factor controlling the seed germinationof this species. (Received August 21, 1964; )     

Effects of after-ripening and gibberellic acid on the thermoinduction of seed germination in Solarium melongena

Daily alternating temperatures or a short exposure to low orhigh temperatures were necessary for the germination of eggplantseeds at the initial stage of after-ripening. But requirementsbecame less strict with the progress of after-ripening, andafter 4 to 8 months of afterripening, germination occurred easilyboth at constant (20 and 25) and daily alternating temperatures(30 for 16hrs and then 20 for 8hrs). With further progress in after-ripening, however, daily alternatingtemperatures or a short exposure to low or high temperaturesbecame again indispensable for attaining a high percentage ofgermination. The progress of after-ripening was greatly influencedby the degree of seed ripening, that is, by the period beforethe seeds were sampled from fruits after anthesis (ripening). The effect of GA on the germination of egg plant seeds varieddepending on the concentration of GA, temperature and the degreeof maturity (ripening and after-ripening) of the seeds. (Received March 8, 1968; )     

A Physiological Study of Embryo Development in Heracleum sphondylium L: II. The Effect of Temperature on After-ripening

The action of low temperature in the after-ripening of seedsof Heracleum sphondylium is to make available the endospermreserves, without which the embryo is starved at room temperature.There is no development of 'secondary dormancy' in the embryo,since the effect of low temperature in after-ripening is strictlyadditive, and the total length of low-temperature treatmentrequired for germination is in no way influenced by periodsat room temperature before or during after-ripening.     

Effect of Hormones on Embryo After-Ripening of Panax ginseng G. A. Mey. Seeds

Panax ginseng C. A. Mey seed has a deep dormancy for the morphologica and physiological after-ripening of embryo. This paper described the changes of some enzymic activities and of soluble-protein content during after-ripening of seeds, in the first stage of morphological after-development the activities of amylase, peroxidase and catalase increased gradually, whereas the soluble-protein content decresed rapidly. A high level of enzymatic activities and increasing protein content were also observed, indicating vigorous metabolism in physiological after-ripening of seeds. Hormone treatment increased the activities of the above-mentional enzymes, promoted the development and differentiation of embryo, causing the time of seeds germination one year earlier than that of untreated ones.     

Effects of SO2 on Photosynthesis and Nitrogen Fixation

Spikelets of Themeda triandra are dormant when mature and require an after-ripening period in dry storage of approximately 12 months before full germination potential is realized. Successful germination of spikelets entails the splitting of the tough upper glumes by radicles. Dormany appears to result from a combination of embryo dormancy and mechanically resistant glumes. Glume removal from dormant spikelets increases germination while glume removal plus gibberellic acid increases germination even more. During the after-ripening period, the growth potential of spikelets and caryopses increases as measured by their ability to germinate in the presence of the osmoticum polyethylene glycol 6000. The inhibition of germination by decreasing osmotic potential of the germination medium significantly interacts with the promotion caused by gibberellic acid indicating that both factors affect germination by altering the growth potential of the embryos. The increase in growth potential during after-ripening is probably related to the synthesis of gibberellin-like substances. It is hypothesized that dormancy breaking during after-ripening occurs because the growth potential of embryos increases and this consequently increases the ability of radicles to split the upper glumes during germination.