毛决明种子不同发育时期发芽力和脱水耐性的初步研究

毛决明种子发芽力在花后39d后逐渐上升,发芽率和发芽指数在花后53d,活力指数在花的67d最大值,而后有所降低,花后39-74d,含水量逐渐下降,但下降速度不等,花后67d种子干重达到最大值,花后67-74d含水量显著下降,花后39-74d,含水量逐渐下降,但下降速度不等,花后67d种子干重达到最大值,花后67-74d含水量显著下降。种子存在明显的成熟脱水阶段。种子的脱水耐性在花后46-60d逐渐增强,60d达到最大值,后有所下降,轻微脱水可显著提高花后46d和67d的种子的发芽率,花后60-67d的种子能忍耐10%含水量,毛决明种子极可能是正常性种子。     

不同发育时期黄皮种子脱水敏感性的研究

自花后４６ｄ到８８ｄ果实成熟．黄皮种子的发芽率由０升至１００％．而活力指数逐渐上升,到花后７４ｄ达到最大值,之后略有下降．每粒种子的呼吸强度在花后４６－６７ｄ持续增加,此后则渐渐减弱,但湿藏２ｄ后又回升．黄皮种子的发育明显超前于果实．花后７４ｄ时．每粒种子的干重已接近最大值,这时种子活力最大．而果实的鲜重虽然已接近最大值．但其干重却只有成熟时的７３％。花后４６－５３ｄ的种子,其发芽率小于１００％,轻微脱水能提高种子的发芽率及活力指数,花后６０ｄ至果实成熟．种子发芽率均为１００％．这时任何程度的脱水都会引起活力指数的下降,但不同发育时期的黄皮种子耐脱水力有差别．其中以花后６７ｄ的耐脱水力最强．花后８８ｄ果实成熟时种子的耐脱水力最弱。     

九里香种子脱水耐性和萌发生理的研究

九里香种子自花后 42～ 77d,含水量和电导率逐渐降低 ,种子干重、发芽率、发芽指数和活力指数逐渐增加。硅胶脱水 1～ 6d后 ,种子含水量下降 1 0 %～ 3 5 % ,发芽率、发芽指数和活力指数均有不同程度的降低 ,不同发育时期九里香种子的脱水耐性有别 ,花后 42～ 70d不断增强 ,77d有所减弱。花后 70d的种子含水量降至 1 0 % ,种子发芽率无明显降低 ;含水量为 9%的种子在 4°C和 2 0°C的低温条件贮存 3 0d和 42d ,多数种子仍能萌发 ,这表明九里香种子是一种正常型种子。光照能促进种子的萌发 ;在 2 0～ 3 0°C、室温和 2 0 /3 0°C变温条件下种子萌发较好 ;光照和温度对种子萌发有单独影响 ,但又相互作用 ,同时光照对萌发的影响还与种子含水量有关。     

白木香种子脱水耐性的发育变化及贮藏特性

研究白木香种子发育进程中种子性状、萌发能力和脱水耐性的变化,以及不同光温条件对种子萌发的影响和种子的贮藏特性。结果表明：白木香种子在花后78d获得最大干重,进入生理成熟期,此时萌发率接近最大值;胚在花后57～85d,脱水耐性逐渐增强,并在花后85d获得最大脱水耐性。种子萌发的适宜温度范围为25℃-35℃,光照对种子萌发有一定的抑制作用。新鲜自木香种子（含水量27．45％）在4℃低温条件下贮藏1个月后萌发率仅为30％左右,而含水量7．38％的干燥种子在4℃低温条件下贮藏120d,萌发率仍有53．33％,因此,4℃低温和适度脱水有利于种子短期贮藏。白木香种子能忍耐一定程度的脱水,但干燥至含水量7．50％以下时种子会发生损伤,因此推测白木香种子是一种中间性种子。     

假槟榔种子脱水耐性的发育变化

对假槟榔（Archontophoenix alexandrae）种子和胚发育过程中脱水耐性的变化、不同脱水速率对脱水耐性的影响及种子的萌发和贮藏特性进行了研究。种子含水量在花后55～70d逐步降低,随后不再变化,并保持在较高水平（37％）;花后90d的种子获得最大干重。花后60d后种子获得萌发能力,花后70d达到最大值。在交替光照下（14h光照,10h黑暗,12μnmol m^-2s^-1）,种子在15℃～40℃下均能萌发,其萌发的适宜温度范围为30℃～35℃;但光照对种子的萌发有较大的抑制作用。种子和胚在花后55～90d,脱水耐性逐渐增强;花后90d种子和胚的脱水耐性最强,此时种子和胚的半致死含水量分别为0．18g／g和0．3g／g。脱水至相同含水量,快速脱水的种子的存活率明显高于慢速脱水。无论是否进行脱水处理,-18℃下贮藏1个月后,种子均丧失萌发能力;在4℃,10℃和15℃下,适度脱水能延长种子的贮藏寿命。假槟榔种子不耐脱水,不适合在低温、低含水量条件下长期贮藏,属顽拗性种子。     

成熟度与烘干温度对结球甘蓝种子质量的影响

以结球甘蓝品种冬升种子为材料,研究了不同成熟度和烘干温度下种子秕粒率、千粒重、发芽率、生理活性情况以及不同烘干温度下种子的含水量.结果表明,结球甘蓝冬升开花后45～55 d采收的种子,发芽率均达到了95%以上;随着种子成熟度提高,其种子质量、发芽活力及其超氧化物歧化酶(SOD)、过氧化物酶(POD)、脱氢酶活性显著上升,而相对电导率显著下降.与对照(自然风干)相比,30～50℃的烘干温度对种子千粒重和秕粒率无显著性影响,也仅在50℃下可使种子的发芽活力显著降低;随着烘干温度的升高,种子的SOD、POD和脱氢酶活性逐渐显著下降,相对电导率则逐渐显著上升;30～50℃烘干6 h种子的含水量由13.3%降至5.4%左右.研究发现,结球甘蓝冬升开花授粉后45 d种子已达到了采收程度,30～50℃烘干6 h种子含水量已达到储藏要求,并且愈接近自然干燥温度(30～40℃)的处理,种子发芽能力愈好;甘蓝种子活力与其SOD、POD和脱氢酶活性呈正相关,而与其相对电导率呈负相关.     

不同发育时期小麦种子活力的变化及其对环境温度的响应

以济麦22和山农23号为试验材料,利用标准发芽试验法对不同年份小麦种子发育过程中的种子活力变化进行研究,分析环境温度对不同发育时期小麦种子活力变化的影响,为早期小麦种子的利用及高活力种子的生产提供参考依据.结果表明: 伴随着小麦种子发育,鲜种子在花后26 d左右出现发芽能力,之后其发芽率整体呈上升趋势;干种子发芽势、发芽率和发芽指数在花后5～8 d迅速升高,之后保持相对稳定,活力指数主要受到幼苗单株干质量的影响而持续升高,一般在完熟前4～6 d达到最大值;不同发育时期小麦干种子的田间种植及其后代种子的活力测定表明,济麦22花后17 d以后的干种子田间出苗较好,并可成穗结实,其后代种子的发芽率和活力指数在不同样品间无显著差异.环境温度对不同发育时期小麦种子活力变化的影响显著,小麦花后日平均温度均值、日最高气温均值以及日最低气温均值均高,且花后日温差均值大的年份,种子发育时间短、百粒重及种子活力达到最大值的时间较早;反之,发育时间较长、百粒重及种子活力达到最大值的时间较晚,但完熟期积温高,种子活力较高.     

小芸木胚发育过程中脱水耐性的变化

对热带植物小芸木的种子和胚在整个发育阶段的形态学特征、含水量、萌发率和电导率进行了研究。结果显示:(1)小芸木种子在发育过程中形态学特征、电导率、萌发率和胚的脱水耐性有明显的变化;(2)在55~80 d种子鲜重和干重逐渐增加,随后又稍微降低,整个发育过程未经历明显的成熟脱水阶段;种子萌发率从55~85 d逐渐达到最大,随后又稍微降低;(3)胚的脱水耐性从55~90 d逐渐增加,于85~90 d达到最大,在95~103 d时又有所下降。表明小芸木胚的最大脱水耐性的获得时间与种子干物质积累达到最大的时间一致。     

元江干热河谷木棉蒴果形成和纤维发育过程

采取石蜡切片和扫描电子显微镜等方法研究了元江干热河谷木棉蒴果形成和纤维发育过程.结果表明: 木棉蒴果形成过程分为4个阶段: 花后0～5 d为形成期(FS),5～35 d为质量增加期(MGS),35～50 d为缓慢生长或脱水期(DS),50 d以后为成熟爆裂期(BS).与木棉蒴果形成过程相对应的纤维发育过程为:果皮内壁细胞分化(花后0～2 d)、膨大(花后2～5 d)、突起(花后5～10 d)、纤维伸长(花后10～40 d)、纤维脱离内壁及脱水成熟(花后40～50 d).在纤维发育过程中,纤维长度和投影宽度均呈幂函数曲线增长,花后第20天日均增长率达到最大.纤维鲜质量呈先增加后下降的趋势,花后25～30 d日均鲜质量增长率达到最高,而纤维干质量呈逐渐增长趋势,且花后20～25 d纤维干质量日均增长率达到最高.花后第30天,木棉种子和纤维质量继续增加,而果皮呈现下降趋势,表明果皮开始脱水老化.木棉纤维在蒴果壳体内壁的附着力小,较棉花等种子纤维更容易分离.花后5～35 d是蒴果生长和纤维发育最关键的时期,需做好水肥管理;而花后50 d后果实开始爆裂,需做好采收准备.     

木波罗种子脱水敏感性与膜脂过氧化的研究

刚采收的木波罗种子含水量为５８．６％。随着含水量下降,种子的发芽率和发芽指数迅速下降,种子对脱水非常敏感,是典型的顽拗性种。自然脱水时,种子胚轴和子叶中超氧物歧化酶的活性先上升,然后下降,丙二醛和脂质氢过氧化物的含量显著增加。其脱水敏感性的原因可能是当种子脱水时,植物酶ＳＯＤ的活性下降,膜脂过氧化作用加强,从而使膜的结构和功能受到破坏,种子生活力丧失。     

聚乙二醇（PEG）浸种对茎瘤芥老化种子活力及其幼苗生长的影响

茎瘤芥品种‘永安小叶’老化种子经聚乙二醇（PEG）浸种后,其种子活力和幼苗生长与PEG浓度有一定的相关性,不同浓度PEG浸种后的茎瘤芥种子膜透性均降低,种子发芽率、发芽势、发芽指数和活力指数增大,幼苗根干重、茎干重和根长也均增大,幼苗叶片中丙二醛（MDA）含量降低。幼苗生长与种子活力的变化趋势一致,PEG浓度小于30%时呈增大趋势,大于30%时呈减小趋势,但均大于不做PEG处理的;幼苗叶片中MDA含量与种子膜透性变化趋势一致,PEG浓度小于25%时,呈降低趋势,大于25%时则呈升高趋势,但这些指标均低于不做PEG处理的。     

濒危植物毛柄小勾儿茶种子休眠与萌发生理的初步研究

毛柄小勾儿茶（Berchemiella wilsonii （Schneid．）Nakai var．pubipetiolata H．Qian）为中国特有种,国家三级保护植物。TTC染色法测得毛柄小勾儿茶种子的生活力较低,仅为32％,空粒和无生活力的种子分别为28％和40％,说明毛柄小勾儿茶发育完全的种子较少。种子吸水速度试验证明毛柄小勾儿茶种皮透水性较差,不利于种子萌发时对水分的吸收,发芽抑制物的生物鉴定结果表明,毛柄小勾儿茶种子的不同部位都存在发芽抑制物,且种胚中的含量最高,不利于种子的萌发,使毛柄小勾儿茶种子处于休眠状态之中。几种不同浓度GA。溶液浸种24h的预处理可以不同程度地提高毛柄小勾儿茶种子的发芽率和发芽指数,其中300mg／L GA3的效果最显著,并且300mg／L GA3的预处理可以在萌发初期（萌发前3天）显著地提高毛柄小勾儿茶种子中过氧化物酶、过氧化氢酶和脱氢酶的活性。毛柄小勾儿茶种子生活力低,且处于休眠状态,再加上与种子发芽力有关的几种酶的活性较低,致使毛柄小勾儿茶种子的发芽率较低,同时这些也是从种子萌发生理方面导致毛柄小勾儿茶濒危的重要原因。     

Water Status Changes During Development in Relation to the Germination and Desiccation Tolerance of Aesculus hippocastanum L. Seeds

Seed growth characteristics of Aesculus hippocastanum were examinedin detail during development from about 70 to 140 d after anthesis(DAA), mainly in 1988 and 1989. Mean fresh and dry weights increasedfor both the axis and the whole seed up to the time of peakseed fall at 135 DAA with no cessation before fruit abscission.Water per seed increased up to 100 DAA, after which no furtherincrease occurred; moisture content declined for the embryonicaxis and whole seed respectively from above 75 and 65% at 95DAA to 65 and 50% at 130 DAA. At fruit shedding in 1990 waterpotential values of -1·2, -2·6 and -1·1MPa were observed for the testa, cotyledon and axis tissuesrespectively; relevant sorption isotherms are presented. Decreases in seed moisture content during development were accompaniedby increases in desiccation tolerance and in germinability,both reaching their maximum at the time of peak seed fall. Atmaturity, only about 10% viability was retained on drying seedto 20% moisture content; it is confirmed that the seeds are'recalcitrant'. The exact relationship between moisture contentand germination during development was dependent on the deptof dormancy, as judged by the period of chilling required; eachduration of chilling at 2°C within the range 3-12 weeksyields a curve of sigmoid shape. No germination occurred at26°C without chilling, but nearly full germination can beobserved for samples collected at 6 weeks before maximum seedfall with 12 weeks chilling. The rate of moisture loss duringdesiccation at 15°C and 15% rh becomes reduced during development.The ontogeny of these 'recalcitrant' seeds is compared withthat of 'orthodox' seeded species and the implication of sigmoid-shapedcurves for the relationship between seed moisture content andgermination are considered.Copyright 1993, 1999 Academic Press Aesculus hippocastanum L., horse chestnut, seed development, water status, germination, desiccation intolerance, desiccation rate     

Water Relations of Seed Development and Germination in Muskmelon (Cucumis melo L.) : I. Water Relations of Seed and Fruit Development

Total water potential (ψ), solute potential, and turgor potential of field-grown muskmelon (Cucumis melo L.) fruit tissue (pericarp) and seeds were determined by thermocouple psychrometry at 5-day intervals from 10 to 65 days after anthesis (DAA). Fruit maturity occurred between 44 and 49 DAA, and seed germination ability developed between 35 and 45 DAA. Pericarp ψ was essentially constant at approximately −0.75 megapascal (MPa) from 10 to 25 DAA, then decreased to a minimum value of −1.89 MPa at 50 DAA before increasing to −1.58 MPa at 65 DAA. Seed ψ remained relatively constant at approximately −0.5 MPa from 10 to 30 DAA then decreased to −2.26 MPa at 50 to 60 DAA before increasing to −2.01 MPa at 65 DAA. After a rapid increase to 20 DAA, seed fresh weight declined until 30 DAA due to net water loss, despite continuing dry weight gain. As fruit and seed growth rates decreased, turgor potential initially increased, then declined to small values when growth ceased. A disequilibrium in ψ was measured between seeds and pericarp both early and late in development. From 20 to 40 DAA, the ψ gradient was from the seed to the tissue, coinciding with water loss from the seeds. From 50 to 65 DAA, seed ψ decreased, causing a reversal of the ψ gradient and a slight increase in seed water content. The partitioning of solutes between symplast and apoplast may create and maintain ψ gradients between the pericarp and seed. The low solute potential within the pericarp due to solute accumulation and loss of cellular compartmentation during ripening and sensecence may be involved in prevention of precocious germination of mature seeds.     

Water Relations of Seed Development and Germination in Muskmelon (Cucumis melo L.): II. DEVELOPMENT OF GERMINABILITY, VIGOUR, AND DESICCATION TOLERANCE

The germinability, vigour, and desiccation tolerance of muskmelon(Cucumis melo L. cv. Top Mark) seeds was studied in relationto changes in seed water content during development within thefleshy fruit. Seed water content (fresh weight basis) declinedfrom 91% to 42% between 10 d and 35 d after anthesis (DAA) (whenmaximum dry weight was attained), then declined more slowlyto a minimum of 35% at 50 DAA before increasing again to 43%at 65 DAA. Fresh intact seeds were first germinable at 25 to30 DAA and attained maximum germination percentages at 45 DAA.Between 15 and 35 DAA, cotyledons, hypocotyls, radicles andepicotyls of isolated embryos (testa and perisperm enveloperemoved) sequentially developed the ability to grow when incubatedon water. Dehydration to water contents less that those attainedwithin the fleshy fruit is not a requirement for developmentof germination capacity of muskmelon seeds. Seeds became tolerantof rapid desiccation after 25 DAA, and drying of immature seeds(25 to 40 DAA) increased their germination percentages uponsubsequent imbibition. Washing, drying, or washing followedby drying increased seedling vigour (root length) as comparedto fresh seeds, which had very poor vigour. Water absorptionisotherms were constructed to test whether changes in water-bindingcomponents were correlated with the development of desiccationtolerance. Isotherms for seeds older than 25 DAA fit well tothe D'Arcy/Watt model, which postulates the existence of high-affinity,low-affinity and multi-molecular water-binding sites. Desiccation-intolerantseeds younger than 25 DAA lacked the component of the absorptionisotherm characteristic of the high-affinity water-binding siteswhich have been hypothesized to confer desiccation tolerance.However, we were unable to determine whether the absence ofhigh-affinity binding characteristics was specifically relatedto desiccation intolerance or was artifactual due to the lossof volatiles when immature seed samples were dried at high temperatures. Key words: Muskmelon, embryo, germination, development, vigour, desiccation     

Water Relations of Seed Development and Germination in Muskmelon (Cucumis melo L.): VI. INFLUENCE OF PRIMING ON GERMINATION RESPONSES TO TEMPERATURE AND WATER POTENTIAL DURING SEED DEVELOPMENT

Seed priming (imbibition in water or osmotic solutions followedby redrying) generally accelerates germination rates upon subsequentre-imbibition, but the response to priming treatments can varyboth within and among seed lots. Seed maturity could influenceresponsiveness to priming, perhaps explaining variable primingeffects among developmentally heterogeneous seed lots. In thecurrent study, muskmelon (Cucumis melo L.) seeds at two stagesof development, maturing (40 d after anthesis (DAA)) and fullymature (60 DAA), were primed in 0?3 M KNO₃ for 48 h at 30 ?C,dried, and imbibed in polyethylene glycol 8000 solutions of0 to –1?2 MPa at 15, 20, 25, and 30 ?C. Germination sensitivitiesto temperature and water potential () were quantified as indicatorsof the influence of seed maturity and priming on seed vigour.Germination percentages of 40 and 60 DAA control seeds weresimilar in water at 30 ?C, but the mean germination rate (inverseof time to germination) of 40 DAA seeds was 50% less than thatof 60 DAA seeds. Germination percentages and rates of both 40and 60 DAA seeds decreased at temperatures below 25 ?C. Reductionsin also delayed and inhibited germination, with the 40 DAAseeds being more sensitive to low than the 60 DAA seeds. Primingsignificantly improved the performance of 40 DAA seeds at lowtemperatures and reduced , but had less effect on 60 DAA seeds.Priming lowered both the minimum temperature (T_b) and the minimum (_b) at which germination occurred. Overall, priming of 40 DAAseeds improved their germination performance under stress conditionsto equal or exceed that of control 60 DAA seeds, while 60 DAAseeds exhibited only modest improvements due to priming. Asthe osmotic environment inside mature fruits approximates thatof a priming solution, muskmelon seeds may be ‘primed’in situ during the late stage of development after maximum dryweight accumulation. Key words: Cucumis melo L., seed priming, germination, vigour, development, temperature     

人工老化处理对结球甘蓝种子生理生化特性的影响

以结球甘蓝品种‘冬升’种子为材料,研究高温(40℃)高湿(相对湿度100%)人工老化处理过程中种子的萌发特性、种子浸出液相对电导率和丙二醛、可溶性蛋白、可溶性糖含量以及抗氧化酶活性的变化,以揭示种子劣变的机理。结果表明:(1)人工老化处理甘蓝种子的含水量和不正常苗率均随着老化时间的延长逐渐增加,而种子发芽势、发芽率、发芽指数和活力指数的增加均逐渐降低。(2)随着处理天数的延长,老化处理甘蓝种子的浸出液电导率显著增大,浸出液可溶性糖含量逐渐升高,可溶性蛋白含量表现出显著下降趋势,而种子MDA含量呈先升高后逐渐下降的趋势。(3)在结球甘蓝种子老化进程中,其种子中SOD、POD、CAT活性变化的趋势相似,均随老化程度的加深而逐渐降低;而APX活性在老化处理的最初2d显著增加,第6天显著降低。研究发现,在结球甘蓝种子老化进程中,种子活力和萌发率显著降低,其种子浸出液电导率、可溶性蛋白含量、可溶性糖含量、保护酶活性变化与种子老化及劣变程度密切相关,膜脂过氧化作用可能是引起或加剧种子老化劣变的重要原因之一。