提高黄皮种子活力的途径

黄皮种子经脱水至40％左右或持续贮藏（一年以上）后种子活力迅速下降,PEG对劣变种子直接引发不但不能提高其活力,反而使其活力更为下降,甚至丧失萌发能力而引发加速了代谢物质的消耗和渗漏。在黄皮种子脱水前用ABA、Ca2 、茶多酚（抗氧化剂）预处理,明显降低了黄皮种子的脱水敏感性。结合用PEG引发技术,则能较大幅度提高黄皮种子脱水后的活力,Ca2 短时高温引发也能提高黄皮种子贮藏一年后的活力,说明预处理是提高脱水和贮藏后黄皮种子活力的必要措施。     

在蔗糖预培养诱导耐脱水性过程中黄皮胚轴的水分状态和可溶性蛋白含量的变化

逐步增加培养基的蔗糖浓度可提高黄皮胚轴的耐脱水性。用差示扫描量热仪（DSC）和SDS—PAGE方法探讨了黄皮胚轴在耐脱水性获得过程中的水分状态和可溶性蛋白的变化。DSC图谱显示,蔗糖预培养胚轴的升温图谱与对照不同,有比较明显的台阶式变化,有玻璃化形成的倾向;应用线性回归方程法或冰熔化热法计算黄皮胚轴的不可冻结水,发现蔗糖预培养胚轴的不可冻结水含量与对照胚轴无显著差异。蛋白分析表明,蔗糖预培养诱导黄皮胚轴中可溶性蛋白增加68％,其中尤以20kD蛋白的增幅最大。     

氰化钾预处理对黄皮［Clausena lansium（Lour.） Skeels］种子脱水敏感性的影响

比较了ＫＣＮ 预处理与未处理黄皮种子在脱水后活力的变化,表明ＫＣＮ 预处理可有效降低黄皮种子脱水敏感性。电解质渗漏率分析表明,ＫＣＮ 预处理在一定程度上推迟了黄皮种子胚轴在脱水过程中的膜损伤。此外,ＫＣＮ 预处理显著抑制了黄皮胚轴在脱水初期的呼吸速率,在脱水过程中也维持在较低水平,但复水后该抑制很快消失, 在脱水６ ｄ 后的复水吸胀过程中呼吸速率恢复较对照为快,并维持在较高水平。呼吸途径分析表明,黄皮胚轴及其线粒体的呼吸以细胞色素途径为主。还分析了脱水对黄皮胚轴线粒体蛋白质及其氧化磷酸化水平的影响。     

氰化钾预处理对黄皮[Clausena lansium（Lour.）Skeels]种子脱水？…

比较了ＫＣＮ预处理与未处理黄皮神经在脱水后活力的变化,表明ＫＣＮ预处理可有效降低黄皮种子脱水敏感性。电解质渗漏率分析表明,ＫＣＮ预处理在一定程度上推迟了黄皮种子胚轴在脱水过程中的膜损伤。此外,ＫＣＮ预处理抑制了黄皮胚轴在脱水初期的呼吸速率,在脱水过程中也维持在较低水平,但复水后该抑制很快消失,在脱水６ｄ后的复水吸胀过程中呼吸速率恢复较对照为快,并维持在较高水平。呼吸途径分析表明,黄皮胚轴及其线粒体     

快速干燥对黄皮胚轴贮藏寿命及抗氧化酶活性的影响

以黄皮种子离体胚轴为材料 ,研究了快速干燥对胚轴贮藏寿命的影响及与抗氧化酶活性的关系。未经脱水的胚轴在 15℃贮藏 12 8d仍具有较高的存活率和活力指数。快速脱水 1.5和 3.0h后胚轴的存活率和活力指数并未因脱水而下降 ,但它们在 15℃贮藏的寿命分别只有 8和 2d。未经脱水胚轴的抗氧化酶(SOD、POD、CAT)活性在贮藏过程中能较好地保持 ,但经快速脱水后其抗氧化酶活性在贮藏过程中则迅速下降 ,脱水时间越长 ,酶活性在贮藏过程中的下降就越快。     

顽拗性黄皮种子脱水过程中活性氧清除酶活性的变化

以正常性种子花生为对照,研究了顽拗性黄皮种子脱水过程中活性氧清除酶、膜脂过氧化作用以及电解质渗漏率的变化。随着含水量的下降,黄皮胚的电解质渗漏率和膜脂过氧化产物丙二醛(MDA)含量均显著增加;当黄皮胚含水量下降至40％后,SOD活性开始急剧下降,而POD和CAT活性在胚含水量下降过程中呈现出缓慢下降的趋势。花生胚在含水量从45％降至14％的过程中,电解质渗漏率没有明显增加,MDA含量只有少量增加;当含水量降至14％后,电解质渗漏率出现少量增加。花生胚脱水初期,活性氧清除酶活性明显增加,并在整个脱水过程中维持较高的水平。以上结果表明顽拗性种子黄皮的脱水敏感性与活性氧清除酶相对活性变化有关。脱水引起黄皮胚活性氧清除酶活性降低,活性氧清除能力下降,膜脂过氧化作用加强,膜透性增大。黄皮胚的膜系统可能是脱水伤害的靶位之一。     

黄皮种子脱水敏感性与萌发事件的研究

黄皮种子对脱水非常敏感,含水量从51％下降至22.4％,种子的发芽率和发芽指数为零,是典型的顽拗性种子。自然脱水时,种子中可溶性糖的含量增加,淀粉的含量下降;磷酸化酶,异柠檬酸裂解酶以及旺轴中α—和β—淀粉酶的活性先增加然后下降;子叶中α—和β—淀粉酶的活性呈下降趋势。这些变化类似于吸水萌发的黄皮和豌豆种子。可以认为黄皮种子脱水敏感性的原因是在脱落时萌发。随着萌发过程的进行,水分成为限制因子,使种子生活力丧失。     

黄皮种子脱水敏感性与萌发事件的研究

黄皮种子对脱水非常敏感,含水量从51%下降至22．4%,种子的发芽率和发芽指数为零,是典型的顽拗性种子。自然脱水时,种子中可溶性糖的含量增加,淀粉的含量下降;磷酸化酶,异柠檬酸裂解酶以及胚轴中α-和β-淀粉酶的活性先增加然后下降;子叶中α-和β-淀粉酶的活性呈下降趋势．这些变化类似于吸水萌发的黄皮和豌豆种子。可以认为黄皮种子脱水敏感性的原因是在脱落时萌发。随着萌发过程的进行,水分成为限制因子,使种子生活力丧失。     

顽拗性黄皮种子税水过程中活性氧清除酶活性的变化

以正常性种子花生为对照,研究了顽拗性黄皮种子脱水过程中活性氧清除酶、膜脂过氧化作用以及电解质渗漏率的变化。随着含水量的下降,黄皮胚的电解质渗漏率和膜脂过氧化产物丙二醛（MDA）含量均显著增加;当黄皮胚含水量下降致40％后,SOD活性开始急剧下降,而POD和CAT活性在胚含水量下降过程中呈现出缓慢下降的趋势。花生胚在含水量从45％降至145的过程中,电解质渗漏率没有明显增加,MDA含量只有少量增加;当含水量降至14％后,电解质渗漏率出现少量增加,花生胚脱水初期,活性氧清除酶活怀明显增加,并在整个脱水过程中维持较高的水平。以上结果表明：顽拗性处子黄皮的脱水敏感性与活性氧清除酶相对活性变化有关。脱水引起黄皮胚活性氧清除酶活性降低,活性氧清除能力下降,膜脂过氧化作用加强,膜透性增大。黄皮胚的膜系统可能是脱水伤害的靶位之一。     

黄皮种子发育过程中脱水敏感性与细胞膜透性的关系

黄皮（Ｃｌａｕｓｅｎａ ｌａｎｓｉｕｍ （Ｌｏｕｒ．） Ｓｋｅｅｌｓ）胚轴与完整种子的发育模式以及发育中电解质渗漏率变化有些不同． 种子生理成熟前、后的胚轴对脱水的反应也不同,前者经轻微脱水可提高萌发率和活力指数,后者不耐任何程度的脱水．活力指数的急剧下降伴随着电解质渗漏率的迅速上升．实验表明,黄皮种子在发育过程中没有形成耐脱水性． 细胞膜透性变化可反映脱水对种子的伤害程度     

Relation Between Desiccation Sensitivity and Membrane Permeability of Developing Clausena lansium Seeds

Desiccation sensitivity and its relation to membrane permeability of the embryonic axes of the developing wampee (Clausena lansium (Lour.) Skeels) seeds were studied by measuring the changes in electrolyte leakage, germination and vigor index after the embryonic axes were rapidly air-dried to various water contents. During development, the fresh and dry weight per seed reached nearly maximum value at 72 d after anthesis, but the dry weight per embryonic axis continuously increased until 85 d after anthesis. The embryonic axes acquired the full capacity for germination at 58 d after anthesis and their vigor index continuously rose up from 51 to 92 d after anthesis. The electrolyte leakage of the developing the embryonic axes linearly declined to the minimum value at 72 d after anthesis and then went up again. The electrolyte leakage of the embryonic axes was higher than that of the whole seeds at the same time. The immature embryonic axes did not germinate completely, while mild desiccation could improve their viability. Any degree of desiccation decreased the vigor index of the embryonic axes which have reached physiological maturation and the decline of vigor index was corresponded to the increase of electrolyte leakage. According to this experiment, the authors concluded that wampee seeds did not gain desiccation-tolerance which was a characteristic of orthodox seeds during development. High water content was essential for maintaining membrane integrity and stabiligy of matured wampee seeds. The injury of seed viability during dehydration could be estimated by using the electro-conductivity method.     

顽拗性黄皮胚脱水过程中核酸、蛋白质代谢的变化

黄皮种子发育晚期,胚内核酸、蛋白质合成能力增强,而花生胚的核酸、蛋白质合成能力在发育晚期则呈下降趋势。黄皮胚的发育在达到生理成熟后维持着活跃的生理代谢并转入萌发状态;而花生胚的代谢活性逐步降低并转入生理静止状态。脱水处理引起生理成熟期黄皮胚核酸、蛋白质合成能力急剧下降,核酸水解酶活性增强。不同程度脱水的黄皮胚吸胀２４ｈ,核酸、蛋白质的合成能力随脱水程度的加深而降低;生物大分子代谢能力的变化是顽拗性     

黄皮种子脱水敏感性与脂质过氧化作用

黄皮种子自然脱水时,种子的发芽率和发芽指数迅速下降;种子浸泡液的电导率和可溶性物质的量大大增加;线粒体膜和质膜ATPase的活性下降;种子中SOD活性先上升,然后下降;脂质过氧化产物MDA和脂质氢过氧化物的量大大增加。DDC、MDA和Fe2 促进脂质过氧化作用,降低种子生活力;ASA和甘露醇对脂质过氧化有抑制作用,提高种子生活力。     

Homoiohydrous (recalcitrant) seeds: Developmental status,desiccation sensitivity and the state of water in axes of Landolphia kirkii Dyer

The desiccation sensitivity in relation to the stage of development was investigated in embryonic axes from the homoiohydrous (recalcitrant) seeds of Landolphia kirkii. Electrolyte leakage, used to assess membrane damage after flash (very rapid) drying, indicated that axes from immature (non-germinable) seeds were the most desiccation-tolerant, followed by those from mature seeds, while axes from seeds germinated for increasing times were progressively more desiccation-sensitive. Differential scanning calorimetry was used to study the relationship between desiccation sensitivity and the properties of water in the tissues. Axes from immature seeds had a lower content of non-freezable water than that of any other developmental stage and a higher enthalpy of melting of freezable water. For mature and immature axes electrolyte leakage increased at the point of loss of freezable water. At other developmental stages the water content at which electrolyte leakage increased markedly correlated with the other properties of the water, such as the change in the shape of the melting endotherm and the onset temperature. Ultrastructural studies of axes at the various developmental stages showed changes in the degree and pattern of vacuolation, the presence and quantities of lipid and starch, and the degree of endomembrane development. The results are discussed in relation to current hypotheses on the basis of desiccation tolerance.Abbreviation DSC differential scanning calorimetry     

Effects of osmotic priming and ageing on the germination and emergence of carrot and leek seed

Carrot and leek seed was osmotically primed in polyethylene glycol solution (273 g/kg water and 342 g/kg water respectively) for 10, 14 or 17 days before accelerated ageing for 0, 24, 48, 72 or 96 h. Priming reduced the germination time compared with non-primed seed. Accelerated ageing increased germination and emergence times and decreased percentage germination and emergence to a greater extent for the primed seeds than for non-primed seeds in both species. Primed and dried but non-aged seed from both species was stored at 10°C for 12 months. There was no loss of viability and improvements in germination time due to priming were maintained throughout the storage period for all the priming treatments in leek, and for the 10 and 14 day priming treatments in carrot. Carrot seed primed for 17 days lost some viability after 12 months storage compared with non-stored seed.     

Homeohydrous (Recalcitrant) Seeds: Dehydration, the State of Water and Viability Characteristics in Landolphia kirkii

Differential scanning calorimetry was used to study the relationships among drying rate, desiccation sensitivity, and the properties of water in homeohydrous (recalcitrant) seeds of Landolphia kirkii. Slow drying of intact seeds to axis moisture contents of approximately 0.9 to 0.7 gram/gram caused lethal damage, whereas very rapid (flash) drying of excised embryonic axes permitted removal of water to approximately 0.3 gram/gram. The amount of nonfreezable water in embryonic axes (0.28 gram H₂O/gram dry mass) did not change with drying rate and was similar to that of desiccation-tolerant seeds. These results suggest that the amount of nonfreezable water per se is not an important factor in desiccation sensitivity. However, flash drying that removed all freezable water damaged embryonic axes. Differences between desiccation-sensitive and -tolerant seeds occur at two levels: (a) tolerant seeds naturally lose freezable water, and sensitive seeds can lose this water without obvious damage only if it is removed very rapidly; (b) tolerant seeds can withstand the loss of a substantial proportion of nonfreezable water, whereas sensitive seeds are damaged if nonfreezable water is removed.     

Glassy State and Seed Storage Stability: The WLF Kinetics of Seed Viability Loss at T>Tgand the Plasticization Effect of Water on Storage Stability

The relationship between the glassy state in seeds and storage stability was examined, using the glass transition curve and a seed viability database from previous experiments. Storage data for seeds at various water contents were studied by Williams–Landel–Ferry (WLF) kinetics, whereas the glass transition curves of seeds with different storage stability were analysed by the Gordon–Taylor equation in terms of the plasticization effect of water on seed storage stability. It was found that the critical temperatures (T_c) for long-term storage of three orthodox seeds were near or below their glass transition temperatures (T_g), indicating the requirement for the presence of the glassy state for long-term seed storage. The rate of seed viability loss was a function of T-T_gat T>T_g, which fitted the WLF equation well, suggesting that storage stability was associated with the glass transition, and that the effect of water content on seed storage was correlated with the plasticization effect of water on intracellular glasses. A preliminary examination suggested a possible link between the glass transition curve and seed storage stability. According to the determined WLF constants, intracellular glasses in seeds fell into the second class of amorphous systems as defined by Slade and Levine (Critical Reviews in Food Science and Nutrition30: 115–360, 1991). These results support the interpretation that the glassy state plays an important role in storage stability and should be a major consideration in optimizing storage conditions.     

八棱海棠种子超低温保存中含水量对糖代谢的影响

含水量是影响种子超低温保存效果的关键因素，而其作用机制尚不完全清楚。为探讨含水量对种子超低温保存生活力的影响途径，该研究以八棱海棠种子为材料，通过硅胶干燥法获得不同含水量的种子，测定超低温保存后种子生活力、糖含量及相关酶指标的变化并分析相关性。结果表明：(1)超低温保存15 d后，不同含水量种子生活力不同，随着种子含水量的降低，种子生活力呈现先升高后降低的趋势，含水量为9.02%的八棱海棠种子生活力最高，为53.33%;超低温保存120 d后，种子生活力随着含水量下降一直升高，含水量为6.40%生活力最高，为27.78%。这表明八棱海棠种子含水量对超低温保存后的生活力有明显影响，但受液氮保存时间影响，随着液氮保存时间的延长，最适含水量降低。(2)相关分析显示，超低温保存后种子含水量与生活力呈极显著负相关(r=-0.82);与果糖和蔗糖含量、酸性转化酶、果糖激酶呈显著负相关，而种子萌发率与这些指标呈显著正相关。这表明种子含水量通过影响酸性转化酶活性而影响蔗糖和果糖含量，进而影响蔗糖代谢，响应低温和脱水胁迫，最终导致生活力差异。种子生活力还受到介导果糖激酶的果糖代谢影响。此外，海藻糖也是种...