空间飞行与回转器回旋条件下青菜开花与花粉发育的研究

比较研究了SJ-8返回式卫星留轨舱微重力条件与地面三维回转模拟微重力条件下青菜生长与发育情况.研究发现空间微重力条件下青菜开花过程需要大约18 h,明显长于地面对照5 h左右.回转器模拟实验结果表明,改变重力影响了花瓣的伸展与发育及花粉的产量,回转条件下花粉细胞中的微管排列明显不同于静止对照.细胞骨架受到干扰可能是改变重力条件下花粉产量降低的原因之一.本研究首次报道了在空间飞行试验中成功地采用了显微实时图像技术观察植物的开花过程,并获得了从花蕾到开花结束各阶段清晰的图像.      

微重力对拟南芥长势影响的代谢网络流平衡分析

微重力作为典型的空间环境因素,对植物生长发育的影响机制是空间生命科学的研究热点。微重力环境直接或间接影响植物代谢,并引起许多生理适应。 随着系统生物学的发展,代谢网络模型使微重力环境下的植物代谢建模成为可能。采用流平衡分析方法对模式植物拟南芥不同组织的代谢网络进行分析,研究微重力对拟南芥生长发育的影响机制。通过比较空间与地面条件下拟南芥的生物质产量,发现空间条件下拟南芥黄化幼苗、幼苗、芽、根、下胚轴的生物量分别下降了33.00%,51.52%,6.89%,12.53%,11.70%,与空间环境下拟南芥的长势变化趋势一致。代谢通路富集分析发现,微重力使得拟南芥的碳固定等通路下调,而磷酸戊糖途径上调,初步解析了微重力对拟南芥生长发育的影响机制,也验证了流平衡方法用于微重力生物学效应研究中的可行性。      

微重力环境下植物培养箱设计

基于空间微重力下植物的生物学效应及其微重力信号转导研究需要,在微重力条件下培养拟南芥,获得经微重力条件生长的拟南芥样品.在空间实验过程中实时采集、存储和传输植物样品的数字图像,并根据生物样品的生长周期对生物样品进行低温固定和储存,再由返回式卫星带回地面,开展微重力植物生物学效应研究.      

重力对植物细胞生长的效应

从地基研究植物向重性和在神舟八号卫星微重力条件下培养植物细胞出发,探讨重力变化对植物细胞发生作用时产生的生物学效应.已有结果显示,在植物向重性反应和处于失重状态时,重力方向和大小变化对细胞壁代谢具有一定影响.推断细胞形状的维持是由细胞壁的刚性与细胞内膨压平衡所致,当细胞膨压大于细胞壁刚性导致上述平衡打破时就会引起细胞体积增大.因此,重力的变化可能会通过影响植物细胞壁刚性与细胞内膨压的平衡影响细胞生长.      

LED光谱对模拟空间培养箱中植物生长发育的影响

通过研究在空间植物培养箱中利用LED作为光源对植物生长发育的作用, 并以荧光灯作为对照, 评估LED光源在空间植物培养中的优缺点, 可为中国即将在空间实验室天宫二 号和空间站中开展的高等植物生长实验提供参考. 利用不同比例的红光与白光LED组合光源, 研究光谱组成(红蓝光比例)、光照强度、光周期和气体流通等条件对于模拟空间 植物培养箱中拟南芥和水稻生长发育的影响. 结果表明, 与荧光灯相比, 红蓝光比例高的LED会导致拟南芥提早开花和水稻叶片的早衰. 红蓝光峰值比在3.9左右时, 拟南芥 和水稻生长最为有利; 红蓝光峰值比超过16则明显抑制拟南芥和水稻的生长, 导致叶片早衰. 另外, 在密闭培养箱中, 光强小于150μmol·m-2·s-1时, 增加光照强度可以部分抵消气体流通不足导致拟南芥植物生长的抑制, 而光照强度大 于150μmol·m-2·s-1时, 光强越大拟南芥的生长发育受到抑制越严重. 水稻对密闭培养环境中高光强的耐受性明显好于拟南芥. 因此, 在设计空间植物培养箱的LED光照系统时, 红蓝光的比例选择是关键, 此外还需综合考虑空间微重力条件下气体对流变化影响植物对光的反应.      

回转处理对雨生红球藻细胞结构、光合活性、糖及虾青素代谢的影响研究

通过利用二维回转器模拟微重力,对20d回转条件下雨生红球藻细胞结构、光合活性、初级糖代谢及次生代谢产物变化情况进行分析,发现回转作用使得藻细胞体积变小,形状变得不规则.超微结构分析显示,回转处理后,藻细胞的淀粉粒变小,类囊体膜结构排列松弛.叶绿素含量在回转前期降低,中后期提高.类胡萝卜素含量及光合系统II活性在整个回转过程中均降低.由此得出藻细胞光合活性的下降与叶绿体类囊体膜结构的变化及色素含量下降有关.藻细胞淀粉粒变小、淀粉含量下降与淀粉酶活性的上升有关,说明回转作用通过提高淀粉酶水解活性造成淀粉含量下降.蔗糖和海藻糖的积累在藻细胞对早期回转条件的适应过程中发挥了一定保护作用,同时造成合成此两种糖的单糖底物葡萄糖和果糖含量下降.在被称作适应期的回转中期,叶绿素、葡萄糖和果糖均出现补偿性合成,而蔗糖和海藻糖的积累相比回转前期出现相应下降.雨生红球藻次生代谢产物虾青素在整个回转过程中均下降,分析认为这是由虾青素的原初合成底物即类胡萝卜素合成的降低所导致.     

中国微重力科学研究回顾与展望

微重力科学主要研究微重力环境中物质运动的规律,以及不同重力环境中重力对物质运动的影响.中国微重力科学研究起步于20世纪60年代,兴起于80年代中后期,经过多年发展,目前已初具规模,在一些重要方向具有明显特色和一定优势.本文回顾了中国微重力科学研究的早期历程,评述了近年来中国微重力科学研究进展,特别是利用实践十号科学实验...     

A1CuMgZn单晶合金的空间凝固

重力对合金凝固过程与缺陷形成具有重要影响.在常规地面条件下难以清晰揭示凝固过程中的重力效应及其作用规律,而在微重力环境中重力对熔体的作用以及对凝固过程的影响大大降低.利用天宫二号空间实验并结合地面对比实验,研究AlCuMgZn单晶合金在微重力和重力环境下枝晶生长形貌和特征参数差异以及成分偏析和缺陷形成的异同,揭示重力对枝晶生长过程和成分偏析等现象的影响及其在凝固缺陷形成中的作用.     

地面模拟静止微重力环境中导线先期着火特性研究

针对在微重力环境中运行的载人航天飞行器上的电缆和导线在工作时由于电流过载导致温度升高而引起着火的情况,提出了"功能模拟"实验原理,并且利用地面实验设备对微重力环境下导线的着火前期特性进行了功能模拟实验研究.通过实验,得到了在微重力情况下由于浮升力的减小使自然对流减弱导致电流过载时导线的热平衡温度高于地面正常重力情况,从而证明了这正是引起航天飞行器着火的潜在点火源.      

DMFC内部气液两相流动与电性能的短时落塔实验研究

利用国家微重力实验室落塔提供的短时微重力实验环境,对常重力和微重力条件下直接甲醇燃料电池(DMFC)内部的气液两相流动形态和相应电性能等的影响进行了实验研究,发现在微重力条件下,DMFC阳极流道内CO₂气泡速度很小,气泡尺寸随着时间的推移而不断长大,甚至堵塞流道;流道堵塞现象随电流增大而急剧强化.电性能曲线显示,在浓差极化区存在显著的重力效应,电性能的恶化随浓差极化程度的加强而增大.      

The state of gravity sensors and peculiarities of plant growth during different gravitational loads.

In the primary roots of lettuce shoots grown under altered gravitational conditions--180 degrees inversion on the centrifuged clinostat, horizontal clinostat and in dynamic weightlessness--localization of the cellular organelles, cell morphology and peculiarities of growth have been studied. Significant changes took place in the localization of amyloplasts on the horizontal clinostat. The changes of amyloplast position in the cap cells on the horizontal clinostat and under weightlessness are similar. A change of the normal shoot position (180 degrees inversion and horizontal clinostat) causes an inhibition of growth. Weightlessness increases the length of axial organs and cells in the zone of elongation, but decreases the nitotic index in comparison to the centrifuged control. The anlysis of the formation of generative organs has been carried out for Arabidopsis plants grown on board the orbital station Salyut-6. The ability of plants to undergo vegetative growth and to pass through early phases of generative development under weightlessness was confirmed.     

Ontogeny of plants under various gravity condition.

The results of experiments performed under conditions of microgravity (MG) or under its simulation on the horizontal clinostat (HC) with the callus, seedlings of various species and embryogenic structures have revealed a definite role of gravity as an ecological factor in the processes of cytomorphogenesis, growth, and development. The transformation of differentiated somatic cells of arabidopsis seed into undifferentiated callus was not inhibited under MG, though modifications of the whole callus morphology and of mean cell and nucleus size were observed. The morphogenesis of polar structures such as root-hair bearing cells of Lactuca primary root has been shown to be modified in the course of differentiation under mass acceleration diminished below 0.1 g. Seed germination and seedling morphogenesis under MG follow their normal course, but a significant stimulation of shoot growth with no effect on primary root growth has been determined. A successful in vitro regeneration of Nicotiana tabacum plantlets from leaf cells and subsequent formation of shoots and roots on a continuously rotating HC as well as the formation of viable seeds during seed-to-seed growth of Arabidopsis plants under MG have indicated that gravity plays but a limited role in the processes of embryogenesis and organogenesis.     

Growth of pea epicotyl in low magnetic field implication for space research

A magnetic field is an inescapable environmental factor for plants on the earth. However, its impact on plant growth is not well understood. In order to survey how magnetic fields affect plant, Alaska pea seedlings were incubated under low magnetic field (LMF) and also in the normal geo-magnetic environment. Two-day-old etiolated seedlings were incubated in a magnetic shield box and in a control box. Sedimentation of amyloplasts was examined in the epicotyls of seedlings grown under these two conditions. The elongation of epicotyls was promoted by LMF. Elongation was most prominent in the middle part of the epicotyls. Cell elongation and increased osmotic pressure of cell sap were found in the epidermal cells exposed to LMF. When the gravitational environment was 1G, the epicotyls incubated under both LMF and normal geomagnetic field grew straight upward and amyloplasts sedimented similarly. However, under simulated microgravity (clinostat), epicotyl and cell elongation was promoted. Furthermore, the epicotyls bent and amyloplasts were dispersed in the cells in simulated microgravity. The dispersion of amyloplasts may relate to the posture control in epicotyl growth under simulated microgravity generated by 3D clinorotation, since it was not observed under LMF in 1G. Since enhanced elongation of cells was commonly seen both at LMF and in simulated microgravity, all elongation on the 3D-clinostat could result from pseudo-low magnetic field, as a by-product of clinorotation. (i.e., clinostat results could be based on randomization of magnetic field together with randomization of gravity vector.) Our results point to the possible use of space for studies in magnetic biology. With space experiments, the effects of dominant environmental factors, such as gravity on plants, could be neutralized or controlled for to reveal magnetic effects more clearly.     

The effect of gravity on plant germination.

An axis clinostat was constructed to create micro and negative gravity also a rotated flat disk was constructed with different rotation rates to give increased gravity, by centrifugal force up to 48 g. Rice seeds were grown on agar in tubes at the constant air temperature of 20 degrees C under an average light condition of 110 micromol/m2/sec(PPF). Humidity was not controlled but was maintained above 90%. Since the tube containers were not large enough for long cultivation, shoot and root growth were observed every 12 hours until the sixth day from seeding. The lengths of shoots and roots for each individual plant were measured on the last day. The stem lengths were increased by microgravity but the root lengths were not. Under the negative gravity, negative orthogeotropism and under microgravity, diageotropism was observed. No significant effect of increased gravity was observed on shoot and root growth.     

Amphibian egg cytoplasm response to altered g-forces and gravity orientation

Elucidation of dorsal/ventral polarity and primary embryonic axis development in amphibian embryos requires an understanding of cytoplasmic rearrangements in fertile eggs at the biophysical, physiological, and biochemical levels. Evidence is presented that amphibian egg cytoplasmic components are compartmentalized. The effects of altered orientation to the gravitational vector (i.e., egg inversion) and alterations in gravity force ranging from hypergravity (centrifugation) to simulated microgravity (i.e., horizontal clinostat rotation) on cytoplasmic compartment rearrangements are reviewed. The behavior of yolk compartments as well as a newly defined (with monoclonal antibody) non-yolk cytoplasmic compartment, in inverted eggs and in eggs rotated on horizontal clinostats at their buoyant density, is discussed.     

Plant reproduction systems in microgravity: experimental data and hypotheses.

Elucidation of the possibilities for higher plants to realize complete ontogenesis, from seed to seed, and to propagate by seeds in microgravity, is a fundamental task of space biology connected with the working of the CELSS program. At present, there are results of only 6 spaceflight experiments with Arabidopsis thaliana, an ephemeral plant which will flower and fruit in orbit. Morphogenesis of generative organs occurs normally in microgravity, but unlike the ground control, buds and flowers mainly contain sterile elements of the androecium and gynoecium which degenerate at different stages of development in microgravity. Cytological peculiarities of male and female sterility in microgravity are similar to those occurring naturally during sexual differentiation. Many of the seed formed in microgravity do not contain embryos. Hypotheses to explain abnormal reproductive development in microgravity are: 1) nutritional deficiency, 2) insufficient light, 3) intensification of the influence of the above-mentioned factors by microgravity, 4) disturbances of a hormonal nature, and 5) the absence of pollination and fertilization. Possible ways for testing these hypotheses and obtaining viable seeds in microgravity are discussed.     

Induction of hypoxic root metabolism results from physical limitations in O2 bioavailability in microgravity.

Numerous spaceflight experiments have noted changes in the roots that are consistent with hypoxia in the root zone. These observations include general ultrastructure analysis and biochemical measurements to direct measurements of stress specific enzymes. In experiments that have monitored alcohol dehydrogenase (ADH), the data shows this hypoxically responsive gene is induced and is associated with increased ADH activity in microgravity. These changes in ADH could be induced either by spaceflight hypoxia resulting from inhibition of gravity mediated O2 transport, or by a non-specific stress response due to inhibition of gravisensing. We tested these hypotheses in a series of two experiments. The objective of the first experiment was to determine if physical changes in gravity-mediated O2 transport can be directly measured, while the second series of experiments tested whether disruption of gravisensing can induce a non-specific ADH response. To directly measure O2 bioavailability as a function of gravity, we designed a sensor that mimics metabolic oxygen consumption in the rhizosphere. Because of these criteria, the sensor is sensitive to any changes in root O2 bioavailability that may occur in microgravity. In a KC-135 experiment, the sensor was implanted in a moist granular clay media and exposed to microgravity during parabolic flight. The resulting data indicated that root O2 bioavailability decreased in phase with gravity. In experiments that tested for non-specific induction of ADH, we compared the response of transgenic Arabidopsis plants (ADH promoted GUS marker gene) exposed to clinostat, control, and waterlogged conditions. The plants were grown on agar slats in a growth chamber before being exposed to the experimental treatments. The plants were stained for GUS activity localization, and subjected to biochemical tests for ADH, and GUS enzyme activity. These tests showed that the waterlogging treatment induced significant increases in GUS and ADH enzyme activities, while the control and clinostat treatments showed no response. This work demonstrates: (1) the inhibition of gravity-driven convective transport can reduce the O2 bioavailability to the root tip, and (2) the perturbation of gravisensing by clinostat rotation does not induce a nonspecific stress response involving ADH. Together these experiments support the microgravity convection inhibition model for explaining changes in root metabolism during spaceflight.     

Auxin polar transport in Arabidopsis under simulated microgravity conditions — Relevance to growth and development

Activity of auxin polar transport in inflorescence axes of Arabidopsis thaliana grown under simulated microgravity conditions was studied in relation to the growth and development. Seeds were germinated and allowed to grow on an agar medium in test tubes on a horizontal clinostat. Horizontal clinostat rotation substantially reduced the growth of inflorescence axes and the productivity of seeds of Arabidopsis thaliana (ecotypes Landsberg erecta and Columbia), although it little affected seed germination, development of rosette leaves and flowering. The activity of auxin polar transport in inflorescence axes decreased when Arabidopsis plants were grown on a horizontal clinostat from germination stage, being ca. 60% of 1 g control. On the other hand, the auxin polar transport in inflorescence axes of Arabidopsis grown in 1 g conditions was not affected when the segments were exposed to various gravistimuli, including 3-dimensional clinorotation, during transport experiments. Pin-formed mutant of Arabidopsis, having a unique structure of the inflorescence axis with no flower and extremely low levels of the activity of auxin polar transport in inflorescence axes and endogenous auxin, did not continue its vegetative growth under clinostat rotation. These facts suggest that the development of the system of auxin polar transport in Arabidopsis is affected by microgravity, resulting in the inhibition of growth and development, especially during reproductive growth.     

Growth of Prunus tree stems under simulated microgravity conditions.

Stem growth of Prunus trees under simulated microgravity conditions was examined using a three-dimensional clinostat. The stems elongated with bending under such conditions. Stem elongation and leaf expansion were both promoted, whereas the formation of xylem in the secondary thickening growth was inhibited under the simulated microgravity condition. In secondary xylem, sedimentable amyloplasts were observed in the 1g control. The present results suggest that stem elongation and leaf expansion may be inhibited at 1g, while growth direction and secondary xylem formation depend on a gravity stimulus. A space experiment is expected to advance research on thickening growth in trees.