Hammond E C, Bridgers K, Berry F D
Department of Physics, Morgan State University, Baltimore, MD 21239, USA.
Radiat Meas. 1996 Nov;26(6):851-61. doi: 10.1016/s1350-4487(96)00093-5.
The purpose of the experiment was to determine cosmic rays long-term effects on living tissue. A batch of tomato seeds were flown in orbit aboard the Long Duration Exposure Facility (LDEF) for almost 6 y. During this time, the seeds received an abundant exposure to cosmic radiation. Upon the return of the LDEF to Earth, the seeds were distributed throughout the United States and 30 foreign countries for analysis. Our university analysis included germination and growth rates as well as scanning electron microscopy (SEM) and X-ray analysis of the control as well as space exposed tomato seeds. In analyzing the seeds under the electron microscope, usual observations were performed on the nutritional and epidermis layer of the seed. These layers appeared to be more porous in the space exposed seeds than on Earth-based control seeds. This unusual characteristic may explain the increases in the space seeds growth pattern. (Several test results showed that the space-exposed seeds germinated sooner than Earth-based seeds. Also, the space-exposed seeds grew at a faster rate.) The porous nutritional region may allow the seeds to receive necessary nutrients and liquids more readily, thus enabling the plant to grow at a faster rate. Roots, leaves and stems were cut into small sections and mounted. After sputter coating the specimens with argon/gold palladium plasma, they were viewed under the electron microscope. Many micrographs were taken. The X-ray analysis displayed possible identifications of calcium, potassium, chlorine, copper, aluminum, silicon, phosphate, carbon, and sometimes sulfur and iron. The highest concentrations were shown in potassium and calcium. As a result of the electron interaction and X-ray production within the open seeds, the traditional layers of the space-exposed seed gave peaks of Mg, P and S, while the Earth seed gave an iron peak, which was not detected in the space-exposed seed because of electron beam positioning difference. The space-exposed seed and the Earth-control seed specimens displayed high concentrations of copper.
该实验的目的是确定宇宙射线对生物组织的长期影响。一批番茄种子搭乘长期暴露设施（LDEF）在轨道上飞行了近6年。在此期间，这些种子受到了大量的宇宙辐射。LDEF返回地球后，这些种子被分发到美国和30个其他国家进行分析。我们大学的分析包括发芽率和生长速率，以及对对照种子和太空暴露番茄种子的扫描电子显微镜（SEM）和X射线分析。在电子显微镜下分析种子时，对种子的营养层和表皮层进行了常规观察。与地面对照种子相比，太空暴露种子的这些层似乎孔隙更多。这种不寻常的特征可能解释了太空种子生长模式的增加。（一些测试结果表明，太空暴露种子比地面种子发芽更快。此外，太空暴露种子的生长速度更快。）多孔的营养区域可能使种子更容易获得必要的营养物质和液体，从而使植物生长得更快。将根、叶和茎切成小段并进行固定。在用氩/金钯等离子体对标本进行溅射镀膜后，在电子显微镜下观察。拍摄了许多显微照片。X射线分析显示可能鉴定出钙、钾、氯、铜、铝、硅、磷酸盐、碳，有时还有硫和铁。最高浓度出现在钾和钙中。由于开放种子内部的电子相互作用和X射线产生，太空暴露种子的传统层给出了镁、磷和硫的峰值，而地球种子给出了一个铁峰值，由于电子束定位差异，在太空暴露种子中未检测到该峰值。太空暴露种子和地球对照种子标本显示出高浓度的铜。
