Plant Development under Simulated Microgravity Conditions

Abstract

Bioregenerative Life Support Systems will represent one of the future needs in context of long-term manned space missions. The demand for nutrition, recycling of carbon dioxide, production of oxygen and other chemical compounds and also the psychological well-being of humans can be fulfilled with plant based life support systems in an improved way. However, there are some fundamental differences between plant cultivation on Earth and in space, mainly due to the lack of gravity and increased radiation. Therefore, it is aimed to modify plants by breeding or genetic engineering to obtain germination, growth rates and reproduction under space conditions as optimal as possible. The first step to such an approach is to study the effects of gravity on plant development with hypergravity and simulated microgravity experiments on earth. Cell walls, functioning as an exoskeleton of a plant cell, provide the stability and shape of different cell types needed to form tissues and organs in presence of gravitational force. In order to understand early processes in alteration of cell wall composition in microgravity, 2D-clinorotated Arabidopsis thaliana roots were investigated in an immunohistochemical and electron microscopical approach. The parameters of simulation were chosen for the plant system due to results obtained by a comparative approach, testing the effect of fast clinorotation versus real random mode operation on a random positioning machine with respect to the displacement of statoliths. Based on these results, the 2D-clinostat was selected to provide a qualitative good simulation. Pectins, important cell wall matrix polysaccharides, were immunhistochemically visualized, revealing a relative lower abundance of pectins in 3 h clinorotated samples compared with the 1 g control samples. Interestingly, short term exposure to microgravity reduces pectins without impact on cell wall thickness as revealed by electron microscopy.