CHANGES IN THE RHEOLOGICAL PROPERTIES OF THE CELL-WALL OF PLANT SEEDLINGS UNDER SIMULATED CONDITIONS

In this review article, we discuss the changes in the mechanical prope rties of the primary cell wall of different organs of several species of plant seedlings grown under simulated microgravity conditions. We c ompared growth and tropistic responses of these organs growing under d ifferent microgravity conditions, namely: 1) 3-D clinostat (three-dime nsional clinostat with two axes); 2) water-submergence for rice seedli ngs, and 3) for comparison, an accelerated. gravity using a specifical ly designed centrifuge. We measured the minimum stress-relaxation time as the parameter representing the mechanical property of the cell wal l. We also measured extensibility, in mm/g. The 3-D clinostat conditio n disturbed the normal gravitropic response of organs but affected gro wth rate and mechanical properties of the cell wall very little. Water -submergence of rice seedlings caused an acceleration of coleoptile el ongation in the dark and caused a marked change in the mechanical prop erty of the cell wall. However, the additional gravity of 30-135 xg sh owed only a small effect on growth and the mechanical property of the cell wall.