Root-hair response to vector-free gravity: role of Ca2+ ions.
In plants, apical growth is demonstrated by a variety of cells, including root hairs (RH) which are tubular outgrowths of root epidermal cells. They are likely to be involved in uptake of nutrients and water, anchorage of plants, maintenance of contact between roots and soil, and root exudation. Over the last years, it has become clear that calcium is involved in various processes which result in tip growth. Previous studies from our laboratory have demonstrated an increase in calcium level in root cells of pea seedlings grown under conditions of space flight and clinorotation. On the basis of these data, we have suggested that such effects of microgravity and clinorotation might be due to the enhancement of Ca2+ influx into hyaloplasm evidently through Ca2+ channels. In this regard, it was interesting to examine the effects of clinorotation and Ca2+ channel blockers (verapamil and nifedipine) on orientation and structure of growing RH that might be an appropriate model system being sensitive to calcium for studying the gravitational effects at cellular level.