Plant Movements

Even though plants cannot relocate the way animals do, their cells, tissues and organs are still capable of changing position in response to signals from inside or outside the plant, and this capacity is collectively called plant movement (Figure 15.14). The overall classification splits these movements into two very different categories: vital movements, shown only by living cells or organs and always connected to the irritability of the protoplasm, and physical movements (also called hygroscopic movements), which occur in already-dead plant parts and have nothing to do with living protoplasm at all. Vital movements are further split into movements of locomotion (the movement of protoplasm within a cell, or of a whole free-living unicellular/mo …