Plants are complex communicators, using chemical and electronic signals to coordinate responses to their environment, and warn other plants of danger nearby. Similarly, plants can detect pollinators and release chemicals to attract them. Plant movements are guided by light, water, nutrients and in response to grazing by animals and competition from other plants. While plants may appear destined to remain where their seeds germinate, they constantly adjust their leaves, roots and stems to improve their chances of survival. Plants can grow in space - scientists have grown 17 different species of plants in specialized chambers, including crops like corn, wheat, tomatoes and lettuce. One in ten plants grow on other plants, using their host for physical support. Organisms are very sensitive to changes in their environment and plants in particular have been used to detect these changes for centuries.