Chapter Outline

 Photo shows a plant with oval leaves that oppose each other on long, thin branches.
Figure 23.1A locust leaf consists of leaflets arrayed along a central midrib. Each leaflet is a complex photosynthetic machine, exquisitely adapted to capture sunlight and carbon dioxide. An intricate vascular system supplies the leaf with water and minerals, and exports the products of photosynthesis. (credit: modification of work by Todd Petit)

Plants are as essential to human existence as land, water, and air. Without plants, our day-to-day lives would be impossible because without oxygen from photosynthesis, aerobic life cannot be sustained. From providing food and shelter to serving as a source of medicines, oils, perfumes, and industrial products, plants provide humans with numerous valuable resources.

When you think of plants, those that first come to mind are likely to be vascular plants. These plants have tissues that conduct food and water (the word “vascular” means “having vessels”). While each vascular plant species is unique, all are made up of a plant body consisting of stems, roots, and leaves. They also all transport water, minerals, and sugars produced through photosynthesis through the plant body using the same mechanism, and they all respond to environmental factors, such as light, gravity, competition, temperature, and predation. Scientists recently discovered that two plants, the giant goldenrod and spicebush, each make five different compounds that disrupt the life cycles of insect pests. Further investigation into the chemicals could lead to a new class of pesticides.//cnx.org/contents/This email address is being protected from spambots. You need JavaScript enabled to view it.:3BbDXj5J@10/Introduction#footnote1">1 You can read more about it in ScienceNews magazine.