In a vascular plant, the stele is the central part of the root or stem containing the tissues derived from the procambium. These include vascular tissue, in some cases ground tissue (pith) and a pericycle, which, if present, defines the outermost boundary of the stele. Outside the stele lies the endodermis, which is the innermost cell layer of the cortex.
The concept of the stele was developed in the late 19th century by French botanists P. E. L. van Tieghem and H. Doultion as a model for understanding the relationship between the shoot and root, and for discussing the evolution of vascular plant morphology. Now, at the beginning of the 21st century, plant molecular biologists are coming to understand the genetics and developmental pathways that govern tissue patterns in the stele.
The earliest vascular plants had stems with a central core of vascular tissue. This consisted of a cylindrical strand of xylem, surrounded by a region of phloem. Around the vascular tissue there might have been an endodermis that regulated the flow of water into and out of the vascular system. Such an arrangement is termed a protostele.
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, evolution, distribution, and taxonomy. Modern biology is a vast and eclectic field, composed of many branches and subdisciplines. However, despite the broad scope of biology, there are certain general and unifying concepts within it that govern all study and research, consolidating it into single, coherent fields. In general, biology recognizes the cell as the basic unit of life, genes as the basic unit of heredity, and evolution as the engine that propels the synthesis and creation of new species. It is also understood today that all organisms survive by consuming and transforming energy and by regulating their internal environment to maintain a stable and vital condition.
Subdisciplines of biology are defined by the scale at which organisms are studied, the kinds of organisms studied, and the methods used to study them: biochemistry examines the rudimentary chemistry of life; molecular biology studies the complex interactions among biological molecules; botany studies the biology of plants; cellular biology examines the basic building-block of all life, the cell; physiology examines the physical and chemical functions of tissues, organs, and organ systems of an organism; evolutionary biology examines the processes that produced the diversity of life; and ecology examines how organisms interact in their environment.
Biology is a quarterly, peer-reviewed, open access, scientific journal covering research on all aspects of biology. It was established in 2012 and is published by MDPI. The editor-in-chief is Chris O'Callaghan (University of Oxford). The journal publishes reviews, research papers, and communications.
This journal covers all topics related to biology. More detail about the journal and its scope is available in the first editorial. Research fields of interest include, but are not limited to:
Biology: The Unity and Diversity of Life is a college-level introductory biology textbook that covers basic biochemistry, anatomy, taxonomy, evolution, biotechnology and ecology. The book is designed to create in students a broad foundation of knowledge in biology and is frequently used in AP Biology classes in American high schools. Each book includes an interactive CD-ROM with links to additional instructional material. Like many textbooks new versions are printed every few years and reflect new gains in scientific knowledge. The book is published by Brooks/Cole and is currently in its twelfth edition. It was primarily compiled by Cecie Starr and Ralph Taggart with pictures and illustrations by Lisa Starr.
The book was translated into few languages, among others into Hebrew, published by the Open University of Israel.