مناعة نضري ١٤

• Plant Physiology
• Lecture 14 - Theoretical Lecture
• Department of Life Sciences - Fourth Stage
• Prepared by Asst. Prof. Dr. Arshad Naji Alhasnawi
• Meristematic tissues or Meristems


  Specific tissues in the plant responsible for growth, constantly producing new cells as a result of the successive division of some or all of their cells under suitable conditions
• Main types of meristems


  • Apical - root meristem

  2. Apical - stem meristem

  3. Lateral meristem, called the Cambium

  4. Intercalary meristem, found in the stems and leaves of some monocotyledonous plants
• Secondary growth


  Growth resulting from the activity and division of the lateral meristem, the vascular cambium or the cork cambium, responsible for the increase in the diameter of the stem or root.
• Cambium


  Vascular cambium
• Secondary growth


  Growth resulting from the division and activity of the cork cambium or the vascular cambium
• Secondary growth


  Cells of the vascular or cork cambium divide, responsible for the increase in the diameter of the stem or root
• Plant cell growth


  • Occurs in three stages: Embryonic or Meristematic Stage, Enlargement Stage, Differentiation Stage
• The growth rate of a plant organ is not uniform during its growth, but follows a characteristic pattern known as the grand period of growth
• The changes in growth rate during the grand period of growth are attributed to the specific way in which plant cells grow
• The grand period of growth applies to the growth of the entire plant as well as to the growth of individual plant organs and tissues
• After the grand period of growth, the plant establishes its final size and form
• Other growth periods include the photosynthetic period and the reproductive period