In calcium-deficient plants,meristematic regions of the stem and root tips are greatly affected,and chlorosis of the margins of young leaves takes place. These symptoms eventually lead to the death of leaf,stem,and root apices. These observations are related to the role of calcium in plant growth as it is:

• A
  $A$ constituent element of chlorophyll
• B
  Required for the formation of the middle lamella
• C
  Involved in the synthesis of chloroplast proteins
• D
  Involved in the hydration and permeability of cells