Primary Growth: Apical meristem is responsible for primary root and stem growth in vascular plants.
Primary Root Growth: is concentrated near the tip and results in the root growing in length. The root tip contains 4 zones of development: The root cap, which protects the area behind it and softens the soil ahead of it by producing a polysaccharide. The apical meristem, is an area of rapidly dividing cells. It will replace the cells of the root cap as they wear away and push cells above them that will develop into the main tissues of the plant. The zone of elongation, is an area where the cells elongate 10 times their original length. This elongation helps push the root into the soil. The zone of maturation, is the area farthest from the root tip. Here the new cells will specialize and carry out the functions of the epidermal, ground, and vascular tissue. The primary tissues in a dicot root are arranges in a central x pattern for the xylem with the phloem located in each of the angles of the xylem. In a monocot the vascular tissues are alternated in a circle.
Primary Stem Growth: begins at the tip of the terminal bud in the area called the apical meristem. The cell divisions are responsible for the stem's growth in length. The primary vascular tissue in monocots takes on a scattered arrangement. In a dicot, it takes a circular pattern.
Secondary Growth: Increases the girth of a stem it is caused by the vascular and cork cambium.
vascular cambium: meristematic parenchyma produces xylem on the inside and phloem on its outer side. The secondary xylem accumulates and forms the wood. The secondary phloem does not accumulate and is sloughed off with the bark.
Cork Cambium: forms in the outer cortex. Produces cork and epidermal tissues.
Wood has 2 zones: Heartwood- the older (inner) layers of xylem blocked with resins. It is non -functional in water transport. Sap wood- outer xylem, vascular cambium, phloem and cork cambium. Conducts water and food.
