According to origin, connective tissue is divided into three parts.
(i) Promeristem: The dividing tissue that originates from the root and apical region of the plant is called promeristem or primitive dividing tissue. It is located at the root and apex of the plant. The cells of this tissue are small, immature, vacuolated and have thin cell walls. The first growth of plants starts from this region. It is divided into different layers and forms different organs.
(ii) Primary meristem: The dividing tissue that originates in the embryonic stage of the plant is called primary meristem. It arises from early dividing tissue. This tissue is capable of dividing forever. It is located at the tip of the root, stem and branch, in the middle and at the periphery of the stem. It never becomes permanent tissue. It increases the length of the plant. Eg- fascicular cambium.
(iii) Secondary meristem: The dividing tissue that originates from the permanent tissue is called secondary meristem. This tissue is located in phellogen or cork cambium, between phases, between xylem and phloem, between two vascular bundles and in cortex. Secondary division tissue increases plant vigor. Heals plant wounds. Eg – cork cambium, interfascicular cambium etc.