Tissues in plants and animals
Connective tissue in animals are mostly made up of collagen



Tissue is not like a simple chemical mixture ; rather tissue means a group or assemblage of cells, obeying certain defining-characteristics. 
Animal connective tissues contain collagen mostly in the extracellular matrix. There are also other cell-constituents like phospholipid(membranes), DNA, RNA, etc.  Blood is a liquid connective tissue which do not contain collagen in its matrix (plasma)



  What is the equivalent connective tissue in plants? 



Connective tissue is defined as all the tissues originated from the mesoderm layer of the animal embryo. 


Now plants have a different mode of development than animals (plausibly due to evolution in separate route). So no part of a plant-body is homologous with a part of animal-body. It is impossible to bring a compare. 



However; plants too; have their extracellular matrix; which is more popular as plant's cell wall (that contain cellulose, hemicellulose, etc.) as well there are intercellular spaces. 



Still, if you forcefully want to bring a comparison; then the ground-tissue system of plant maybe called as a rough analogy with connective tissues in animals ( Similarly epidermal tissue of plant maybe a rough analogy with epithelial tissue of animals)