Epidermis is a protective tissue of angiospermic plants. It provides protections to underlying tissues. Epidermis forms outer covering of various plant organs such as roots, stem, leaves, and flowers and remains in direct contact with the environment. Any substance whether solid, liquid or gas can enter into the plant or move outside only after passing through this layer. Epidermis helps in absorption, secretion, gaseous exchange and transpiration. It helps in preventing the entry of pathogens.
In Fig. 9.26, A, B, C and D are four points on a circle. AC and BD intersect at a point E such that ∠ BEC = 130° and ∠ ECD = 20°. Find ∠ BAC.
Look up the dictionary entries for the words sympathy, familiarity, comfort, care, and surprise. Use the information given in the dictionary and complete the table.
Noun, Adjective, Adverb, Verb, Meaning:
sympathy
familiarity
comfort
care
surprise
The epidermal tissue system forms the outer-most covering of the whole plant body and comprises epidermal cells, stomata, and the epidermal appendages – the trichomes and hairs. The epidermis is the outermost layer of the primary plant body. It is made up of elongated, compactly arranged cells, which form a continuous layer. The epidermis is usually single-layered.
All tissues except the epidermis and vascular bundles constitute the ground tissue. It consists of simple tissues such as parenchyma, collenchyma, and sclerenchyma. Parenchymatous cells are usually present in the cortex, pericycle, pith, and medullary rays, in the primary stems and roots. In leaves, the ground tissue consists of thin-walled chloroplast-containing cells and is called mesophyll.
The vascular system consists of complex tissues, the phloem, and the xylem. The xylem and phloem together constitute vascular bundles. In dicotyledonous stems, cambium is present between phloem and xylem. Such vascular bundles because of the presence of cambium possess the ability to form secondary xylem and phloem tissues and hence are called open vascular bundles. In the monocotyledons, the vascular bundles have no cambium present in them. Hence, since they do not form secondary tissues they are referred to as closed.
Read More: Plant Tissue