Some phloem cells may also fill with secondary cell wall material and therefore develop into a phloeic fiber cell. Concepts to be developed using the sections of Stems, Leaves and Root. Epidermal layer - the outer most layer of stems, leaves and root which developed from the protoderm. The epidermis protects the plant from invading organisms, and in stems and leaves is covered with a waxy substance known as cuticle that the epidermis has secreted to protect these organs from losing too much water by evaporation. In the stems and leaves the epidermis has developed pores that are called stomates which are the openings through the epidermis and cuticle which allows the exchange of Carbon dioxide and oxygen between the inside and the outside of the plant.
Guard cells surround a stoma and control the stoma opening and closing.
Cortex is a type of ground tissue that develops from ground meristem and is seen particularly in stems and roots. Thin walled parenchymous tissue that if it has a function it is usually in storage of organic compounds. The cells arrangement in the veins or vascular bundles of monocot often look like monkey faces. Around the vein there is a layer of cell known as the bundle sheath cells that gives support to the vascular tissues in these veins. The cortex and pith are the thin walled parenchymous cells.