Stems and their function: A stem is a collection of integrated tissues arranged as nodes and internodes. Nodes are locations where leaves attach to stems, and internodes are the parts of stems between nodes.   Nodes and internodes perform several important functions: Support leaves-Turgor pressure in stems provides a hydrostatic skeleton that supports young plants. Leaves are also supported by a stem's internal structure of collenchyma and sclerenchyma. Produce carbohydrates-Stems of plants are green and photosynthetic. Although photosynthesis in stems is usually not significant compared to leaves, in some plants such as cacti it accounts for most of the plants carbon fixation. Store materials-Parenchyma cells in stems store large amounts of starch and water. Water accounts for as much as 98% of the weight of many cactus stems. Transport water and solutes between roots and leaves-The vascular system of stems maintains an aquatic environment in leaves and transports sugars and other solutes between leaves and roots. Stems link leaves with the water and dissolved nutrients of the soil. Control of Stem Growth: Leaf control: The growth of stems is controlled by many factors, leaves being the most important. Leaf primordia control the differentiation of procambium in stems. There is no procambium above the youngest primordium, and vascular tissues in developing leaves along and connect with mature vascular tissues of the stem. Light also controls stem growth. Hormones: Stems elongate in subapical regions in response to auxin and gibberellins. These hormones elongate stems by stimulating cellular elongation and division. In a lot of plants, elongation occurs throughout the internode; while in some others it continues as a wave originating at the base of the internode. Plants whose stems do not elongate are called rosette plants; these plants have short internodes with tightly packed leaves. The stems of rosette plants are short and made almost entirely of overlapping leaf bases. Most rosettes fail to elongate because they do not make enough physiologically active gibberellins. Treating rosettes with gibberellins usually causes internodal elongation. Intercalary meristems. Grasses such as bamboo elongate at meristems intercalated between mature tissues at the bases of their nodes and leaf sheaths. These meristems are called intercalary meristems. These remain important because they reform the stem or leaf of a grass when its tip is torn off by an animal or lawn mower. Intercalary meristems can produce high rates of growth in many plants. They also have a direct impact on us-no matter how many afternoons we spend behind the lawn mower, we are assured that the grass blades will grow back quickly because of intercalary meristems.