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Created By: Kyana Pereira & Sindy Morales March 11, 2011 Period 08. Woody & Herbaceous Plants. Woody Plants. Woodiness is one of the most important and noticeable stem distinctiveness. These plants are created with thick cell walls that sustain the plant body.
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Created By: Kyana Pereira & Sindy Morales March 11, 2011 Period 08 Woody & Herbaceous Plants
Woody Plants • Woodiness is one of the most important and noticeable stem distinctiveness. • These plants are created with thick cell walls that sustain the plant body. • Woody plants include trees, shrubs, and vines. • Woody plants dominate the vegetation wherever conditions are favorable for plant growth. • Their large, permanent stems and stable root systems place their leaves in position to capture most of the incoming light energy. • The woody habit has been independently acquired in various divisions of the plant kingdom in the past.
Woody Plants (Part 2) • Today only the three divisions of gymnosperms and the anthophyta are truly woody, because of their scattered, closed vascular bundles monocots ca • In dicots a small apical meristem can give rise to a massive tree because the bundles retain active cambium which can expand the diameter of the stem. • Tree-like monocots such as palms have a massive apical meristem that generates the full width of the stem immediately form wood. • The vascular cambium derives from the procambium which in the stems of dicots persists between the phloem and xylem of the bundles and as interfascicular cambium. • In the root the cambium arises partly in the pericycle and partly in the arches between xylem and phloem.
Herbaceous Plants • Herbaceous plants have plant stems that are smooth and nonwoody. • These plants do not produce wood as they grow. • Examples of these plants are dandelions, zinnias, petunias, and sunflowers. • In the mature root the epidermis has lost its root hairs, the cortex is greatly enlarged and serves for food (starch) storage, and the central stele is surrounded by the endodermis. • Each cell in this layer is suberized in a (Casparian) strip around the radial walls initially and later over its whole surface.
Herbaceous Plants (Part 2) • Inside the endodermis are a few layers of cells that remain meristematic, then the phloem and finally the xylem which is often arranged in a band or cross. • The root apical meristem does not branch. • Roots continue their exploration of soil space by developing new apical meristems from the pericycle. • The new roots break through the cortex as they grow. • Although they are not as diverse as shoots, roots are sometimes modified for special purposes, particularly food storage. • Some of our "root crops" are really stems but carrots, parsnips and sweet potatoes are roots. • In dicots such as sunflower each bundle consists of phloem on the outside and xylem on the inside of the stem. • There are usually some fibers associated with the bundle which can be in a cluster outside the phloem or a sheath around the whole bundle (or both). • Across the middle of the bundle is a band of small cells which are capable of cell division. This cambium may extend across the pith rays between the bundles when it is called interfascicular cambium. • In monocots such as corn the bundles are scattered, and contain xylem (inside) and phloem (outside) - there are fibers around the outside and the large air-filled cavity in the mature bundle from destruction of the first formed xylem and phloem. • There is no cambium and certainly no interfascicular cambium .
