Plant Organs We are focusing on the flowering plants, or angiosperms , and their characteristic organs and tissues. An organ is a structure that contains different types of tissues and performs one or more specific functions. The vegetative organs of a flowering plant – the root , stem , and leaf – allow the plant to live and grow. The body of a plant has a root system and a shoot system .
Organization of the plant body
Roots The root system of a plant often has a main root, or taproot , and many branch or lateral roots . The root system absorbs water and minerals from the soil for the plant. The cylindrical shape of the root allows it to penetrate the soil. Root hairs greatly increase the absorptive capacity of the root.
Roots can also have other functions. Roots produce hormones that stimulate the growth of stems and coordinate their size with the size of the root. Generally the root system is equivalent in size and extent to the shoot system. Perennial plants often store the products of photosynthesis in their roots.
Stems also contain vascular tissue that transports water and minerals from roots to leaves, and also transports the products of photosynthesis in the opposite direction. A cylindrical stem can expand in girth as well as in length. Some stems have functions other than transport; some are specialized for storage.
Leaves A leaf is a broad, thin organ that carries on photosynthesis . This shape maximizes the surface area for collection of solar energy and absorption of carbon dioxide. The wide portion of a leaf is the blade , a petiole is the stalk of the leaf, and axillary buds are found at the leaf axil . Some leaves have other functions.
Plant Tissues A plant grows throughout its lifespan because of meristem (embryonic tissue) in stem and root tips (apexes). Three specialized tissues are in plants: 1) Epidermal tissue – forms the outer protective covering 2) Ground tissue – fills interior of a plant 3) Vascular tissue – transports water and nutrients and provides support.
Epidermal Tissue Epidermal tissue forms the outer protective covering of a herbaceous plant and is modified in roots, stems, and leaves. Exposed epidermal cells are covered with waxy cuticle to minimize water loss. Epidermal cells in roots have root hairs . Lower leaf epidermal cells have guard cells and stomata .
Stoma of leaf
In older woody plants, the epidermis of the stem is replaced by cork tissue .
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- Fall '16
- Lambda Thomas
- Psychology, phloem, Plant anatomy, Dicot Root, Monocot Roots