Presentation on theme: "Plant Organs. The Plant System The Root System 1. Fibrous Root System – the root of grass or of any weed at the base of its stem. Some fibrous root systems."— Presentation transcript:
The Root System 1. Fibrous Root System – the root of grass or of any weed at the base of its stem. Some fibrous root systems do not penetrate deeply into the soil but extend to a distance outward from the base of the plant. Examples are grass, corn, rice and beans
The Root System 2. Taproot system – usually grow deep in the ground. The primary root becomes large, long and slender with short lateral rootlets. Example: alfalfa
Taproot 3 functions Endodermis Function of the leaf (1) 7 opposite arrange 8Parallel venation 9 netted palmate phyllotaxy
The Root System 3.Adventitious Roots – roots that grow from the stem or leaves. Examples: katakataka, pandan, corn and rubber tree 4.Brace or prop root – grow from the nodes. They grow in circles and help support the plant. Examples: corn and sugarcane 5.Climbing roots – found along the stems that cling to the walls and other means of support. Examples: ampalaya, squash, upo 6.Propagation roots – found in plants where roots develop on the stem when placed in wet soil or water, and new plants grow. Examples: San Francisco, climbing roses, begonias
Functions of Roots 1.Anchorage - keeps the plant rooted to the ground 2.Absorption - roots absorb water and other mineral matter from the soil. This is called diffusion, the process by which water from the soil moves into the root hairs 3.Nitrogen Fixation – Together with S and P, nitrogen is needed by plants to build proteins. Some roots have nodules which contain bacteria that fix nitrogen from the atmosphere for plant use. 4.Storage – all roots have a small amount of food stored temporarily in them. The food is usually stored as insoluble starch or as sugar 5.Conduction – Roots transport water, mineral salts and sometimes stored food to the stems and the leaves
Structure of the Roots Longitudinal Section – growth in length a. Root cap – protects the apical meristem of roots, sheds cells that facilitate the growth of the root through the soil, gives off carbon dioxide to the soil b. Meristematic region – cell division takes place. They add new cells to the root cap and to the region of elongation c. Zone of elongation – located 1-3 mm above the meristem, this is the region where the cell stops dividing, but the cell wall expand and vacuoles increase in size making the cells longer d. Zone of maturation – just above the zone of elongation, this region has cells which are all almost uniform in structure. The cells begin to differentiate and develop into many tissues.
Structure of the Roots Cross Section of Primary Root Tisssues 1. epidermis – the outermost tissue from which the root hairs extends. Its function is for protection and absorption 2. endodermis – the innermost layer of cells; serves as a boundary layer; controls the movement of substances between the cortex and the interior tissues of the root.
Stems Herbaceous Stems – green and do not develop tough, woody tissues. Their sizes are limited because their soft stem tissues cannot support much weight. Woody Stems – Vascular plants that live for more than one year often have woody stems. The roots and stems of these plants increase in diameter every season. They even reach tremendous heights.
-may be simple, branched, upright or creeping -can form underground food storage organs (rhizomes, bulbs, corms or tubers) -can produce suckers, shoots, stolons, runners or tendrils. Runners, for example, will put down adventitious roots when they reach a suitable new location. Tendrils are modified stems that attach themselves to nearby objects for support.
The Leaf All leaves are responsible for: absorbing the sun's rays the majority of photosynthetic production (which can take place in any green part of a plant) taking in carbon dioxide and releasing oxygen and water vapor (breathing) removing waste products from the plant using osmotic pressure to draw water up from the roots
The Leaf External Structure - vary in size and shape - slender petiole or leaf stalk is present in the leaves of most flowering plants. It is a continuation of the stem to the rest of the leaf - sessile – leaves without petioles - blade – flattened, expanded portion of the leaf and is usually green
Types of Leaves Simple leaves – have single expanded portion Compound leaves – the leaf blade may be subdivided into several separate expanded parts, or leaflets. Bicompound – each leaflet may consist of an extended portion and a short stalk attached to the rachis, which is a continuation of the petiole. Leaves may be pinnately compound or bipinnately compound
Venation Venation – the arrangement of veins in a leaf 1. Parallel venation – characteristic of most monocotyledonous plants, such as corn, onion and common grasses 2.Net venation – found in dicotyledonous plants such as santol, gumamela, rose, mango. In these plants, one or more veins are prominent, and the smaller veins form a conspicuous network
Types of Net Venation Pinnately net veined – if a leaf has one main vein from which the others branch off Palmately net veined – leaf has several main veins extending from the base
Leaf Arrangement and Phyllotaxy Phyllotaxy – the system of leaf arrangement 1.Opposite – leaves are arranged in pairs on each node of a stem (Ex. Guava leaf) 2.Alternate or spiral – leaves are arranged around the stem, one on each node (santol, atis and star apple) 3.Whorled – several leaves are arranged at a node around the stem