Roots and Soil Chapter 5

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1 Roots and Soil Chapter 5

2 Plant Organs Plant organs are groups of several types of tissues that together perform a particular function. Vegetative organs roots, stems, leaves make and use food, absorb water and minerals, transport materials throughout the plant, and store foode. Reproductive organs such as flowers and cones- participate in sexual reproduction.

3 Plant Organs Roots anchor the plant in the ground and absorb water and minerals from the soil. Stems support the leaves and transport water, minerals, and sugars throughout the plant. Leaves make sugars through the process of photosynthesis.

4 How Roots Develop When a seed germinates, the embryo produces the first root, called the radicle. The radicle grows producing many branch roots and forming the root system of the plant.

5 How Roots Develop Root systems for a single plant can be huge in relation to the plant itself. Some plant roots extend deep into the soil; others spread out over a great area. Two main types of root systems.. tap roots fibrous root

6 Tap root systems produce thick main roots that have much smaller branch roots. Some tap roots, like those of a carrot, are swollen because they are specialized for food and water storage. Most dicots make tap root systems. How Roots Develop

7 How Roots Develop Fibrous root systems produce many fine roots of similar diameter. Grasses, and most other monocots, have fibrous root systems.

9 Root Structure Botanists divide roots up into four sections, based on the major activities in each area. The Root Cap.. is located on the very tip of the root, where it provides protection to the apical meristem. is a thimble-shaped mass of parenchyma cells covering each root tip. function in gravity perception [know which way is down]. produces a slippery substance that helps roots slide down through the soil. The substance also supports the growth of beneficial bacteria that add to the nitrogen supplies available to the plant.

10 Root Structure Region of Cell Division is.. located just behind the root cap. composed of apical meristem in the center of the root tip. where the cells of the apical meristem divide to produce new cells. Most cell division occurs at the edge of the inverted cup-shaped zone.

11 Root Structure Just like stems, root apical meristems consist of three types of meristematic tissue: Protoderm that produces the outer layer of cells called the epidermis. Ground meristem, to the inside of the protoderm, that produces parenchyma cells of the cortex. Procambium, which appears as a solid cylinder in the center of the root that produces primary xylem and phloem.

13 Region of Maturation Cortex cells mostly store food. Contain endodermis - Located at just the innermost layer of the cortex and adjacent to the vascular tissue. - Checkpoint for materials entering the plant through the roots. - Cell walls impregnated with suberin bands called Casparian Strips. Forces all water and dissolved substances entering and leaving the central core to pass through plasma membranes of the endodermal cells.

14 Region of Maturation

16 Region of Maturation Vascular Cylinder lies at the inside of the endodermis. Pericycle lies directly against the inner boundary of the endodermis-just outside of the vascular cylinder. Produces lateral roots that branch off the main root Lateral roots are multicellular structures with all the tissues of a primary root.

17 The cells from the outside to the inside of a dicot root are.. Epidermis- root epidermal cells can become root hairs Ground tissue- cortex Endodermis- innermost layer of cortex, contains suberin and casparian strip Pericycle- outer layer of vascular cylinder from which lateral roots originate Phloem- part of vascular cylinder Xylem- inner part of vascular cylinder

18 Region of Maturation In both roots and stems, growth may be determinate (stops at a certain size) or indeterminate (new tissues added indefinitely).

23 2 Roots Slide 2 of 36

23 2 Roots Slide 2 of 36 2 of 36 Types of Roots Types of Roots What are the two main types of roots? 3 of 36 Types of Roots The two main types of roots are: taproots, which are found mainly in dicots, and fibrous roots, which