Chapter 2 - B

Parts Of Plant And Their Functions

► Most

plants are made up of 4 basic parts:    

Leaves Stems Roots Flowers (become fruits or seeds)

LEAVES Food factory Vary in shape and size Help in identification of plants: ►Flat

(most) ►Needlelike ►Cylindrical

► The

arrangements are difference: alternate on the stem, opposite one another, and whorled (arranged in circle around the stem)

Leaves consist of petiole (leaf stalk), and blade (flat part of leaf).

► Leaf

blade have veins and midrib (the large center vein )

► Veins

of the leaf form its structural framework

► Most

leaves have forms, leaf margins (edges of plant leaves) which assist in plant identification.

► The

skin of leaf = Epidermis

 A single layer of cells which function to protect the leaf from loss of water or too much moisture ► Stomata

Special cells in the leaf skin, Guard cell Open and close the small space or pore on the underside of the leaf  To allow the leaf to breathe and transpire (give off moisture and exchange gasses such as oxygen and carbon dioxide)   

•Guard cells - Crescent shaped and inner walls are thick. As the wall become turgid (due to water pressure in the cell) the stomata opened. •Center of the leaf are food making cells (mesophyll) Contain chloroplast (the green color bodies which contain chlorophyll and give green color of the leaf).

 Food are made through the process of photosynthesis  Food manufactured in the leaves moves downward through the stem or root (phloem) in the form of sugar, starch or protein  Leaves ► Used

as food for various animals (including human beings) ► the most nutritious parts of the plant.

► 6C02

602

+ 6H20 + 672 kcal  C6H1206 +

Stems Have 4 main functions:

►

»

» » »

The movement of materials (water and minerals) from roots to upwards (xylem) and movement of manufactured food from leaves to downwards (phloem) Support of the leaves and reproductive structures (flowers and fruit or seeds) Food storage Reproduction methods (stem cutting or grafting)

►

Green stem manufactured food just as leaves do

►

The outside of the stem consists :   

Lenticels (breathing pores), Bud scale scars Leaf scars

 Bud scale scars indicate where a terminal bud has been located,  Distance between two scars represents one year of growth  Leaf scars show where leaves were attached.  Center of the stem there are a vascular bundle consist of xylem which translocated water and

Dicots stem continue to increase in diameter because the cambium builds phloem cells on the outside and new xylem cells on the inside. Monocots, such as grass have different stem structure where their vascular bundles that contain both phloem and xylem tissue in each small bundle. Monocots stem has no outside circling cambium Stems of some plants such as potato and asparagus are used as food. Others are used as building materials such as lumber from the tree trunks.

Roots  Are usually underground  Function to: o o o o

Anchor the plant and hold it upright Absorb water and minerals from the soil and conduct them to the stem Store large quantities of plant food Propagate or reproduce some plants

 The internal structure are much like of a stem

 Older roots (shrubs and trees) have phloem (old outer layers form cork-like bark) on the outside, a cambium layer and xylem (wood) inside.  The phloem carries manufactured food down to the root for food and storage and the xylem carries water and minerals up to the stem  Stem has a terminal buds to initiates new growth and root have a root cap.  Behind the root cap are many root hairs.  The root hairs function is to absorb moisture and minerals that are conducted to the larger roots and to the stem of the plant.  Many roots are important as cash crops for food such as carrots and sweet potatoes.

► There

are two types of root system: Fibrous Root System & Tap Root System.

o Plants

with fibrous root system are much easier to transplant than plants that have tap root system

o The

fibrous root system is short, small and more compact.

o Tap

root system has longer and fewer roots

Flowers, fruits and seeds  Flowers are differs in size, shape and color but generally have the same basic parts.  A complete flower has both male and female parts and only one parent is needed (can pollinate itself)

The complete flower contains 4 main parts: sepal, petals, stamens and pistil.

 Sepals = Green leaf-like parts, cover and protect the flower bud before it opens. They form the calyx after the flower open.  Petals = Most striking part of the flower. The bright colors of the petals flowers act to attract insects for pollination.  A group of petals = Corola  The stamens = Male reproductive part of the flower. Each consists of a short stalk called a filament and a saclike structure on top of the filament called an anther. The anther contains pollen, which is the male sex cell.

 The pistil (located in the center of the flower) ► Female

part of the flower. It produces the female sex cells, the eggs (ovules). These eggs once fertilized become seeds. ► Pistil has three main parts:   

Sticky stigma on top to catch pollen; Style, a tube that leads to the third parts; Ovary, which egg cells develop in the ovary.

 After fertilization, the ovary grows to become a fruit or seed coat. The ovule become seeds.  An incomplete flower has only the male parts or the female parts of the flower but not both. Thus a male flower has sepals, petals and stamens, but no pistil. A female flower has sepals, petals and pistil but no stamens.  Flowers play an important role in the florist and nursery business. They are grown solely for the beautiful flowers they produce.

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