BOTANY Take Notes on Page 91
Plants are either woody (long living) or herbaceous (short lived and green). Woody plants have both woody and herbaceous structures.
Plant Organs and Tissues There are two groups of plant organs: • Vegetative - which have leaves, roots and stems • Reproductive - which have flowers, fruits and seeds
Root Systems Roots have four main functions: • They anchor the plant • They absorb water & minerals necessary for plant growth • They transport absorbed substances to where they are needed in the plant • They store food (in carrots, radishes, & beets)
A taproot system has the original root that sprouted from a seed. It continues to grow as the predominant root. Taproots are often long, thin, and produce small, branching secondary roots. A fibrous root system has no taproot but has many secondary roots. In general, roots usually spread outward more than they grow downward. Why do you think this type of growth would be beneficial for the plant?
Taproots are: • Deep penetrating in soil • Often used for food storage • Form small lateral roots from the tap root • Taproots are often deep and provide excellent anchorage for the plant
Fibrous roots are: • Shallow, wide spreading • Several, equal diameter roots or root masses • Good for soil erosion control. Fibrous roots cling to soil particles well.
Tap Roots / Fibrous Roots 1. Which root stops soils erosion the best? 2. Which root is the best for food storage? Name some that you eat. 3. What type of root do grasses have?
Root hairs 4. What do you think root hairs do for the plant?. • In one study a rye plant had 14 billion root hairs with an absorption surface area of 401 square meters…..
BULB underground storage organ from the plant stem and leaves. • In the growing season, the plant uses the food stored in the fleshy scales, and at the end of the season, the leaves divert food into new scale leaves for the next season. • The old scale leaves form the dried papery covering New bulbs are formed around the base of the old bulb.
tubers • a fleshy storage organ formed from stem or root. • A potato tuber is at the end of the underground stem, and can produce new shoots from eyes or buds on its surface. 5. Name 3 different ways plants store energy
Rhizome A rhizome is a swollen stem bearing leaves and roots, which grows horizontally on or just below the surface. 6. Name a plant with rhizomes. What are the benefits of rhizomes for a plant?
Stems Stems have two major functions: • They manufacture, support and display leaves • They conduct many of the materials needed for and manufactured by photosynthesis to and from the leaves
The Leaf The function of a plant’s leaves is to absorb energy from the sun (photosynthesis). The blade of the leaf is a large, flattened area connected to the stem by a petiole (if there is no petiole the leaf is sessile). Stipules may cover the leaf during development. They may be wing-like, photosynthetic, or may be thorns. Make a drawing of a leaf, including the blade, petiole, stipules and stem.
The Covering of a Leaf • The upper and lower epidermis are one cell layer thick. They protect the leaf. • The cuticle consists of a waxy substance secreted by the epidermis. It helps the leaf retain water in hot weather
Leaves may have several shapes, or margins (the edge of the leaf). Make drawings of the following margins: entire, lobed, serrate, and repand See http://www.fnr.purdue.edu/extension/kp/lm.html
Leaves may also have several venations: 1.parallel - found in corn, grass, iris’ and orchids 2.netted - where large veins branch to form a network of smaller veins a. pinnate - the veins branch off of one central vein, as in oaks, African violets, and apple trees b.palmate - two or more main veins coming from a single point, as in maples, ivies and geraniums See: http://www.pssc.ttu.edu/pss1411cd/STRUCTUR/leaves/venation.htm
Leaves may also be simple, where there is one blade on one petiole, or compound, with leaflets. The difference between a leaf and a leaflet is that leaves have stipules and leaflets don’t.
3. The stomata are for gas exchange. They are found on the underside of the leaf and are regulated by the guard cells. Guard cells make sugars that will cause a change in the turgor pressure of the cells. When turgor pressure in the guard cells is high, the stomata are open; when the turgor pressure in the guard cells is low, the stomata are closed.
The Internal Structure of a Leaf • The parenchyma consists of the palisade and spongy mesophylls. They are the primary photosynthetic areas of the leaf. The palisade mesophyll has a larger number of cells in a smaller surface area. The cells contain many chloroplasts. The spongy mesophyll is involved in carbon dioxide-oxygen exchange.
2. The vein is composed of the xylem, phloem and the collenchyma. We have already discussed the xylem and phloem; the collenchyma strengthens the vein. Draw and label a diagram of a leaf on your paper. Include the palisade mesophyll, spongy mesophyll, upper epidermis, lower epidermis, cuticle, stomata, guard cells, xylem, and phloem. See page 647 in your textbook.
How Plants Use Water Plants use water in four ways: • For photosynthesis (think about the equation) • For turgor-using water to stiffen parts of the herbaceous plant • For hydrolysis-adding water to break large molecules apart • For translocation-moving dissolved materials from one place to another
What causes the movement of water in plants? Translocation is the movement of water and dissolved minerals within a plant. The movement of water may result from: • Root pressure - which causes the movement of water up the xylem • Passive absorption - which is the movement of water according to a concentration gradient
C. capillarity - which is the tendency of water to move up a thin tube (like the xylem) D. transpiration - which is the release of water vapor, by the plant, into the atmosphere E. cohesion - which is the “sticking together” of a group of water molecules F. transpiration-cohesion theory - which states that as water molecules are removed from the top of the plant (due to transpiration) additional water molecules that are “stuck together” rush into the bottom
Plant Hormones Plant hormones are chemical growth regulators produced by the plant. There are two main groups of plant hormones: • Auxins - which are found in stems, seeds, leaves, fruits and roots, Auxins cause elongation of cells, cause unfertilized flowers to develop into seedless fruits, and stimulate the formation of roots in wood stem cuttings.
B. Gibberellins - stimulate cell division and elongation, growth of seeds, flower formation, pollen formation and fruit formation.
Tropisms A tropism is a growth response in plant that is caused by hormonal action. There are four kinds of tropisms: • phototropism - a growth response to light • thigmotropism - a growth response to touch C. chemotropism - a growth response to chemicals; for example, hydrotropism is a growth response to water D. geotropism - a growth response to gravity
In general, a positive tropism is a growth response toward a particular factor and a negative tropism is a growth response away from a particular factor.
Plants and Light Light is important for plants. A plant that does not receive enough light may be pale green, yellow or white. The stem elongates abnormally and the plant bends toward any available light. Such a plant is said to be etiolated.
Photoperiodism is the response of a plant to changes in light intensity and length of days. • Short day plants flower when the period of light is less than 12 hours. • Long day plants flower when the period of light is more than 12 hours. • Neutral day plants flower independently of the photoperiod; they usually flower continuously if proper conditions are met.
Reproduction of Flowering Plants Accessory Flower Parts • Sepals – leaflike, green structures that encircle the flower stem beneath the petals • Petals – leaflike, colorful structures arranges in a circle called a corolla around the top of a flower stem
Reproductive Flower Parts • Stamen (male) • filament – the long structure that supports the anther • anther – the structure at the tip of the filament that produces pollen containing sperm
B. Pistil (female) • stigma – at the top of the pistil; a sticky or feathery surface on which the pollen grains land and grow • style – the slender stalk of the pistil that connects the stigma to the ovary • ovary – eventually becomes the fruit; contains the ovules • ovules – will become seeds if they are fertilized
Kinds of Flowers • Complete – a flower that has all 4 organs (sepals, petals, stamens and pistils) • Incomplete – a flower that lacks one or more organs • Male – have stamens but no pistils • Female – have pistils but no stamens
Use the diagram on page 612 to draw a typical flower and label the accessory and reproductive parts.