Plant Growth and Development Plant Science/Horticulture I Instructor: Mr. Dixon
Dec 22, 2015
Plant Growth and Development
Plant Science/Horticulture I
Instructor: Mr. Dixon
VEGETATIVE PLANT PARTS
UNIT OBJECTIVE
After completion this unit, students should be able to match terms and definitions and identify the parts of a plant.
Students should also be able to list functions of plant parts and name the root systems.
Terminology
I. Terms & Definitions
Node--The part of a stem where a leaf is attached
Internode--The part of stem between two nodes
Bud--An embryonic shoot of a plant
Leaf scar--A scar left on the stem when a leaf falls
Vascular bundle scar--A spot within a leaf scar left by the vascular bundles when a leaf falls
Terminology
Monocot--Plant having one seed leaf (cotyledon) as in cereals and corn
Dicot--Plant having two seed leaves (cotyledons) as in beans and peas
Vascular bundle--A strand of tissue containing xylem and phloem enclosed by a sheath of cells
Xylem--Vascular tissue that transports water and minerals from the root system to the leaves
Phloem--Vascular tissue that conducts food from the leaves to regions of growth or storage
Terminology
Pistil--Seed bearing organ of a flower, composed of the ovary, style and stigma
Stamen--Part of the flower producing the pollen; composed of the filament and anther
Fertilization--Union of the male (pollen) nucleus with the female (egg) cell
Pollination--Transfer of pollen from the anther to the stigma
Embryo--The young plantlet within the seed; the germ
Terminology
Radicle--The embryonic root
Hypocotyl--The part of an embryo between the cotyledons and the radicle. The Stem: Usually emerges before the leaves.
Plumules--The part of the embryo above the cotyledons.
Bean Seed Cross section
Germination of Seeds
Proper temperature. Water. Water is always needed to allow vigorous metabolism to
begin. It is also sometimes needed to leach away a germination inhibitor within the seed. This is especially common among desert annuals. The inhibitor is often abscisic acid (ABA).
Oxygen. A preceding period of dormancy (often). The seeds of many
temperate-climate angiosperms will germinate only after a prolonged period of cold. An inhibitor within the seed (probably abscisic acid - ABA) is gradually broken down at low temperatures until finally there is not enough to prevent germination when other conditions become favorable. This mechanism is of obvious survival value in preventing seeds from germinating during an unseasonably warm spell in the autumn.
Correct photoperiod (often).
Germination in Dicots
The primary root emerges through the seed coats while the seed is still buried in the soil.
The hypocotyl emerges from the seed coats and pushes its way up through the soil. It is bent in a hairpin shape - the hypocotyl arch - as it grows up. The two cotyledons protect the epicotyl structures - the plumule - from mechanical damage.
Once the hypocotyl arch emerges from the soil, it straightens out. This response is triggered by light. The cotyledons spread apart exposing the epicotyl, consisting of two primary leaves and the apical meristem
In many dicots, the cotyledons not only supply their food stores to the developing plant but also turn green and make more food by photosynthesis until they drop off.
Germination in Dicots
Bean Germination Steps
Pea Germination Steps
Sectional views of a corn kernel
per. = pericarp, end. = endosperm, sc. = scutellum, col. = coleoptile, pl. = plumule, rad. = radicle
Cross Section of Corn
Germination in Monocots
When grass seeds, e.g. corn (maize) or oats (shown here), germinate
the primary root pierces the seed (and fruit) coverings and grows down;
the primary leaf of the plant grows up. It is protected as it pushes up through the soil by the coleoptile - a hollow, cylindrical structure.
Once the seedling has grown above the surface, the coleoptile stops growing and
the primary leaf pierces it.
Germination in Monocots
Corn Germination Steps
Corn Germination Con,t
Corn Germination
Visible Corn Germination
Day Four
Day Four Con’t
Primary parts of a plant
II.Primary parts of a plant
A. Roots
B. Stem
C. Leaves
D. Flowers