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Plant Structure and Taxonomy
Unit 15 Agriscience
When early man started the practice of growing plants for food it allowed
Them to stay in one place and produce food there. The beginning of
Civilization started here.
With out the equation of life, photosynthesis, we would have neither food
Or oxygen. Photosynthesis uses the sun energy to convert non-organic
Material into organic sugars.
The Plant
Roots- May be the largest part of the plants, absorbs water and minerals
Adventitious –appear where roots are not expected to appear
Tap – Thick root that grows straight down used for food
storage
Fibrous – Thin hair like structures helps to stabilize soils.
Structure – parts of the root
Root Cap – penetrates the soil and is the area of cell division and
Elongation.
Xylem carries water and minerals up Phloem carries food down
Root hairs – Area of cell maturation and absorption of minerals and
Water.
Stems
Support leaves, flowers, and fruit.
Woody – Tough and winter hardy
Herbaceous – Succulent full of water or sap
Modified stems – special stems
Bulbs – short stems surrounded by scales
Corms – fleshy stems stem parts grows up and root part goes down
Rhizomes – thick stems that run below ground and rise up to form
New plants
Tubers – thick underground stems for food storage
Stem Parts
Dicots have vascular bundles where xylem and phloem are together in the
Monocots have the xylem and phloem separated into specialized areas of
Node – swollen area where leaves or buds will grow
Internode – area in between nodes.
Axillary buds – appear in the angle above a leaf or flower.
Leaf or branch formation
Lenticels – pores in the stem
Terminal bud – tip of a stem. If the terminal bud is vegetative a
Stem or vine will grow. If the terminal bud is flowering or floral
The stem will not grow but produce a flower.
Leaves
Produce food - phototropism
Margins – edges of the leaf (smooth, serrate) Identify species
Shape and form – (ovate, spatulate) used for identification
Types of leaves –
Simple leaves have one blade and one stem
Compound leaves have many blades attached to one stem
a blade is the wide part of the leaf while the petiole is the stem of
the leaf.
Structure
Cuticle – outer coating of a leaf. Can be waxy
Epidermis – surface on the upper and lower surface of the leaf
Palisade cells – elongated, vertical cells for food production and strength.
Spongy layer – also contain chloroplasts
Chloroplasts – contain chlorophyll for photosynthesis
Mesophyll – the palisades and spongy tissue collectively
Xylem – minerals and water up Phloem – food down
Stoma – openings in the leaves
Guard Cells – control the open and closing of the stoma
Flowers
Production of seeds
Bract – modified leaf often mistaken for a flower (poinsettia)
Stamen – male part of the flower made up of the filament (stalk) and the anther
(produces the pollen)
Pistil – female part of the flower made up of the stigma (catches the pollen), the
style (neck), and the ovary (which contains the ovules or eggs)
Perfect flowers contain both male and female parts, while imperfect flowers only have
One or the other.
Corolla – the colored part of the flower (petals)
Sepals – the protective covering for the immature flower
Calyx – all the sepals collectively
Fruit – a pistil that enlarges and produces flesh that covers the seed (aids in seed
dispersal
Vegetable – any plant that is grown for an edible part.
Nut – a specialized type of fruit
Plant Taxonomy
The classification of plants that is based on similarities and differences.
The Latin language is used because it is a “dead” language. It is
Not used and does not change.
This system was developed by Carl Linnaeus
A shorter version is called the binomial system in which only the
Genus and Species of a plant is used to identify it.
Varieties are a sub group of species such as Ladak alfalfa. (Alfalfa
Is Metacago Sativa.