Biodiversity of Plants

BIODIVERSITY OF PLANTS

BIODIVERSITY

·  A measure of the number and abundance of different species living in a particular ecosystem

Plants provide food and shelter for other organisms. Therefore if an ecosystem has a lot of different plant species, it will be able to support many different animal species.

HIGH PLANT DIVERSITY = HIGH ANIMAL DIVERSITY

TROPICAL RAINFORESTS have the highest biodiversity, both plant and animal on the planet.

MONOCULTURE

·  A habitat dominated by a single plant species

·  Examples – food crops (corn, carrots), lawn, apple orchard

LOW PLANT DIVERSITY = LOW ANIMAL DIVERSITY

Just as animals compete for resources (food, shelter, space), plants also compete for resources. Plant species that are introduced into an area may out-compete the native species and crowd them out. These are called INVASIVE SPECIES.

PICTURES OF INVASIVE SPECIES

RAGWEED CANADIAN THISTLE

OVERVIEW OF PLANT STRUCTURE

Plants are:

·  KINGDOM - Plantae

·  Multicellular

·  Usually autotrophic (make their own energy by photosynthesis)

·  Sexual and Asexual reproducers

·  Mostly terrestrial (land) and some aquatic (water)

Plants can be placed in 2 categories:

1.  SEED PLANTS

2.  NON SEED PLANTS

Seed Plant / Non Seed Plant Concept Map

CHARACTERISTICS OF MONOCOTS AND DICOTS

Root System – Fibrous Root System - Taproot

PLANT TISSUES

There are 4 types of plant tissue:

1.  Meristematic Tissue

2.  Dermal Tissue

3.  Ground Tissue

4.  Vascular Tissue

MERISTEMATIC TISSUE

·  Cells divided by mitosis;

·  These cells differentiate into other plant cell types;

1)  Apical Meristems

·  Found at the tips of roots and shoots

·  Responsible for primary growth (lengthening shoots and roots)

2)  Lateral Meristems (Cambium)

·  Cylindrical regions which increase the diameter of roots and shoots (secondary growth)

3)  Vascular Cambium

·  Produces the cells for new xylem (water) and phloem (food)

DERMAL TISSUE

·  Outermost cell layers

·  Function:

o  protection from cuts;

o  microorganism invasion;

o  water loss;

·  Examples

o  Leaves and stems may produce wax (prevent water loss) or fine hairs or painful irritants (to discourage herbivores)

o  Epidermal root tissues develop root hairs to increase water and nutrient absorption

o  Woody plants produce bark for further protection (bark consists of dead cells)

GROUND TISSUE

·  All internal cells except vascular tissues

·  Function

o  Storage

o  Support

o  Photosynthesis

·  Examples

o  Fleshy portion of apples, pears, potatoes

VASCULAR TISSUE

·  For transport of substances in the plants

Xylem

o  Transports water and dissolved minerals from roots to the rest of the plant

o  These cells die at maturity and become hollow

o  Appearance – thick walls, may be long and thin or shorter with open ends

o  When arranged end to end they make continuous tubes for transport

o  Wood is 100% xylem tissue à good support for trees

Phloem

o  Transports sugar and other nutrients from the leaves (site of photosynthesis) to the rest of the plant

o  Living cells

o  Sieve tube element

·  Long thin cells with pores at the ends of their cell walls

·  No nuclei, mitochondria or vacuoles

·  Arranged end to end to form tubes

o  Companion cells

·  Found beside sieve-tube elements

·  Have all the cell organelles that the sieve-tube is lacking

·  Control the functions of the sieve tube

DIAGRAMS OF THE VASCULAR TISSUE

ROOTS

·  Usually below the ground

·  Serves 5 functions

o  Anchor the plant to the ground

o  Absorbs water and minerals

o  Store extra sugar during photosynthesis

o  Transport water, sugar, minerals and hormones to the remainder of the plant

o  Produces some hormones

·  Edible roots include:

o  Carrots, radishes, sweet potatoes

·  2 forms:

1.  Tap root

o  Large tapering main root

o  Example - carrot

2.  Fibrous root

o  Many smaller roots of equal size that grow out of the bottom of the plant

o  Example – grass

ROOT GROWTH AND DIFFERENTIATION

STEMS

·  Provide support for the above ground portion of the plant;

·  Connect roots with the remainder of the plant;

·  Store water and food;

·  Transportation system – xylem and phloem are located in the stems

·  Examples – potatoes

·  2 types

1.  Woody

o  Stems are hard and not easy to bend; strong

o  Composed of dead xylem tissue

2.  Non-woody

o  Soft and bend easily; weak

o  Height limits

LEAVES

·  Green leaves (chlorophyll) are the site of photosynthesis

SIMPLE AND COMPOUND LEAVES

LEAF STRUCTURE

Epidermal Cells

·  1 cell layer of cells covering the upper and lower surfaces of the leaf blade

Palisade Mesophyll Layer

·  Cells at right angle to the leaf surface; rich in chloroplasts; site of photosynthesis

Spongy Mesophyll Layer

·  Loosely packed cells with large air spaces; air spaces allow for efficient gas exchange; site of photosynthesis; leaf veins run through this layer

Stoma

·  A small opening in the surface of the leaf which permits the exchange of gases

Transpiration – process of water loss through evaporation out of the leaf when the stoma are open

Guard Cells

·  Control the opening and closing of the stoma; a pair of crescent shaped cells that surround the pore opening

SEEDS AND FRUIT

Most of the species we eat are angiosperms.

Most commonly the seeds and fruit are used to feed the 6 billion (+) people on the planet.

SEEDS

The worlds’ 3 most important crops are:

1.  Wheat

2.  Corn

3.  Rice

·  Other important crops are soybeans or other beans.

·  The edible portion of these crops are the seeds

·  The seeds of these plants are high in protein, carbohydrates and fibre.

FRUIT

·  Structure that develops in the ovary of a pollinated angiosperm

·  Fruits help the plant spread its seeds

o  Maple keys, dandelion fluff are examples of fruits with a form that helps them spread

o  Consumed in animals and pass through the digestive tract unharmed and are deposited in another location

·  Many vegetables are actually fruits – cucumbers, pumpkin, tomatoes, zucchini, squash

·  Other common fruits include bananas, mangoes, apples

POLLINATION

·  Process by which pollen is moved from the anther (portion of male reproductive structure – STAMEN) to the female egg cells and fertilizes these cells.

·  Some plants can fertilize themselves and others need pollen from a different plant.

·  Some plants even have separate male plants and female plants.

·  The pollen is able to travel between plants in many different ways, wind, animals, birds, and insects (BEES).

·  Once the eggs are fertilized they become seeds.

·  The petals fall and in some species the ovary develops into the fruit.