Plant Structure & Function

Monocots & Dicots Angiosperms are the class of plants that produce flowers. They can be broken down into two main groups – the monocots and dicots. Monocots are a class of plants whose seeds have one seed leaf. Dicots are a class of plants whose seeds have two seed leaves. These are not the only notable differences between monocots and dicots. The next slide presents several characteristics that can help you discern between the two.

Monocots vs. Dicots

Roots, Stem & Leaf Ask anyone what are the three parts of a plant and you will get the answer of, “Roots, stem & leaf”. The roots are normally below the ground – their role is to anchor the plant in the soil and absorb water. The stem (or trunk) is there to support the plant above the ground and to try to get the leaves into a position where they are exposed to sunlight. The leaves are the sites of photosynthesis – they provide the glucose (energy) for the plant.

Roots – In Detail There are two main types of root systems in plants – taproots and fibrous roots. Taproots involve a long, thick primary root from which smaller secondary roots grow. (Dicots) Fibrous roots are highly branched, thinner roots. (Monocots)

Roots – In Detail The roots: –anchor the plant. –absorb water and minerals from the soil. –transport the water and minerals to the stem. The roots have vascular tissue in them that allows them to transport substances throughout the plant. There are two types of vascular tissue: –Xylem – Vascular tissue in plants that carries water. –Phloem – Vascular tissue in plants that carries food (nutrients). Roots are also important to us as they may carry out phytoremediation – a process by which plants extract toxic substances from the soil or water.

Stems – In Detail Stems hold the leaves up to the sun. There are two main types of stems – herbaceous and woody. Herbaceous – Soft stems, usually green and thin. Woody – Thicker, tougher stems that increase in size each year and can survive the winter.

Leaves – In Detail Basically, the leaves are solar panels that harness the energy in sunlight to make glucose. 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 So…These plants supply us with all of our food energy and with the bulk of oxygen we breathe…It only makes sense then to cut them all down and make parking lots… Excuse the blatant sarcasm – lets take a closer look at the leaf.

The Leaf – S & F Cuticle – Waxy layer on top side of leaf. Upper Epidermis – Protective cell layer – also secretes cuticle Palisade Layer – Site of photosynthesis – cells have a lot of chloroplasts. Spongy Layer – Contains spaces for air (CO 2 ) storage. Vein – Vascular tissue containing xylem and phloem. Stomata – Tiny openings on bottom of leaf that allow for gas exchange. Guard Cells – Special cells that control the opening and closing of the stoma. Lower Epidermis – More protection for underside of leaf.

Plant Tissues A tissue is a group of similar cells that work together to perform a common goal. There are four basic types of plants tissue. –Vascular tissue – Transport of substances – xylem & phloem. –Ground tissue – Most of the plant is made of ground tissue. It aids in support, storage of glucose and water, and photosynthesis. –Meristematic tissue – Produces new cells via mitosis - new plant growth is due to the actions of meristematic cells. –Protective tissue – Epidermal cells protect the outer surfaces of plants. Cork is another tissue that protects the inner tissue of the plant from injury.

That’s All I Got…