To classify a seed, examine the seed and discover the number of cotyledons. If the seen only have one cotyledon then it is a monocot. If the seed has two cotyledons then it is a dicot.
The alfalfa is a dicot. Dicots have two cotyledons. When a dicot seed sprouts, it sends up one stem and two leaves.
Monocots-Have one cotyledon -Light, strong structure -Flowers/Petals occur in groups of four or five or multiples of four or five -Vascular tissue in leaves is found in parallel lines -Palm trees, Bamboo, Orchids, Lilies, Tulips, Spring bulbs Dicots-Have two cotyledons
-Rich in starch -Flower/Petals occur in groups of three or multiples of three -Vascular tissue in leaves is found in branching veins -Lettuce, Tomatoes, Radishes, Potatoes, Roses, Daisies The onion is a monocot. Monocots send up a single leaf due to the fact that they have one cotyledon.
Gymnosperms-Do not have a seed coat -Attach to scales of cones -Adapted to thrive in environments with long, cold winters and low amounts of nutrients in the soil -Dominate in large areas of Canada, Northern Europe and Northern Asia -Conifers, Cycads, Ginkgos, Yews, Allies Angiosperms-Very diverse
-Widely spread around the world -Also known as flower plants because that is their reproductive organ -Seeds are protected by fruit -Sunflowers, Orchids, Apple trees, Maple trees, Burrs -Includes different types of herbs, trees, vines, vegetables and shrubs Root System
Shoot SystemThe shoot system includes the stem, appendages, leaves, buds and flowers. The shoot grows upward. In the spring there can be new plant growth from the ground which are herbaceous plants or there is new flower growth on woody plants. Stems are integral parts of shoots because they provide an axis for buds fruits and leaves. Young shoots are often eaten by animals because the new fibers in the new growth have not completed secondary growth cell wall development and therefore the stems are softer and easier for animals to chew. A secondary wall is a hard and tough structure.
Herbaceous plants are plants with very flexible stems. Their leaves and stems die down to soil level at the end of every growing season. Herbaceous plants can be annual, biennial or perennial. Annual herbaceous completely die every year then grow back again from the seed. With biennial and perennial herbaceous only the stems and leaves die at the end of growing season but parts of the plant survives and grows back from those parts the next year.
Woody plants are plants with very strong and not easily bendable stems such as trees. Woody plants produce wood as a structural tissue. The stems branches and roots are usually covered with a layer of bark. The wood that woody plants produce is a structural cellular adaptation that allows them to survive harsh winters and continue growing instead of dying. This adaptation therefore makes them the largest and tallest terrestrial plants. Wood is primarily composed of xylem cells with cell walls made up of cellulose and lignin. Woody plants form a new layer of woody tissue each year, increasing the diameter of the stem. You can see these tissue layers inside a tree if you were to cut it down. In some monocots such as palms, the wood is formed in bundles that are scattered through the interior of the trunk. Dermal Tissue
Ground Tissue
Vascular TissueVascular tissue includes the xylem and the phloem along with some collenchyma and parenchyma cells.
The xylem is the main tissue for carrying water and minerals throughout the plant. The xylem contains fibers and water conducting cells called tracheids and vessels. Tracheids are xylem cells with tapered, over-lapping ends and pits in their cell walls for conducting water and dissolved materials in the plant. The pits in the walls of the tracheids are unthickened for easy transfer of materials between neighboring cells. Tracheids are longer than vessel elements which make up vessels. Vessels are long tubes of vessel elements that are used to conduct water and dissolved materials in plants. The are long continuous tubes of individual vessel elements that have been joined end to end. Vessel elements have thickened walls and large perforations in the end walls. Tracheids and vessels are both dead at maturity and their lignified cell walls remain. Tracheids and vessels continue to transport water and dissolved substances until they get filled with various deposits. Both tracheids and vessels are found in angiosperms but only tracheids are found in gymnosperms. The phloem transports sugars and other solutions. The phloem is living tissue unlike the xylem. Sieve tubes are long tubes formed by many sieve elements to allow easy passage for water and dissolved minerals.These provide and obstruction-free pathway for movement of materials. Sieve elements are long thin phloem cells with sieve plates at the end walls. Sieve plates have large pores which allow for easy passage of water and materials. Sieve elements have pits on their side walls. Sieve elements are associated with companion cells which lay next to the sieve elements and direct the activity of sieve tubes and supply needed substances when required. These cells lack a nucleus, ribosomes, golgi bodies, cytoskeleton and vacuoles.
All trees living today are either gymnosperm or angiosperm. The ending "sperm" means that both groups grow from seeds. The total number of angiosperm species is far greater than the total number of gymnosperm species.
Gymnosperms have seeds without a seed coat and are attached to the scales of cones. Gymnosperms have a disadvantage compared to angiosperms because once gymnosperm seeds fall or are blown out of their cones they only have a thin cover for protection. Many gymnosperms such as coniferous are adapted to thrive in environments with long cold winters and low amounts of nutrients in their soil. Gymnosperms dominate large parts of Canada, Northern Europe and Northern Asia. Gymnosperms are vital to Canada's economy because they provide fiber for making paper and wood. Angiosperms are more diverse in structure and are widely spread around the world. Angiosperms are also known as flower plants because that is their reproductive organ which mature to seed-containing fruit. The fruit covering on the seed gives angiosperms an advantage over gymnosperms because they have better protection. The fruit of angiosperms are adapted to facilitate seed dispersal. Some seeds are tasty such as apples and other fruit that is consumed and the seeds disperse when the fruit is eaten. Some seeds are sticky such as burrs and gets dispersed in feathers or fur of animals. Other fruit is shaped for flight such as maple keys and disperse by the wind. Angiosperms include trees, grasses, vegetables, wildflowers and herbs. |