Plants Essay, Research Paper
Plants are the basis of the food pyramid for all living things, even other plants. They have always been very important to people, not only for food, but also for clothing,weapons, tools, dyes, medicines, shelter and a great many other purposes. Both humansand animals benefit from plants. We eat many different types of plants such as fruits andvegetables. We also use plants for our herbs. Plants are also used to manufacture manydifferent products such as shampoos, rubber, paper, and camera film. In some countries,fermented sugar cane is used instead of gasoline. Animals use plants in many differentways also. They eat many fruits and other plants. Many animals use plants for shelter. Plants also provide animals with protection from predators. The destruction of differentplants sometimes leads to animals becoming endangered or extinct. The basic structure of plants consists of roots, stem, leaves, flower and/or fruit or seeds. A flower is the part ofthe plant that makes the seeds. The main parts of a flower are the carpels and stamens. These parts are often found in the center of the flower. There are egg cells in the carpeland pollen cells in the stamen. All flowers have four basic parts: sepals, petals, carpels,and stamen. Different flowers have different numbers and shapes of these parts. Mostplants can be divided into one of two general categories: herbaceous or woody plants. Herbaceous plants have soft stems, while woody plants are tree-like. Herbaceous plantsproduce completely new stems each year. The approaching cold weather causes the newstems to die back to the ground. Some herbaceous plants survive periods of cold byforming underground bulbs, or tubers used for food storage. Many herbaceous plantscomplete their life cycles within one growing season and the whole plant dies, even theroots. These annuals produce seeds that will form new plants the next year.Land plantsare divided into two groups based on whether they have vascular tissues or not. Allnonvascular plants are placed in one division. There are nine divisions of vascular plants. These are divided based on whether they form seeds or not.Division Bryophyta -nonvascular plantSClass – Musci – the mossesDivision Pterophyta – ferns, group ofseedless plantsDivision Coniferophyta – cone-forming seed plantsDivision Anthophyta -fruit-forming seed plants Class – Monocotyledonae Class – DicotyledonaeChapter2ROOTSRoots help to anchor a plant in the ground. . Plants generally conform to one oftwo root systems, a taproot system or a fibrous root system. . When the plant is grownfrom cuttings, a fibrous root system will form.Every root grows a mass of tiny hairs nearits tip to absorb water from the soil. These tiny hairs are called root hairs, and they aremade from cells. They take water to the main root. The main root brings the water to themain plant. The roots also help hold the plant in the ground. The inside of a roothas four different parts. The epidermis is the outside part. It is like our skin. It protectsthe inside parts of the root, like our skin protects us. Plants take in water from the soilthrough their roots. The water passes through the vascular rays until it reaches the centerof the root, the stele. This is where the veins are located. The veins are called xylem. They carry the water and food through the plant. Between the epidermis and the stele isthe fleshy cortex.Land plants are divided into two groups based on whether they havevascular tissues or not. All nonvascular plants are placed in one division. There are ninedivisions of vascular plants. These are divided based on whether they form seeds or not.Stems support the plant. They transport vitamins, minerals and water up and down insidethe plant. They also serve as a storage area for plants.There are several different types ofstems such as, woody, herbaceous, stolons, rhizomes, and bulbs. These are describedbelow. Herbaceous, non-woody, plants have vascular tissues arranged in bundles. Thesevascular bundles are either scattered throughout the stem or found in a ring toward theedge of the stem. The stems of herbaceous plants remain upright because of the structureof the cells in the stem. The individual cells have rigid walls. . In woody plants, thephloem is located in a ring near the stem while the xylem is located more to the inside. The stem also takes on different appearances depending on the season. Springwood cellsoccur when water is plentiful. This is when wide xylem cells with thin walls are produced. During dry weather, new xylem cells are smaller with thicker walls and it is calledsummerwood. These changes produce a visible difference in the appearance of the woodystem. Since one sequence of this occurs each year, the age of a tree can be closelyestimated by counting the “rings.” Heartwood occurs when the xylem becomes clogged, itcan no longer transport water and will take on a dark color. This can be seen in the centerof most trees. Sapwood is the lighter-colored wood in a tree. Even if the cells are nolonger living, they can still function to transport water. An example of a woody plantwould be an oak tree.Rhizomes are grown from thickened, underground stems. Iris plantsare rhizomatous-type plants. They can get overcrowded after growing in the same spotfor a long time. When they don’t have enough space, there are fewer blooms. After theflowers have bloomed, they need to be cut back to the remaining healthy leaves in orderfor it to come back the next year. Then they are replanted below the soil surface.Stolensare aboveground stems that grow parallel to the soil surface. The strawberry plantreproduces itself asexually by stolons, which are known as runners. Runner plants developfrom axillary buds on the crown of the mother plant under long-day photoperiodicconditions of summer. When the days become shorter, the strawberry ceases to makerunners and develops flower buds for the following season. Soon after the daughter plantreaches the soil, it develops vigorous roots (peg roots) that anchor it to the soil. It canremain attached to the mother plant for a long time, but it usually is capable of livingindependently within three to four weeks. A single mother plant can produce up to 1000daughter plants in a single season. Bulbs are like “storage tanks”. They help a plantsurvive dormant periods when it is too cold or hot for it to flower, and they nourish theplant during the growing and flowering season. There are three major types of bulbs,including true bulbs, such as hyacinths, daffodils, and tulips. Iris plants also have bulbs. After the blooming season is over, bulbs can be left in the ground. Some will, in time,spread out from their planting position and form new bulbs. This is called “naturalizing.” After a few years, some of the bulbs need to be dug up and divided to preventovercrowding. Leaves are specialized for capturing sunlight for photosynthesis. The bladeof a leaf is attached to the stem by a stalklike petiole. A simple leaf has one blade and onepetiole. In compound leaves, the blade is divided into leaflets on the same petiole. Animals inhale oxygen and exhale carbon dioxide. Green plants are the only plantsthat produce oxygen and make food, which is called photosynthesis. Photosynthesismeans “putting together with light.” This takes place in chloroplasts, which havechlorophyll in them. Chlorophyll absorbs the sunlight. From sunlight, green plantscombine carbon dioxide and water to make sugar and oxygen. Green plants use sugar tomake starch, fats and proteins. These are tiny pores called stomata. Stomata are plantspores, which enable gas exchanges to take, place, and water to vapor to be lost. This hasthe benefit of moving water up the plane in a process called transpiration. The pore andthe guard cells make up a single stoma. There may be as many as 6 million per typicalleaf. The area just inside the internal structure of the leaf and below the stoma is the airspace, which brings carbon dioxide very close to the palisade parenchyma tissue. Oxygenand carbon dioxide enter and leave through the stomata. Plants also sleep at night byclosing their stomata. They cannot make food at this time. When green plants absorbsolar energy, they convert it to chemical energy. This chemical energy aids in the growthand functions of the plant. When an organism eats the plant, it gets energy to carry out itsprocesses. Without solar energy, plants could not grow, and life on earth would cease toexist. Chlorophyll, found in plants, is used to trap solar energy. This solar energy isimport for the separation of H atoms from H2O. When water splits, H2 is released andbuilt into ATP and NADPH2. O2 is given off, as well, which aids in the respiration ofliving organisms. The ATP and NADPH2 produced in the light phase is ready to be usedfor the reduction of CO2 to form glucose in the dark phase. The chemical equation forphotosynthesis in green plants:light6CO2 + 12H2O =====? C6H12O6 + 6O2 + 6H20 All life on Earth depends on plants to provide good, shelter, and oxygenfor other living things. Plant reproduction is important to all other life on this planet. Thefirst step in plant reproduction is called pollination. This occurs when pollen grains, themale germ cell of a plant, reach the stigma, the female reproductive part of the samespecies of plant. Depending on the plant species, a flower can produce male, female, orboth structures. Pollination can also occur within the same flower. Most flowering plantsdepend on animals to make the vital pollen-grain delivery. The remaining flowering plantsrely on wind and sometimes splashing raindrops to ferry pollen, but this is a less precisemethod. Pollinating animals do the job for a reward: food, usually in the form of nectar. The female reproductive part of a flower is receptive to pollen only at certain timesof the year. Creatures like insects and birds, which move from flower to flower in searchof food, are a fast and often guaranteed way for plants to distribute their pollen.Both themale and the female reproductive parts of a plant are in the center of the flower. Themale, pollen-producing part is called the anther, held up by a stalk called a filament. Theentire male part is called a stamen. Teach pollen grain is unique to its species. The femalereproductive part of a plant, the stigma, sits on top of a style, or stalk, which leads to anovary at the base. A seed has everything it needs to produce new plants. No seed cangrow with the fruit around it. A seed has to have enough water, good soil, and sunlight. BIBLIOGRAPHY Wright, Alexandra. Will We Miss Them?. Watertown, MA: Charlesbridge Publishing, 1992. The Plants. New York, NY, Time Life Books,1971Sunset Books/Magazines.