Introduction

Plant growth is controlled by a variety of environmental factors, such as temperature, pH levels, soil composition, nutrients and climate change. These factors conrol whether or not a plant can succed in that particular environment.

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(Available from http://animal-world.com/encyclo/fresh/plants/PlantSubstrates.htm)

How Temperature Affects Plant Growth

Temperature directly influences the growth and development of plants. Plants are able to undergo growth successfully when they are exposed to a day temperature that is approximately 10 to 15 degrees F higher than the temperature at night1. Under these conditions, the plant is able to photosynthesize and respire during the day and decrease respiration rates during the night, since the growth of a plant is limited when the respiration rate is greater than the rate of photosynthesis1. (This means that the products are being used faster than they are being produced).

When the daily temperature is too high, the rate of respiration increases, causing the respiration rate to exceed the rate of photosynthesis1. When the daily temperature is too low, photosynthesis rates decrease1. Therefore, the overall growth of the plant is slowed.

Different types of plants require different daily temperatures to grow at a successful rate. Flowering plants such as Daffodils often require cooler temperatures in order for their buds to mature1.

How Soil Composition Affects Plant Growth

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(Available from http://www.funsci.com/fun3_en/exper1/exper1.htm)


Plants receive the nutrients nitrogen, phosphorus, potassium, calcium, magnesium and sulfur from the soil2. These nutrients are changed into ions, which are forms of the nutrients that plants are able to use2. These essential nutrients promote growth and development of the roots, the stem and leaves and provide the plant cells with more energy.

Soil composition is also important to plant growth because it often provides an environment suitable for roots to anchor and develop2. The texture of soil affects how the roots shape to the environment and how well the roots are able to anchor the plant. If the soil texture does not support root development, the plant will not last long in the environment because its structure and support system will be too weak to support stem development2.

Soil type can also influence the growth of a plant. The texture of the soil affects how the well nutrients and water can be retained2. If the soil is composed primarily of clay, the plant will not be able to grow successfully because it doesn’t allow the roots to develop and is unable to drain effectively2. If the soil’s texture is too sandy, it will drain too quickly and the plant will not be provided with the essential amount of water2. When water in sandy soil is drained, nutrients often follow. Ideal soil is composed of sand, silt, clay and organic matter2. Soil with these elements is able to obtain nutrients and water for plants, making it an ideal environment that allows plants to thrive.
Moisture in the soil external image Organic_Fertilizer_Soil_Conditioner_.jpgencourages nutrient uptake, which supports plant growth, development and the upkeep of required energy3. Water helps a plant because it transports nutrients from the soil through the plant3. If there is a lack of water in the plant cells, plants droop because they are not able to support their own weight. Water also transports dissolved sugar and nutrients throughout the plant3. The pore spaces in the plant hold the moisture that promotes the changing of nutrients into ions as well as the air that prevent plants from becoming waterlogged3. Plant growth can also be negatively affected by high levels of moisture in soil. High moisture levels can cause the roots to rot and the pore spaces to become clogged, meaning the plant will no longer be able to access gases and nutrients from the soil3. These elements cause plant growth to slow, because a plant cannot grow without healthy roots or proper nutrients and air.

How Sunlight Affects Plant Growth


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(Available from http://masterman535.hubpages.com/hub/A-Simple-Diagram-of-Photosynthesis)

Light is a significant factor in effecting plant growth. Certain plants require a specific amount of sunlight per day, and if that sunlight is not provided, the growth of the plant can be negatively affected. The leaves of the plant fail to grow to their full potential if not enough light is provided, and stems become weakened4.

Sunlight is essential for a plant to photosynthesize4. Photosynthesis is the process in which plants convert energy from the sun4. Sunlight is absorbed in the leaves in molecules of chlorophyll (in chloroplasts)4. This energy is converted into glucose, which is an essential nutrient for plant growth4. Glucose is carried through the phloem tissue and is provided to all plant cells, which provides energy to the entire plant4. Without photosynthesis, it is impossible for a plant to survive since it is its main source of nutrients for growth and developme

How the Intake of Nutrients Affects Plant Growth


The amount of nutrients a plant absorbed through the soil and photosynthesis affects the growth of the plant because nutrients provide energy throughout the plant since nutrients are the main energy source for plants4. Nutrients are mainly absorbed through the soil, and are dispersed throughout the plants2. More information about nutrients that are essential for plant growth and development can be accessed in the previous sections.


How pH Levels in the Soil Affect Plant Growth

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(Available from http://masterman535.hubpages.com/hub/A-Simple-Diagram-of-Photosynthesis)


pH levels in the soil are one of the most significant properties that directly affect the availability of nutrients. In soils with a low pH, macronutrients are less available to plants5. These nutrients are essential for plant growth and development, and if they are not available for intake, the plant is unable to provide energy to the plant, slowing growth5.

When the pH levels in the soil are higher, micronutrients become less available for plants5. These nutrients are also essential to provide the plant with energy and support the overall growth and development.

An ideal pH level in soil is 6.0 to 6.55. In this range, nutrients are available for plants to intake, making this environment a suitable

area for plants to grow successfully5. Ways to achieve this desired range is to add Lime to the soil to make it less acidic5. This method also enhances the physical properties to promote water and air movement in this soil as well as supply plants with calcium and magnesium5.

Climate Change



(Available from http://www.youtube.com/watch?v=Er3iD5PIR00&feature=player_embedded)



Article

http://www.reuters.com/article/2007/07/25/us-warming-ozone-idUSN2527873420070725

This article explains the potential effects that climate change/global warming will have on plant growth. This generation is familiar with the idea of climate change and its effects on the environment, and the goal of this article is to use the knowledge we have on this topic to connect the two ideas. Although carbon dioxide is a major fossil fuel that is currently being released into the atmosphere, it can also have a positive effect on plant growth. However, the article states that the ozone is damaging plants and is limiting their ability to absorb carbon dioxide. As learned in this article, plants require carbon dioxide to carry out life functions and cellular activity. This has a direct impact on plant growth that we could potentially see in the future.

This article can be used to apply the knowledge about plant growth learned on this page to real and current environmental conditions that have an effect on plant growth.

Glossary


Pore Spaces: The portion of the soil occupied by air and water, located between soil particles.

Macronutrient: A substance required in relatively large amounts by living organisms

Micronutrient: A chemical element or substance required in trace amounts for the normal growth and development of organisms.

Respire: The process in which a plant carries out respiration at night when photosynthesis has ceased.

Photosynthesis: The process by which plants use sunlight to synthesize foods from carbon dioxide and water.

Silt: Fine sand, clay or other material carried by running water and deposited as a sediment.

Bibliography


1 Evans E. Temperature Effect on Plants [Internet]. NC: NC State University: 2011 [updated 2011; cited January 15 2012]. Available from http://www.ces.ncsu.edu/depts/hort/consumer/weather/tempeffect-plants.html

2 Scherer T. Soil, Water and Plant Characteristics Important to Irrigation [Internet]. North Dakota; February 2006 [updated 2006; cited January 15 2012]. Available from http://www.ag.ndsu.edu/pubs/ageng/irrigate/eb66w.htm

3Armstrong S. How Does Water Affect Plant Growth [Internet]. Bedford, OH; 2012 [updated 2012; cited January 15 2012]. Available from http://www.gardeningknowhow.com/children-in-the-garden/how-does-water-affect-plant-growth.htm

4Biology Online. Lights’ Effect on Growth [Internet]. 2012 [updated 2012; cited January 15 2012]. Available from http://www.biology-online.org/3/9_effect_light.htm

5Troxler S. Plant Nutrients [Internet]. Raleigh, NC; 2012 [updated 2012; cited January 15 2012]. Available from http://www.ncagr.gov/cyber/kidswrld/plant/nutrient.htm