Factors Affecting Plant Growth
Lema Najibi

Introduction

Plants have been significantly important to the ecosystem from the day life evolved. They are a major source of energy, provided to all organisms including humans. This is either directly or indirectly. Furthermore, herbivores directly get their energy from consuming plants, while carnivores obtain their energy from plant-eaters; herbivores (1). However, omnivores are able to obtain their energy from eating plants either directly or by eating herbivores (1). Plants obtain the source of energy from the sunlight that reaches the earth each day. Specifically, it goes through two main processes known as respiration and photosynthesis (2,3). In respiration, plants intake carbon dioxide from the atmosphere and exhale oxygen back into the environment (2,3). However, in order to exhale oxygen it primarily goes through the process of photosynthesis (2,3). Photosynthesis is a process where carbon dioxide is converted into glucose using sunlight energy that has been absorbed by the plant (3). The carbon dioxide results in oxygen, which is then released into the environment (3). In today's environment, many external and internal factors are affecting the plant growth and/or development.

Nutritional Factors
The growth and/or development of plants is very similar to the human body. In comparison, of the human body, plants as well need proper nutrients, water and healthy environmental conditions including light, temperature, non-mineral and mineral nutrients (2). Scientists and plant nutritionists have discovered that there are at least 16 elements for plants that are essential (4). Out of many nutrients, these essential nutrients provide healthy growth and/or development for plants. The 16 essential elements for better plant growth and/or development are divided into two main categories; macronutritional and micronutritional elements (4). The two elements are a source of mineral nutrients, while there are three non-mineral nutrients, which are Hydrogen, Carbon, and Oxygen (2,4).

Macronutrients

Macronutrients are categorized into two parts; primary and secondary nutrients (5). Primary nutrients in soil include nitrogen, phosphorus and potassium (5, 6). The soil usually does not have enough of these nutrients because of the large amounts being used by plants for growth (6). Moreover, nitrogen's functional role is stimulating leaf growth; phosphorus is specialized to produce flowers (flowering), and potassium helps the plants develop stronger root growth (7). On the other hand, secondary nutrients include calcium, magnesium and sulfur (5). In contrast to primary nutrients, secondary nutrients have enough of these nutrients in the soil that is why fertilization is not always necessary (6). In conclusion, each of these macronutrients has an effect on plant growth.
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Micronutrients

Micronutrients are factors that help cellular processes (8). Moreover, it helps chlorophyll synthesis, cell division and enzyme production (8). Alike to macronutrients, micronutrients are also mineral nutrients (2). Micronutrients� main factor that affects plant growth is plant metabolism (8,9). They are found in the soil and is needed in small quantities, rather than macronutrients, which are needed in large quantities (8, 9). Micronutrients are essential for plant growth and include seven elements; Boron, Chlorine, Copper, Iron, Manganese, Molybdenum, and Zinc (8, 9).
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Non-mineral Nutrients

Non-mineral nutrients found are either in the air or water or both (2). A plant has about 90% of water contained (10). The water in a plant plays a major role in the plant growth and
non_mineral.jpg
Carbon, Oxygen & Hydrogen
/or development. It is a source of transportation for non-mineral nutrients in distributing throughout the plant (10). Non-mineral nutrients include oxygen, carbon and hydrogen (2). These minerals are mainly involved in the processes of photosynthesis, transpiration, and respiration. During photosynthesis, plants absorb energy from sunlight that been trapped through a plant's leaf (10). The energy's task is then to change carbon dioxide and water into starches and sugars (2, 10). These are a food source for plants. During the process of photosynthesis, transpiration takes place as well (2, 10). Furthermore, when stomata of leaves are open for carbon dioxide and oxygen to pass through, it is known as transpiration (2, 10). Then carbon dioxide converts into oxygen, which is released into the atmosphere, known as respiration (2, 10).



Soil pH

Soil pH is the measure of how acidic or basic the soil is for plant growth and/or development. (5) In the picture, Soil pH Scale, it shows the ranges of acidic pH, to neutral pH, to basic pH. The soil pH mostly affects nu
PH_SCALE.jpg
Soil pH Scale
trient availability (11). (8) The various soil pH measures, strongly affect the plants' quality. (8) However, each plant does have a certain pH level that is sustainable for growth and/or development. For instance, Russian olives are capable of growing healthy in soil with a basic pH, while potatoes are plants capable of growing in acidic soils (11).

The major affect of plants growing in different pH soils is the impact that it may have. Furthermore, highly acid soils receiving more manganese will create more toxic to the plant (11). Meanwhile, a high pH is when soils are alkaline and the nutrients become less available for the plants to absorb (11). The increase in toxics available to plants and fewer nutrients available for plants to absorb are contributors on affecting plant growth and/or development (11).


Light

The quality, intensity and amount of light per day plays a major role in the growth and/or development of plants (10). Light is one of the most important factolighhhhht.jpgrs in the growth and/or development of plants. It is used as an energy source for plants through the process of photosynthesis. The intensity of light defines the concentration of light waves and the amount that is being absorbed by the plant (10, 12). Cloud or moisture in the air reduces the level of intensity of light because of water vapour absorbing the radiation (10, 12). This affects the rate of photosynthesis because it decreases (10, 12). The more sunlight that is being absorbed by plants, the higher the rate of photosynthesis. The photosynthetic rate being higher than the respiration rate results in poor growth (10, 12). Another contributor on how plants are grown and/or developed is the range of wavelengths of light (10, 12). The range of wavelengths of light is divided into various colours; red, orange, yellow, green, blue, indigo, and violet (12). Blue and red are the most impacting colours for plant growth because they are the ones being absorbed (12). Moreover, blue light affects the growth of vegetative (leaf), while red with blue light is responsible for flowering (12). On the other hand,a plant receiving more sunlight results in its leaves being thicker with extra layers of palisade parenchyma than leaves in shady areas (10, 12). Plants absorbing more sunlight tend to have a higher capacity for producing food (10, 12). However, plants have evolved to detect th
wavelenght.jpg
Wavelength of Light
e changes in light through molecules, known as photoreceptors (13). The photorecptor helps the plant to react when struck with a certain condition that may not be suitable for its growth and/or development (13). The signal sent by the photoreceptor alerts plants to change in order to adapt to the new conditions (13). This allows plants to adapt to the light in a healthier way.






The Effect of Sunlight on Plants







Temperature

The temperature range for plants to grow and/or develop healthy is from 4.5-36 degrees Celsius. (10) Due to the changes in the temperature, it has become another factor affecting plant growth and/or development. The levels of intensity heat, amount of time, day or night are all contributors in impacting plant growth and/or development (4, 10, 14) It specifically affects photosynthesis, respiration and transpiration. As temperatures rise to a point, photosynthesis, respiration and transpiration increase as well (14). Sometimes due to an increase in temperature, respiration is higher than photosynthesis (10, 14). This causes slower growth leading to lower productions (10, 14). Moreover, a higher respiration rate than photosynthesis means that products of photosynthesis is being used at a faster rate than made. Therefore, in order for growth and/or development to take place the photosynthetic rate must be higher than the respiration rate (14).
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Ripe Winter Squash
On the other hand, low temperatures results into poor growth and/or poor development of plants (10, 14). This is because the low temperature decreases t
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Snapdragon Flowers
he rate of the process of photosynthesis. Additionally, low temperatures reduce the plants' energy use, which results into more sugar that was stored in the process of photosynthesis, leading to more sweetness in products (10). For instance, in the winter the ripe winter squash is grown that develops a very sweet taste because of the abundant of sugar that was once stored (14). The growth of a plant is also dependant on the type of plant and conditions; it either speeds up or slows down the growth and/or development (4, 14). Some plants have a better growth and/or development sprout in the nighttime rather than the daytime (14). For instance, snapdragons have a better growth and/or development in the nighttime (14).





Climate Change

Climate change is a continuous process that occurs each day, affecting the plant greatly each year. It can either be beneficial and/or non-beneficial in some regions. There are a couple main factors that is causing current, rapid climate change; pollution and cutting down trees. The abundant air pollution that is produced each day by exhaustion from vehicles, planes, power plants and factories and the aspect of deforestation or cutting down trees are contributors to climate change (15). These contributors lead to an increase in current and new diseases (15). It also influences the growth and/or development of plants (15, 16). Some plants may not be capable for adapting to the new changes leading to a lower chance of survival (15, 16). Meanwhile, most plants may react responsively and grow faster (15, 16). This is because due to pollution there will be an excess amount of carbon dioxide in the atmosphere (15, 16). Plants will then absorb more carbon dioxide due to more availability of it (15). On the other hand, another beneficial aspect of climate change are the discoveries and developments of new plants. Lastly, for some regions, this may be beneficial or non-beneficial, but various plants growing in a certain region may shift to a different region due to climate change, for an adaptable environment (15).

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Tar Sands- Before & After

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Lake Powell



The Importance of Plants


Plants are significantly important not only to humans, but for all biotic factors. Plants are a source of food for humans, other animals, and insects. In today's society, humans rely on plants heavily. For instance, a tree is a woody plant that is being heavily used by humans every day. Moreover, humans use trees for constructing houses
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Purple Coneflower
, paper, tables and desks. In addition, many animals and insects are dependent on woody plants and other plants because it is their habitat. . Without plants, biotic things; living things', survival would be extremely difficult. This is because plants are specialized to take in carbon dioxide and through photosynthesis produce oxygen. Oxygen is greatly required to sustain life. Without oxygen, our health begins to suffer and/or the chance of survival becomes highly unlikely. Lastly, 75% to 80% of the world's medicine is made from plants (17). The usage of plant medicines has been going on for many centuries up until today (17). For example, to treat viral illness plains Indians used the Purple Coneflower (17).






Article: Earth's Plant Growth Fell Because of Climate Change
By: John Collins Rudolf
This article talks about the effects that climate change is currently having on plants. Researchers and scientists hypothesized that the increase in temperatures will benefit the global, economically. Their prediction on the increase in temperatures led them to believe for longer growing seasons and improvement on plant growth. However, statistics of 2000 and 2009 demonstrate that plant growth decreased by a percentage of one. With further research that has been done, it shows that more than half the world has benefitted from the increase in temperatures, while less than half are in serious conditions. Moreover, the Northern Hemisphere is benefitting from the increase in temperatures because of growing seasons being extended. Meanwhile, the Southern Hemisphere that is already slightly warmer than the Northern Hemisphere is suffering from droughts. This is because of the growing seasons being extended for a much longer period than normal. In addition, an increase in temperatures means the rate of respiration is higher than photosynthesis. Thus, the cause of this is slower growth leading to lower productions. In conclusion, this article clearly shows the effect that climate change is having on plant growth.

NASA: Climate Change - Plant Productivity in a Warming World





Glossary

Alkaline: Having a pH greater than 7 (basic).
Macronutrients: Mineral required in large quantities by living organisms.
Micronutrients: Mineral required in small quantities by living organisms for growth and/or development.
Photoreceptor: Sensory object for light falling, responded by living organisms.
Photosynthetic: Formed by photosynthesis.
Photosynthesis: Process of green plants using sunlight to synthesize food.
Respiration: Breathing in and out.
Russian Olives: Deciduous shrubby tree of Europe and western Asia.
Snapdragons: Plant from the figwort family.
Soil pH: The measure of acidity or alkalinity in the soil.
Transpiration: The passage of gases through tubes.
Wavelengths: Electromagnetic light of wavelength, visible to the human eye.

Bibliography

  1. http://www.qrg.northwestern.edu/projects/marssim/simhtml/info/whats-a-plant.html
  2. http://www.ncagr.gov/cyber/kidswrld/plant/nutrient.htm
  3. http://www.biology4kids.com/files/plants_main.html
  4. http://www.buzzle.com/articles/plant-growth-factors.html
  5. http://www.soil.ncsu.edu/lockers/Broome_S/ssc051/Lec3.htm
  6. http://houseplants.about.com/od/howtousefertilizer/a/Plant-Macronutrients.htm
  7. http://ecorestoration.montana.edu/mineland/guide/analytical/chemical/solids/macronutrients.htm
  8. http://www.back-to-basics.net/efu/pdfs/Micronutrients.pdf
  9. http://www.landscape-and-garden.com/garden-soil/basic-nutrients.aspx
  10. http://www.hydrofarm.com/articles/factors_plantgrowth.php
  11. http://www.esf.edu/pubprog/brochure/soilph/soilph.htm
  12. http://ag.arizona.edu/pubs/garden/mg/botany/environmental.html#temp
  13. Biology Textbook
  14. http://extension.oregonstate.edu/mg/botany/heat.html
  15. http://www.gcrio.org/gwcc/booklet2.html
  16. http://labspace.open.ac.uk/mod/oucontent/view.php?id=426626&section=1.2.3
  17. http://www.rainforesteducation.com/medicines/PlantMedicines/rfmedicines.htm


Pictures

Oxygen, Carbon & Hydrogen [[http://www.google.ca/imgresq=oxygen+carbon+hydrogen&hl=en&sa=X&rlz=1R2ADFA_enCA414&biw=1440&bih=672&tbs=itp:photo&tbm=isch&tbnid=uIWqAnWmLnFIUM:&imgrefurl=http://www.picarro.com/markets_served/food_traceability/the_science&docid=U7GkYBn2-YEWpM&imgurl=http://www.picarro.com/assets/images/slides/foodfraud_2 1.jpg&w=720&h=542&ei=GKITT5C2AceJgweQ16T5Aw&zoom=1&iact=hc&vpx=329&vpy=182&dur=78&hovh=195&hovw=259&tx=167&ty=92&sig=107574433782616799818&page=1&tbnh=137&tbnw=182&start=0&ndsp=21&ved=1t:429,r:1,s:0]]

Soil pH Scale
http://www.google.ca/imgres?q=soil+ph+scale&um=1&hl=en&sa=N&rlz=1R2ADFA_enCA414&biw=1440&bih=672&tbm=isch&tbnid=cIDScoWGEvk0jM:&imgrefurl=http://crabapplelandscapexperts.blogspot.com/2011/09/benefits-of-adding-lime-to-soil-this.html&docid=yAouQUyTxxlswM&imgurl=http://4.bp.blogspot.com/-G8UKP6QgQ6w/TnzaR8NZWdI/AAAAAAAAAs0/wTT6kYA6tUE/s1600/pHScaleUAB_edu.jpg&w=516&h=291&ei=Wa4TT4esCYL50gG446WyAw&zoom=1&iact=hc&vpx=455&vpy=322&dur=3354&hovh=168&hovw=299&tx=105&ty=77&sig=108956405675383462650&page=1&tbnh=100&tbnw=178&start=0&ndsp=21&ved=1t:429,r:9,s:0

Wavelength of Light
http://www.google.ca/imgres?q=wavelength+of+light+in+plant&hl=en&rlz=1R2ADFA_enCA414&biw=1440&bih=672&tbm=isch&tbnid=5QqamHiOUNdWyM:&imgrefurl=http://www.free-press-release.com/news-led-grow-lights-why-light-wavelengths-matter-when-choosing-a-grow-light-1275323274.html&docid=FTOsQ8gqToU-3M&imgurl=http://www.free-press-release.com/uploads/news/2010/05/31/1275323274_img1.jpg&w=955&h=328&ei=1qQTT_P0DMHugge0hqT0Aw&zoom=1&iact=rc&dur=234&sig=107574433782616799818&page=1&tbnh=68&tbnw=197&start=0&ndsp=20&ved=1t:429,r:10,s:0&tx=84&ty=20

Ripe Winter Squash
http://www.google.ca/imgres?q=ripe+winter+squash&hl=en&biw=1440&bih=672&gbv=2&tbm=isch&tbnid=s8tbhpv48RmDrM:&imgrefurl=http://www.naturespride.eu/our-products/product-detail/butternut-squash/&docid=5kQTIt5u55PNmM&imgurl=http://www.naturespride.eu/uploads/tx_npdata/Butternut-Squash_02.jpg&w=400&h=251&ei=UKgTT8SmIMeqgwfJ3bn4Aw&zoom=1&iact=hc&vpx=808&vpy=330&dur=1700&hovh=178&hovw=284&tx=148&ty=107&sig=108956405675383462650&page=4&tbnh=110&tbnw=176&start=59&ndsp=21&ved=1t:429,r:4,s:59

Snapdragon Flowers
http://www.hort.purdue.edu/ext/senior/flowers/snapd94.htm

Tar Sands
http://blog.sfgate.com/green/category/climate-change/

Lake Powell
http://www.southwestclimatechange.org/impacts/water

Purpe Coneflower
http://www.google.ca/imgres?q=purple+coneflower&um=1&hl=en&rlz=1R2ADFA_enCA414&biw=1440&bih=672&tbm=isch&tbnid=SYA0J01d-VPIqM:&imgrefurl=http://www.alexanderspagesonanything.com/deer-proof-flowers-for-clare.php&docid=eJ1Yw8oihTBuTM&imgurl=http://www.alexanderspagesonanything.com/resources/Purple_Coneflower%252520deer%252520resistant.jpg&w=390&h=282&ei=0KoTT-GHHcKs0AGCus3SCQ&zoom=1&iact=hc&vpx=618&vpy=314&dur=1154&hovh=191&hovw=264&tx=168&ty=95&sig=108956405675383462650&page=1&tbnh=152&tbnw=203&start=0&ndsp=19&ved=1t:429,r:9,s:0