1) These five environmental factors: Amount of sunlight, Soil pH, Water, Gravity, and Thigmotropism. Describe five environmental factors that affect a plant's growth rate and give an example of how...

1) These five environmental factors: Amount of sunlight, Soil pH, Water, Gravity, and Thigmotropism.

Describe five environmental factors that affect a plant's growth rate and give an example of how they do so. These can include both physical and chemical factors.

2) Describe how fertilizers and herbicides both can be detrimental for shorelines.

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gsenviro | College Teacher | (Level 1) Educator Emeritus

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The five environmental factors, listed in the question, affect the plant's growth rate as described:

  • Amount of Sunlight: Sunlight is used for photosynthesis, i.e. production of food; higher the quantity of sunlight, more would be the food produced and higher would be the plant growth.
  • Soil pH: it limits the availability of certain nutrients necessary for plant growth. For example, acidic soils contain low quantity of phosphates. Also, some plants require a certain pH for growth, e.g., potato swab needs a soil pH of less than 5.5.
  • Water: It is key to plants survival and growth. Water maintains the turgor pressure of tissues and transports the nutrient throughout the plant. It also helps stabilize the plant's temperature by evaporation. 
  • Gravity: Plant roots grow downwards in response to Earths gravity. Gravity also helps keep the upper portions of the plant clean by bringing dirt, dust, detritus, etc., thus leaving the upper portions clean and free to receive sunlight. Gravity also restricts the height and size of the plant because beyond a certain size and height, the plant will not be able to sustain its mass against the gravity.
  • Thigmotropism: refers to movement of plant in response to contact or touch and is important for plants that need support for growth. Chief among these are vines that grow on walls, pots, etc. Compared to this, the roots of plants have negative contact response and grow away from surfaces. This is how the roots avoid rocks while growing in the subsurface. 

Detrimental effects of fertilizers and herbicides on shorelines:

Herbicides and pesticides are toxic to the living organisms and when washed off into the surface water, will likely kill the aquatic life forms. Fertilizers add nutrient to the water bodies and promote growth of algae and other aquatic plants. This inhibit the amount of sunlight that is available for photosynthesis and also consume dissolved oxygen for decay, again adversely affecting the marine life forms. 

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