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| Factors Influencing Plant Growth
| Trump’s Executive Effects
| Many factors influence how a plant grows. Several are very well known while others are not as clearly defined. Plants are the primary factor in most food chains and some of their products, such as wood, play an integral role in our everyday lives. Therefore, understanding this topic is very important.
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| Light is a critical factor in the growth of plants. Chlorophyll absorbs sunlight and is the source of energy for photosynthesis. This endothermic chemical reaction uses water and carbon dioxide as the reactants and oxygen and glucose are the products. This therefore produces the oxygen we requires for survival and the stored energy present in the food we consume. Plants grow better when more sunlight is available and this is why plants grow in a way that directs them toward this source of energy.
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| Like carbon dioxide, water is a necessary reactant for photosynthesis. Carbon dioxide enters a plant's leaves through small pores called stomata, which also release water molecules in a process called transpiration. Water is absorbed from the ground through a plant's root system. The growth of the roots is thus influenced by the amount of water and where it is. A single large, healthy oak tree can absorb 100 gallons of water on a single summer day. Plant growth definitely suffers in a period of limited rainfall.
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| When seeds sprout, gravity directly influence the growth of the roots. It directs them to grow downward. This increases the likelihood that they will find water in the soil, making it possible for the plant to survive and grow. Amyloplasts in the plant cells respond to gravity, directing the roots to grow downward and the stems to grow upward. A reservoir of energy in the seed helps the plant survive until it is able to absorb water and sunlight, letting it become self-sufficient.
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| Temperature also has a direct impact on plant growth. Different plants have evolved to grow under varying conditions, but each species has an optimal temperature range. For most plants, this is between 59oF and 86oF. When the temperature is within this range, plants grow more rapidly, seeds are more likely to germinate, and photosynthesis, respiration and transpiration all occur more optimally. If the temperature is too low, plant growth slows down or stops. The plant can become dormant and, if it is too cold, new growth or buds can be damaged. If the temperature is too high, growth will similarly slow down and the plants may undergo stress. These aspects are also altered by climate change.
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| Wind likewise influences how a plant grows. If it is minimal or if the direction changes consistently, wind only has momentary effect on a plant. However, when it flows repeatedly in the same direction with a measurable force, it shows a visible impact on the growth of a plant. Branches of trees and the growth of the trunk will reflect this influence in a very visible manner. They thereby reflect the repeated influence on the resulting plants.
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| Nutrients also influence plant growth. In addition to carbon dioxide and water, plants require additional elements that are classified as macronutrients and micronutrients. These are absorbed from the soil by the roots of the plants. The macronutrients are nitrogen, phosphorus, potassium, calcium, magnesium and sulfur. The first three (N, P and K) are commonly included in plant fertilizers. Nitrogen is critical for the development of leaves and the production of chlorophyll. Phosphorus plays a role in energy conversion and strong root growth, being a component of the phosphate-sugar backbone of DNA molecules. Potassium influences overall plant strength, water regulation, resistance to disease and nutrient transport within the plant. The other three macronutrients influence to strength of cell walls, creating chlorophyll and the formation of amino acids and proteins. Micronutrients also play a role in plant growth, but to a lesser degree. They include iron, manganese, zinc, copper, boron, molybdenum, chlorine and nickel.
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| Humidity significantly affects plant growth. Humidity is a measure of the water content in the atmosphere. It affects transpiration, nutrient uptake and the susceptibility of a plant to disease. Both high and low humidity can have negative impacts on plant growth. High humidity hinders the release of water, limiting transpiration, photosynthesis and nutrient transport. It also contributes to root rot and fungal disease. Low humidity closes stomata, causing water stress, reduced photosynthesis and leaf damage. For most plants, optimal humidity ranges between 40% and 60%.
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| Plant hormones are called phytohormones. They act as signaling molecules within cells, regulating processes that occur in plant cells. Auxins promote cell elongation, affecting the growth of roots, stems and buds. Cytokinins promote the division of plant cells. Abscisic acid influence the dormancy in seeds while gibberellins are critical in the germination of those seeds. Ethylene regulates the ripening of fruits and the shedding of leaves and flowers.
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| Pests and diseases can result in stunted plant growth, reduced harvest of food components and, in the worst cases, the total death of the plants. Pests eat parts of plants, suck juices from the plants or bore into roots and stems. Diseases are the results of pathogens which can be fungi, bacteria or viruses. Diseases can reduce photosynthesis or impair the uptake of nutrients and water. They can inhibit plant growth, damage vascular systems that control the flow of water or fluids or cause the death of plant tissue.
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| Allelopathy is the process where a plant uses compounds called allelochemicals to influence other plants in its environment. These factors can be either beneficial or harmful to the other plants. Harmful compounds can be toxins that suppress the growth of competing species. An example is juglone, which is released by black walnut trees and is toxic to plants such as tomatoes, peppers and pines. Alfalfa releases a natural pesticide that requires crop rotation by inhibiting the growth of a new alfalfa crop in the same field. Allelochemicals can be used in sustainable agriculture as a natural way to control diseases, weeds and insects.
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| Competition also influences the growth of plants. When on plant expands its foliage to absorb more sunlight, it limits the availability to other plants. In like manner, plants compete for the available water and nutrients. Available space is likewise a competitive factor. When plants are competing in such manner, it limits the size of the resulting plants. Such competition can be intraspecific or interspecific, meaning that the competition is either between separate plants of the same species or plants of differing species.
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| Genetics likewise influences the competition between plants. Darwin's "survival of the fittest" applies directly to the evolution of plants. This variation accounts for the broad range of plants able to survive in even extreme environments. If a new factor is beneficial, it will assist the plant in its ongoing competition, thereby increasing the probability of survival and of passing on this trait to future generations. Genetic variation produces new proteins and enzymes that then result in changes in the species. If it is beneficial, it is more likely to be reproduced in the species, aiding in future plant growth.
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| Human influence has directly impacted the variation in plants that produce agricultural products that we now depend upon for our healthy survival. This is one more factor supporting the theory of evolution!
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