Effective plant growth is determined by multiple environmental factors, some of which can be affected by human activity. The main conditions determining plant growth regulation are: light, water, temperature, nutrient intake, soil composition, pH of the soil, and climate change.


Light

The [[#|process]] essential to plant growth and survival is photosynthesis, wherein sunlight is absorbed and used to create glucose. Not surprisingly, the amount of light reaching the plant is going to have a [[#|direct]] relationship with the growth of the plant. Due to this, plants have formed photoreceptors molecules to react with different wavelengths of light, at different times of the day. As the spectrum of red light increases as the day progresses, photoreceptive molecules send signals that result in plant growth. For example, photoreceptors are responsible for the autumn colour change in deciduous trees,as well as the germination of many light-dependent plants.

Temperature

In plants, all cellular functions are affected by the surrounding temperature. For each plant, there is an optimal temperature range at which these cellular processes are performed ideally. For example, in warm sunny weather many species of flora will begin to wilt as a result of increased transpiration (water loss). In any case, if the surrounding temperature is either above or [[#|below]] the plant's ideal range, the species will grow [[#|more]] slowly. Strangely, many species of plants undergo a developmental stage initiated by temperature, such as the loblolly pine, which can only germinate after experiencing cold weather. Not only gymnosperms are affected, as the flowering time of most angiosperms are determined by external temperature. This is to ensure that pollinating species are able to reach the plants during a period in which both species can benefit.

Nutrient Intake

As opposed to ingesting nutrients, most plants obtain all of their required molecules from inorganic compounds within their [[#|environment]] (With the exception of carnivorous species, which grow in areas where nutrient intake is not possible). The compounds required by plants for survival are grouped into two categories, macronutrients and micronutrients. As the [[#|name]] suggests, macronutrients are needed in large amounts, and include chemicals like nitrogen, phosphorus, and potassium. Insufficient quantities of these nutrients can result in stunted growth, deformed leaves, poor root growth, and chlorosis, among other conditions. Micronutrients are only required in very small amounts, and they include chemicals such as: boron, chlorine, iron, copper, molybdenum, zinc, manganese, and nickel. These compounds are used in a wide range of cellular processes from chlorophyll production to cell division.
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Soil Composition

Soil is one of the most important factors affecting plant growth, as it is the medium in which the majority of floral species are grown. In addition, soil retains water and important nutrients, as well as providing the roots of the plant with [[#|air]]. Since soil is essential to plant growth, the composition of the soil is also very important. For example, sandy soil (silt) does not manage water moisture effectively, so it dries out quickly, whereas soil with high clay content retains too much water, drowning the plant's roots. Decomposed organic matter known as humus is also integral to plant growth, particularly due to its nitrogen content (along with other macronutrients).

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pH of the Soil

Technically a factor of soil composition, the acidity of water in the soil can greatly affect the growth of a plant species. The pH level affects the absortion rate of nutrients that can be taken into the roots. Most plants grow effectively in mildly acidic soil, but some species (such as cacti) prefer basic soil.

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Climate Change

Since the industrial revolution, human activity (particularly burning of fossil fuels) has been increasing the average temperature of the Earth. It has been estimated that for every 1C increase in global temperature, the flowering period of (most) angiosperms will occur 5 days sooner. This alarming relationship can negatively affect the co-dependency between flowering date and the appearance of pollinating species (either insect or avian).

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