This paper examines the fundamental relationship between humans and plants, focusing on photosynthesis as the process that makes life on Earth possible. It explains how plants, algae, and cyanobacteria convert carbon dioxide into carbohydrates and release oxygen, and outlines the key environmental factors — temperature, light, CO₂ concentration, water, and minerals — that regulate this process. The paper then connects the degradation of these factors to human industrial activity, air pollution, population growth, and unsustainable consumption. It argues that environmental regulation, behavioral change, and a shift away from treating nature purely as a commodity are essential to preserving the plant-human relationship on which all life depends.
The connection between humans and nature has been a primordial one, actively discussed not only in the life sciences but also in literature. Ever since the start of the evolutionary process, plants have been an incredible source of food, medicine, and even shelter. However, the greatest benefit plants have given the human race is oxygen.
Photosynthesis is the process that converts energy in sunlight into chemical forms of energy that can be used by biological systems. This procedure is carried out by plants and bacteria; a higher form of photosynthesis is completed by algae, cyanobacteria, and their relatives, which are notably responsible for photosynthesis in the oceanic ecosystem. These organisms convert CO₂ to organic material by reducing this gas to carbohydrates through a complex set of reactions (Vermaas, 1998). Each year, more than 10% of the total atmospheric carbon dioxide is reduced to carbohydrate by photosynthetic organisms. Through biomass combustion and plant and animal metabolism, the reduced CO₂ is returned to the atmosphere as carbon dioxide. The quality of the photosynthetic process depends on Earth's atmosphere and climate, and during the last century, highly industrialized human activities have had a profound impact on photosynthetic organisms (Whitmarsh and Govindjee, 1995).
There are two important steps in photosynthesis: energy transfer and electron transfer. "Molecules of the light-harvesting system transfer electronic excitation energy to special chlorophyll molecules, whose role is to initiate the directional transfer of electrons across a biological membrane; the electron transfer, which takes place in a pigment-protein complex called the reaction center, then creates a potential difference that drives the subsequent biochemical reactions that store the energy" (Fleming and Grondelle, 1994, p. 48).
The following factors must be present in the right capacities and in proper balance for photosynthesis to occur naturally:
Temperature — When temperatures are higher than 35°C, the process slows down, and at a certain point the enzymes involved are destroyed. Keeping the temperature at a constant level is therefore vital for the process.
Light intensity — An increase in light intensity accelerates photosynthesis in a leaf until a maximum rate is reached.
CO₂ concentration — An increase in the amount of CO₂ in the air around the plant will intensify the rate of photosynthesis.
Water — Any shortage of water will slow the process, reducing the exchange rate between CO₂ and O₂ as well as the number of stomata.
Minerals — Magnesium and nitrogen are needed to make chlorophyll molecules. Other essential minerals required for the process include zinc, manganese, iron, and copper (Energy, Matter and Organization, 2011).
One of these five factors warrants further discussion, as it is arguably the most important: light. The absence of light becomes a limiting factor, and experiments have shown that a plant kept in a dark environment will not initiate the photosynthesis process regardless of the quantity of CO₂ it receives (Toole and Toole, 1997). This finding illustrates, even at a small scale, the effects that air pollution — which blocks and filters light — can have on vegetation.
"Pollution, land use, and ecosystem degradation"
"Policy, behavioral change, and sustainability solutions"
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