Insights into the photosynthesis process

1. Introduction

Photosynthesis is the process plants, algae, and some bacteria use to make food by taking in carbon dioxide (CO2) and water (H2O) from the air and soil. Within the plant cell, the water is oxidized, meaning it loses electrons, while the carbon dioxide is reduced, meaning it gains electrons. This transforms the H2O into O2 and the CO2 into glucose, meaning sugar. The plant then releases the O2 into the air and stores energy within the glucose molecules [1,2]. Photosynthesis also enables life on Earth. Without this process, oxygen wouldn’t be released into the air for living organisms to breathe. Because of this, without photosynthesis, life on Earth, as we know it, wouldn’t be possible [3]. 

Photosynthesis occurs inside the chloroplasts that sit in the mesophyll of the leaves. The thylakoids sit inside the chloroplast, containing chlorophyll which absorbs the different colors of the light spectrum to create energy [4]. Photosynthesis uses mentioned green pigment   chlorophyll. This pigment is a molecule with a particular color and can absorb light at different wavelengths, depending on the color. There are many kinds of pigments in nature, but chlorophyll is unique in enabling plants to absorb energy. This is used to build tissues [5].

There is a lot of information about photosynthesis, which is widely known, considering the importance of this process. However, there is also a range of information about photosynthesis that is unknown and not often mentioned. This Review will give a deeper insight into some parts of the photosynthesis process.

2. Plants aren’t the only organisms that perform photosynthesis

The ability to photosynthesize is found in both eukaryotic and prokaryotic organisms. The most well-known examples are plants. But very few known that parasitic or mycoheterotrophic species contain chlorophyll and produce their food. Algae are the other dominant group of eukaryotic photosynthetic organisms. All algae, which include massive kelps and microscopic diatoms, are important primary producers [6,7]. Now, if other organisms can do photosynthesis, some plants can not. These plants are called “Non-photosynthetic plants”. A plant with no chlorophyll is equal to a plant that does not produce its food via photosynthesis. There are approximately 3000 non-photosynthetic plants around the world. Rather than producing their food, they can parasitize other plants or fungi. Some examples are broomrape, beechdrops, indian pipe, etc. [8].

Beechdrops (Epifagus Americana), a holoparasitic plant, live off beech trees. Its genus name Epifagus means “upon beech.” Beechdrops has neither leaves nor chlorophyll. Instead, its haustoria connect to the roots of the beech below ground. What you see of this plant above ground is just the flowering part of the plant. It becomes dormant in the winter with its host beech tree to avoid exhausting its only food supply [8].

Indian pipe (Monotropa uniflora), ghost plant, or corpse plant is also a holoparasitic plant. Its hosts are mycorrhizal fungi, mutualists that derive their energy from a host tree. So the Indian pipe is ultimately feeding off a host tree, but it does so through an intermediary. It is not clear whether this relationship harms the mycorrhizal intermediary, or it benefits in some way from this. Indian Pipe has no chlorophyll and, in fact, no pigments. It says that its waxy, corpulent white, although rare variants are a deep red color, is a genetic vestige of its ancestral coloration. Its tiny, scale-like leaves are also without pigmentation (Figure 1). It grows only 2–12 inches tall, with one drooping, bell-shaped flower per stem. Indian pipe prefers shaded sites with rich soils. It is often found close to decaying matter, tree roots, or leafy mulch. It could be found with beech or sometimes pines or oaks [8].