In the light phase of photosynthesis, ATP and NADP · H are synthesized.2 due to radiant energy. It happens on chloroplast thylakoidswhere pigments and enzymes form complex complexes for the functioning of electrochemical circuits, through which electrons and partly hydrogen protons are transferred.
The electrons ultimately end up in the coenzyme NADP, which, being charged negatively, attracts part of the protons to itself and turns into NADPH2. Also, the accumulation of protons on one side of the thylakoid membrane and electrons along the other creates an electrochemical gradient, the potential of which is used by the enzyme ATP synthetase to synthesize ATP from ADP and phosphoric acid.
The main pigments of photosynthesis are various chlorophylls. Their molecules capture the radiation of certain, partly different light spectra. At the same time, some electrons of chlorophyll molecules transfer to a higher energy level. This is an unstable state, and, in theory, electrons, by the same radiation, must transfer into space the energy received from outside and return to the previous level. However, in photosynthesizing cells, excited electrons are captured by acceptors and, with a gradual decrease in their energy, are transmitted along a carrier chain.
On thylakoid membranes, there are two types of photosystems that emit electrons when exposed to light. Photosystems are a complex complex of mostly chlorophyll pigments with a reaction center, from which electrons break away. In the photosystem, sunlight catches many molecules, but all the energy is collected in the reaction center.
The electrons of the photosystem I, passing through the carrier chain, reduce NADPH.
The energy of electrons detached from photosystem II is used to synthesize ATP. And the electrons of photosystem II themselves fill the electron holes of photosystem I.
The holes of the second photosystem are filled with electrons resulting from photolysis of water. Photolysis also occurs with the participation of light and is the decomposition of H2O to protons, electrons and oxygen. It is as a result of photolysis of water that free oxygen is formed. Protons are involved in the creation of an electrochemical gradient and the reduction of NADPH. Electrons receives chlorophyll photosystem II.
The approximate total equation of the light phase of photosynthesis:
H2O + NADF + 2ADF + 2F → ½O2 + NADF · H2 + 2ATP
Cyclic electron transport
The above is the so-called non-cyclical light phase of photosynthesis. Is there some more cyclic electron transport when NADP recovery does not occur. In this case, the electrons from the photosystem I go to the carrier chain, where ATP is synthesized. That is, this electron transport chain gets electrons from photosystem I, not II. The first photosystem seems to be implementing a cycle: the electrons emitted back to it are returned to it. On the way, they spend part of their energy on ATP synthesis.
Photophosphorylation and oxidative phosphorylation
The light phase of photosynthesis can be compared with the stage of cellular respiration — oxidative phosphorylation, which occurs on the mitochondrial cristae. There, too, ATP is synthesized by transferring electrons and protons along the carrier chain. However, in the case of photosynthesis, energy is stored in ATP not for the needs of the cell, but mainly for the needs of the dark phase of photosynthesis. And if, when breathing, organic substances are the primary source of energy, then during photosynthesis - sunlight. ATP synthesis during photosynthesis is called photophosphorylationrather than oxidative phosphorylation.
The dark phase of photosynthesis
For the first time the dark phase of photosynthesis was studied in detail by Calvin, Benson, Bassam. The cycle of reactions opened by them was subsequently called the Calvin cycle, or C3- photosynthesis. Certain groups of plants have a modified photosynthesis pathway - C4Also called the Hatch-Slack cycle.
In the dark reactions of photosynthesis, CO is fixed.2. The dark phase proceeds in the stroma of the chloroplast.
CO recovery2 occurs due to the energy of ATP and the reducing force of NADF · H2generated in light reactions. Without them, carbon fixation does not occur. Therefore, although the dark phase does not directly depend on light, it usually also proceeds in light.
The first reaction of the dark phase is the addition of CO2 (carboxylatione) to 1,5-ribulezobifosfaty (ribulose-1,5-diphosphate) – Ribf. The latter is a double phosphorylated ribose. This reaction is catalyzed by the enzyme ribulose-1,5-diphosphate carboxylase, also called rubisco.
As a result of carboxylation, an unstable six-carbon compound is formed, which decomposes into two three-carbon molecules as a result of hydrolysis. phosphoglyceric acid (PGA) - the first product of photosynthesis. PGA is also called phosphoglycerate.
PGA contains three carbon atoms, one of which is part of the acid carboxyl group (-COOH):
PGC forms three carbon sugar (glyceraldehyde phosphate) triosephosphate (TF)already includes an aldehyde group (-CHO):
FGK (3-acid) → TF (3-sugar)
The ATP energy and the reducing force of NADP · H are spent on this reaction.2. TF is the first carbohydrate of photosynthesis.
After that, most of the triose phosphate is spent on the regeneration of ribulozobifosfat (ReBP), which is again used to bind CO2. Regeneration includes a series of ATP-related reactions involving sugar phosphates with 3 to 7 carbon atoms.
In such a cycle of RibF and is the cycle of Calvin.
From the cycle of Calvin comes the smaller part of the formed TF. In terms of 6 bound carbon dioxide molecules, the yield is 2 triosophosphate molecules. Total cycle response with input and output products:
At the same time, 6 RIB molecules participate in the binding, and 12 PGA molecules are formed, which turn into 12 TF, of which 10 molecules remain in the cycle and are converted into 6 RIB molecules. Since TF is three-carbon sugar, and RibBP is five-carbon, then with respect to carbon atoms we have: 10 * 3 = 6 * 5. The number of carbon atoms providing the cycle does not change, all the necessary RibF is regenerated. And the six molecules of carbon dioxide that entered the cycle are spent on the formation of two triosophosphate molecules leaving the cycle.
On the cycle of Calvin per 6 bound CO molecules2 18 ATP molecules and 12 NADP · H molecules are consumed2, which were synthesized in the reactions of the light phase of photosynthesis.
The calculation is carried out on two molecules leaving the cycle of triosophosphate, since the glucose molecule that is subsequently formed includes 6 carbon atoms.
Triosephosphate (TF) is the end product of the Calvin cycle, but it is difficult to call it the end product of photosynthesis, since it almost does not accumulate, and, reacting with other substances, turns into glucose, sucrose, starch, fats, fatty acids, amino acids. In addition to TF plays an important role FGK. However, such reactions occur not only in photosynthetic organisms. In this sense, the dark phase of photosynthesis is the same as the Calvin cycle.
PGCs produce six carbon sugar by step enzymatic catalysis. fructose 6-phosphatewhich turns into glucose. In plants, glucose can polymerize into starch and cellulose. The synthesis of carbohydrates is similar to the process of reverse glycolysis.
What else is important for plants?
Like humans, plants also need nutrients to maintain health, grow, and perform their vital functions well. They get minerals dissolved in water from the soil through the roots. If the soil lacks mineral nutrients, the plant will not develop normally. Farmers often check the soil to ensure that it has enough nutrients to grow crops. Otherwise, resort to the use of fertilizers containing basic minerals for nutrition and plant growth.
Why is photosynthesis so important?
Explaining photosynthesis briefly and clearly for children, it is worth mentioning that this process is one of the most important chemical reactions in the world. What are the reasons for such a loud statement? Firstly, photosynthesis feeds plants, which, in turn, feed all other living creatures on the planet, including animals and humans. Secondly, as a result of photosynthesis, oxygen necessary for respiration is released into the atmosphere. All living things breathe in oxygen and exhale carbon dioxide. Fortunately, the plants do the opposite, so they are very important for humans and animals, as they give them the opportunity to breathe.
Plants, it turns out, also know how to breathe, but, unlike people and animals, they absorb carbon dioxide rather than oxygen from the air. Plants also drink. That is why you need to water them, otherwise they will die. With the help of the root system, water and nutrients are transported to all parts of the plant body, and carbon dioxide absorption occurs through the small holes in the leaves. The trigger for triggering a chemical reaction is sunlight. All the metabolic products obtained are used by plants for nutrition, oxygen is released into the atmosphere. This is how you can explain briefly and clearly how the process of photosynthesis proceeds.
Photosynthesis: light and dark phases of photosynthesis
The process in question consists of two main parts. There are two phases of photosynthesis (description and table - hereinafter). The first is called the light phase. It occurs only in the presence of light in the membranes of thylakoids with the participation of chlorophyll, electron transfer proteins and the enzyme ATP synthetase. What else hides photosynthesis? The light and dark phases of photosynthesis alternate with each other as day and night come on (Calvin cycles). During the dark phase, the production of the same glucose, food for plants. This process is also called a light-independent reaction.
1. Reactions occurring in chloroplasts are possible only in the presence of light. In these reactions, the light energy is converted into chemical energy
2. Chlorophyll and other pigments absorb energy from sunlight. This energy is transmitted to the photosystems that are responsible for photosynthesis.
3. Water is used for electrons and hydrogen ions, and is also involved in the production of oxygen.
4. Electrons and hydrogen ions are used to create ATP (energy storage molecule), which is needed in the next phase of photosynthesis.
1. The reaction of the light cycle occur in the stroma of chloroplasts.
2. Carbon dioxide and energy from ATP are used as glucose.
From the foregoing, the following conclusions can be drawn:
- Photosynthesis is a process that allows you to receive energy from the sun.
- The sun's light energy is converted into chemical energy by chlorophyll.
- Chlorophyll gives plants a green color.
- Photosynthesis occurs in chloroplasts of plant leaf cells.
- Carbon dioxide and water are needed for photosynthesis.
- Carbon dioxide enters the plant through tiny openings, the stomata, through which oxygen is released.
- Water is absorbed into the plant through its roots.
- Without photosynthesis in the world there would be no food.
Definition of photosynthesis
Photosynthesis is a chemical process by which plants, some bacteria and algae produce glucose and oxygen from carbon dioxide and water, using only light as an energy source.
This process is extremely important for life on Earth, because thanks to it oxygen is released, on which all life depends.
Why do plants need glucose (food)?
Like humans and other living things, plants also need nutrition to sustain their livelihoods. The value of glucose for plants is as follows:
- Photosynthesis-derived glucose is used during respiration to release the energy needed by the plant for other vital processes.
- Plant cells also convert part of the glucose to starch, which is used as needed. For this reason, dead plants are used as biomass, because they store chemical energy.
- Glucose is also needed to produce other chemicals, such as proteins, fats and vegetable sugars, necessary for growth and other important processes.
External structure of leaves
One of the most important features of plants is the large surface area of the leaves. Most green plants have wide, flat and open leaves that are capable of capturing as much solar energy (sunlight) as is necessary for photosynthesis.
- Central vein and petiole
The central vein and petiole are joined together and are the base of the leaf. The stalk positions the leaf in such a way that it receives as much light as possible.
- Leaf blade
Simple leaves have one leaf plate, and complex - a few. Leaf blade - one of the most important components of the sheet, which is directly involved in the process of photosynthesis.
A network of veins in the leaves transfers water from the stems to the leaves. Allocated glucose is also sent to other parts of the plant from the leaves through the veins. In addition, these parts of the sheet support and keep the sheet plate flat for greater capture of sunlight. The location of the veins (venation) depends on the type of plant.
- Base sheet
The bottom of the leaf is the lower part of it, which is articulated with the stem. Often, at the base of the leaf is a pair of stipules.
Depending on the type of plant, the leaf edge may have a different shape, including: whole, serrated, serrate, notched, gibberish, etc.
- Leaf top
Like the leaf edge, the tip can be of various shapes, including: sharp, rounded, blunt, elongated, drawn, etc.
The internal structure of the leaves
Below is a close diagram of the internal structure of leaf tissue:
The cuticle is the main protective layer on the surface of the plant. As a rule, it is thicker on the top of the sheet. The cuticle is coated with a wax-like substance that protects the plant from water.
The epidermis is a layer of cells that is the integumentary tissue of the leaf. Its main function is to protect the internal tissues of the leaf from dehydration, mechanical damage and infections. It also regulates the process of gas exchange and transpiration.
Mesophyll is the main plant tissue. Here is the process of photosynthesis. In most plants, the mesophyll is divided into two layers: the top is palisade and the bottom is spongy.
- Protective cells
Protective cells are specialized cells in the leaf epidermis that are used to control gas exchange. They perform a protective function for stomata. The stomatal pores become large when water is freely available, otherwise the protective cells become sluggish.
Photosynthesis depends on the penetration of carbon dioxide (CO2) from the air through the stomata into the mesophyll tissue. Oxygen (O2), obtained as a by-product of photosynthesis, leaves the plant through the stomata. When the stomata are open, water is lost as a result of evaporation and must be replenished through the transpiration flow with water absorbed by the roots. Plants are forced to balance the amount of CO2 absorbed from the air and the loss of water through the stomatal pores.
Verified by an expert
1. Where is happening
The light phase of photosynthesis occurs in the granal thylakoids.
2.Processes occurring in this phase
Due to the light energy of the chlorophyll oxidation occurs. Recovery occurs at the expense of electrons of water taken away from hydrogen. A potential difference is created between the inner and outer sides of the thylakoid membrane, and using ATP synthetase, NADP is reduced to NADPH2 (nicothoamide adenine dinucleotide phosphate reduced form)
3. Process results
- photolysis of water (decomposition) at which it is released
- the energy of light is converted into the energy of the chemical bonds of ATP and NADP * H2
1. Where is happening
The dark phase of photosynthesis occurs in the stroma of the chloroplast.
2.Processes occurring in this phase
There is a fixation of CO2 (carbon dioxide).
In the reactions of the Calvin cycle, CO2 is reduced due to ATP and the reducing power of NADP * H2 (nicotamide adenine dinucleotide phosphate reduced form) formed in the light phase.
The concept of photosynthesis, where and what happens in the light phase of photosynthesis
Photosynthesis is a set of processes of formation of light energy into energy of chemical bonds of organic substances with the participation of photosynthetic dyes.
This type of nutrition is characteristic of plants, prokaryotes and some types of unicellular eukaryotes.
In natural synthesis, carbon and water, in interaction with light, are converted into glucose and free oxygen:
6CO2 + 6H2O + light energy → C6H12O6 + 6O2
Современная физиология растений под понятием фотосинтеза понимает фотоавтотрофную функцию, которая является совокупностью процессов поглощения, превращения и применения квантов световой энергии в разных несамопроизвольных реакциях, включая преобразование углекислого газа в органику.
Фотосинтез у растений происходит в листьях через хлоропласты - semi-autonomous two-membrane organelles belonging to the class of plastids. With the flat shape of the leaf plates, a high-quality absorption and full utilization of light energy and carbon dioxide is ensured. The water required for natural synthesis comes from the roots through the water-conducting fabric. Gas exchange occurs through diffusion through the stomata and partially through the cuticle.
Chloroplasts are filled with a colorless stroma and are riddled with lamellae, which when combined with each other form thylakoids. It is in them that photosynthesis occurs. Cyanobacteria themselves are chloroplasts, so the apparatus for natural synthesis in them is not separated into a separate organelle.
Photosynthesis proceeds with the participation of pigmentsChlorophylls are commonly found. Some organisms contain another pigment - carotenoid or fikobilin. Prokaryotes have bacteriochlorophyll pigment, and these organisms do not emit oxygen at the end of natural synthesis.
Photosynthesis passes two phases - light and dark. Each of them is characterized by specific reactions and interacting substances. Let us consider in more detail the process of photosynthesis phases.
The first phase of photosynthesis characterized by the formation of high-energy products, which are ATP, a cellular energy source, and NADP, a reducing agent. At the end of the stage, oxygen is produced as a by-product. The light stage takes place necessarily with sunlight.
The process of photosynthesis proceeds in the membranes of thylakoids with the participation of electron transfer proteins, ATP synthetase, and chlorophyll (or other pigment).
The functioning of electrochemical chains, through which the transfer of electrons and partially of hydrogen protons, occurs, is formed in complex complexes formed by pigments and enzymes.
Description of the light phase process:
- When sunlight hits the leaf plates of plant organisms, chlorophyll electrons are excited in the plate structure,
- In the active state, the particles exit the pigment molecule and fall on the outer side of the thylakoid, which is negatively charged. This occurs simultaneously with the oxidation and subsequent reduction of chlorophyll molecules, which take the next electrons from the water that has entered the leaves.
- Then there is a photolysis of water with the formation of ions, which donate electrons and are converted into OH radicals, capable of participating in the reactions and further,
- Then these radicals combine to form water molecules and free oxygen that goes into the atmosphere,
- The thylakoid membrane acquires, on the one hand, a positive charge due to a hydrogen ion, and on the other, a negative charge due to electrons,
- With a difference of 200 mV between the sides of the membrane, protons pass through the enzyme ATP synthetase, which leads to the conversion of ADP to ATP (phosphorylation process),
- With atomic hydrogen released from water, NADP + is reduced to NADPH2,
While free oxygen in the reaction process is released into the atmosphere, ATP and NADPH2 participate in the dark phase of natural synthesis.
A mandatory component for this stage is carbon dioxide.which plants constantly absorb from the external environment through the stomata in the leaves. The processes of the dark phase take place in the stroma of the chloroplast. Since at this stage a lot of solar energy is not required and ATP and NADPH2 will be sufficiently obtained during the light phase, reactions in organisms can proceed both during the day and at night. Processes at this stage occur faster than the previous one.
The totality of all processes occurring in the dark phase is represented as a kind of chain of successive transformations of carbon dioxide from the external environment:
- The first reaction in this chain is the fixation of carbon dioxide. The presence of the enzyme RibBP-carboxylase contributes to the rapid and smooth course of the reaction, which results in the formation of a six-carbon compound, which breaks down into 2 phosphoglyceric acid molecules,
- Then a rather complex cycle takes place, including a certain number of reactions, upon completion of which phosphoglyceric acid is converted to natural sugar, glucose. This process is called the Calvin cycle,
Together with sugar, the formation of fatty acids, amino acids, glycerol and nucleotides also occurs.
The essence of photosynthesis
From the table of comparisons of the light and dark phases of natural synthesis, it is possible to briefly describe the essence of each of them. The light phase occurs in chlorine grains with the obligatory inclusion of light energy in the reactions. The reactions involve components such as electron-transporting proteins, ATP synthetase, and chlorophyll, which, when interacting with water, form free oxygen, ATP, and NADPH2. For the dark phase occurring in the stroma of the chloroplast, sunlight is not necessary. The ATP and NADPH2 produced at the last stage, when interacting with carbon dioxide, form natural sugar (glucose).
As can be seen from the above, photosynthesis appears to be a rather complex and multi-step phenomenon, including many reactions involving various substances. As a result of natural synthesis, oxygen is obtained, which is necessary for respiration of living organisms and their protection from ultraviolet radiation through the formation of an ozone layer.
1 - chloroplast, 2 - peroxisome, 3 - mitochondria.
This light-dependent absorption of oxygen and carbon dioxide. At the beginning of the last century, it was found that oxygen suppresses photosynthesis. As it turned out, for RibB-carboxylase, the substrate can be not only carbon dioxide, but also oxygen:
ABOUT2 + RibP → phosphoglycolate (2C) + PGA (3C).
The enzyme is called ribf-oxygenase. Oxygen is a competitive carbon dioxide fixation inhibitor. The phosphate group is cleaved off, and the phosphoglycolate becomes glycolate, which the plant must dispose of. It enters peroxisomes, where it is oxidized to glycine. Glycine enters the mitochondria, where it is oxidized to serine, with the loss of already fixed carbon in the form of CO.2. As a result, two molecules of glycolate (2C + 2C) are converted into one PGA (3C) and CO2. Photorespiration leads to a decrease in yield C3-plants by 30–40% (WITH3-plants - plants characterized by C3-photosynthesis).
WITH4- photosynthesis - photosynthesis, in which the first product is a four-carbon (C4) connections. In 1965, it was found that in some plants (sugar cane, maize, sorghum, millet), the first products of photosynthesis are four-carbon acids. Such plants are called WITH4-plants. In 1966, Australian scientists Hatch and Slack showed that4- plants practically do not have photorespiration and they absorb carbon dioxide much more effectively. The path of carbon to C4-plants began to be called by Hatch-Slack.
For C4-plants characterized by a special anatomical structure of the leaf. All conductive beams are surrounded by a double layer of cells: the outer - the mesophyll cells, the inner - the lining cells. Carbon dioxide is fixed in the cytoplasm of mesophyll cells, the acceptor is phosphoenolpyruvate (PEP, 3C), as a result of PEP carboxylation, oxaloacetate (4C) is formed. The process is catalyzed PEP carboxylase. Unlike RibB-carboxylase, FEP-carboxylase has a high affinity for CO.2 and, most importantly, does not interact with O2. In mesophyll chloroplasts there are many grana, where the light phase reactions are active. In the chloroplasts of the cell plates, reactions of the dark phase occur.
Oxaloacetate (4C) is converted to malate, which is transported through the plasmodesma to the lining cells. Here it is decarboxylated and dehydrated to form pyruvate, CO2 and NADP · N2.
Pyruvate returns to the mesophyll cells and regenerates at the expense of ATP energy in PEP. WITH2 again fixed RibB-carboxylase with the formation of PGA. Regeneration of FEP requires ATP energy, so almost twice as much energy is needed as with C3- photosynthesis.
1 - outer layer - mesophyll cells, 2 - inner layer - facing cells, 3 - Kranz-anatomy, 4, 5 - chloroplasts, 4 - numerous facets, little starch, 5 - few facets, a lot of starch.
1 is a mesophyll cell, 2 is a cell of a conducting beam lining.
Conditions required for photosynthesis
Below are the conditions that are necessary for plants to carry out the process of photosynthesis:
- Carbon dioxide. A colorless, odorless natural gas, found in the air and has the scientific designation CO2. It is formed during the combustion of carbon and organic compounds, and also occurs in the process of respiration.
- Water. Transparent liquid chemical odorless and tasteless (under normal conditions).
- Shine. Although artificial light is also suitable for plants, natural sunlight, as a rule, creates the best conditions for photosynthesis, because it contains natural ultraviolet radiation, which has a positive effect on plants.
- Chlorophyll. It is a green pigment found in the leaves of plants.
- Nutrients and minerals. Chemicals and organic compounds that the roots of plants absorb from the soil.
What is the result of photosynthesis?
(Light energy is shown in parentheses because it is not a substance.)
Note: Plants get CO2 from the air through their leaves, and water from the soil through the roots. Light energy comes from the sun. The resulting oxygen is released into the air from the leaves. The resulting glucose can be converted into other substances, such as starch, which is used as an energy reserve.
If the factors contributing to photosynthesis are absent or are present in insufficient quantities, this may adversely affect the plant. For example, a smaller amount of light creates favorable conditions for insects that eat the leaves of the plant, and the lack of water slows down.
Where does photosynthesis occur?
Photosynthesis occurs inside plant cells, in small plastids called chloroplasts. Chloroplasts (mainly found in the mesophyll layer) contain a green substance called chlorophyll. Below are other parts of the cell that work with chloroplast to photosynthesis.
Functions of plant cell parts
- Cell wall: provides structural and mechanical support, protects cells from pathogens, fixes and determines the shape of the cell, controls the speed and direction of growth, and also gives shape to plants.
- Cytoplasm: provides a platform for most chemical processes controlled by enzymes.
- Membrane: acts as a barrier, controlling the movement of substances into and out of the cell.
- Chloroplasts: as described above, they contain chlorophyll, a green substance that absorbs light energy during photosynthesis.
- Vacuole: a cavity inside the cell cytoplasm that accumulates water.
- Cell nucleus: contains a genetic brand (DNA) that controls cell activity.
Chlorophyll absorbs the light energy needed for photosynthesis. It is important to note that not all color wavelengths of light are absorbed. Plants mainly absorb red and blue waves - they do not absorb light in the green range.
Carbon dioxide in the process of photosynthesis
Plants get carbon dioxide from the air through their leaves. Carbon dioxide seeps through a small hole in the bottom of the sheet - the stoma.
The lower part of the leaf has freely spaced cells so that carbon dioxide reaches other cells in the leaves. It also allows oxygen generated during photosynthesis to easily leave the leaf.
Carbon dioxide is present in the air we breathe in very low concentrations and serves as a necessary factor in the dark phase of photosynthesis.
Light in the process of photosynthesis
The leaf usually has a large surface area, so it can absorb a lot of light. Its upper surface is protected from water loss, disease and the effects of the weather wax layer (cuticle). The top of the sheet is where the light falls. This layer of mesophyll is called palisade. It is adapted to absorb large amounts of light, because it contains a lot of chloroplasts.
In the light phases, the process of photosynthesis increases with a lot of light. More chlorophyll molecules ionize and more ATP and NADPH are generated if light photons are concentrated on a green leaf. Although light is extremely important in the light phases, it should be noted that an excessive amount of it can damage chlorophyll and reduce the photosynthesis process.
The light phases are not too dependent on temperature, water, or carbon dioxide, although they are all necessary to complete the photosynthesis process.
Water in the process of photosynthesis
Plants get the water they need for photosynthesis through their roots. They have root hairs that grow in the soil. The roots are characterized by a large surface area and thin walls, which allows water to easily pass through them.
The image shows plants and their cells with enough water (left) and lack of water (right).
Note: Root cells do not contain chloroplasts, as they are usually in the dark and cannot photosynthesize.
If the plant does not absorb enough water, it fades. Without water, the plant will not be able to photosynthesize quickly enough, and may even die.
What does water mean for plants?
- Provides dissolved minerals that support plant health,
- It is a medium for the transportation of mineral resources,
- Maintains stability and uprightness
- Cools and saturates moisture
- It makes it possible to carry out various chemical reactions in plant cells.
The value of photosynthesis in nature
The biochemical process of photosynthesis uses the energy of sunlight to convert water and carbon dioxide into oxygen and glucose. Glucose is used as building blocks in plants for tissue growth. Thus, photosynthesis is the way by which roots, stems, leaves, flowers and fruits are formed. Without the process of photosynthesis, plants will not be able to grow or reproduce.
Because of their photosynthetic ability, plants are known as producers and serve as the basis for almost every food chain on Earth. (Algae are the equivalent of plants in aquatic ecosystems). All the food we eat comes from organisms that are photosynthetic. We eat these plants directly or eat animals such as cows or pigs that consume plant foods.
- The basis of the food chain
Inside aquatic systems, plants and algae also form the basis of the food chain. Algae serve as food for invertebrates, which, in turn, are the source of food for larger organisms. Without photosynthesis in the aquatic environment, life would be impossible.
- Carbon dioxide removal
Photosynthesis converts carbon dioxide to oxygen. During photosynthesis, carbon dioxide from the atmosphere enters the plant, and then released as oxygen. In today's world, where carbon dioxide levels are growing at an appalling pace, any process that removes carbon dioxide from the atmosphere is environmentally important.
- Nutrient cycling
Plants and other photosynthetic organisms play a vital role in the nutrient cycling. Nitrogen in the air is fixed in plant tissues and becomes available to create proteins. Trace elements in the soil can also be incorporated into plant tissue and become available to herbivores, further along the food chain.
- Photosynthetic dependence
Photosynthesis depends on the intensity and quality of light. At the equator, where sunlight is abundant throughout the year and water is not a limiting factor, plants have high growth rates and can become quite large. Conversely, photosynthesis in the deeper parts of the ocean is less common, since light does not penetrate into these layers, and as a result, this ecosystem is more barren.