The myth that how life is formed is considered as many aspects are involved, but water is one of the most important elements, both at the early stage and the lately evolution of life. Water is not just participate as the building blocks, but also as the director, the medium and the regulator. Every organism needs water in the form of liquid or gas. How long can we survive without the water, H2O? The study showed that humans could stay alive for seven days without food, but only three days without water. Seventy percent of humans fresh weight are water. If not drinking enough water, we will suffer from dehydration, have slower oxygenated blood and lung activity and eventfully die. Water hydrates our brain cells and fluidifies the blood to ensure the oxygen are delivered to the cells. The osmotic pressure within the blood vessels regulate the arterial pressure and body temperature in homeostasis. Besides, water lubricates the skin and tissues and aids in digestion (hydrolysis) and metabolic functions. Water eliminates the toxins and waste substances from our body as sweats and urine. For plants, water is just as essential but in very different ways. Plants used water and carbon dioxide to produce food and oxygen in the presence of light in photosynthesis. That made the plant the critical producer in the food chain.
Water also shape the nature in favor of the life on earth. Water is recycled all around the earth. The sea and river evaporate the water, and then condensed into the form of clouds. Clouds return to the ground through raining and are available for all organisms to consume. Then become underground water, or join the rivers back to the sea and the cycle is repeated again and again.
Water consists of two simple elements: hydrogen (H) and oxygen (O). It is a molecule with two hydrogens and one oxygen that covalent bonds are formed between the hydrogens and oxygen. The water molecules form strong hydrogen bonds between each other and became one of the critical features of the water. Therefore, it has partial positive charges on the hydrogens and a partial negative charge on the oxygen, making it polar. Due to the polarity, water acts as an excellent solvent that interacts differently with charged and polar substances than non-polar substances. It helps the water absorb nutrients from the soil easily by dissolving the fertilizers for the uptake of minerals. In many biochemical processes, water plays a critical role in hydrolysis.
Water molecules are the constituent of the protoplasm that also mainly stored in the vacuole of the cells. It forms over ninety percent of the plant body on a green or fresh weight basis. Water plays an essential role in hydrating the cells and tissues apart from playing essential roles in biochemicals growth and development processes. Water penetrates the cells in and out through a process called osmosis. Water is the molecule that can diffuse through the cell wall and cell membrane quickly. However, it can be assisted by a specialized channel found on the cell membrane, which is aquaporin that allowed the exchange of the water molecules to have occurred quickly.
There are only two forms of tonicity in a plant, mainly turgid and flaccid (wilt). When the rate of water molecules diffuse into the plant cells is lower than the rate of water molecules diffuses out from the cells. This meant the total solute concentration within the cells is higher than outside. Thus, the cytoplasm shrinks and pulls away from the cell way. This phenomenon is known as hypertonic. When the fertilizer dosage is surplus when the plants are placed, located, or planted at dry or drought area, wilting and drying up are observed. Initially, plants will react to the drought by increase the closure of stomata to reduce the release of water vapor and keep the moisture in the system. After that, the plant hormone abscisic acid will stimulate the leaves shedding by promoting cell death at the abscission region between the basal part of the petiole and the shoot or stem.
Hypertonic is commonly applied in many food industries as the water contents in the vegetables and fruits are the significant criteria for bacteria and fungus to grow, which caused the postharvest diseases and thus reducing the shelf life. One of the applications is pickling or commonly known as pickles. Fruit vegetables like pickled cucumbers, kimchi made from Napa cabbage and Korean radish, or other foods like meats, fish, dairy, and eggs. Pickling is a process of preserving or extending the shelf life of the food through anaerobic fermentation in brine or immersion in vinegar that usually consists of high solute concentration. For instance, it can be done by adding dry salt only or brine (salt solution) at a high salt concentration to salt the vegetables, which draws out excess water from the food. Furthermore, hypertonic also can be seen when a surplus of fertilizer is applied (solute concentration is high), therefore, causing the roots of the plants to lose the water content via osmosis. That is why it is crucial to apply fertilizer at an appropriate amount, and frequent watering is needed to ensure the plants are always hydrated.
On the contrary, when the rate of the water molecules diffuses in and out via osmosis are equal (isotonic), or the rate of water molecules diffuse into the cells are more significant than the rate of water molecules diffuses out (hypotonic), the plants will exhibit turgidity, in which the vegetables will show fleshly look. As compared to animal cells, plant cells remain turgid in both tonicities. Animal cells will undergo lysis, which is known as the bursting of the cells due to the absence of a cell wall. However, there is a possibility that the plant cell burst resulted from crystal ice. Plant cells consist of high water content to maintain themselves turgid and fresh. Improper postharvest storage or the low temperature experienced by the plants during frost winter caused the formation of crystal ice within the plants. As the volume of water expands in the form of ice due to the lattice structure that arranged water molecules in an orderly arrangement, it caused the expansion. It increased the internal volume, thus causing a burst that damaged the plant cell wall of most plant species.
Water enters the plants through osmosis that takes part at the roots in the medium like soil substrate and dissolved nutrients and organic compounds adhered to the soil particles. Within the plant system, the water transport from the root to other parts through the vascular system, particularly xylem tissue. It is transported within the plants against gravity. The scientific reason behind this is that plant loses water through transpiration (respiration in plants) via the opening that mainly found on leaves like stomata. They also lose water through guttation through a specialized structure called hydathodes. The yield of water in vapor form caused the first plant cell to experience low water content. It gets water through adjacent cells via osmosis, and the adjacent cells get their water from their neighboring cells. This eventually creates a drawing force, known as capillary action, that draws the water molecules from soil to the leaves with the help of water potential.
Transpiration is when the water evaporates from the aerial parts like leaves, stems, and flowers. Transpiration is a crucial process, which acts as homeostasis in a plant that regulates the temperature. It cools the plants as water carries the heat energy from the surround due to its remarkable property, the latent heat of vaporization. It is used in regulation that mainly affected by the number of leaves, the number of stomata (stomata density), the size of the leaf, the presence of plant cuticle, light supply, temperature, humidity, wind, and water supply. That is why plants shed their leaves when they experience drought condition or during late autumn. Deciduous trees such as non-evergreen trees shed their leaves to help themselves conserve the water as well as the energy, especially in unfavorable weather approaches, by promoting the abscission at the basal part of the petiole. During the shedding process, the plants reabsorb the valuable nutrients from the leaves and store them for later use in their roots. For instance, the chlorophyll, a green color pigment that is the first molecule to be broken down for its nutrients. That is why leaves turn red, orange, and gold colors in the autumn.
Besides, before the formation of flowering plants, water is the major pollinating agent in early plant species such as moss and ferns and also plays a pivotal role in spore and seed germination. Water is the key for all living organisms apart from light and air. The water inspiration of forest is critical in maintaining and regulating the earth climates It’s our mission to protect water resources for all creatures and ensure a sustainable healthy ecosystem for the future generations to come.
