Question

The relationship between \(\psi_{w}, \psi_{s}\) and \(\psi_{p}\) can be given as: (a) \(\psi_{s}=\psi_{w}+\psi_{p}\) (b) \(\psi_{p}=\psi_{w}+\psi_{s}\) (c) \(\psi_{w}=\psi_{p}+\psi_{s}\) (d) All of these

Short answer

Only equation (a) \(\psi_{s}=\psi_{w}+\psi_{p}\) is correct

Step-by-step solution

Examine Option (a)

In this step, check if \(\psi_{s}=\psi_{w}+\psi_{p}\) holds true. If we consider an instance where the \(\psi_{w} = 2\), \(\psi_{p} = 3\), the \(\psi_{s} = 2 + 3 = 5\). So, this equation seems to hold.

Examine Option (b)

Now, let's check if \(\psi_{p}=\psi_{w}+\psi_{s}\) holds true or not. Following from the earlier values, \(\psi_{w} = 2\), \(\psi_{s}=5\), then \(\psi_{p} = 2 + 5 = 7\), which is not equal to our earlier \(\psi_{p}=3\). So, this equation doesn't hold.

Examine Option (c)

Lastly, check if \(\psi_{w}=\psi_{p}+\psi_{s}\) holds. Using our previous values, \(\psi_{p}=3\), \(\psi_{s}=5\), then, \(\psi_{w} = 3 + 5 = 8\), which is not equal to our earlier \(\psi_{w}=2\). So, this equation doesn't hold.

Check Option (d)

Option (d) states that all of these are true. But, from the analysis above, only option (a) holds true. Therefore, option (d) doesn't hold.

Key concepts

Osmotic Potential

Osmotic potential, often denoted by the symbol \( \psi_s \), is a key concept in understanding how water moves through biological systems. It is also known as solute potential because it is determined by the solute concentration of a solution. In simple terms, osmotic potential is a measure of the tendency of water to move into a solution by osmosis due to the presence of dissolved substances.

The concept is foundational in understanding processes in plant physiology, especially how plants absorb water through their roots and how they manage hydration and nutrients. A higher concentration of solutes in the cell than the surrounding environment will result in a negative osmotic potential, which indicates the potential of water to move into the cell. Conversely, a lower concentration of solutes compared to the environment results in a positive osmotic potential, suggesting that water can potentially leave the cell.

Pressure Potential

Pressure potential, shown with the symbol \( \psi_p \), is another component of water potential in plants. It refers to the physical pressure on water, which can either facilitate or oppose the movement of water. It includes the turgor pressure within plant cells, which is the pressure exerted by the cell contents against the cell wall, as well as any external pressures, such as those exerted by gravity or a pump in an experimental setup.

This pressure can be positive, such as when water fills plant cells, creating turgidity, or negative as in the case of water being pulled through the xylem vessels of a plant due to transpiration. Understanding pressure potential is crucial in plant physiology as it helps explain not only how plants manage water but also supports the plant mechanically.

Biological Concept in NEET

The National Eligibility cum Entrance Test (NEET) is a standout examination for students aspiring to pursue a career in medicine in India. It rigorously tests various biological concepts, including those related to water potential, which comprises both osmotic and pressure potential.

Students preparing for NEET must have a firm understanding of these concepts to excel in questions related to plant physiology and other biological phenomena. The examination assesses whether students can apply the concept of water potential to real-world biological systems, such as understanding the movement of water in plants, animal cells, and across different environments.

Plant Physiology

Plant physiology is the study of how different parts of a plant function and contribute to the life of the plant. Within this field, water potential is a pivotal concept relevant to several processes such as water transport, nutrient uptake, and cell turgidity.

Water potential integrates both osmotic and pressure potentials, signifying its overall ability to perform work during water movement. It quantifies the direction and rate at which water will diffuse across a semipermeable membrane. These concepts are deeply connected to other physiological processes like photosynthesis, respiration, and transpiration, making the understanding of water potential critical for students studying botany or preparing for exams like NEET.