Question

The cells of a certain plant species can accumulate solutes to create very low solute potentials. Which of these statements is correct? a. The plant's transpiration rates will tend to be extremely low. b. The plant can compete for water effectively and live in relatively dry soils. c. The plant will grow most effectively in soils that are saturated with water year-round. d. The plant's leaves will wilt easily.

Short answer

The correct statement that describes a plant with a low solute potential is: b. The plant can compete for water effectively and live in relatively dry soils.

Step-by-step solution

Understand Solute Potential

Solute potential is the potential energy of water molecules caused by the presence of solutes (dissolved substances) in the plant cell. A lower solute potential indicates that there is a higher concentration of solutes in the cell, which can cause water to move into the cell through osmosis.

Analyze the Options

Let's analyze each option and discuss its relationship with low solute potential. a. The plant's transpiration rates will tend to be extremely low. Transpiration rates are related to the loss of water from the plant's leaves, not directly to solute potential. So, this statement doesn't give enough information about the low solute potential of the plant species. b. The plant can compete for water effectively and live in relatively dry soils. A plant with low solute potential can attract more water because of the high concentration of solutes in its cells. This makes it easier for the plant to draw water from the soil, even in dry conditions. This statement is accurate and could be the correct answer. c. The plant will grow most effectively in soils that are saturated with water year-round. A plant with low solute potential can survive in dry conditions as it can attract water more effectively. However, this statement suggests that the plant needs saturated soils to grow effectively, which is not the case. d. The plant's leaves will wilt easily. Wilting occurs when the plant loses more water than it can absorb from the soil. A plant with low solute potential can attract water in dry conditions, so its leaves are less likely to wilt.

Select the Correct Statement

Based on the analysis of each option, the correct statement that describes a plant with a low solute potential is: b. The plant can compete for water effectively and live in relatively dry soils.

Key concepts

Solute Potential

In plant physiology, solute potential refers to the potential energy of water molecules affected by the presence of solutes, such as ions or sugars, within a plant cell. Solute potential is a crucial component of the whole water potential equation. The formula for water potential (\( \Psi \)) combines solute potential (\( \Psi_s \)) with pressure potential (\( \Psi_p \)). Whenever the concentration of solutes in a plant cell is high, the solute potential becomes very low, leading to an increase in the tendency for water to move into the cell by osmosis.
This process of osmosis is essential since it allows plants to absorb water even from their surrounding environment efficiently. When solute potential is low, it acts like a magnet for water, pulling it into the cell and keeping the plant hydrated.
Ultimately, low solute potential aids plants in staying turgid and firm, essential for optimizing photosynthesis and growth.

Water Competition

Water competition describes the ability of different plants to obtain water from their environment, especially when resources are limited. When a plant species can lower its solute potential, it becomes adept at competing for water against other plants. This is an evolutionary advantage, especially in arid or drought-prone regions.

• Plants with lower solute potentials have cells filled with high solute concentrations.
• This setup creates a strong attraction for water molecules to enter the plant’s roots through osmosis.
• These plants can effectively suck up moisture from dry soils where water availability might be scarce otherwise.

In short, these plants have evolved mechanisms to persist and thrive in challenging, water-scarce environments.

Plant Transpiration

Plant transpiration is the process by which water evaporates from the surface of plant leaves, primarily through openings called stomata. While one might assume low solute potential affects transpiration, it's important to understand the distinct difference between water absorption and water loss.
Transpiration plays multiple roles in plant physiology:

• It assists in nutrient transport from the soil to all parts of the plant.
• Provides cooling to the plant by evaporative loss of water.
• Regulates internal plant pressure, contributing to structural stability.

However, while transpiration rates are necessary, they are not directly tied to solute potential. Instead, they depend on aspects like humidity, temperature, and wind speed. This differentiation is crucial to understand why some statements about solute potential misleadingly imply direct effects on transpiration.

Osmotic Pressure

Osmotic pressure in plants is the pressure exerted by water as it moves across a semi-permeable membrane due to differences in solute concentrations. It’s a fundamental concept in plant physiology that determines how plants regulate water intake and maintain cell turgidity.
Consider the steps in osmotic pressure:

• Solutes like sugars and salts lower the solute potential within plant cells.
• This creates a scenario where water is drawn into the cell, raising the internal pressure—the osmotic pressure—which helps maintain cell shape.
• High osmotic pressure ensures that cells remain turgid, supporting structural integrity and aiding growth.

Understanding osmotic pressure clarifies how plants thrive even in environments where water is not freely available, as they efficiently manage their internal water balance to optimize health and productivity.