Question

Which one of the following essential elements plays an important role in opening and closing of stomata? (a) \(\mathrm{Mg}\) (b) \(K\) (c) \(\mathrm{Mn}\) (d) \(P\)

Short answer

Potassium (K) is the essential element involved in the opening and closing of stomata.

Step-by-step solution

Understand the Function of Stomata

Know that stomata are small openings on the underside of a plant leaf which open and close to regulate gas exchange. They allow for the intake of carbon dioxide and release of oxygen.

Identify the Essential Element for Stomatal Movement

Recognize that certain essential elements play a role in the physiological functions of plants. For the opening and closing of stomata, potassium ions (K+) are known to be crucial.

Choose the Correct Option

From the choices provided, identify the element that is associated with the opening and closing of stomata based on scientific knowledge. Here, potassium (K) is the correct answer.

Key concepts

Stomatal Movement

Stomata are microscopic pores found on the surface of leaves, primarily on the underside in most plants. These pores are essential for a plant's ability to breathe and transpire, and their regulation is crucial for maintaining plant health.

Stomatal movement refers to the opening and closing of these stomata, which is a process guided by the plant's need to exchange gases – taking in carbon dioxide (CO2) for photosynthesis and releasing oxygen (O2) as a byproduct, while also managing water loss through transpiration. Opening and closing are influenced by environmental conditions such as light, CO2 concentration, humidity, and the plant's internal water balance.

At the heart of stomatal movement is the interplay between turgor pressure in guard cells that flank each stoma and the accumulation and loss of potassium ions (K+). When K+ ions enter the guard cells, they attract water by osmosis, causing the cells to swell and the stoma to open. Conversely, when K+ ions leave the guard cells, the loss of water leads to a decrease in turgor pressure, resulting in the stomata closing.

Potassium in Plants

Potassium (K) is a vital macronutrient for plant growth and development, second only to nitrogen in terms of the quantity required by plants. It is fundamental for various physiological processes, including the regulation of stomatal movement.

In the context of stomatal movement, potassium plays a key role by acting as a solute that creates a gradient for the movement of water into and out of the guard cells. When potassium levels inside the guard cells are high, water follows by osmosis, increasing turgor pressure and opening the stomata. This mechanism is finely tuned, allowing plants to respond to the slightest changes in environmental conditions swiftly.

Besides its role in stomatal movement, potassium is also important for enzyme activation, protein synthesis, photosynthesis, and it is integral to the plant's water-use efficiency and resistance to diseases and pests. Deficiency in potassium can lead to a variety of plant health issues, including reduced growth, poor yield, and increased susceptibility to stress.

Plant Gas Exchange

Plant gas exchange is an essential biological process that revolves around the movement of gases between the plant and its environment. It is facilitated by the stomata, which control the passage of gases to optimize photosynthesis while minimizing water loss through transpiration.

During the daytime, when photosynthesis typically occurs, stomata open to allow CO2 to enter the leaf for the synthesis of sugars, while oxygen, a byproduct of photosynthesis, is released into the atmosphere. This exchange is crucial for maintaining a balance between the plant's need for carbon for growth and the need to expel oxygen.

Gas exchange is not just limited to CO2 uptake and oxygen release; it also includes the exchange of water vapor. This simultaneous exchange illustrates the complex balance plants must maintain: open stomata can lead to excessive water loss, while closed stomata can hinder CO2 uptake, affecting photosynthesis. Thus, the control of gas exchange is a sophisticated scenario where the plant must continuously adjust to the fluctuating environmental conditions to sustain its metabolic needs.