Effect of Nitric Oxide on Respiration and Stomatal Movement

Stomata are cell structures that assist plants in exchanging carbon dioxide and water with the environment. They are present in the epidermis of tree leaves and needles. Stomata are pores on the surfaces of leaves and stalks that control the movement of gases to and from the leaves. Thus, they affect mitochondrial functionality and other processes. 

Stomatal Movement

Photosynthesis and gas exchange are adapted in plant leaves. Root hair cells absorb water and mineral ions, which are then carried up the plant through the xylem.

Stomata are minute openings that open and close to control and regulate the water loss along with the exchange of gases. They let water vapour and oxygen escape from the leaf into the surroundings, allowing carbon dioxide to enter the plant.

The guard cells are used by the plants in order to control the size and openings of their stomata. The stoma (single stomata) has a pair of guard cells. These guard cells, in response to bright light, collect water by the process of osmosis, making them swell up. 

In low light, the guard cells lose water content and become flaccid, causing the stomata to close. Only when there is no need for carbon dioxide for photosynthesis do they close normally. Guard cells have developed to facilitate gas exchange and minimise water loss within the leaf as part of their function.

The rate of respiration in plants is controlled via the size of the stomatal opening. Hence, the amount of water lost from the leaf is also controlled. This will result in preventing the plant from wilting.

Respiration in Plants

Plants use the sugars created during photosynthesis, along with oxygen, to produce energy for growth. In several areas, respiration is the opposite of photosynthesis. Plants must make their own food in order to live in the natural environment.

For the development and maintenance of plants, plant tissues are required to perform the process of respiration. A plant’s leaves, stems, and roots exchange gases individually. Leaves have stomata for gas exchange. Cells in the leaves use the oxygen consumed through the stomata to break down glucose into water and carbon dioxide.

The roots, which are buried underground, absorb air from the spaces between soil particles. As a result, the energy liberated from adsorbed oxygen via roots is used to move salts and minerals from the soil in the future.

Stomata allow gases to enter and exit during respiration. By diffusion, oxygen from the air enters a leaf through the stomata and reaches all of the cells.

When cells in the leaf photosynthesise during the day, they produce the oxygen needed for the plant to breathe. Thus, more oxygen from the air is not required to permeate into the leaf. During the day, water vapour escapes the leaf through the stomata, which stay open.

Effect of Nitric Oxide on Respiration and Stomatal Movement

Nitric oxide is a gaseous reactive oxygen species that has evolved as a signalling hormone in a variety of animal physiological functions. It has been shown to be a critical regulator of development in plants, operating as a signalling molecule at every stage of the plant life cycle.

• The abscisic acid (ABA)-mediated guard cell signalling network that governs stomatal closure relies heavily on nitric oxide.
• Nitric oxide stimulates plant growth and maturity through interacting with hormones, reactive oxygen species, calcium, and protein post-translational modifications.
• Nitric oxide is essential for ABA-induced stomatal closure in turgid leaves, but not for ABA-enhanced stomatal closure observed following quick dehydration.
• In guard cells, nitric oxide is produced through a Ca²⁺-dependent rather than a Ca²⁺-independent ABA signalling route.
• The membrane-bound enzyme cytochrome c oxidase transforms oxygen to water in aerobic species’ respiratory chains. This process travels through many intermediate states with micro- and millisecond durations at a binuclear metal centre made up of a heme a3 and a Cu ion.

Several nitrogen compounds and diverse methods impair mitochondrial respiration. In various tissues and cells in culture, low doses of NO selectively and reversibly block cytochrome functioning in competing with oxygen. Higher NO and its derivatives concentrations can cause irreversible respiratory chain inhibition, uncoupling, permeability transition, and cell death.

Nitric oxide impairs mitochondrial functionality and slows the mitochondrial respiratory chain, reducing ATP synthesis, increasing oxidant production, and increasing cell death vulnerability.

Conclusion

All plant tissues must undertake the process of respiration in order to produce and sustain plants, as well as to maintain the carbon balance of individual cells, whole plants, ecosystems, and the global carbon cycle.

Nitric oxide affects mitochondrial functionality, slowing down the mitochondrial respiratory chain, reducing ATP synthesis, increasing oxidant production, and increasing cell death vulnerability. Nitric oxide also affects cytochrome functioning.