Oxygen dynamics during submergence in the halophytic stem succulent Halosarcia pergranulata
O Pedersen1, H Vos, T D Colmer
1School of Plant Biology, Faculty of Natural and Agricultural Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
Plant, Cell & Environment
|November 4, 2006
Summary
Submerged succulent plants like Halosarcia pergranulata use underwater photosynthesis to supply oxygen to their tissues. This process leads to diurnal oxygen level changes and radial oxygen loss from roots, even with limited CO2.
Area of Science:
- Plant Physiology
- Halophyte Biology
- Aquatic Plant Adaptations
Background:
- Halosarcia pergranulata is a perennial halophytic stem succulent found on flood-prone salt lake mudflats.
- Understanding oxygen (O2) dynamics in submerged plants is crucial for their survival in waterlogged environments.
- Succulent stems may present challenges for gas diffusion due to their structure.
Purpose of the Study:
- To elucidate oxygen dynamics in the shoots and roots of submerged Halosarcia pergranulata.
- To investigate the influence of light and CO2 on underwater photosynthesis and O2 distribution.
- To determine the contribution of photosynthesis to internal O2 levels and radial O2 loss (ROL).
Main Methods:
- Measurement of internal O2 using microelectrodes in shoots and roots under controlled conditions (waterlogged, submerged, light/dark).
- Measurement of net photosynthesis (PN) and O2 production rates in excised stems at varying dissolved CO2 concentrations.
- In-situ monitoring of O2 partial pressure (pO2) in a submerged plant in its natural habitat.
Main Results:
- Underwater photosynthesis in intact plants supplied O2 to tissues and resulted in ROL from roots, especially after submergence or light periods.
- Despite low PN rates in excised stems at ambient CO2, intact submerged plants exhibited diurnal pO2 fluctuations in stems and roots.
- Stem pO2 increased rapidly with sunrise and decreased at sunset, with root pO2 changes lagging behind stem dynamics.
Conclusions:
- Photosynthesis in submerged Halosarcia pergranulata stems is a significant source of internal O2, creating diurnal pO2 variations.
- Radial O2 loss from roots occurs, indicating O2 transport from shoots to roots.
- Submerged plants also gain O2 from the surrounding water column, contributing to overall O2 supply.
Related Concept Videos
02:02Responses to Salt Stress
Salt stress—which can be triggered by high salt concentrations in a plant’s environment—can significantly affect plant growth and crop production by influencing photosynthesis and the absorption of water and nutrients.
01:29Oxygen Requirements and Growth Patterns
Microorganisms exhibit diverse oxygen requirements and growth patterns driven by their metabolic strategies and environmental adaptations. Oxygen, while essential for many organisms, can also be toxic under certain conditions, shaping how microorganisms grow and survive.Oxygen Requirements of MicroorganismsMicroorganisms are classified based on their ability to use or tolerate oxygen:● Obligate aerobes like Mycobacterium tuberculosis need oxygen for energy production, as it serves as the...
02:41Responses to Drought and Flooding
Water plays a significant role in the life cycle of plants. However, insufficient or excess of water can be detrimental and pose a serious threat to plants.
01:26Oxygenic Photosynthesis
Oxygenic photosynthesis is a fundamental process in which light energy is harnessed to drive the oxidation of water, leading to the production of molecular oxygen (O₂), adenosine triphosphate (ATP), and nicotinamide adenine dinucleotide phosphate (NADPH). This process is essential for sustaining aerobic life on Earth and is primarily carried out by cyanobacteria, algae, and plants. The core of oxygenic photosynthesis lies in the thylakoid membranes, where chlorophyll pigments facilitate light...
01:57Adaptations that Reduce Water Loss
Though evaporation from plant leaves drives transpiration, it also results in loss of water. Because water is critical for photosynthetic reactions and other cellular processes, evolutionary pressures on plants in different environments have driven the acquisition of adaptations that reduce water loss.
01:20Gas Exchange and Transport
Gas exchange, the intake of molecular oxygen (O2) from the environment and the outflow of carbon dioxide (CO2) into the environment, is necessary for cellular function. Gas exchange during respiration occurs largely via the movement of gas molecules along pressure gradients. Gas travels from areas of higher partial pressure to areas of lower partial pressure. In mammals, gas exchange occurs in the alveoli of the lungs, which are adjacent to capillaries and share a membrane with them.