Effect of oxygen concentration on plant growth, lipidperoxidation, and receptivity of tomato roots to Pythium F under hydroponic conditions.

Abstract
The effects of the nutrient solution oxygenation on the growth of tomato plants and colonization of plant roots by Pythium F707, an isolate with filamentous non-inflated sporangia, were investigated under hydroponic conditions. Lipoperoxidation was also estimated determining lipoxygenase activity and conjugated dienes. Tomato plants were grown under either a high (11-14%; Air treatment), a moderate (5.8-7%; Control) or a low (0.8-1.5%; Nitrogen treatment) oxygen concentration and inoculated or not with the pathogen. The high oxygen treatment resulted in a marked increase in plant growth, as measured by shoot and root weights. Root and top weights were about the same in the nitrogen-treated plants and the controls. In these treatments, plants started showing typical symptoms of root decay and infection within 6 days after inoculation with Pythium F, while highly oxygenated plants remained healthy throughout the experiment and showed a significant decrease in root colonization by the pathogen, as estimated by the immunoenzymatic staining procedure and isolation of thalles on selective medium. Nitrogen-treated plants and controls produced higher amounts of conjugated dienes and revealed increased lipoxygenase activities in comparison with highly oxygenated plants. These differences were more pronounced after inoculation with the pathogen. Our data suggest that increases in lipoxygenase activity detected in the present study in tomato roots grown under oxygen stress and inoculated with Pythium F may lead to degradation and disorganization of membrane lipids. That disorganization may facilitate root colonization by the pathogen and appearance of decay.
https://link.springer.com/article/10.1023/A:1008691226213

cannabineer said:

View attachment 5039593

Click to expand...

Fuckin hilarious!

Edit: it's like 10 minutes later and I'm still laughing at that shit! Lol

Did you know that roots can take oxygen from the water for respiration, although not as much as from the air?
https://www.pthorticulture.com/en/training-center/basics-of-plant-respiration/

I am enjoying the boobies. Keep ‘em coming.

zzyx said:

Did you know that roots can take oxygen from the water for respiration, although not as much as from the air?
https://www.pthorticulture.com/en/training-center/basics-of-plant-respiration/

Click to expand...

You mean like, in dwc?

Root respiration in aerobic conditions requires a continuous supply of O2 to the rhizosphere. Radical respiration depends yon various factors: temperature (Rachmilevitch et al., 2006), salinity (Bernstein et al., 2013), heavy metals, water stress (Jiménez et al., 2013) and saturation of the pore space (Liao and Lin, 2001), but the factor that has the most direct relationship is the availability of O2, which allows or not the process, making it a limiting factor both in soil and in substrates (Urrestarazu and Mazuela, 2005; Fagerstedt et al., 2013).

• Rachmilevitch et al., 2006
  Root respiratory characteristics associated with plant adaptation to high soil temperature for geothermal and turf-type agrostis speciesJ. Exp. Botany, 2006
• Bernstein et al., 2013
  Effects of salinity on root growthPlant roots. The hidden half, 2013
• Jiménez et al., 2013
  Physiological, biochemical and molecular responses in four Prunus rootstocks submitted to drought stressTree Physiology, 2013
• Liao and Lin, 2001
  Physiological adaptation of crop plants to flooding stress. Proceedings of the National Science Council, Republic of ChinaLife sciences, 2001
• Urrestarazu and Mazuela, 2005
  Effect of slow-release oxygen supply by fertigation on horticultural crops under soilless cultureSci. Hort, 2005
• Fagerstedt et al., 2013
  Flooding Tolerance Mechanisms in RootsPlant Roots. The hidden half, 2013

As a result, plants can exhibit decreased water consumption, wilting, and reduced stomatal conductance (Bhatla, 201, slow growth, and decreased yield (Bhattarai et al., 2008; Maestre and Martínez, 2010). Damage and death of flooded plants have been attributed to lack of oxygen at the root (Boru et al., 2003; Bhatla, 201.

• Bhattarai et al., 2008
• 
  http://www.scielo.org.mx/scielo.php...2007-09342020000400931&lng=es&tlng=en&nrm=iso

Plant roots are known to orient growth through the soil by gravitropism, hydrotropism, and thigmotropism. Recent observations of plant roots that developed in a microgravity environment in space suggested that plant roots may also orient their growth toward oxygen (oxytropism).
https://pubmed.ncbi.nlm.nih.gov/11536884/

zzyx said:

I am enjoying the boobies. Keep ‘em coming.

Click to expand...

Sorry man. That one in particular had me laughing my ass off. I'm reading what you're posting.

Plants need oxygen to perform cellular respiration. Plants absorb oxygen through their roots. Past research has shown that reducing the concentration of oxygen in the rootzone of hydroponically grown rose plants will compromise the plants' ability to absorb nitrate and water, although this effect has not been quantified. The objective of this research was to quantify the effects of different oxygen concentrations in the rootzone on water and nitrate absorption rates. It was hypothesized that absorption rates would be reduced at the point at which the oxygen concentration in the rootzone became a limiting factor on the plants’ ability to perform cellular respiration. Hydroponically grown rose plants, Rosa hybrida 'Kardinal', were exposed to different oxygen concentrations and the water and nitrate absorption rates of each plant were measured. No noticeable correlation between water and nitrate absorption rates and rootzone oxygen concentration were observed. These results were contrary to past research and have led to the conclusion that data at lower concentrations of oxygen must be gathered to demonstrate a critical oxygen concentration for water and nitrate absorption. Data from lower oxygen concentrations may demonstrate the point at which the rootzone oxygen concentration becomes a limiting factor on cellular respiration.
https://www.actahort.org/members/showpdf?booknrarnr=766_4

Baras said the need for oxygen in an organic hydroponic system is even more important because of the presence of living microbes in the fertilizer solution reservoir.

“These microbes also require oxygen,” he said. “The oxygen demand is often higher in organic systems than conventional systems because not only do the plant roots need oxygen, but the microbes need oxygen as well. In an organic hydroponic system one of the best ways of keeping biofilm in check is to keep the beneficial microbes happy.”
https://hortamericas.com/blog/news/...-levels-in-your-hydroponic-production-system/

Oxygen is required by all of the plant’s living tissues for aerobic respiration. This means everything from the bottom of the roots to the tops of the shoots. If oxygen becomes limited the plant’s respiration rate will dip and its ability to perform its normal activities will decrease. Although, in theory, oxygen could be a limiting factor in the stems, leaves, and flowers, that’s nearly impossible. The place where oxygen stress is a reality is within the plant’s root zone and occurs when oxygen uptake by the plant’s roots outpaces oxygen’s replacement there.

Normoxic conditions mean that the level of oxygen is not a limiting factor for respiration in the root tissue. The roots are actively growing and absorbing nutrients and water sufficiently. Root respiration is heavily dependent on temperature and oxygen concentration. If the oxygen concentration declines with a constant root temperature, the rate of respiration will also slow down. As respiration rates drop, the amount of energy available to do work also decreases. This is the energy the roots need to grow, absorb nutrients, and maintain cellular integrity.
The root environment goes from normoxic to hypoxic when the concentration of oxygen in the root zone drops to a level so low that not enough energy is available from respiration for the roots to properly function. Hypoxic root conditions lead to several problems for the plant. The rate of nutrient absorption declines and root growth decreases and dies. Plant roots signal to the leaves to close the stomata. Water absorption through the roots declines and then stops. This decreases the plant’s ability to photosynthesize since the stomata are closed and no longer allow CO2 to enter the leaves. The combined effects of a hypoxic root zone ranges from a smaller yield to plant failure.
As oxygen concentrations continue to decrease in a hypoxic root environment, the root zone eventually becomes anoxic, that is, it has virtually no oxygen. Root respiration stops completely and usually results in root die-off. Not only does this decrease the surface area for nutrient and water absorption, but the dying roots provide entry points for microbial pathogens such as Phytophthora cinnamomi (Jacobs et al., 1997).
An oxygen-enriched environment makes a big difference in plant vigor, ranging from 50 to 60% more growth for cuttings and 30% more for rooted plants. Root growth and development is best with oxygen saturated media, which is why it is so important to have high oxygen levels when taking cuttings for vegetative propagation. Root initiation from shoot tissue requires adequate oxygen levels.

https://www.edrosenthal.com/the-gur...iting-factor-in-the-root-zone-by-ed-rosenthal

Rhizosphere oxygen profiles are the key to understanding the role of wetland plants in ecological remediation. Though in situdetermination of the rhizosphere oxygen profiles has been performed occasionally at certain growing stages within days, comprehensive study on individual roots during weeks is still missing. Seedlings of Acorus calamus, a wetland monocot, were cultivated in silty sediment and the rhizosphere oxygen profiles were characterized at regular intervals, using micro-optodes to examine the same root at four positions along the root axis. The rhizosphere oxygen saturation culminated at 42.9% around the middle part of the root and was at its lowest level, 3.3%, at the basal part of the root near the aboveground portion. As the plant grew, the oxygen saturation at the four positions remained nearly constant until shoot height reached 15 cm. When shoot height reached 60 cm, oxygen saturation was greatest at the point halfway along the root, followed by the point three-quarters of the way down the root, the tip of the root, and the point one-quarter of the way down. Both the internal and rhizosphere oxygen saturation steadily increased, as did the thickness of stably oxidized microzones, which ranged from 20 µm in younger seedlings to a maximum of 320 µm in older seedlings. The spatial patterns of rhizosphere oxygen profiles in sediment contrast with those from previous studies on radial oxygen loss in A. calamus that used conventional approaches. Rhizosphere oxygen saturation peaked around the middle part of roots and the thickness of stably oxidized zones increased as the roots grew.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0098457