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Effects of stress on photosynthesis : ..

Seedlings of two tomato genotypes, Mill. var. Amalia and the wild thermotolerant type Nagcarlang, were grown under a photoperiod of 16 h light at 25°C and 8 h dark at 20°C. At the fourth true leaf stage, a group of plants were exposed to a heat-shock temperature of 45°C for 3 h, and measurements of chlorophyll fluorescence, gas-exchange characteristics, dark respiration and oxidative and antioxidative parameters were made after releasing the stress. The heat shock induced severe alterations in the photosynthesis of Amalia that seem to mitigate the damaging impact of high temperatures by lowering the leaf temperature and maintaining stomatal conductance and more efficient maintenance of antioxidant capacity, including ascorbate and glutathione levels. These effects were not evident in Nagcarlang. In Amalia plants, a larger increase in dark respiration also occurred in response to heat shock and the rates of the oxidative processes were higher than in Nagcarlang. This suggests that heat injury in Amalia may involve chlorophyll photooxidation mediated by activated oxygen species (AOS) and more severe alterations in the photosynthetic apparatus. All these changes could be related to the more dramatic effect of heat shock seen in Amalia than in Nagcarlang plants.


The list of the anomalies in the behavior of liquid water could be continued on and on. But we have to consider one more: Although water, chemically neutral, it is one of the best solvents known to man. Water has the capability to entrap other substances. In other words, it tends to cluster around every non-water particle, forming conglomerations or complexes, as they are called scientifically.
Water’s capacity to entrap substances results in its high mineral content. The amount of these dissolved minerals being carried by the water determines its hardness. One of the most common minerals in water is calcium carbonate, a substance that forms mountain ranges such as the Alps. When liquid water evaporated the dissolved minerals become over concentrated and must crystallize. This also happens when the temperature of the water increases, or when the solubility of the carbonates in the water decreases. The consequence is a sediment of those minerals on the walls of the container — in our case spas and pools.

These sediments of minerals that grown on the container walls are actually limestone, which is hard and difficult to remove. Very hard water can produce these hard sediments with bad consequences. Unfortunately, this process is a slow one and cannot be recognized immediately. Nevertheless, the effects of hard water are quite noticeable if left to build up over time. Today the water lines that the Romans had used for hundreds of years show accumulations of hard lime scale many inches thick, as in the beautiful Pont du Gard in southern France, for instance.
But it only takes a few years for hard lime scale to take its toll on water pipes and equipment. Such sediment layers in heaters hinder the transfer of heat.
For swimming pools, the removal of existing hard lime scale is usually accomplished by an acid wash, which interrupts the operation of the system. Furthermore, the acid can attack pool walls and open up leaks.
Most water supplied by water districts in the United States is well cared for, analyzed chemically and rendered clean enough for drinking. Most of it contains a good amount of calcium content. This is important for proper taste and a healthy mineral balance. However, it tends to create deposits of scale over the years if no preventative measures are taken.

The effect of heat and salinity stress on the carbon balance of Xanthium strumarium.-

The Quartz Page: Physical Properties

Glycine betaine (GB) is a quaternary ammonium compound that can be found in a wide range of bacterial, plant and animal species (; ; ). In some plants, accumulation of GB is a common response to alleviate the effect of abiotic stresses (). Many studies have shown that increasing the cellular level of GB, either by a transgenic approach or by exogenous application, can effectively improve crop tolerance to various abiotic stresses including heat stress (; ; ; ; ; ).

Although the exact mechanism is still unclear, it has been suggested that GB can mitigate heat stress via a number of different mechanisms. One of them is the protection of photosynthetic machinery (). GB was found to stimulate synthesis of the D1 protein, which supports the repair of photodamaged PSII (). Furthermore, it has been shown that the maximum quantum efficiency of PSII photochemistry of a GB-deficient maize line declined much more than that of a GB-containing line when grown under heat stress conditions (). The accumulation of GB prevented the sequestration of Rubisco activase to the thylakoid membrane, thereby maintaining the activity of Rubisco at a high temperature (). Moreover, it has been found that the accumulation of GB alleviates the inhibition of net photosynthetic rate under heat stress ().

5 Dimension 3: Disciplinary Core Ideas - Physical …

Heat stress limits global crop production and is becoming more severe due to the current global warming trend. It has been estimated that an increase of temperature by one degree Celsius during the growing season could reduce the yields of corn and soybean by up to 17% (). Heat stress adversely affects crop production in many ways, such as by inhibiting seed germination, accelerating leaf senescence, reducing net photosynthesis and triggering early or delayed flowering (; ; ). At the cellular level, heat stress may cause protein and membrane denaturation, damage of Photosystem II (PSII) and increased production of reactive oxygen species (ROS) (; ; ).

The protective effect of GB under various stress conditions is also attributed to its capacity to increase the activity of some enzymes involved in the antioxidant defense system (; ). It has been reported that transgenic tobacco with the ability to synthesize GB had significantly lower levels of H2O2 and O2 than the wild type under heat stress conditions (). This was possibly due to the increasing activity of superoxide dismutase and ascorbate peroxidase in the transgenic plants. In sugarcane, pre-soaking sprouting buds with GB was shown to inhibit H2O2 accumulation under heat stress (). This previous study also indicated the significant negative relationship between H2O2 content and bud dry weight, suggesting that GB may improve thermotolerance mainly by limiting ROS generation. In transgenic wheat that had accumulated a high level of GB, it was found that the levels of several ROS in leaves of transgenic plants were lower than those of control plants under heat stress conditions ().

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Plant Energy Transformations-Photosynthesis - …


» -- An out-of-print classic: Aho's theories about Space, Life, Energy, &c.

» r ~ Hydrogen bond explosions by Mechanical Impact Steam (MIST) system produces superheated steam @ over-unity efficiency. ( See also: )

Nicotinamide adenine dinucleotide - Wikipedia

After exposure to heat stress conditions for 15 days, leaf gas exchange parameters and leaf surface temperature were measured using LCi-SD (BioScientific Ltd., Hertfordshire, UK). Four of the youngest fully expanded leaves of 3 independent plants were measured for each cultivar and treatment. All of the measurements were carried out under photosynthetic photon flux density of 250 μmol·m−2·s−1.

Phytohormones and their metabolic engineering for …

Effectively treated water looks sparkling clear, even if the water supply is murky. Some water experts claim they can recognize a specific silky appearance of magnetically treated water. This might be due to the multitude of microcrystals, which can reflect sunlight. The developing microcrystals, however are so small that they are visible only with high magnification.
In regards to smell, water that comes with a slight sulfur odor loses this smell after being treated with magnetic devices. Of significant interest to this industry, the chlorine odor of chlorinated water is greatly reduced by effective magnetic treatment. In fact, slight chlorination may become unnoticeable to the average user.
For aromatic brews such as teas or coffees, the desired aromas can be achieved with fewer ingredients if the water is effectively treated. The ensuing aromas appear cleaner to perceptive noses. It is said that in some eastern countries — China for instance — many people heat their tea water in a pot containing a magnet.
One of the most obvious effects of magnetic water treatment is the enhanced ability of most cleaning chemicals and detergents. Magnetically treated water increases their effectiveness to the point where just one-third or even one-fourth of the cleaning agent is needed. In the cases of naturally contaminated water from lakes, an intense magnetic treatment has made the lake water fit for human consumption.
Magnetically treated water runs off a cleaned surface faster and in thinner sheets because surface tension is reduced. As a result one sees fewer water spots from drying. This has been applied successfully for the watering of decorative plants by sprinklers.
Surface tension in water is critical to biological life. Surface tension makes water rise in the fibers of the plants. It fills the capillaries in your body and it determines water’s ability to penetrate soil and other materials. Therefore it is not surprising that wherever magnetic water treatment has been practiced, growth patterns have changed. Experiments with groups of growing farm animals and agricultural plants have been conducted at universities and federal institutions with stunning results. Some were hard to believe, so the scientists were reluctant to publish them immediately, pending confirmation.
Following are some of the results of scientific research:
At a California university, two control groups of piglets of 24 piglets each with normal feeding were compared with two groups of 24 piglets that were getting their water from a magnetic treatment device. The latter groups consumed twice as much water and grew an average 12.5 percent faster.
Cotton plantings with various irrigation were compared in California. The cotton plants irrigated with magnetically treated water grew to larger sizes with larger and denser foliage. However, they produced one-third less cotton than the control plantings.
A Washington navel orange tree watered with the magnetically treated water carried less fruit, but each orange became unusually thick and juicy, weighing 20 ounces on average. Similarly, a Eureka lemon tree fed magnetically treated water carries lemons that grow up to one pound each.
One biologist suggests that the slightly reduced surface tension of the magnetically treated water may facilitate its penetration of cell walls. This could accelerate the normal dividing of the cells in growing parts of living individuals. This would account for the faster vegetative growth and the reduced reproductive cell division responsible for the number of flowers and fruit.
The accelerated growth of plants by the use of magnetically treated water is possible because the root tips secrete enzymes that dissolve crystals in the ground, enabling the roots to ingest the dissolved minerals. This is not the case for one-cell organisms that pollute pool water. Algae and bacteria have
to ingest their food directly through their cell wall. They get plenty of water through it, but they cannot receive any nourishment in the form of crystallized minerals, which cannot penetrate the cell walls. Thus, bacteria in magnetically treated water starve.
Observations on swimming pools confirm this effect. The normal chlorine content of treated of swimming pools can be reduced by at least half if the water is efficiently magnetically treated. Even without any chlorination , no algae growth can be detected for about 36 hours. This is the normal duration of the affectivity of the magnetic treatment. After one to two days, the microcrystals formed by the treatment start to redissolve. After this time, a vigorous growth of algae occurs in the non-chlorinated pool if it is not replenished with treated water.
In short a swimming pool benefits by the application of magnetic water treatment for a number of reasons: ...

Cannabis Temperature Tutorial: How to Control Heat in …

Effect of heat stress and GB on chlorophyll fluorescence parameters in three marigold cultivars. Foliar application of GB was performed 1 day before plants were transferred to heat stress conditions for 15 days. Control plants were sprayed with deionized water. (a) ΦPSII or operating efficiency of PSII in a light-adapted state. (b) Fv/Fm or maximum quantum efficiency of PSII in a dark-adapted state. (c) Fo or minimal fluorescence in a dark-adapted state. (d) Fm or maximal fluorescence in a dark-adapted state. Values are means ± SE (n = 4–6). Different letters indicate a significant difference (

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