Feeds:
Posts
Comments

Archive for the ‘Abiotic stress’ Category

Relationship between Nitrogen and crop disease

  1. The Crescent News
  2. By Hoorman Soil Health Services
  3. Feb 25, 2021 Updated Feb 25, 2021
  4.  

Nitrogen (N) is the fourth most abundant plant nutrient with about 80-85% N sequestered in protein, 10% in genetic components (DNA & RNA), and 5% in amino acids (protein building blocks). Nitrogen makes proteins like enzymes (speed up chemical reactions), hormones (regulate plant functions), and N increases cell growth. Nitrogen strengthens plant cell walls (cellulose), is used in plant energy transfer (ATP), and in photosynthesis (chlorophyll); effecting many plant processes. If a plant has balanced N, it has less disease; but when N is either deficient or in excess, expect more disease and insect problems in the field, garden, with ornamentals, or house plants.https://e58b06d6ddf80758d88dccc3cc17f20d.safeframe.googlesyndication.com/safeframe/1-0-37/html/container.html

The rate of N application and the form depends on the plant’s life cycle. Nitrogen deficiency or excess N may change the cell wall to become leaky, promoting more diseases. Early on, plants need more nitrates for growth with ammonium sources increasing as the plant matures to increase yield. N stressed deficient plants can’t make full proteins while excess N lowers plant defenses to both disease and insects. Plants typically absorb N in the oxidized form as nitrate (NO3-) or the reduced form as ammonium ( NH4+). Ammonium is 25% more plant efficient than nitrates because it can be easily converted to amino acids but to avoid toxicity, plants need it in small doses and it is easily converted to soil nitrate. Soil health keeps these N forms plant available to optimize plant growth and yield.

Nitrogen interacts with many other plant nutrients. Potassium (K) promotes the increase of nitrates and plant growth, but too much K decreases yield. Adequate phosphorous plus chlorine decreases nitrates and enhances plant ammonium N forms to increase yield. In soybeans, calcium and cobalt are needed for Rhizobium microbes to fix atmospheric N into protein. Supplementing cobalt (a micronutrient) and calcium in soybeans at the right time may increase soybean yields by 3x. Molybdenum, manganese, iron, and magnesium are involved in nitrogen transformations and protein synthesis. As my high school math teacher (Dave Laudick) use to say: It’s as clear as mud. Soil organic matter is a storehouse of many essential micronutrients and allows soil microbes and plants to thrive in a buffered and safe environment. Yes, it’s complicated but worth knowing if yields improve.

Common N related corn diseases are gray leaf spot, stalk rot due to late season N stress (N deficient), and increased aflatoxin due to high nitrates. In soybeans, to much N increases mosaic virus and Rhizoctonia. In wheat, take-all is increased by nitrates, decreased by ammonium; too much N increased powdery mildew; but higher N levels decreases Stagonospora nodurum. Balanced N fertilization is a key to decreasing most diseases.

Time of N fertilization is important. Corn side dressing reduces N leaching and denitrification losses but also decreases Pythium and Rhizoctonia BUT may increase Fusarium and Gibberella stalk rot. Adding a N inhibitor to fertilizer or liquid manure may decrease corn stalk rot by keeping N in the ammonium form late season. In soybeans, avoid over using glyphosate because it chelates or ties up manganese, iron, calcium, and zinc which can affect plant N fixation. In wheat, delaying N fertilizer until spring promotes take-all but avoids excess winter N when its cold and wet, so less Rhizoctonia. Best solution, put on a small amount of N in fall to promote tillering and delay spring N applications until late spring using granular or urea forms of N to reduce foliar leaf stress from liquid N sources.

There are four strategies to reducing diseases associated with nitrogen. The 4 R’s are the right form, right time, right rate, and right place. Use a balanced N fertilizer program with sufficient N in the right form for optimum growth. For corn starter, 25% nitrates and 75% ammonium, is a good mix but placement (2”X2”, 2”X4”) is critical to avoid root stress. Weather, pH, soil conditions (compaction), soil texture, moisture, biological activity, etc. all affect N transformations and plant uptake. Building SOM buffers soils and helps control or moderate these factors. Make timely N applications to avoid N deficiency, excesses, or losses. Modify the soil environment by changing pH (lime), add cover crops to build soil organic matter, reduce soil compaction, add a N inhibitor, avoid over using glyphosate, or supplement with micronutrients to assist in optimal N utilization and less crop disease. Source: Mineral Nutrition and Plant Disease, 2018.

Read Full Post »

science daily

Nanosensor can alert a smartphone when plants are stressed

Carbon nanotubes embedded in leaves detect chemical signals that are produced when a plant is damaged

Date:
April 15, 2020
Source:
Massachusetts Institute of Technology
Summary:
Engineers can closely track how plants respond to stresses such as injury, infection, and light damage using sensors made of carbon nanotubes. These sensors can be embedded in plant leaves, where they report on hydrogen peroxide levels.
Share:
FULL STORY

MIT engineers have developed a way to closely track how plants respond to stresses such as injury, infection, and light damage, using sensors made of carbon nanotubes. These sensors can be embedded in plant leaves, where they report on hydrogen peroxide signaling waves.

Plants use hydrogen peroxide to communicate within their leaves, sending out a distress signal that stimulates leaf cells to produce compounds that will help them repair damage or fend off predators such as insects. The new sensors can use these hydrogen peroxide signals to distinguish between different types of stress, as well as between different species of plants.

“Plants have a very sophisticated form of internal communication, which we can now observe for the first time. That means that in real-time, we can see a living plant’s response, communicating the specific type of stress that it’s experiencing,” says Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT.

This kind of sensor could be used to study how plants respond to different types of stress, potentially helping agricultural scientists develop new strategies to improve crop yields. The researchers demonstrated their approach in eight different plant species, including spinach, strawberry plants, and arugula, and they believe it could work in many more.

Strano is the senior author of the study, which appears today in Nature Plants. MIT graduate student Tedrick Thomas Salim Lew is the lead author of the paper.

Embedded sensors

Over the past several years, Strano’s lab has been exploring the potential for engineering “nanobionic plants” — plants that incorporate nanomaterials that give the plants new functions, such as emitting light or detecting water shortages. In the new study, he set out to incorporate sensors that would report back on the plants’ health status.

Strano had previously developed carbon nanotube sensors that can detect various molecules, including hydrogen peroxide. About three years ago, Lew began working on trying to incorporate these sensors into plant leaves. Studies in Arabidopsis thaliana, often used for molecular studies of plants, had suggested that plants might use hydrogen peroxide as a signaling molecule, but its exact role was unclear.

Lew used a method called lipid exchange envelope penetration (LEEP) to incorporate the sensors into plant leaves. LEEP, which Strano’s lab developed several years ago, allows for the design of nanoparticles that can penetrate plant cell membranes. As Lew was working on embedding the carbon nanotube sensors, he made a serendipitous discovery.

“I was training myself to get familiarized with the technique, and in the process of the training I accidentally inflicted a wound on the plant. Then I saw this evolution of the hydrogen peroxide signal,” he says.

He saw that after a leaf was injured, hydrogen peroxide was released from the wound site and generated a wave that spread along the leaf, similar to the way that neurons transmit electrical impulses in our brains. As a plant cell releases hydrogen peroxide, it triggers calcium release within adjacent cells, which stimulates those cells to release more hydrogen peroxide.

“Like dominos successively falling, this makes a wave that can propagate much further than a hydrogen peroxide puff alone would,” Strano says. “The wave itself is powered by the cells that receive and propagate it.”

This flood of hydrogen peroxide stimulates plant cells to produce molecules called secondary metabolites, such as flavonoids or carotenoids, which help them to repair the damage. Some plants also produce other secondary metabolites that can be secreted to fend off predators. These metabolites are often the source of the food flavors that we desire in our edible plants, and they are only produced under stress.

A key advantage of the new sensing technique is that it can be used in many different plant species. Traditionally, plant biologists have done much of their molecular biology research in certain plants that are amenable to genetic manipulation, including Arabidopsis thaliana and tobacco plants. However, the new MIT approach is applicable to potentially any plant.

“In this study, we were able to quickly compare eight plant species, and you would not be able to do that with the old tools,” Strano says.

The researchers tested strawberry plants, spinach, arugula, lettuce, watercress, and sorrel, and found that different species appear to produce different waveforms — the distinctive shape produced by mapping the concentration of hydrogen peroxide over time. They hypothesize that each plant’s response is related to its ability to counteract the damage. Each species also appears to respond differently to different types of stress, including mechanical injury, infection, and heat or light damage.

“This waveform holds a lot of information for each species, and even more exciting is that the type of stress on a given plant is encoded in this waveform,” Strano says. “You can look at the real time response that a plant experiences in almost any new environment.”

Stress response

The near-infrared fluorescence produced by the sensors can be imaged using a small infrared camera connected to a Raspberry Pi, a $35 credit-card-sized computer similar to the computer inside a smartphone. “Very inexpensive instrumentation can be used to capture the signal,” Strano says.

Applications for this technology include screening different species of plants for their ability to resist mechanical damage, light, heat, and other forms of stress, Strano says. It could also be used to study how different species respond to pathogens, such as the bacteria that cause citrus greening and the fungus that causes coffee rust.

“One of the things I’m interested in doing is understanding why some types of plants exhibit certain immunity to these pathogens and others don’t,” he says.

Strano and his colleagues in the Disruptive and Sustainable Technology for Agricultural Precision interdisciplinary research group at the MIT-Singapore Alliance for Research and Technology (SMART), MIT’s research enterprise in Singapore, are also interested in studying is how plants respond to different growing conditions in urban farms.

One problem they hope to address is shade avoidance, which is seen in many species of plants when they are grown at high density. Such plants turn on a stress response that diverts their resources into growing taller, instead of putting energy into producing crops. This lowers the overall crop yield, so agricultural researchers are interested in engineering plants so that don’t turn on that response.

“Our sensor allows us to intercept that stress signal and to understand exactly the conditions and the mechanism that are happening upstream and downstream in the plant that gives rise to the shade avoidance,” Strano says.

The research was funded by the National Research Foundation of Singapore, the Singapore Agency for Science, Technology, and Research (A*STAR), and the U.S. Department of Energy Computational Science Graduate Fellowship Program.


Story Source:

Materials provided by Massachusetts Institute of Technology. Original written by Anne Trafton. Note: Content may be edited for style and length.


Journal Reference:

  1. Tedrick Thomas Salim Lew, Volodymyr B. Koman, Kevin S. Silmore, Jun Sung Seo, Pavlo Gordiichuk, Seon-Yeong Kwak, Minkyung Park, Mervin Chun-Yi Ang, Duc Thinh Khong, Michael A. Lee, Mary B. Chan-Park, Nam-Hai Chua, Michael S. Strano. Real-time detection of wound-induced H2O2 signalling waves in plants with optical nanosensors. Nature Plants, 2020; 6 (4): 404 DOI: 10.1038/s41477-020-0632-4

Cite This Page:

Massachusetts Institute of Technology. “Nanosensor can alert a smartphone when plants are stressed: Carbon nanotubes embedded in leaves detect chemical signals that are produced when a plant is damaged.” ScienceDaily. ScienceDaily, 15 April 2020. <www.sciencedaily.com/releases/2020/04/200415133512.htm>.

Read Full Post »

Reblogged from The Economic Times BENGALURU: While India reaped the benefits of the Green Revolution in the 1960s, her neighbour China is now taking the lead in another area of sustainable agriculture — developing crops that meet the challenges posed by global warming. Chinese agricultural scientists are working to convert seasonal crops into perennial crops […]

via Could perennial crops be an answer to climate change? — The Plantwise Blog

Read Full Post »

MILTECH

Fires, storms, insects: climate change increases risks for forests worldwide

“When climate is changing, there are initially direct effects on the growth of the trees. But the chain of climate impacts is considerably longer: if, for instance, more rain saturates the soils or if soils are less frequently frozen, the trees will have less stability to withstand storms and damage will increase. The many dead and dying trees will then provide ideal breeding material for insects such as bark beetles to reproduce quickly. At the same time, the trees that are still alive will be weakened and will thus be more vulnerable to insect attacks,” explains lead author Rupert Seidl from the University of Natural Resources and Life Sciences in Vienna. “Our study shows that climate change significantly influences disruptive factors all around the world – and that a further increase of disturbances in forests has to be expected in the future.”

Stress is normal for the forests – while the increase of disturbances is not

“Whether in the giant boreal forests of Scandinavia and Russia or in the wide woodlands of North America – fundamentally, natural disturbances like fires, insect attacks or storms are normal aspects of these ecosystems,” says project leader Christopher Reyer of the Potsdam Institute for Climate Impact Research. To get shaken up a little through natural disturbances can even be good for forests, as the natural renewal for instance promotes a greater biological diversity.

“But through climate change, these usual disturbances have already changed in the last years”, explains Reyer. “This has impacts on the ability of the forests to provide services for us humans – for example in terms of their wood, in terms of protection against avalanches, or simply as recreational spaces. If climate change keeps on increasing disturbances, this clearly is a risk for the coping capacities of the forests – in the long run, ecosystems as we know them today might change profoundly.”

Climate change as a challenge for forest management

For the review study, forest experts from Austria, Germany, Switzerland, Finland, Italy, Spain, the Czech Republic, Scotland, Slovakia and Slovenia analyzed more than 1600 different findings from academic publications which establish links between disruptions and climate factors. Additionally, the scientists examined how indirect climate impacts, such as the alteration of tree species in the forests, influence the occurrence of disturbances. In particular the indirect effects and the interactions between different disruptive factors were collated in an unprecedentedly comprehensive manner in the research on forest disturbances.

Already today it is clear that risks caused by fires, pests and fungi will increase in the context of climate change – the devastating forest fires in Canada and Russia in the last years are an example of possible impacts. Fires are currently the most significant disruptive factor in many forests around the world, and will become an even more serious threat in the coming decades, according to the scientists. The forests of Northern and Central Europe, however, have until present primarily been impaired by storms such as Cyclone Kyrill in 2007, and the insect damage that follows them – a type of damage which will also increase under climate change. Damage caused by ice and snow were the only disruptive factors examined by the study that will likely decrease under continuing climate change. However, this positive effect cannot compensate the negative effects from other factors.

“Our analysis clearly shows that climate change brings enormous challenges for forests – the forest sector has to adapt and to increase its resilience, as it seems impossible to prevent damage completely”, says Seidl. “In the long term, reductions of greenhouse-gas emissions and effective climate protection measures will help the most,” adds Reyer.

Article:  Rupert Seidl, Dominik Thom, Markus Kautz, Dario Martin-Benito, Mikko Peltoniemi, Giorgio Vacchiano, Jan Wild, Davide Ascoli, Michal Petr, Juha Honkaniemi, Manfred J. Lexer, Volodymyr Trotsiuk, Paola Mairota, Miroslav Svoboda, Marek Fabrika, Thomas A. Nagel, and Christopher P. O. Reyer (2017): Forest disturbances under climate change. Nature Climate Change [10.1038/NCLIMATE3303]

Weblink to the article: https://www.nature.com/nclimate/journal/v7/n6/full/nclimate3303.html

Read Full Post »