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Measure photosynthesis & plant stress
Measure photosynthesis & plant stress
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Researchers at UC Davis show evidence that the SIK1 enzyme is “the firing pin” of plant immunity to invasions by plant pathogens.

Plants use reactive oxygen species to kill bacteria, fungi and other pathogens. SIK1 connects “toll-like receptors” that detect pathogens with the enzyme that produces reactive oxygen in a plant immune process.

They are looking for homologs of SIK1 in crop plants and other plants to find treatments for plant diseases and breed more disease resistant crops.

Journal Reference:

Meixiang Zhang, Yi-Hsuan Chiang, Tania Y. Toruño, DongHyuk Lee, Miaomiao Ma, Xiangxiu Liang, Neeraj K. Lal, Mark Lemos, Yi-Ju Lu, Shisong Ma, Jun Liu, Brad Day, Savithramma P. Dinesh-Kumar, Katayoon Dehesh, Daolong Dou, Jian-Min Zhou, Gitta Coaker. The MAP4 Kinase SIK1 Ensures Robust Extracellular ROS Burst and Antibacterial Immunity in Plants. Cell Host & Microbe, 2018; 24 (3): 379 DOI: 10.1016/j.chom.2018.08.007

University of California - Davis. "Newly discovered enzyme is 'firing pin' for plant immunity: SIK1 gene opens possibilities for treating disease, breeding resistant crops." ScienceDaily. ScienceDaily, 17 September 2018. <www.sciencedaily.com/releases/2018/09/180917153612.htm>.

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Researchers in Switzerland and Canada use a drone to sample tree top twigs for chlorophyll content measurement.

They are offering another method to collect samples from trees using a special device and a drone.

The researchers used a CCM-330 chlorophyll content meter to measure chlorophyll content at different leaf canopy levels. They find that “chlorophyll content of the top leaves is significantly lower than that of leaves in the lower canopy”.

Florian K¨aslin, Thomas Baur1, Philip Meier, Patrick Koller, Nina Buchmann, Petra D’Odorico, and Werner Eugster (2018) Novel twig sampling method by unmanned aerial vehicle (UAV). Frontiers of Forests, http://homepage.agrl.ethz.ch/~eugsterw/publications/pdf/Kaeslin.2018.FFGC-FINAL.pdf

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Calcium in plants allows long distance electrical signaling, plant wide, when a plant is under attack from herbivory.

“The signal moved quickly, about one millimeter per second”. ...”quick enough to spread out to other leaves in just a couple minutes.” “It took just a few more minutes for defense-related hormone levels to spike in distant leaves. These defense hormones help prepare the plant for future threats by, for example, increasing the levels of noxious chemicals to ward off predators.”

Glutamate receptors were also required for electrical responses. fluorescent videos...”suggest that glutamate spilling out from wound sites triggers the burst in calcium that spreads across the plant.”

“Glutamate leads to calcium leads to defense hormones and altered growth and biochemistry, all without a nervous system.”

Journal Reference:

Masatsugu Toyota, Dirk Spencer, Satoe Sawai-Toyota, Wang Jiaqi, Tong Zhang, Abraham J. Koo, Gregg A. Howe, Simon Gilroy. Glutamate triggers long-distance, calcium-based plant defense signaling. Science, 2018; 361 (6407): 1112 DOI: 10.1126/science.aat7744

University of Wisconsin-Madison. "Blazes of light reveal how plants signal danger long distances." ScienceDaily. ScienceDaily, 13 September 2018. <www.sciencedaily.com/releases/2018/09/180913142026.htm>.

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Unexpectedly, controlled burns and low temperature fires can damage soil structure and organic matter.

A group from UC Merced found that if the soil was investigated immediately after a controlled burn, soil structure degradation was not detectable. They had to wait weeks or even months for the evidence of soil structure degradation to appear.

They also found that wet soils showed more damage than dry soils.
While controlled burns are known to return nutrients to the soil and eliminate vegetation, CO2 is released from the soil at a later time along with moisture. They are not sure whether controlled or prescribed burns positive effects outweigh the negative effects. They found that temperatures as low as 175 degrees C or 347 degrees F were high enough to cause damage.

Journal References:

1. Mathew Jian, Asmeret Asefaw Berhe, Markus Berli, Teamrat A. Ghezzehei. Vulnerability of Physically Protected Soil Organic Carbon to Loss Under Low Severity Fires. Frontiers in Environmental Science, 2018; 6 DOI: 10.3389/fenvs.2018.00066

2. M. Jian, M. Berli, T. A. Ghezzehei. Soil Structural Degradation During Low-Severity Burns. Geophysical Research Letters, 2018; 45 (11): 5553 DOI: 10.1029/2018GL078053

Desert Research Institute. "Low-severity wildfires impact soils more than previously believed: Negative effects of low-severity fire on soil structure and organic matter." ScienceDaily. ScienceDaily, 10 September 2018. <www.sciencedaily.com/releases/2018/09/180910160632.htm>.

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Researchers from the Netherlands and Australia investigate the effects of canopy leaf position on various measuring parameters including chlorophyll content. A CCM-300 was used to measure chlorophyll content. Samples from upper, mid canopy and lower canopy were tested for a variety of species. Camellia japonica, a flowering tree or shrub, Chamaedorea elegans, small palm tree, Fatshedera lizei, tree ivy and Ficus benjamina, a tree.

Chlorophyll content increased from lower canopy to upper canopy leaves for all species. Nitrogen also increased from lower to upper canopy leaves. The paper also investigated spectral reflectance heterogeneity across canopy levels.


Journal Reference:

Tawanda W. Gara, Roshanak Darvishzade, Andrew K. Skidmore, and Tiejun Wang (2018) Impact of Vertical Canopy Position on Leaf Spectral Properties and Traits across Multiple Species. Remote Sensing February 2018
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A new method allows the non-destructive rapid screening of a plants ability to use mycorrhizal fungi to improve tolerance to drought, infection and herbivory.

By using mass spectrometry, researchers at the Max Plank institute were able to find mycorrhizal-specific changes in above-ground parts of plants.

"Our diagnostic marker for the colonization with arbuscular mycorrhiza fungi can be very useful for studying mycorrhizal associations, not only for breeding programs which rely on high-throughput screenings, but also for basic research into fundamental questions about the information transferred from plant-to-plant through fungal networks."

Journal Reference:

Ming Wang, Martin Schäfer, Dapeng Li, Rayko Halitschke, Chuanfu Dong, Erica McGale, Christian Paetz, Yuanyuan Song, Suhua Li, Junfu Dong, Sven Heiling, Karin Groten, Philipp Franken, Michael Bitterlich, Maria J Harrison, Uta Paszkowski, Ian T Baldwin. Blumenols as shoot markers for root symbiosis with arbuscular mycorrhizal fungi. eLife, 2018; 7 DOI: 10.7554/eLife.37093

Max Planck Institute for Chemical Ecology. "Leaf molecules as markers for mycorrhizal associations: Metabolites in above-ground parts of a plant reveal a plant's successful mutualism with mycorrhizal fungi." ScienceDaily. ScienceDaily, 28 August 2018. www.sciencedaily.com/releases/2018/08/180828103953.htm

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Why use an Opti-Sciences chlorophyll fluorometer?

... another important reason:

AFFORDABLE DARK ADAPTION CLIPS and Fv/Fm make field work an act of pleasure instead of an act of drudgery when measuring plant stress.

Dark clips allow measurement at any time of day or night, on large populations of plants, instead of making field measurements predawn, in the dark. Opti-Sciences has made a very affordable dark adaption clip for just that purpose. We have several researchers that buy from 250 to 1000 dark adaption clips at a time. Some other instrument manufactures charge as much as five times the price of our dark adaption clips.

Fv/Fm is the gold standard of chlorophyll fluorescence work. It allows comparison of different samples at the same known dark-adapted state. Other measuring protocols have additional issues when it comes to comparison. For example: the light adapted test Y(II) requires light levels at steady state photosynthesis (the same light level for 20-30 minutes) with the same light intensity and similar light history for reliable comparative measurement.

Dark adaption is the other issue that should be considered. Views vary, to some degree, on this subject. While several researchers agree that dark adaption times can be as short as 20 to 30 minutes, there are others that will only accept the equivalent of overnight predawn dark adaption. As a result, unless you want to get up in the dark and make measurements on populations of plants, dark adaptation clips are the acceptable and preferable alternative.

We offer application notes on checklists for reliable Fv/Fm measurements, reliable Y(II) measurements, reliable quenching measurements, and reliable rapid light curve measurements on our main web page.

Journal references for claims made here, regarding Fv/Fm, Y(II) and dark adaptation times, are available on our check list application notes for Fv/Fm and Y(II).

www.optisci.com

Researchers from the University of British Columbia, the University of Saskatchewan, and the University of Manitoba discover the feedback loop that controls plant growth and stagnation.

“Plants use this messaging system to survive under harsh conditions or to compete successfully when conditions are favourable. It tells them when to grow, when to stagnate, when to flower, and when to store resources -- all based on the prevailing conditions. Understanding how it all works could enable innovations in agriculture, forestry and conservation as climate change takes hold.”

“...the system is driven by a protein called CLASP. The protein, found in plants, animals and fungi, plays an essential role in cell growth and division by coordinating the assembly of filaments within cells.” “...production of CLASP is reduced by a plant-growth hormone called brassinosteroid.” “... the researchers discovered that CLASP prevents the degradation of brassinosteroid receptors, so when CLASP is scarce, brassinosteroid becomes less effective, which results in CLASP levels rising again. Essentially, the protein and the hormone affect each other in a negative-feedback loop.”

"You can liken it to the predator-prey feedback loop..." "We know that fox populations plummet if they over-consume rabbits. In the absence of foxes, rabbit populations explode, causing the eventual collapse of their ecosystem.”

"These findings are unique because they show, for the first time, that CLASP is governing its own destiny by directly sustaining the hormone pathway that regulates its expression."

“These new insights are of particular interest to agriculture as the industry looks for new ways manage the effects of climate change,...”

"One of the aims of the future is to be able to have smart plants that can sense their environment and adjust their development, so that they will reliably produce crops under increasingly adverse conditions. This mechanism is pivotal to that."

Journal Reference:

Yuan Ruan, Laryssa S. Halat, Deirdre Khan, Sylwia Jancowski, Chris Ambrose, Mark F. Belmonte, Geoffrey O. Wasteneys. The Microtubule-Associated Protein CLASP Sustains Cell Proliferation through a Brassinosteroid Signaling Negative Feedback Loop. Current Biology, 2018; DOI: 10.1016/j.cub.2018.06.048

University of British Columbia. "Secrets of plant development unlocked." ScienceDaily. ScienceDaily, 23 August 2018. <www.sciencedaily.com/releases/2018/08/180823113626.htm>.

Part of the mechanism used by plants to efficiently shut off photosynthesis at night was discovered.

“They do this by a process called 'redox regulation' -- the activation and deactivation of proteins via changes in their redox (reduction/oxidation) states. What happens in light is well understood: the ferredoxin-thioredoxin reductase (FTR)/thioredoxin (Trx) pathway is responsible for the reduction process, which activates the photosynthetic pathway. However, scientists have long been in the dark about what happens when light is not available, and how plants reset photosynthetic proteins to be ready to function when light is resumed.”

“TrxL2, unlike similar, better-known proteins, seems to be specialized for the 'switching off' process; it's an efficient oxidizer of many proteins, but only reduces 2CP, allowing the energy drained by TrxL2 from several upstream reactions to pass to 2CP and thence hydrogen peroxide. This cascade thus keeps photosynthesis on standby until light is available again.”

“TrxL2/2CP do work in light as well, but are overshadowed by the normal activation machinery in plants and only take center stage in the absence of light.”

...”mutant plants without 2CP behave normally in light; however, the 'switching off' mechanism is significantly less efficient in these mutant plants than in wild-type plants. Moreover, the fact that this process is less efficient, rather than absent altogether, suggests that other, as yet unknown, proteins serve similar functions in plants.”

Journal Reference:

Keisuke Yoshida, Ayaka Hara, Kazunori Sugiura, Yuki Fukaya, Toru Hisabori. Thioredoxin-like2/2-Cys peroxiredoxin redox cascade supports oxidative thiol modulation in chloroplasts. Proceedings of the National Academy of Sciences, 2018; 201808284 DOI: 10.1073/pnas.1808284115


Tokyo Institute of Technology. "How do plants turn off photosynthetic activity at night?." ScienceDaily. ScienceDaily, 16 August 2018. <www.sciencedaily.com/releases/2018/08/180816102000.htm>.

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Can agricultural plants call for help?

A study at the University of Delaware found that volatile odors given off by maize under insect herbivory stress attract foraging birds. The birds apparently smell the volatile scent and search for insects on plants near the source of the scent. On Control plants, there were significantly fewer bird pecks. The hope is that this research will supplement pest management programs.

Artificial insect larvae were used. The researchers “attached dispensers using a synthetic odor blend that replicated the volatiles” on test plants and a dispenser with an organic solvent on control plants.

University of Delaware. (2018, August 15). How plants protect themselves by emitting scent cues for birds. ScienceDaily. Retrieved August 21, 2018 from www.sciencedaily.com/releases/2018/08/180815124009.htm
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