Dandelion vortexes

Surprisingly, dandelion seeds use a method of flight previously thought impossible.

Abstract
Wind-dispersed plants have evolved ingenious ways to lift their seeds1,2. The common dandelion uses a bundle of drag-enhancing bristles (the pappus) that helps to keep their seeds aloft. This passive flight mechanism is highly effective, enabling seed dispersal over formidable distances3,4; however, the physics underpinning pappus-mediated flight remains unresolved. Here we visualized the flow around dandelion seeds, uncovering an extraordinary type of vortex. This vortex is a ring of recirculating fluid, which is detached owing to the flow passing through the pappus. We hypothesized that the circular disk-like geometry and the porosity of the pappus are the key design features that enable the formation of the separated vortex ring. The porosity gradient was surveyed using microfabricated disks, and a disk with a similar porosity was found to be able to recapitulate the flow behaviour of the pappus. The porosity of the dandelion pappus appears to be tuned precisely to stabilize the vortex, while maximizing aerodynamic loading and minimizing material requirements. The discovery of the separated vortex ring provides evidence of the existence of a new class of fluid behaviour around fluid-immersed bodies that may underlie locomotion, weight reduction and particle retention in biological and manmade structures.

Dandelion seeds fly using ‘impossible’ method never before seen in nature
Nature, Revealed: the extraordinary flight of the dandelion
Paper, A separated vortex ring underlies the flight of the dandelion
Research Gate project, The form and function of the dandelion fruit

Dandelion pollen
2018 PhotoMicrography Competition
Dandelion fiber
2018 PhotoMicrography Competition

Antarctic fungi found to be effective against citrus canker

Citrus canker is a disease that affects all citrus species and varieties. It is caused by Xanthomonas citri, a bacterium originally from Asia, where it is endemic in all citrus-producing countries. Although the bacterium can be combated in several ways, none is sufficient to eradicate the disease. Therefore, new chemical or biological methods of protecting citrus groves have to be pursued.

In an article published in Letters in Applied Microbiology, a team led by Daiane Cristina Sass, Lara Durães Sette and Henrique Ferreira, professors in São Paulo State University’s Bioscience Institute (IB-UNESP) in Rio Claro, Brazil, identify 29 fungi with proven action against X. citri. The origin of the fungi is surprising. They were isolated from samples of soil and marine sediment collected in Antarctica. read more…

Terrestrial and marine Antarctic fungi extracts active against Xanthomonas citri subsp. citri
Biotechnological potential of secondary metabolites from Antarctica fungi with activity against plant pathogenic bacteria

National Invasive Species Week

Feb 26 – Mar 2, 2018

Do you know what’s sneaking into your garden?

National Invasive Species Awareness Week
Texas Invasives
Aggressive Invaders in Texas
Texas Dept of Agriculture, Noxious and Invasive Plants
The Woodlands Invasive Species
Houston Arboretum and Nature Center

What traits make introduced plants likely to be invasive?
Similarity of introduced plant species to native ones facilitates naturalization, but differences enhance invasion success

Dodder vine (Cuscuta pentagona)

Dodder vine

Dodder vine is an amazing plant, it is orange rather than green due to its lack of chlorophyl, it can’t make its own food.

Instead the dodder vine hatches in the spring from a seed and very slowly moves in a circle searching the air for beta-myrcene a volatile chemical emitted into the air by tomatoes and other plants. When it picks up the scent of beta-myrcene it grows in the direction of the odor until it finds the plant emitting it.

Once it reaches the plant it tightly winds itself around the plant, sinking roots into the host plant. The roots then suck up the juices in the host plant to feed itself. The host plant will then wilt and die.

Dodder vine also appears to exchange RNA with the host plant. Whether this is a way of exchanging information with the host plant or a way to reprogram it, much the way viruses reprogram our DNA is unknown.

Plants use RNA as a way to send messages through out the plant. When a dodder vine attacks a plant some of the plant’s RNA gets sucked up by the dodder vine. The dodder vine can then read the RNA to better evaluate how to attack the host.

Professor Neelima Sinha and colleagues at the UC Davis Section of Plant Biology studied dodder vines growing on tomato plants in the lab. They found that RNA molecules from the host could be found in the dodder up to a foot (30 cm) from the point where the parasite had plumbed itself into the host.

Plants often use small RNA molecules as messengers between different parts of the plant. In a paper published in Science in 2001, Sinha’s group showed that RNA could travel from a graft into the rest of the plant and affect leaf shape. Plants can also use specific RNAs to fight off viruses. . . [ read more Plant Parasite Wiretaps Host ]

Dodder is a member of the Morning Glory family.

It has very tiny leaves that are more like scales than leaves and tiny white flowers.

It is considered an invasive plant and a threat to the local ecology in Texas.

A new method of plant communication?
Genomic-scale exchange of mRNA between a parasitic plant and its host
YouTube video of dodder vine locating and reaching for a tomato plant
Dodder management guide lines

Insect damage to plants inoculates future generations

Black Swallowtail caterpillar


“We show that exposing tomato plants to some level of caterpillar herbivory will increase resistance for future plants—it’s sort of like a plant vaccine,” says Sergio Rasmann, a biologist at the University of Lausanne in Switzerland.

Rasmann isn’t the only one seeing this effect. In a similar study, Ann Slaughter of the Universite de Neuchatel in Switzerland infected Arabidopsis thaliana plants with a benign strain of the bacteria Pseudomonas syringae (PstavrRpt2). The offspring were more resistant to disease than control groups, which were not infected in the first generation.

How does pest resistance get inherited? Researchers point to epigenetic mechanisms, which regulate gene expression and can be passed from one generation to the next without any changes to DNA sequences. The studies suggest known epigenetic factors like DNA methylation and histone modification mediate these effects, and are among the first to demonstrate siRNAs act as an epigenetic mechanism in plant defense responses.

original story

Papers
Descendants of Primed Arabidopsis Plants Exhibit Resistance to Biotic Stress
Herbivory in the Previous Generation Primes Plants for Enhanced Insect Resistance

Is Imprelis herbicide killing your trees?

The NYTimes is reporting that several tree deaths are being linked to the use of the new herbicide Imprelis.

Imprelis uses pyrimidine carboxylic acid (trade name Aptexor )
A recently approved herbicide called Imprelis, widely used by landscapers because it was thought to be environmentally friendly, has emerged as the leading suspect in the deaths of thousands of Norway spruce, eastern white pine and other trees on lawns and golf courses across the country.

Manufactured by DuPont and approved for sale last October by the federal Environmental Protection Agency, Imprelis is used for killing broadleaf weeds like dandelion and clover and is sold to lawn care professionals only. Reports of dying trees started surfacing around Memorial Day, prompting an inquiry by DuPont scientists.

Read more at the NYTimes Story on Imprelis

There have been several reports from both outside and within the state of Michigan of herbicide injury on Norway spruce and white pine following application of the turfgrass herbicide Imprelis (a.i. aminocyclopyrachlor). Damaged trees have symptoms consistent with growth regulator type herbicides. Injury includes curling and twisting of new growth. Pictures and comments of damage observed in Indiana can be viewed at Purdue Extension’s Plant and Pest Diagnostic Laboratory website.

Read more at the Michigan State Extension Office

DuPont is looking into this and recommends that you do not use Imprelis near spruces or white pines for now.

Fungus and bees help orchids diversify


Scientists have discovered why orchids are one of the most successful groups of flowering plants – it is all down to their relationships with the bees that pollinate them and the fungi that nourish them.

The orchid family is one of the largest groups of flowering plants, with over 22,000 species worldwide. Today’s research suggests that there is such a huge range of species because orchids are highly adaptable and individual species can interact with bees, and other pollinators, in different ways.

For example, when orchids Pterygodium pentherianum and Pterygodium schelpei live side by side, Pterygodium pentherianum puts its pollen on the bee’s front legs, whereas Pterygodium schelpei puts it on the bee’s abdomen. This means that one bee can carry pollen from two distinct species without mixing it.

The study also shows how orchids are able to live harmoniously together, with different species working in partnership with different microscopic fungi in the soil, ensuring they do not compete with each other.

Prior to today’s study, it was known that orchids have strong interactions with bees, which pollinate the flowers in return for food such as nectar or oils, and also with fungi, which supply minerals to the roots in return for sugars. These relationships are amongst the best examples of nature’s system of ‘mutual benefit’ and are believed to have been important for enabling orchids to evolve into so many different species. However, the mechanisms by which these relationships affect the number of plant species, and these species’ ability to coexist, had remained obscure.

The group studied 52 orchid species in a small region of South Africa, which all secrete oil inside their flowers that female bees collect to feed to their larvae. In order to investigate which pollinating bees were visiting the different species, they collected orchid pollen from the bees for DNA sequencing and analysis. They found strong evidence that when an orchid moved to a new geographical area it adapted to a different pollinating bee species, and interestingly, some competing orchid species were able to adapt by placing pollen on different body parts of the same bee.

“What is remarkable in these orchids is that diversity is generated not only through switches between bees, but also by switches between different body parts of the same bee, so two closely related orchids might place pollen on different segments of one bee’s front leg,” added Professor Barraclough. “It’s given us a fundamental insight into how so many new species can originate, and once they originate how they are able to coexist without exchanging genes.”

The researchers also studied the microscopic fungi living on the roots of the orchid, to see how this relationship was affecting plant diversity. Most flowering plants host microscopic fungi in their roots that help the plant take up nutrients from the soil. Until now it has been difficult to investigate this interaction, as most of the fungi belong to species that are difficult to culture. The researchers overcame this challenge by combining a molecular technique known as DNA barcoding with field experiments. In contrast to the bees, where co-occurring orchid species normally share the same insect pollinator, the plants needed to use different fungal partners in order to coexist in the same region.

“By tapping into different kinds of fungi, different plant species access different pools of nutrients and so the problem of living together without competing for the same resources is solved,” said Professor Barraclough. However, the same fungal partners are found in different geographical areas and so orchid species that originate in different areas, by adapting to different pollinators, tend still to use the same fungi.

The team’s fieldwork shows that shifts in pollination traits were important for bringing about new species and allowing coexistence in a diverse group of orchids, whereas shifts in fungal partner were important for coexistence but not for speciation. Many other groups of flowering plants enter into similar relationships with pollinators and fungi, and both the origins and the future survival of that diversity could depend critically on understanding these relationships.

source

The Effects of Above- and Belowground Mutualism on Orchid Speciation and Coexistence