biology

Phragmidium

Phragmidium is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Phragmidium rather than just read about it. In short: Phragmidium is a genus of rust fungus that typically infects plant species in the family Rosaceae. It is characterised by having stalked teliospores borne on telia each having a row of four or more cells.

Key takeaways

Phragmidium belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Phragmidium to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Phragmidium from memory before moving on to harder problems.

Reference excerpt

Phragmidium is a genus of rust fungus that typically infects plant species in the family Rosaceae. It is characterised by having stalked teliospores borne on telia each having a row of four or more cells. All species have a caeoma which is a diffuse aecidium lacking a peridium. There are a number of species of Phragmidium, most of which are restricted to one or a few host species. Examples include:

Phragmidium acuminatum on Rubus saxatile Phragmidium bulbosum on Rubus fruticosus and Rubeus caesius Phragmidium mucronatum Phragmidium sterilis on Potentilla sterilis Phragmidium potentillae on Potentilla anglica Phragmidium rosae-pimpinellifoliae Phragmidium rubi-idaei on raspberry Phragmidium tuberculatum on some rose cultivars Phragmidium violaceum on cultivated blackberry and loganberry Possibly the most commonly encountered is P. mucronatum, found on most species of wild roses including Rosa canina and Rosa arvensis.

Hosts and symptoms Phragmidium tuberculatum, also known as rose rust, is a parasitic fungus that feeds on living cells of a host plant. It can affect all species of the family Rosaceae. This includes all species of roses. Rose rust causes distortion and discoloration on stems. Sometimes it will cause galls and lesions. In the spring, there are yellow spots on the upper portion of the leaf and during the Spring and Summer there are orange spores on the abaxial surface of the leaf.

Environment The climate most favorable to rose rust is mild temperatures with high moisture. Most of this strain of Phragmidium is found in Europe but there have been cases found in Asia and North America. Most of the cases of rose rust in the United States are found on the coasts, mainly the Pacific Coast. The Midwest is poor for this pathogen because of its extreme winter and summer temperatures.

Disease cycle In the spring, the very first spores, spermatogonia, arise out of the debris on the ground and infects the young stem, distorting them and producing orange pustules. These pustules break open and infect the leaves. In the Summer, these darker orange spores called urediniospores spread through wind. Eventually in late August, the urediniospores and sori become speckled with black fascicles and dark resting spores called teliospores. The teliospores turn into aeciospores which are the spores that adhere to stems and leaves to overwinter.

Pathology Roses infected with species of Phragmidium will show a characteristic orange mass of spores and distorted growth at specific locations on the bush. The rose may be substantially weakened and lack vigour and may die. Later in the year, small black spots or raised areas will be visible. These are telia containing overwintering teliospores.

Prevention Rose growers recommend the use of fungicides some of which may have health implications for the gardener. Many cultivated roses are now bred to have resistance to rust diseases. In wild roses, Phragmidium infections are one of a normal range of pests and diseases which are part of the normal ecological pressures affecting all species. Non-chemical controls include pruning out the spring infections as soon as possible along with collecting and destroying fallen leaves to prevent overwintering.

References

External links http://www.apsnet.org/publications/plantdisease/2014/November/Pages/98_11_1581.2.aspx http://hort.uwex.edu/articles/rose-rust/ Bailey, AG (1988). "2. Rose rust". Mycologist. 2 (2): 70. doi:10.1016/S0269-915X(88)80010-7.

Illustrations

Worked examples

Example 1 — a first encounter with Phragmidium

Start with the simplest possible case. Write down what Phragmidium claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Phragmidium before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Phragmidium ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Phragmidium

In research: Phragmidium appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Phragmidium in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Phragmidium is common in secondary-school and first-year university syllabi. It links to neighbouring topics Basidiomycota genera, Fungal plant pathogens and diseases, Pucciniales, so understanding it makes those chapters shorter.
In everyday life: Look for Phragmidium outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Phragmidium in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Phragmidium means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Phragmidium out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Phragmidium in simple terms?

Why does Phragmidium matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Phragmidium?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Phragmidium.