Ruppia

Key takeaways

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

Reference excerpt

Ruppia, also known as the widgeonweeds, ditch grasses or widgeon grass, is the only extant genus in the family Ruppiaceae, with 11 known species. These are aquatic plants widespread over much of the world. The genus name honours Heinrich Bernhard Rupp, a German botanist (1688–1719). They are widespread outside of frigid zones and the tropics.

Description

These plants are aquatic, rhizomatous with roots set in the substratum. They can be annual (commonly) or perennial (rarely); stem growth is conspicuously sympodial, but sometimes is not. These species are adapted to be in brackish water estuaries. The leaves are small or medium-sized. Their disposition can be alternate, opposite, or whorled (usually alternate except when subtending an inflorescence). Even, lamina keep entire and are setaceous or linear. The leaf just shows one vein without cross-venules. Stomata are not present. The mesophyll leaks calcium oxalate crystals. The minor leaf veins do not present phloem transfer cells and leaks vessels. These plants have stems without secondary thickening and xylem without vessels. The sieve-tube plastids are P-type. The root xylem does not present vessels. These plants are hermaphroditic, with anemophilous or hydrophilous pollination. The flowers are ebracteate, small, and regular. Commonly, the flowers are aggregated in ‘inflorescences’, but sometimes they are solitary. Often, they grow in racemes, spikes, or umbels. The scapiflorous inflorescences are terminal, in short spikes, or subumbelliform racemes, sometimes one- or few-flowered. They do not have hypogynous disks. These flowers do not have perianth, except when small staminal appendages are regarded as perianth segments. The androecial members are all equal. The androecium just presents two fertile stamens with sessile anthers dehiscing by longitudinal slits. The pollen is polysiphonous and its grains are three-celled and nonaperturate. The gynoecium (2–)4(−16) is superior, carpelled, and euapocarpous. The carpel is not stylate, apically stigmatic with the stigma peltate, or umbonate. These flowers only present one ovule pendulous, nonarillate, campylotropous, bitegmic, and crassinucellate. The placentation is apical and embryo-sac development is of the polygonum type. Before fertilization, they fuse polar nuclei. The fruit is drupaceous and fleshy, forming an aggregate. The fruiting carpel is indehiscent, commonly on a long, spirally twisted peduncle, with each drupelet becoming very long-stalked. The fruit contains one nonendospermic seed with starch. The embryo can be straight or slightly curved. Membranous testa do not have phytomelan.

Species 11 species are accepted.

Ruppia bicarpa Yu Ito & Muasya – Western Cape, South Africa Ruppia brevipedunculata Shuo Yu & Hartog – China (Jiangsu) Ruppia cirrhosa (Petagna) Grande (synonym Ruppia spiralis) – temperate regions: Europe, Asia, north + south (but not tropical) Africa, North America, West Indies, Argentina. The name is a homotypic synonym of R. maritima. Ruppia didyma Sw. ex Wikstr. – Mexico, West Indies Ruppia drepanensis Tineo – western and central Mediterranean Ruppia filifolia (Phil.) Skottsb. – southern South America, Falkland Islands Ruppia maritima L. – seashores and lakeshores around the world Ruppia megacarpa R.Mason – Australia, New Zealand, Asia (Korea, Japan, and Russia) Ruppia polycarpa R.Mason – Australia, New Zealand (including Chatham Islands) Ruppia sinensis Shuo Yu & Hartog – China (Jiangsu) Ruppia tuberosa J.S.Davis & Toml. – Australia

Taxonomy The Cronquist system of 1981 placed the family in order Najadales of subclass Alismatidae in class Liliopsida [=monocotyledons] in division Magnoliophyta [=angiosperms]. The APG II system of 2003 (unchanged from the APG system of 1998) does recognize such a family and places it in the order Alismatales, in the clade monocots. According to the AP-Website the family is doubtfully distinct from the family Cymodoceaceae: the plants in the three families Cymodoceaceae, Posidoniaceae, and Ruppiaceae form a monophyletic group. A genus-level taxonomy was briefly revised by Zhao and Wu in 2008. Marine grasses families: Zosteraceae, Cymodoceaceae, Ruppiaceae and Posidoniaceae. Related families: Potamogetonaceae, Zannichelliaceae (not consistently).

Phylogeny and evolution The first molecular phylogeny of the monogeneric family discerned three distinct species, R. tuberosa, R. megacarpa, and R. polycarpa, and one species complex comprising six lineages. The species complex, named R. maritima complex, was later updated as a group of eight lineages. These studies revealed that multiple hybridization and polyploidy events as well as chloroplast capture have occurred in the evolution of the genus.

Phytochemistry These plants present an anatomy non-C4 type. Seven labdanes have been identified from this genus:

ent-14,15-Dinor-8(17)-labden-13-one Methyl ester of (ent-12S)-15,16-Epoxy-12-hydroxy-12-oxo-8(17),13(16),14-labdatrien-19-oic acid. (-)-15,16-epoxy-8(17),13(16),14-labdatrien-19-ol. Methyl ester of (-)-15,16-epoxy-8(17),13(16),14-labdatrien-19-oic acid. (-)-15,16-Epoxy-8(17),13(16),14-labdatrien-19-al. (-)-15,16-Epoxy-8(17),13(16),14-labdatrien-19-yl acetate (ent-13E)-8(17),13-Labdadien-15-ol Three steroids have been also isolated:

(3β,5α,6β,7α,22E,24R)-Ergosta-8(14),22-diene-3,6,7-triol. (3β,5α,6β,7α,22E,24R)-Ergosta-8,22-diene-3,6,7-triol (24R)-Ergost-4-ene-3,6-dione.

References

External links

Ruppiaceae in the Flora of North America NCBI Taxonomy Browser links at CSDL, Texas

Illustrations

Worked examples

Example 1 — a first encounter with Ruppia

Start with the simplest possible case. Write down what Ruppia 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 Ruppia 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 Ruppia 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 Ruppia

In research: Ruppia 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 Ruppia 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: Ruppia is common in secondary-school and first-year university syllabi. It links to neighbouring topics Alismatales genera, Brackish water plants, Ruppia, so understanding it makes those chapters shorter.
In everyday life: Look for Ruppia 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.

How to study Ruppia in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Ruppia 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 Ruppia out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Ruppia in simple terms?

Ruppia, also known as the widgeonweeds, ditch grasses or widgeon grass, is the only extant genus in the family Ruppiaceae, with 11 known species. These are aquatic plants widespread over much of the world.

Why does Ruppia 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 Ruppia?

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 Ruppia.