General Information About Hydrilla And Photosynthesis Biology Essay

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All green parts of a plant have chloroplasts in their cells and can carry out photosynthesis. In most plants, however, the leaves have the most chloroplasts (about half a million per square millimeter of leaf surface) and are the major sites of photosynthesis. Their green color is from chlorophyll, a light-absorbing pigment in the chloroplasts that plays a central role in converting solar energy to chemical energy. Pp 109 (Campbell, N.A. et. Al. 2009

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Many aquatic weed scientists consider Hydrilla verticillata the most problematic aquatic plant in the United States. This plant, native to Africa, Australia, and parts of Asia, was introduced to Florida in 1960 via the aquarium trade. Hydrilla is now well established throughout water bodies in the southern states where control and management costs millions of dollars each year. From 1980 to 2005, Florida alone spent $174 million on hydrilla control. On the West Coast, California, Washington, and Idaho all have limited populations of hydrilla. Managers in all three states are serious about eradicating these infestations. Washington’s hydrilla infestation, discovered in 1995 in two interconnected lakes in King County, is the only known occurrence of hydrilla in Washington and eradication efforts are ongoing. Hydrilla is also increasingly being discovered in the northern tier states and in the Midwest.  


Hydrilla forms dense mats of vegetation that interfere with recreation and destroy fish and wildlife habitat. Hydrilla has several advantages over other plants. It will grow with less light and is more efficient at taking up nutrients than native species. It also has extremely effective methods of propagation. Besides making seeds (seedlings are actually rarely seen in nature), it can sprout new plants from root fragments or stem fragments containing as few as two whorls of leaves. Recreational users can easily spread these small fragments from water body to water body.  

However, hydrilla’s real secret to success is its ability to produce structures called turions and tubers. (Presence of these structures is also a characteristic that distinguishes this species from similar looking plants.) Turions are compact and produced along the leafy stems. They break free from the parent plant and drift or settle to the lake bottom to start new plants. They are generally about a quarter inch long, dark green, and appear spiny. Tubers are underground and form at the end of roots. They are small, potato-like or pea-like, and are usually white or yellowish. Hydrilla produces an abundance of tubers and turions in the fall and the tubers may remain dormant for several years in the sediment. The hydrilla variety found in Washington will also make tubers in the spring and will produce non-dormant turions throughout the growing season. Tubers and turions can withstand ice cover, drying, herbicides, and ingestion and regurgitation by waterfowl. One square meter of hydrilla can produce 5,000 tubers!   

There are two varieties of hydrilla in the United States. Many of the plants in the southern United States are all one sex (female) and are dioecious. Dioecious plants cannot produce seed. The plants in Washington are monoecious (having both male and female flowers on the same plant) and can produce seed. In New Zealand, where hydrilla is not native, the hydrilla plants are all male. Generally, the northern-most populations of hydrilla in the United States are monoecious. Although the hydrilla in Idaho is dioecious, all of Idaho’s dioecious hydrilla populations are associated with warmer geothermal-influenced waters. Monoecious hydrilla looks and grows somewhat differently than dioecious hydrilla. It tends to have a delicate appearance and sprawls along the lake bottom. The tubers from these monoecious plants are smaller than tubers produced by their southern female relatives.


Hydrilla is a federally listed noxious weed, listed as a Class A weed on Washington’s Noxious Weed List, and is on the Washington State Department of Agriculture’s Quarantine list. Weed scientists suspect that some of the hydrilla infestations in California resulted from hydrilla tubers hitch hiking on mail order water lily rhizomes. Plant managers also speculate that Washington’s only hydrilla infestation in Pipe and Lucerne Lakes near Seattle also resulted from contaminated water lilies. Non-native water lilies were once common in these two lakes (before lake managers started herbicide treatments for hydrilla).

Since the hydrilla discovery in 1995 in Pipe and Lucerne Lakes, there have been no other reports of hydrilla in Washington. State and local governments (King County and the cities of Covington and Maple Valley) are working together to eradicate the hydrilla infestation by using a combination of an aquatic herbicide called fluridone and diver and snorkeler hand removal. This is a multi-year ongoing effort because hydrilla tubers are long-lived and they do not all sprout at once. Prior to herbicide treatments (started in 1995) hydrilla densely covered the bottom of Pipe and Lucerne Lakes and had started to grow over the tops of Eurasian watermilfoil plants also in the lakes. As of 2009, surveyors have not detected any hydrilla plants in Lucerne Lake since 2004 and no hydrilla plants in Pipe Lake since 2006.  


Hydrilla closely resembles two other aquatic plants found in Washington: The non-native plant Brazilian elodea – Egeria densa and the native plant American waterweed – Elodea canadensis. You can distinguish hydrilla from these look-alike species by the presence of tubers (0.2 to 0.4 inch long, off-white to yellowish, pea-like structures buried in the sediment). Neither Brazilian elodea nor waterweed has tubers.

Other characteristics to look for include:  

Leaves in whorls around the stem (generally five leaves per whorl).

Serrations or small spines along the leaf edges.

The midrib of the leaf is often reddish when fresh.

We are especially concerned about new introductions of hydrilla in the Pacific Northwest. If you think that you have seen hydrilla growing in Washington, please contact Kathy Hamel ([email protected]) or Jenifer Parsons ([email protected]) immediately. 

The hydrilla line drawing is the copyright property of the University of  Florida Center for Aquatic Plants (Gainesville). Used with permission. 

Follow This Link for Technical Information About Hydrilla

Trouble in Paradise: Factors that Impact Coral Health

Part C: Impact of Climate Change on Coral Reefs

Scientists monitor coral health in a variety of ways. Sometimes they are able to take direct measurements, but at other times they must rely on remote measurements taken by satellites or on indicators such as ocean temperature or the presence of algal blooms algal blooms: the rapid excessive growth of algae, generally caused by high nutrient levels. Algal blooms can result in decreased oxygen in a body of water when the algae die, threatening the health of local marine life..

The rise of global temperatures due to increased levels of greenhouse gases-namely carbon dioxide- in the atmosphere is a major concern around the world. But did you know that as the amount of CO2 in the atmosphere increases, the amount of CO2 in the oceans rises as well? In fact, estimates indicate that the oceans have absorbed as much as 50% of all CO2 released into the atmosphere by human activity since 1750. What does this mean for ocean life and coral reefs in particular?

Explore what happens to the ocean when CO2 content increases.

Show me materials needed for this experiment


300 mL bromothymol blue (a dye used as an acid-base indicator) aqueous solution

500 mL beaker

drinking straw

Pour the bromothymol blue solution into the beaker. Observe the color of the solution.

Show me more information about bromothymol blue solution


When a bromothymol blue solution is neutral (like pure distilled water) it will appear green. If the solution is slightly basic, the solution will appear blue. If the solution is acidic, it will appear yellow.

Bromothymol Blue pH indicator dye in an acidic, neutral, and alkaline solution (left to right).

Take a drinking straw and place it into the solution.

Exhale through the straw into the solution. BE CAREFUL NOT TO INHALE ANY OF THE SOLUTION!

Keep blowing into the solution until you see a change in color.

Checking In

What happened to the bromothymol blue solution when you added carbon dioxide?

Stop and Think

1: Based on what you observed in the experiment, what do you think the effect of increased carbon dioxide levels has on the ocean? What consequences might this have for coral reefs?

Look at the image below showing the ocean’s involvement in Earth’s carbon cycle.


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Scientific classification













H. verticillata

Binomial name

Hydrilla verticillata

(L.f.) Royle

in Lotus Pond, Hyderabad, India.

Wikimedia Commons has media related to: Hydrilla verticillata

Hydrilla (Esthwaite Waterweed or Hydrilla) is an aquatic plant genus, usually treated as containing just one species, Hydrilla verticillata, though some botanists divide it into several species. Synonyms include H. asiatica, H. japonica, H. lithuanica, and H. ovalifolica. It is native to the cool and warm waters of the Old World in Asia, Europe, Africa and Australia, with a sparse, scattered distribution; in Europe, it is reported from Ireland, Great Britain, Germany, and the Baltic States, and in Australia from Northern Territory, Queensland, and New South Wales.[1][2][3]

Foliage detail

It has off-white to yellowish rhizomes growing in sediments at the water bottom at up to 2 m depth. The stems grow up to 1-2 m long. The leaves are arranged in whorls of two to eight around the stem, each leaf 5-20 mm long and 0.7-2 mm broad, with serrations or small spines along the leaf margins; the leaf midrib is often reddish when fresh. It is monoecious (sometimes dioecious), with male and female flowers produced separately on a single plant; the flowers are small, with three sepals and three petals, the petals 3-5 mm long, transparent with red streaks. It reproduces primarily vegetatively by fragmentation and by rhizomes and turions (overwintering buds), and flowers are rarely seen.[2][4][5][6]

Hydrilla has a high resistance to salinity (>9-10ppt) compared to many other freshwater associated aquatic plants.

The name Esthwaite Waterweed derives from its occurrence in Esthwaite Water in northwestern England, the only English site where it is native, but now presumed extinct, having not been seen since 1941.[7] Hydrilla closely resembles some other related aquatic plants, including Egeria and Elodea.

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[edit] Status as an invasive plant

Hydrilla is naturalised and invasive in the United States following release in the 1960s from aquariums into waterways in Florida. It is now established in the southeast from Connecticut to Texas, and also in California.[8] By the 1990s control and management were costing millions of dollars each year.

Hydrilla can be controlled by the application of aquatic herbicides and it is also eaten by grass carp, itself an invasive species in North America. Insects used as biological pest control for this plant include weevils of genus Bagous and the Asian hydrilla leaf-mining fly (Hydrellia pakistanae). Tubers pose a problem to control as they can lay dormant for a number of years. This has made it even more difficult to remove from waterways and estuaries.

As an invasive species in Florida, Hydrilla has become the most serious aquatic weed problem for Florida and most of the U.S. Because it was such a threat as an invasive species, restrictions were placed, only allowing a single type of chemical, fluridone, to be used as an herbicide. This was done to prevent the evolution of multiple mutants. The result is fluridone resistant Hyrdilla. “As hydrilla spread rapidly to lakes across the southern United States in the past, the expansion of resistant biotypes is likely to pose significant environmental challenges in the future.” [9]

This abundant source of biomas is a known hyperaccumulator of Mercury, Cadmium, Chromium and Lead, and asuch can be used in phytoremediation.[10] s

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Bromothymol blue

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Bromothymol blue

IUPAC name[hide]



CAS number

76-59-5 Y







Molecular formula


Molar mass

624.38 g mol−1


1.25 g/cm3

Melting point

202 °C, 475 K, 396 °F

Acidity (pKa)


Supplementary data page

Structure and


n, εr, etc.



Phase behaviour

Solid, liquid, gas

Spectral data


 Y (what is this?)  (verify)

Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Infobox references

Bromothymol blue (also known as bromothymol sulfone phthalein, Bromthymol Blue, and BTB) is a chemical indicator for weak acids and bases. The chemical is also used for observing photosynthetic activities or respiratory indicators (turns yellow as CO2 is added).

Bromothymol blue acts as a weak acid in solution. It can thus be in protonated or deprotonated form, appearing yellow and blue respectively. It is bluish green in neutral solution. It is typically sold in solid form as the sodium salt of the acid indicator. It also finds occasional use in the laboratory as a biological slide stain. At this point it is already blue, and a drop or two is used on a water slide. The cover slip is placed on top of the water droplet and the specimen in it, with the blue coloring mixed in. It is sometimes used to define cell walls or nuclei under the microscope.

Bromothymol blue is mostly used in measuring substances that would have relatively low acidic or basic levels (near a neutral pH). It is often used in managing the pH of pools and fish tanks, and for measuring the presence of carbonic acid in a liquid.

A common demonstration of BTB’s pH indicator properties involves exhaling through a tube into a neutral solution of BTB. As carbon dioxide is absorbed from the breath into the solution, forming carbonic acid, the solution changes color from green to yellow. Thus, BTB is commonly used in middle school science classes to demonstrate that the more that muscles are used, the greater the CO2 output.

Bromothymol is also used in obstetrics for detecting premature rupture of membranes. Amniotic fluid typically has a pH > 7.2, bromothymol will therefore turn blue when brought in contact with fluid leaking from the amnion. As vaginal pH normally is acidic, the blue color indicates the presence of amniotic fluid. The test may be false-positive in the presence of other alkaline substances such as blood, semen, or in the presence of bacterial vaginosis.

The pKa for bromothymol blue is 7.10.

[edit] Indicator colors

BTB indicator in pH acidic, neutral, and alkaline solutions (left to right).

Bromothymol Blue (pH indicator)

below pH 6.0

above pH 7.6

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