Main Page/Culturing Chara
Overview.Chara is used for teaching labs in Biology and Biophysics. In BIOL2010 (Plant Biology), it is used for diversity labs. In BIOL2070 (Methods in Cell and Molecular Biology), it is used to explore molecular motors. In BPHS4090 (Biophysics II), it is used to measure action potentials []. Here, we provide a description of how to culture Chara.
Chara australis planting technique.Chara is a multicellular freshwater algae which roots itself in soil, and grows upward to the surface of the water. So, our aquarium tank cultures of Chara normally uses a soil base covered with a growth medium. The size of the tanks will affect the quantity of the algae. We use either small (20 cm width by 41 cm length by 26 cm depth) or large (27 cm width by 49 cm length by 30 cm depth) aquaria tanks.
Soil preparation.We obtain our soil from a local woodlot (Boyer Woodlot —northwest corner at the edge of a path leading to the road, click on the map).
Planting Chara.The soil is added to the aquarium tanks to a depth of about 2–3 cm, and saturated with Broyer-Barr medium (see stock make-up, below). Sections of Chara are cut from an existing culture. The explants include the plant top and 2 to 4 internodes (total length about 10–20 cm). The Chara explants are buried in soil by making a groove in the soil by hand and gently placing the explant in the groove (horizontally), then covered with additional ‘sprinkle’ of soil. The apex is allowed to extend above the soil surface. Broyer-Barr medium is added gently by pouring slowly onto cheese cloth adhering to the aquarium tank wall to minimize any disturbance of the soil. We usually start with a liquid depth of about 3 cm. Over time, as the Chara grows, the height of the medium is increased (usually every week or so), eventually to the top of the tank. An alternative planting technique is to cut the plant top with 1 mature internode. A whorl cell at the bottom of the plant top is held with forceps, and the bottom whorl inserted into the soil, leaving the top in solution. Continued growth of the plant apex is often observed within days (see montage below). Sometimes, above-ground plant parts will die off (turning black). This is normal: new sprouts will emerge from the underground Chara plantlets. Once planted, the tanks are covered with plexiglas covers, or plastic wrap (to minimize evaporation).
Growth of Chara The montage is snapshots from a time lapse movie (every five hours). For scale, the internode cell diameter is about 1.5 mm. Movies in quicktime format are available at http://www.yorku.ca/planters/movies.html#Chara.
Illumination should not be too bright (to discourage growth of planktonic algae and cyanobacteria). Normally, photosynthetically-active radiation (PAR) should be about 20 µmole m–2 s–1, measured with a radiometer (less intensity is insufficient for growth, greater intensity encourages growth of cyanobacteria). We normally use T8 fluorescent lamps with the highest color temperature we can find (4100 K for 24 inch or 6500 K for 48 inch lamps) on a 12 hour dark / 12 hour light cycle. We have noticed that the lamps become dimmer over time, and now replace the bulbs every 1-2 years to ensure sufficient light intensity.
Below is a make-up list for Broyer-Barr media, available as a png image file.
Chara Disposal.In keeping with the view that organisms should not be introduced into the environment, we routinely destroy Chara cultures when the cultures are no longer required. To do this, we siphon the medium from the tank, add household bleach (5% sodium hypochlorite) so that the soil is complete saturated and then cover the tank top. After 1 day, the Chara will have died, as evidenced by its straw-like color due to chemical bleaching of the chlorophyll. At this point we discard in the greenhouse bins for soil disposal, flush the tank with water, and clean with a standard glassware detergent to remove algal biofilms from the glass sides of the tank. Now, all is ready for the next round of Culturing Chara!
We thank Professor Mary Bisson (University at Buffalo) for getting us started with Chara in support of teaching exercises.
- Created and maintained by RR Lew, Biology Department at York University