Elodea Lab

Elodea” was put into a tank labelled “chemically treated Elodea”. Three drops of phenolphthalein were added to each beaker and then all of them were placed on a sheet of white paper. 0.02N NaOH was slowly added to the “tap water with Elodea” beaker with a dropper that delivers 0.025 mL per drop. Each drop was counted and the solution was stirred thoroughly before adding the next drop. This was continued till a faint pink color appeared in the solution. The number of drops was noted.
The procedure, from the addition of NaOH to the noting of number of drops, was repeated for the other three beakers. The number of drops for the beaker labelled “tap water” was subtracted from the number of drops for the beaker labelled “tap water with Elodea” and

The converse was true for the 5% NaCl solution without Elodea and the 5% solution with Elodea (table 1). A comparative observation revealed that the beaker with Elodea in salt solution required more NaOH than did the beaker with Elodea in tap water (figure 1).
Table 1. The number of drops of NaOH in each beaker
Beaker Name Number of Drops
Tap Water

Hence experiments on the effect of salinity on photosynthesis need to be carried out. Hart, et al. (1990) have carried out experiments investigating the effects of salinity on river, stream and wetland ecosystems in Victoria, Australia. Stofberg, et al. (2012) explore the effect of salinity increase on the photosynthesis, growth and survival of the Mediterranean seagrass Cymodocea nodosa. In their experiment, they placed large pieces of C. nodosa were placed in a range of hypersaline conditions over a period of 47 days. Such a method could also be applied to E. canadensis in order to obtain a detailed understanding of the effect of salinity on photosynthesis. Once the general trends in the effect of increased salinity on different kinds of plants has been established, research could be focused on increasing the salt tolerance of plants, the treatment of saline soils and waters and the prevention of further