Hydroponic Lettuce Experiment - Week 2

Introduction

On May 5, 2013, I planted some lettuce seeds in my simple hydrogarden set-up in the hopes that something would grow. I have attempted similar experiments some months ago, but they were dismal failures. This experiment, on the other hand, appears to be at least somewhat successful thus far.

The purpose of this experiment is to gain some insight on how plants grow in a hydroponic environment. I need this information because I am not very familiar with growing plants without soil (or even with soil). Because of the philosophy of this experiment, it is not a true experiment, but rather an all-out test performed with some scientific principles.

It should be noted that no automated components are currently in use.

My hydroponics rig, as stated previously, is quite simple. It contains the following components:

• 473 mL plastic container
• Schell-Toogood v.1 nutrient solution
• Sponge (inert medium)
• Aquarium pump
• Lindenburg "Grand Rapids" lettuce seeds (Lactuca sativa).

You may have noticed the material called "Schell-Toogood v.1 nutrient solution." This solution was created by my chemistry teacher and I and it provides all nutrients necessary for plant growth. It is a slightly modified version of the PrometheusWiki's version of Hoagland Solution. If the solution is successful, I may write a more detailed explanation of what it is and how to create it.

For each day that the experiment is active, I will record the height of the plants and the length of the roots, the overall condition of the plants (especially any notable changes), and any alterations to the hydroponic system (e.g. replaced nutrient solution, turned off aeration pump, etc.).

Observations

Fig. 1 shows some pictures of the lettuce plants at various days throughout the experiment. The lettuce appears to be pale green in colour, but this may be due to the type of lettuce rather than resulting from any nutrient deficiencies. Additional observation and research are required to make any definite claim.

Fig. 1 - Lettuce plants on May 9, 15, and 18, respectively. Note the growth of additional leaves.

I also noticed a slight discolouration on one of the leaves (Fig. 2). Whilst it does not appear to be spreading, it does appear to be impeding the leaf's growth.

Fig. 2 - Lettuce leaf with discolouration on May 9 and 18, respectively.

Fig. 3 shows the growth of the lettuce plants in chart form. A trough in plant height occurs on May 17. My experiment journal claims that the plant appeared to be wilting on that day; as a result, the nutrient solution was replaced. However, it is unclear if the plant was indeed wilting or if it was spreading out to accommodate for new leaves.

Fig. 3 - A chart outlining the growth of both the lettuce plants and their roots over the past week.

Conclusion

Fig. 4 - A not-as-successful attempt at growing hydroponic lettuce.

This current attempt at growing plants hydroponically is much more successful than previous attempts have been (Fig. 4). In the last two weeks, lettuce plants have germinated and grown to a respectable height.

Several observations were made that require additional examination:

• Plants appear pale green, which is a sign of malnourishment, but this may simply be the nature of this particular type of lettuce.
• A discolouration was found on one of the leaves which should be kept in mind.
• A period of wilting may have occurred on May 17, although this may have been caused by leaves being spread out to allow new ones to grow instead.

I plan to do blog posts similar to this on a weekly basis every Sunday. Each post will contain my observations for the week and some analysis on it.