Scientific Method Research



Name of journal: Photosynthesis research

Volume and date: 113, 1 April 2012

Photosynthesis, photoprotection, and growth ofshade-tolerant tropical tree seedlings under full sunlight

Authors: Krause G. H., Winter K., Matsubara S., Krause B., Jahns P.,Virgo A. &amp García M.

Statement of hypothesis

Increasing the leaf area of a plant results in increased amount ofcarbon dioxide produced when the plant is exposed to direct sunlight


Thephysicochemical process by which green plants, algae, andphotosynthetic bacteria make food by the use of light energy isreferred to as photosynthesis. In plants, this process results in therelease of molecular oxygen. Carbon dioxide is assimilated from theatmosphere for the synthesis of carbohydrates. Photosynthesis yieldsenergy and regulates the concentration of carbon dioxide. These twoprocesses facilitate the survival of all life forms on the planet.Knowledge of the physicochemical process that takes place duringphotosynthesis is necessary for one to understand the relationshipbetween living things and the atmosphere which creates the balance oflife on earth. Krause et al. (2012) carried out a study toinvestigate the effect of exposing shade-tolerant plants to fullsunlight. This paper discusses the scientific methods that wereemployed in the study that aimed at examining the relationshipbetween the leaf area and carbon dioxide assimilated duringphotosynthesis. The benefits of this experiment to the society arealso discussed.

Problem statement

The objective ofthis experiment was to find out the ways and conditions through whichthe leaf area of a plant affects the amount of carbon dioxide to beproduced during photosynthesis. The study shows the benefits thatplants give to other living things in an ecosystem as well as therole in the purification of the atmosphere. Through of thisexperiment, Krause et al. (2012) explored the dangers of theaccumulation of carbon dioxide in the atmosphere to plants and man.Plants also play a significant role in regulating the amount of airpollutants. The dependent variable in this experiment was carbondioxide. Time, soil type and leaf area were the dependent variablessince they are the ones being changed in the experiment to achievethe desired results (Krause, 2012). The control variable was thenumber of seedlings since it remained constant. The dependentvariables are observed so as to determine their effects onindependent variable.

Relationship between dependent and independent variable

The amount ofcarbon dioxide is proportional to the rate of photosynthesis.

Measurement of variables

All the variablesused in this experiment were controlled adequately. The levels ofcarbon dioxide were regularly monitored, and the associated data wascollected for statistical analysis. An LI-6400 system was used forgaseous exchange measurement. Assimilation of CO2 byleaves was done below saturating ambient PAR ([800 µmol photons m-2s -1) at ambient carbon (IV) oxide level (380µL L-1) in the morning (8:30–9:40 h) and midday (11:40–13:15 h).Air was flowing at the rate of 500 µmol s-1. The soil type was notsimilar in all the plants. The leaf area was also determined, so asto create a variation of the leaf pigments exposed to sunlight. Notall the plants had the same leaf area.

Research design

The researchdesign for this experiment was valid. The experiments conducted inthis study were helpful. There are some biases in the research. Theexperiment could have included a variety of plants from differentenvironments. Different plant species have different capacities toassimilate carbon dioxide. Therefore the plants could have beentested in their natural environments so as to get accurate results.It could have been better to conduct this experiment in the naturalenvironment of the plant species.

Data collection

The study wasethical because there were no rules violated. The experiment was doneat the Santa Cruz Experimental Field Facility of the SmithsonianTropical Research Institute, located in Gamboa, Panama, which isdesignated for such activities (Krause, 2012). Graphs and tablesfacilitated the statistical analysis of the data collected. The bargraphs used are not complicated and are easy to interpret. Simpleshading is done on the bars to distinguish the variables easily. Theinterpretation of the tables is a big challenge. The data presentedin the tabular form cannot be interpreted easily. A person withknowledge of how to interpret them is needed to enhance theunderstanding of another person. Simpler tables could have beenbetter for everyone to interpret them and understood easily. Theanalysis of the data is in line with the hypothesis stated. Theresults of this study show that the larger the leaf area of a plantthe more the amount of carbon dioxide to be assimilated when theplant is exposed to a direct source of light.

Personal opinion

Krause et al.(2012) successfully employed systematic scientific research methodsin this experiment. Although there were some faults were detected inchecking the levels of carbon dioxide, the experiment was a success.The way the research was conducted with high precision and accuracy.The only different aspect that could have been done in this study isto change the environment at which it was carried out to the naturalhabitat of the plants and determine if the results would vary. Ithink the results could be the same because the environmental factorsare different.


Krause, G. H., Winter, K., Matsubara, S., Krause, B., Jahns, P.,Virgo, A. &amp García, M.

(2012). Photosynthesis, photoprotection, and growth of shade-toleranttropical tree seedlings under full sunlight.&nbspPhotosynthesisresearch,&nbsp113(1-3), 273-285.