Foundation of Biological Sciences I III. Hypothesis Testing & Graphing in Excel

Question

Foundation of Biological Sciences I III. Hypothesis Testing & Graphing in Excel A) EFFECT OF PLANT HORMONES ON PLANT GROWTH In this exercise you will develop hypotheses and predictions, gather data, and useE Scientifie Method - 4 data. data, and use Excel to analyze and display the Background Information hormones are produced in small amounts in one part of the lnt andaorted into targst celsin erentiation regi and t on, where it causes a physiological response. The physiological response include cell elongation, di of cells, n kguit ripening etc. Some of the well-studied plant hormones include Auxin, Gibsberens Cytokinins, Abscisic acid and Ethylene. Plant Hormones are routinely used in horticulture to regulate plant growth. Experimental setup The lab has rulers and balances available to collect data. Each group has been provided with petri dishes containing cucumber seeds. These sceds have been treated with different concentrations the concentrations of IAA applied). These plates were incubated for I week in dark conditions. of Indoleacetic acid (lAA), a naturally occurring plant auxin. (Plcase ask the instructor for Write two hypotheses for the experiment. Then think about which predictionts) your hy potheses make. W them down Write Hl Which is the dependent variable in your experiment? Which is/are the independent variablets)? .. List some of the standardized variables in the experiment......... What are the replicates in this experiment?

Explanation / Answer

Indole-3-acetic acid (IAA) ia a naturally occuring auxin mainly produced by the plant apex and young leaves. The main function of IAA is in inducing plant growth by cell elongation and cell division. Auxins, generally, are responsible for maintaining apical dominance (by promoting stem elongation) and inhibiting development of lateral buds.

In the given experiment, cucumber seeds treated with IAA are put in petri dishes and kept in dark for one week. The following hypothesis (and their predictions) can be worked out -

H1 - Since no light is present, photomorphogenesis dependent growth does not occur. This leads to the elongation of hypocotyl and reduced cotyledon expansion of the seedlings.

P1 - Auxin levels are inversely proportional to the amount of light received. Elongation of hypocotyl and reduced cotyledon expansion occur only in auxin abundance. This means that the use of IAA is controlled by light.

H2 - Plumule growth is negligible due to high auxin concentration. Radicle growth is noticed. So, auxin favours root apical dominance.

P2 - High abundance of auxins can inhibit shoot dominance, especially without light (since auxin is also responsible for phototropism). The auxin is then utilized in the root apical dominance instead.

Dependent variables - root growth, shoot growth, cotyledon growth, color of cotyledons, auxin utilization

Independent variables - none

Standardized variables - seedling growth in dark

Replicates - The replicates show similar responses as hypothesised. Other sets of replicates can be made by either changing the duration of light exposure, the levels of IAA, the type of seeds, or the type of growth hormone.

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