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3.1.3 - An experimental component

Short-term experiments as part of a study program have already been described briefly in Tim Colmer’s testimonial (section 1.2).

A crucial requirement for any such experiments associated with a study program of this sort is that they are short term and require simple equipment. In the experiment at the Prachinburi (Thailand) workshop, a cylindrical O2 electrode together with ‘cunning’ manipulation of environmental conditions led to a key finding that early in flooding a barrier to radial O2 movement formed in the roots, preventing loss of O2 derived from the shoots to the anaerobic environment around the roots (Colmer et al. 1998). At UWA we used simple tools to achieve rewarding results. Students took part in the planning but were given choices from a list of useful plant material by the tutors depending on suitability and available equipment. For example, meaningful experiments can be done with a ruler to measure elongation of coleoptiles (i.e. the first shoot organ of germinating cereals). Atwell et al. (1982) based nearly an entire research publication on elongation of rice coleoptiles in various oxygen regimes to show differential sensitivity to oxygen deficits during early growth phases. Similarly, elongation of roots can be used as a simple but meaningful criterion, allowing emphasis on designing and testing critical experiments. Rice coleoptiles are particularly useful, since if required the seedlings can be grown in stagnant solutions in the dark, i.e. under very simple conditions. Another possible object of study is duckweed (Lemna), which can be grown in stagnant solution on a windowsill. A sub-species Lemna gibba, is described in Wikipedia (https://en.wikipedia.org/wiki/Lemna_gibba) as merely having a (green) thallus and a single root. Simply counting the number of thalli (fronds) formed per day would be an easy way to test hypotheses. Similarly, for whole plants, leaf numbers vs leaf area can be used to provide a good guide to the contrasting effects of limiting factors on development and growth.

Another suitable experimental set up was used in practicals by the late Professor Michael Pitman (pers. comm. Steve Tyerman). A root of a K+-deficient barley plant was immersed in a dilute solution of CaSO4, along with an immersed pH electrode. This system allows measurement of net proton changes in solution with different treatments e.g. K2SO4 was added and the changes of K+ and H+ in solution measured. Students who have participated in the course described here should have little trouble suggesting possible outcomes and further experiments and, if time permitted, in carrying out several intriguing experiments using simple set ups.