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The present paper summarizes theoretical background, practical notes and design of two experiments on plant phototropism to be conducted at high schools. Theoretical introduction describes different types of plant tropisms, e.g. gravitropism, heliotropism and phototropism, and different types of nastic movements not directionally oriented. Phototropism is a type of plant growth reaction oriented towards or against the direction of the source of irradiation, called positive phototropism or negative phototropism, respectively. The Experiment 1 is aimed at the effect of the different irradiation wavelength on the growth of plant shoot of Lepidium sativum. It is demonstrated there that blue light and, thus, blue photoreceptors are determining stem positive phototropic reaction. The use of LED light source to induce irradiation of a narrow wavelength is recommended. The Experiment 2 then demonstrates negative phototropism of plant roots. An important part constitutes the experience gained during the design, accomplishment and verification process for the presented experimentation. Both experiments were designed in cost-effective way for application of scientific approaches and protocols at high schools. [ABSTRACT FROM AUTHOR]