7.5 An experiment was conducted to determine the effect of anoxia (lack of oxygen) on the porosity of roots in nine genotypes of wheat. At an early stage of development, control plants of each genotype were grown in a well-aerated solution, while treated plants of each genotype were grown in stagnant agar which deprived the roots of oxygen. Following this treatment, the plants were grown in pots on a glasshouse bench, in a randomized complete block design with three replications. At the end of the experiment, seminal roots (i.e. those that develop directly from the seed) and nodal roots (i.e. those that originate from a node of the plant at a later stage) were harvested from each plant, and their porosity (% air space per root volume) was measured. On three additional plants of each genotype, the porosity of the seminal root was measured at an early stage of development, prior to the stagnant agar/aerated solution treatment. One of these three plants was assigned to each of the three blocks. The first and last few rows of the spreadsheet holding the data are presented in Table 7.13: the full data set is held in the file ‘root porosity.xlsx’ on this book’s website

(see Preface). (Data reproduced by kind permission of Michael McDonald.)

Genotype, treatment and root type are to be classified as treatment factors.