One potential problem with this approach is that many genes involved in nutrient mobilization may be redundant. Despite the absence of CCH in the cch-1 mutant, the mutant is identi- cal to wildtype in every criteria studied. A likely explanation for the wild-type appearance of the cch-1 mutant is that a gene encoding a redundant function exists. Two sequences from Arabidopsis (Genebank accession numbers AAG51694 and AAG51766) have been identified that are predicted to encode proteins similar in sequence to CCH and these may represent functional homologs of CCH. Analysis of double, tri- ple and higher order mutants may be required to determine whether a redundant gene function, such as that encoded by CCH, is important to nutrient mobilization.